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Development of an Electronic size and colour grader for tomatoes Von Beckmann, Joerg Walter 1976

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DEVELOPMENT OF AN ELECTRONIC S I Z E COLOUR GRADER  FOR  AND  TOMATOES  BY JOERG WALTER jvon B.Sc.  Mount A l l i s o n  M.Sc. U n i v e r s i t y  BECKMANN  University,  1971  o f B r i t i s h Columbia,  1972  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN THE Department o f P l a n t (Bio-Resource  We  accept  the  this  required  thesis  Science  Engineering)  as c o n f o r m i n g  to  standard  THE UNIVERSITY OF B R I T I S H COLUMBIA A P R I L , 1976. (c)  Joerg Walter von Beckmann  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  f u l f i l m e n t o f the requirements  an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree the L i b r a r y I further  s h a l l make i t  freely  a v a i l a b l e for  agree t h a t p e r m i s s i o n f o r e x t e n s i v e  r e f e r e n c e and copying of t h i s  It  i s understood that copying or  thesis  permission.  Department of  Bio-Resource Engineering  The U n i v e r s i t y of B r i t i s h Columbia 20 75 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5  Date  Ayvil  29, 1976.  or  publication  o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my written  that  study.  f o r s c h o l a r l y purposes may be g r a n t e d by the Head of my Department by h i s r e p r e s e n t a t i v e s .  for  i  ABSTRACT The  greenhouse tomato i n d u s t r y  requires  that  and  g r a d e d , b a s e d on  size  t o m a t o e s be  Automatic colour  graders  colour  graded  diameter, for only  t i o n s have been d e v e l o p e d , w h i l e is  commercially  automatic the  size  size  and  requirements accelerate tomato  of  colour  colour  the  of  The  categories,  categories.  category  classifica-  g r a d e r b a s e d on  meet i n d u s t r y  weight  demands,  greenhouse tomatoes development of  which f u l f i l l s  an  industry  reduce production  costs  for  autograding  and  to  complete mechanization  t h e s i s o u t l i n e s the  a grading grading  one  in  at a r a t e of  under a f i b r e of  (2.5  cm)  o p t i c i l l u m i n a t i n g and  pneumatically  ejected  e j e c t mechanisms a r e  second.  The  passed  sensing  i n d i v i d u a l tomatoes a r e measured  appropriate  and  or decreased  and  synchronized  with  the  conveyor  single  head.  each  e j e c t l o c a t i o n , where t h e bin.  t o meet  Size  file and  electronically  i n a memory u n t i l  i n t o a storage  size  size  randomly f e d onto a  minimum s p a c i n g  stored  different  tomatoes per  increased  Tomatoes a r e  information  r e a c h e s an  may"be  five  f a b r i c a t i o n and  simultaneously  tomatoes i n t o f o u r t e e n  needs.  inch  design,  machine c a p a b l e of  categories  individual  the  two  grading  grader,  into four  a size  implementation of  categories  number o f  colour  colour  into four  Columbia  handling.  testing  and  colour  i s needed t o  This  with  and  To  f r e s h market i s necessary.  matic  and  available.  in British  The  tomato tomato i s  memory  and  conveyor b e l t  so  ii  that  changes i n b e l t  s p e e d do  grading rate i s s t r i c t l y operations, eject the  and  system  conveyor  i n the  Colour flected  from the  visible  spectrum.  measurement o f head, w i t h (0.12  cm)-  affect  by  the  ability  allotted  the  i s b a s e d on  pneumatic  the r a t i o of  Size grading t o m a t o , as  i s b a s e d on  i t passes  resolution  size  from  a  was  under the  less  rethe  diameter  of approximately  category  light  narrow bands o f  M i s c l a s s i f i c a t i o n of oversized or  tomatoes i n a g i v e n  handling  time.  t o m a t o s u r f a c e i n two  a grading  of  The  enough a i r t o remove t o m a t o e s  grading  the  grading.  a f u n c t i o n of mechanical  i s limited  to supply  not  than  sensing 3/64  inch  undersized 10%.  iii TABLE OF  CONTENTS PAGE  ABSTRACT  i  TABLE OF CONTENTS  i i i  L I S T OF TABLES  v i i X  L I S T OF FIGURES ACKNOWLEDGEMENTS  xiii  INTRODUCTION  1  LITERATURE  4  REVIEW SECTION  CHAPTER 1  CHAPTER 2  CHAPTER  3  I.  COLOUR GRADER  P h y s i c a l P r o p e r t i e s o f Tomatoes a s Related t o Colour Grading Introduction M a t e r i a l s and Methods Results and,Discussion Theory R e l a t e d t o t h e Development o f a Colour Grader I n i t i a l Considerations A n a l y s i s o f L i g h t S o u r c e , Sample, Detector Approximations f o r the Integrals Results of Analysis E f f e c t s o f Peak T r a n s m i s s i o n E f f e c t s o f F i l t e r H a l f Band W i d t h L i g h t Source E f f e c t s Discussion Design Approach Introduction I n i t i a l Component S e l e c t i o n L i g h t Source Photodetectors Optic F i l t e r s A n a l o g and D i g i t a l F a m i l i e s E l e c t r o n i c C o l o u r Grading System: Overview Analog Signal Processor Divider Circuit P h o t o t r a n s i s t o r and P r e a m p l i f i e r Circuits N o t c h F i l t e r a n d Low P a s s F i l t e r  12 13 14 15 18 24 25 30 33 36 36 36 39 42 45 46 48 48 48 48 49 53 56 56 60 66  iv  CHAPTER 3  CHAPTER 4  CHAPTER 5  CHAPTER 6  Design  Approach  (continued)  PAGE  Peak D e t e c t o r 1 C o m p a r a t o r 1, 2 a n d 3 Summing A m p l i f i e r 1 B e l t Background Monitor Schmitt Trigger C i r c u i t D i g i t a l Signal Processor Timing C i r c u i t Decoding Gates L i g h t Chopper and P h o t o d e t e c t o r Divide-by-3 C i r c u i t D a t a L a t c h e s , T i m e r s a n d Memory Circuits O p t o - I s o l a t o r s and T r i a c s D i s p l a y Timers Power S u p p l i e s M e c h a n i c a l H a n d l i n g System The C o n v e y o r S y s t e m E j e c t System  102 110 114 118 120 121 123  System T e s t i n g M a t e r i a l s and Methods E l e c t r o n i c System E j e c t System R e s u l t s and D i s c u s s i o n  126 127 127 127 128  SECTION I I .  132  S I Z E AND COLOUR GRADER  P h y s i c a l P r o p e r t i e s o f Tomatoes a s R e l a t e d to Size Grading Introduction M a t e r i a l s and Methods Results Discussion Size Determination Using the Colour Grader Schmitt T r i g g e r Pulse Introduction M a t e r i a l s and Methods S i z e Standards P u l s e W i d t h Measurement T e c h n i q u e Measurement o f B e l t Speed E f f e c t o f S t y r o b a l l S i z e on S c h m i t t T r i g g e r P u l s e Width a t Four C o n v e y o r B e l t Speeds E f f e c t o f Off-Center Viewing o f a S t y r o b a l l on t h e M e a s u r e d Diameter  71 75 79 82 85 90 90 93 96 99  133 134 136 138 142 146 147 14 8 148 150 150  150  152  V  CHAPTER 6 S i z e D e t e r m i n a t i o n  (continued)  R e s u l t s and D i s c u s s i o n E f f e c t o f S t y r o b a l l S i z e on Schmitt T r i g g e r Pulse Width a t Four Conveyor B e l t Speeds Resolution Schmitt T r i g g e r P u l s e Width versus Conveyor B e l t Speed f o r Three Styroball Sizes E f f e c t o f Off-Center Viewing o f a S t y r o b a l l on t h e Measured diameter Summary CHAPTER 7  CHAPTER 8  Design Approach Introduction Theory E l e c t r o n i c S i z e and C o l o u r Grader: Overview P u l s e Generator and Timer C i r c u i t s I n t e g r a t o r and Storage C i r c u i t Ramp G e n e r a t o r a n d S t o r a g e C i r c u i t C o m p a r a t o r 4, 5, 6 a n d 7 Decoding Gates Latching C i r c u i t S i z e / C o l o u r Decoder Memory C i r c u i t O p t o - I s o l a t o r and T r i a c C i r c u i t M e c h a n i c a l H a n d l i n g System System T e s t i n g Introduction M a t e r i a l s and Methods R e s u l t s and D i s c u s s i o n T h e o r e t i c a l Size Category L i m i t s versus Experimental Limits E f f e c t o f Tomato C o l o u r o n S i z e Measurement Size Grading A b i l i t y o f the S i z e / C o l o u r Grader Summary  153  153 153  157  157 160 162 163 165 169 173 177 182 185 190 192 194 196 202 203 204 205 206 210 210 212 214 224  FINAL SUMMARY  225  RECOMMENDATIONS  229  CITED REFERENCES  231  GLOSSARY OF TERMS  235  APPENDIX A  F e d e r a l and I n d u s t r y G r a d i n g S t a n d a r d s f o r G r e e n h o u s e Tomatoes  APPENDIX B  G r a d i n g R a t e a t Peak o f . G r o w i n g S e a s o n f o r B.C. Lower M a i n l a n d B a s e d on 1975 Y i e l d P r e d i c t i o n s , Mean W e i g h t i n e a c h S i z e C a t e g o r y , and Approximate Distribution of Size Categories  vii L I S T OF TABLES TABLE 1.1  1.2  1.3  2.1  2.2  2.3  2.4  3.1  3.2  3.3  PAGE "Top 5 0 " W a v e l e n g t h R a t i o s B a s e d on Maximum T o t a l D i f f e r e n c e s Between Means of the Reflectance Ratios f o r Four Colour Categories  19  "Top 5" W a v e l e n g t h R a t i o s f o r E a c h o f T h r e e C o l o u r Comparisons A c c o r d i n g t o P r i o r i t y o f Maximum D i f f e r e n c e B e t w e e n A d j a c e n t Colour Categories  20  "Top 5 " W a v e l e n g t h R a t i o s f o r E a c h o f T h r e e C o l o u r Comparisons A c c o r d i n g t o P r i o r i t y o f Maximum S t u d e n t s t V a l u e s f o r A d j a c e n t Colour Categories  22  N o r m a l i z e d R e f l e c t a n c e R a t i o s o f 600 nm/ 660 nm, f o r C o m b i n a t i o n s o f E q u a l H a l f Band W i d t h F i l t e r s and V a r i o u s % T r a n s missions: V a l u e s O b t a i n e d by I n t e g r a t i n g O v e r t h e Band W i d t h s  37  S t u d e n t s t V a l u e s f o r C o m p a r i s o n o f Mean Reflectance Ratios o f Four Colour Categories B a s e d on D a t a i n T a b l e 2 . 1  38  N o r m a l i z e d R e f l e c t a n c e R a t i o s o f 600 nm/ 660 nm, f o r C o m b i n a t i o n s o f V a r i o u s H a l f Band W i d t h s and Two % T r a n s m i s s i o n s : V a l u e s O b t a i n e d by I n t e g r a t i n g O v e r t h e Band W i d t h s  40  S t u d e n t s t V a l u e s f o r C o m p a r i s o n o f Mean R e f l e c t a n c e Ratios o f Four Colour C a t e g o r i e s B a s e d on D a t a i n T a b l e 2 . 3  41  N o r m a l i z e d R e f l e c t a n c e R a t i o Means, S t a n d a r d D e v i a t i o n s , and S t u d e n t s t V a l u e s f o r F o u r C o l o u r C a t e g o r i e s U s i n g a 550 nm/660 nm Wavelength R a t i o : V a l u e s O b t a i n e d by I n t e g r a t i n g O v e r t h e Band W i d t h s  50  P r e d i c t e d Mean O u t p u t V o l t a g e s f o r F o u r C o l o u r C a t e g o r i e s B a s e d on E q u a t i o n [3-1] and t h e Twenty Tomatoes ( C h a p t e r 1)  59  Output S t a t e s o f Comparators for Four Colour Categories  1,  2 and 3, 78  viii  TABLE 5.1  5.2  6.1 6.2  6.3  6.4  7.1  7.2  7.3 7.4 8.1 8.2  8.3  PAGE Diameter-Weight C o r r e l a t i o n s Regression Equations  and L i n e a r 139  Mean D i f f e r e n c e B e t w e e n D I A . l a n d DIA.2 and 95% C o n f i d e n c e I n t e r v a l s f o r F o u r Size Categories  140  D I A . l , DIA.2 a n d DIA.3 o f T h r e e S t y r o b a l l Size Standards  149  T h e C o l o u r G r a d e r CLOCK A F r e q u e n c y Approximate Conveyor B e l t Speed  Versus 151  Mean, S t a n d a r d D e v i a t i o n , a n d S t a n d a r d E r r o r o f Schmitt T r i g g e r P u l s e Width f o r Three S t y r o b a l l s a t Four Conveyor B e l t Speeds  154  Approximate Diameter Measurement E r r o r a t Various O f f - C e n t e r Distances f o r Three S t y r o b a l l s R e l a t i v e t o t h e On-Center Measurement  159  T h e o r e t i c a l and Measured I n t e g r a t o r Output V o l t a g e s a t V a r i o u s Conveyor B e l t Speeds  181  O u t p u t S t a t e s o f COMP. 4, COMP. 5, COMP. 6 and COMP. 7 f o r F i v e S i z e C a t e g o r i e s  187  O u t p u t S t a t e s o f C o m p a r a t o r s 2, 3, 5, 6, 7 f o r Twelve S i z e / C o l o u r C a t e g o r i e s  189  S h i f t R e g i s t e r Length and Input a t t h e S i x Programmable I n p u t s  199  Conditions  T h e o r e t i c a l a n d E x p e r i m e n t a l V a l u e s o f D, f o r V a r i o u s Diameters  211  Values o f F R e s u l t i n g from a Comparison o f Mean D i a m e t e r s o f T h r e e C o l o u r C a t e g o r i e s i n a Given Size Category  213  Means, S t a n d a r d D e v i a t i o n s a n d 95% Confidence Intervals f o r M i s c l a s s i f i e d T o m a t o e s A r o u n d t h e 2.250 I n c h (5.715 cm) and 3.000 I n c h (7.620 cm) C u t - o f f s  220  P e r c e n t a g e o f O v e r s i z e and U n d e r s i z e Tomatoes f o r E a c h S i z e C a t e g o r y as G r a d e d by t h e S i z e / C o l o u r G r a d e r  X  L I S T OF  FIGURES  FIGURE  PAGE  2.1  T r i f u r c a t e d F i b r e O p t i c Assembly  26  2.2  R e l a t i v e Response Phototransistor  28  2.3  2.4  2.5 3.1  Spectral Filament  of a Typical  D i s t r i b u t i o n of a Tungsten Lamp (3500°K C o l o u r T e m p e r a t u r e )  Schematic o f Source-Sample-Detector System Spectrogram of a T y p i c a l Firm Ripe G r e e n Tomato S t a n d a r d NPN Using  Phototransistor  28  31 and 34  Amplifier  an FPT120A  51  3.2  C o l o u r Grader B l o c k Diagram  54  3.3  Analog Divider  57  3.4  Red  3.5  Notch  3.6 3.7  Peak D e t e c t o r 1 O u t p u t V o l t a g e s f o r T y p i c a l F i r m R i p e , and S e m i - R i p e Tomatoes (a) D i v i d e r Output f o r U n i f o r m l y Ripe Tomato (b) D i v i d e r Output f o r Non-Uniformly R i p e Tomato (c) Peak D e t e c t o r O u t p u t f o r (a) a n d (b)  73  3.8  Comparator  76  3.9  Summing A m p l i f i e r  3.10  B e l t Background  Monitor  83  3.11  Schmitt Trigger  Circuit  86  3.12  Timing C i r c u i t  91  3.13  Decoding Gates  94  Circuit  and Green P h o t o t r a n s i s t o r and Low  Amplifiers  Pass F i l t e r s  Circuit 1  61 68 72  80  xi  FIGURES  PAGE  3.14  L i g h t Chopper P h o t o d e t e c t o r  97  3.15  Divide-by-3  3.16  Latching C i r c u i t  103  3.17  Data L a t c h  105  3.18  D a t a L a t c h Waveforms  106  3.19  Memory C i r c u i t  109  3.20  Opto-Isolators  3.21  D i s p l a y Timer C i r c u i t  3.22  Power S u p p l y C i r c u i t  3.23  (a)  Circuit  100  Timers  Sensing  and T r i a c s  112 115  forTriacs  119  Head a n d (b) L i g h t  Chopper Assembly  122  3.24  Pneumatic E j e c t Mechanism  125  4.1  C o l o u r Groupings a t V a r i o u s Comparator Voltage Settings Mean S c h m i t t T r i g g e r P u l s e W i d t h v s . S t y r o b a l l Diameter a t Four Conveyor B e l t Speeds  6.1  7.1  S i z e G r a d e r , and S i z e / C o l o u r Digital  Processor  Generator  Block  129  155  Grader  Diagram  and Timer C i r c u i t  170  7.2  Pulse  7.3  I n t e g r a t o r and Storage  7.4  Ramp G e n e r a t o r  7.5  Comparator C i r c u i t  186  7.6  Decoding Gates  191  7.7  Latching Circuit  193  7.8  Size/Colour  195  7.9  One o f 13 S h i f t R e g i s t e r C i r c u i t s U s e d i n t h e S i z e / C o l o u r Memory C i r c u i t  Circuit  and Storage  Circuit  Decoder C i r c u i t  174 178 183  198  xii  FIGURE  PAGE  7.10  S i z e / C o l o u r Memory C i r c u i t  201  8.1  Machine Graded F i r m  Tomatoes  215  8.2  M a c h i n e G r a d e d S e m i - R i p e Tomatoes  216  8.3  Machine Graded T u r n i n g  217  Ripe  Tomatoes  9  ACKNOWLEDGEMENTS The Bulley  author. wtthei  [Vepan.tment  oh Bn,tttih  oh Bto-RzAoufic.il  Columbta),  hon, ht& gutdance  to t>tncen,ely  and cK.tttcti>m  ht& enthu&ta&m The  Runeckleb  ofl  tht.6  oh Bto-Re.AouK.ce. Engtneen.tng,  the, thesis,  Special typings  thanks  Sincen,est  the  research  Counctl  bpent  to Mn.s. E. Stewan,t  have  The  research  oh  Canada.  and h  ofl  hen,  is extended  B.C. who supplied  at no cost.  would  the Ve.pan.tme.nt by the. V*-- C . A . Hon,nby,  Vn,. E.O. Nybon,g, tn fLe.vte.wtng  gratitude  Burnaby,  research  n,ei>ean.ch wtth  acknowledged.  oh the manuscript,  Co-operative,  appreciated.  Vn.. P . A . Jollthh<^>  and especially  an.e  a& ex.pe.cted  Chatn,man, Vn,. (/. C .  and the. ttme  memben,i> oh the. commtttee, Vn,. G . W . Eaton  yeaK.&.  0Vifl  wen.e, an.e greatly  m  tn co-oK-dtnattng  Untven.&tty  n,ei>ean.ch pK.oje.ct,  wen,e not gotng  °i fJ Commtttee  &  Engtne.nn.tng,  oven, the pa-t>t h  when they  ehh ^  Vn,. N. R.  the. VtK.eo.toK. oh thti>  Hti> zncoLLK.age.me.nt when thtngA and  thank  been  Without dihh^^lt  was h^  - ^  nanc  Z(  their  h - the many oH  pattence. to Western  Greenhouse  a l l the tomatoes co-operation  to carry  the  out.  by the Nattonal  Research  h oh  1  INTRODUCTION Approximately of  4.2 m i l l i o n  pounds  (1.9 m i l l i o n k g ) *  g r e e n h o u s e t o m a t o e s were p r o d u c e d i n t h e B r i t i s h  Lower M a i n l a n d occurs  i n 19 75.  from A p r i l  About  87% o f t h e a n n u a l p r o d u c t i o n  t o l a t e August, with  280,000 l b (126,000  Columbia  kg) p e r week.  a peak  M o s t Lower  production of Mainland  tomatoes a r e m a r k e t e d by t h e W e s t e r n Greenhouse  Co-operative  i n B u r n a b y , B.C. Tomatoes colour  as w e l l  as f o r g e n e r a l q u a l i t y  and C o - o p e r a t i v e operation  are graded according  Standards**.  to both according  At present,  i s the r e s p o n s i b i l i t y  is  inspected The  standard cases  to Federal  the major  of the i n d i v i d u a l  g r a d e d p r o d u c e i s p a c k e d i n 20 l b (9 kg) b o x e s to t h e co-op warehouse  s i z e and  grading  grower. The  and d e l i v e r e d  where a s m a l l p e r c e n t a g e o f t h e b o x e s  and g r a d e d . inspection  o f a few b o x e s w h i c h a r e b e l o w  c a n down-grade  i s inequitable  an e n t i r e  s h i p m e n t w h i c h i n many  t o the grower.  S i m i l a r l y , many  boxes  c a n c o n t a i n b e l o w a v e r a g e p r o d u c e b u t be g r a d e d as p r i m e quality  resulting  f r o m random  federal  standards  lack  tolerances  ment, and c o l o u r g r a d i n g each grower g r a d i n g  * **  sampling  inspection.  f o r a single  i s subjective,  Since  size  measure-  i t i s probable  tomatoes based on t h e p r e s e n t  that  standards,  Data c o u r t e s y o f Western Greenhouse C o - o p e r a t i v e , B u r n a b y , B.C. The S t a n d a r d s f o r tomato g r a d i n g a r e f o u n d i n A p p e n d i x A.  2  will  deliver  individual  v a r y i n g grades of  need f o r one  a l l g r o w e r s and  these  standards  n o t meet t h e will  be  s e t of  the grading  i s evident.  standards  paid f a i r l y  size  of  and  every  If only  and  was  beneficial  accomplished has  size  and  automatic  grader,  categorize  do  grower  and  size  The  and  into  own  size by  and  ungraded, Larger  produce  standards  if i t can  colour grader,  federal  be which  graders.  t h e d e v e l o p m e n t o f an  colour grader t o be  unneces-  grading  standard.  maintenance of  verified  i n order  tomatoes  to avoid  a seasonal  c o l o u r grade t h e i r  report deals with  electronic  every  d e l i v e r e d t o the warehouse  t o them.  been c a l i b r a t e d  matic  be  in hiring  by use of an automatic  This  tomatoes which  and  there according to a uniform  growers c o u l d  to  f o r h i s product d e l i v e r e d .  produce should  graded  standards  tomato a c c o r d i n g  a r e down-graded, t h e n  expense t o each grower  staff,  colour  those  Ideally, to minimize handling sary  to  interpretation. The  for  tomatoes a c c o r d i n g  f o r tomatoes.  autoThe  a c c e p t a b l e must be  able  to  f o u r c o l o u r c a t e g o r i e s and  four  size  categories. The size  and  process  of automatically grading  c o l o u r i n v o l v e s the  a)  Load  tomatoes onto a  b)  Arrange  c)  Transport  tomatoes  tomatoes  following steps:  conveyor.  in single  t o a s e n s i n g and  file  (singulate).  grading  area.  by  3  d)  Categorize  individual  colour e)  Store  f)  Transport  information u n t i l  colour category  E j e c t the  an  electronic  t h r o u g h g)  research and  are  reported  mechanical  as d e s c r i b e d  research  available, to develop The  aim  speed e l e c t r o n i c  size  and  ing only eject  the  preliminary  tests  appropriate  cross-conveyor. here  not  conveying  i n v o l v e s the d e s i g n  the  grading  o b j e c t i v e of  system f o r  r e s e a r c h was  a single handling not  downstream  of  c)  conveying systems w h i c h s i n g u l a t e  c o l o u r grade tomatoes  s y s t e m was  station  system to i n c l u d e steps  i t was  a new  high  eject  above.  and  of  i t s size  station.  conveyor i n t o  b i n or onto a  Many l o a d i n g and fruit  and  area.  tomato from the  storage The  size  tomato r e a c h e s  eject  tomato t o a p p r o p r i a t e  from s e n s i n g g)  specific  categories.  category and  tomatoes i n t o  tomatoes.  the development of  system which would i n one  process.  this  operation, The  of major importance  simultaneously thus  involv-  development of in this  of a pneumatic system are  a  study  described.  an although  4  LITERATURE The e v a l u a t i o n methods the  REVIEW  of f r u i t  ripeness  such as t h e measure o f r e f l e c t e d  fruit  surface  fruit,  or optical  density  27,30,31,36,37), f i r m n e s s the  Magness-Taylor F r u i t  Universal Tester  light  included i n t e n s i t y from  (1,4,5,8,9,10,11,13,14,15,16,17,24,25,28,  29,33,35)*, t h e measure o f t r a n s m i t t e d the  has  light  i n t e n s i t y through  (2,3,5,10,11,18,21,22,23,25,26,  t e s t i n g using Pressure  instruments  Tester  and an  (11,15,24,25) a n d v i b r a t i o n a l  such as  Instron techniques  (25,32). The most p o p u l a r fruit  are those  involving colour  tance o r transmittance. a grading  criterion  "The o v e r a l l  methods  One  i s best  f o r "on-line" grading  evaluation  reason  e i t h e r by  of  reflec-  f o r t h e use o f c o l o u r  as  s u m m a r i z e d by B i t t n e r e t a l . ( 4 ) ,  quality of fruit  i s a f u n c t i o n o f many f a c t o r s ,  but  a p p e a r a n c e i s t h e m a i n f a c t o r o n w h i c h t h e c o n s u m e r makes  the  decision". Firmness t e s t i n g o r v i b r a t i o n a l techniques  that  the f r u i t  usually  be s t a t i o n a r y and p h y s i c a l l y h a n d l e d w h i c h  r e q u i r e s more t i m e t h a n a c o l o u r m e a s u r e m e n t .  c o l o u r measurement may motion.  be o b t a i n e d  while  the f r u i t  The  is in  F i r m n e s s t e s t s o n t o m a t o e s h a v e shown g o o d c o r r e l a -  tions with  visual  colour  evaluation  and r e f l e c t e d  light  measurements a t s p e c i f i c w a v e l e n g t h s i n t h e v i s i b l e as  require  described  by Hood e t a l . ( 1 5 ) .  Colour  alone  Numbers i n p a r e n t h e s e s r e f e r t o a p p e n d e d  spectrum,  therefore, i s  references.  5 a reasonable  measure o f  fruit  T h e r e a p p e a r s t o be which of the  two  firmness no  tion  d f one  mitted surface peel,  transmittance  s i d e of the  through  u n i v e r s a l agreement as  l i g h t measuring techniques,  o r r e f l e c t a n c e i s most s u i t a b l e The  i n tomatoes.  the  c o l o u r o f the  technique  fruit  fruit,  and  such  to the  as  transmittance  grading.  i n v o l v e s the  the  u s u a l l y on  fruit,  contributes l i t t l e  for fruit  sensing of the o t h e r the  optical  transmittance into  a cup  required  o r o n t o an  around the  aperature,  sealant  (21,22,23);  conform w e l l t o the  in direct  complicates  (3).  For be  fruit  o f the  fresh-market  most s u i t a b l e  as  fruit fruit,  fruit  light  has  as  blue-  the  fruit  sealant i s cup  must have  receptor i s  (36), which f u r t h e r  at high  sorting  rates.  r e f l e c t a n c e would appear  a r i p e n e s s measurement, s i n c e t h e c o l o u r , i s what t h e  Reflectance  better to high  itself  a  is  clay  supporting  a light  of  placed  seal  such  in size,  appearance, or r e f l e c t e d lends  must be  I n t e g r a t i n g spheres  (3), or the  fruit  i s generally  Modelling  For  uniform  shape.  contact with  handling  a good  however, t h e  fruit  been p l a c e d around the placed  and  fruit.  disadvantage  fruit  i l l u m i n a t e d area.  b e r r i e s , which are r e l a t i v e l y necessary  The  measurement i s t h a t t h e  b e e n u s e d as a l i g h t  not  This technique  for processing.  apple  d e n s i t y o f the  external colour. fruit  The  c o l o u r o f an  colour  used i n g r a d i n g  trans-  side.  t h e r e f o r e , i s a measure o f i n t e r n a l  not  illumina-  light  Transmittance, and  to  consumer  speed g r a d i n g  to  external sees. systems  6  than transmittance. special  cups, only  fruit.  A light  illuminated  and t h e r e f l e c t e d  source  o r sensor  system. special  past Fruit  that the f r u i t  with  the f r u i t .  the sensing size  uniformity  i s an i m p o r t a n t  tomatoes.  since the f r u i t i s  received  f r o m t h e same  i s l o c a t e d from t h e l i g h t since neither i s placed The f r u i t  can flow  con-  conveyor  i s not a necessity to carry the f r u i t .  since The s i z e  c o n s i d e r a t i o n when d e a l i n g  S i z e s r a n g e f r o m u n d e r two i n c h e s  3 1/2 i n c h e s  from t h e next  e l e m e n t on a s i m p l e  cups a r e n o t r e q u i r e d  variation  light  i s n o t as c r i t i c a l  contact  tinuously  b y some d i s t a n c e  seal i s not required,  The d i s t a n c e  direct  d o e s n o t h a v e t o be p l a c e d i n  separated  side.  in  Fruit  with  (5 cm) t o  (9 cm) i n d i a m e t e r .  The  reflected  over the v i s i b l e  light  intensity  spectrum alone  colour of the f r u i t .  from a f r u i t  surface  does n o t c o r r e l a t e w i t h t h e  However, t h e i n t e n s i t i e s  at specific  w a v e l e n g t h s , o r n a r r o w w a v e l e n g t h b a n d s does c o r r e l a t e the to ted  surface  colour  (4,5,8,11,15,28).  The q u e s t i o n  with  a r i s e s as  which wavelength o r combination o f wavelengths o f r e f l e c light  produces  the best  c o r r e l a t i o n with  F u r t h e r m o r e , how s h o u l d  t h e measured l i g h t  intensities,  i n order  Should  t o produce  s i g n a l s be a d d e d , s u b t r a c t e d , As  colour.  intensity, or a colour  a s i n g l e measurement be u s e d , o r s h o u l d  electronic  three  be h a n d l e d  fruit  index?  two o r more  divided,  etc.?  e a r l y a s 1953, Powers e t a l . (29) d i s c u s s e d  criteria  w h i c h c o u l d be used  f o r s o r t i n g lemons b a s e d  7  on  the  The  intensity  first  of  light reflected  i s a measure o f  w a v e l e n g t h band i n the  a  single  m e a s u r i n g i n s t r u m e n t as  from the the  sensor  measure o f  at  different  The  effects  cancelled  and the  size  of  using  this  This  method i n v o l v e s  i s the the  reflected  l i g h t at  at  the  used  f o r the It  that  at  lemon  two  two  d i v i s i o n to  b e e n i g n o r e d by  prise  a  from the  reflected  that  by  produce a  spectrum.  and  size  are  sensitivity using  a  difference  visible The  between  by  to  percen-  narrow bands i n the  the  the  intensity  l a t t e r c r i t e r i o n was  work o f  Powers e t  the  either signal  d i v i s i o n , or proportional  many r e s e a r c h e r s , late  intensity  Burkhardt et  al.  al.  l i g h t i n t e n s i t i e s are  extraneous i n t e r f e r e n c e s .  single  intensities  visible  Greater  wavelengths d i v i d e d  h a v e b e e n d e v e l o p e d as only  light  obtained  the  The  distance  one  grader.  i s clear  least  two  in  second c r i t e r i o n i s  reflected  be  measure o f  wavelengths.  independent of  use  The  technique.  at  reflec-  changes i n o b j e c t  t h i r d c r i t e r i o n discussed.  combined a r i t h m e t i c a l l y and  two  i n c o l o u r may  narrow  single  s e n s i t i v i t y , distance  t a g e change i n r e f l e c t a n c e  of  as  fruit.  r a t i o of  a  sensitivity variations  well  of  instrument  small variations  one  to  surfaces.  of  The  narrow w a v e l e n g t h bands i n the  out  spectrum.  intensity  v i s i b l e spectrum.  t a n c e measurement i s s u b j e c t the  from t h e i r  as  1969  and  "new"  and  measurement. (9)  required,  subtraction to  The  colour  findings  colour  1974  and have  graders  (1,9,33) w h i c h  I t i s of  encountered  (29)  sorting  no  sur-  problems  8  when t h e f r u i t intensities division  varied i n size.  to fruit  maturity  The c o r r e l a t i o n o f t h r e e b y B i t t n e r e t a l . (5) b y t h e  o f one b y t h e p r o d u c t o f t h e o t h e r  significant  advantage over  the simple  ratio  two showed no o f two i n t e n s i -  ties . As in  a ratio,  t o the choice  no two w a v e l e n g t h s a r e i d e a l  wavelength r a t i o s 520  nm/670 nm  red  o f 670 nm/730 nm  (14),  t o s o r t tomatoes. primarily  four  t o m a t o e s i n t o two c o l o u r f o r the f i r s t ,  used  categories,  w h i c h was c o r r e l a t e d  the i d e a l wavelength r a t i o  a g r a d e r d e p e n d s o n t h e number o f c o l o u r  separated.  have been  used  categories.  Apparently, in  The  (15) h a v e a l l b e e n  The a b o v e w a v e l e n g t h r a t i o s  t o separate  colour  f o ra l l f r u i t .  ( 5 ) , 540 nm/630 nm ( 1 1 ) ,  a n d 525 nm/670 nm  and green, except  over  o f two w a v e l e n g t h s t o be c o m b i n e d  Two c o l o u r  category  d i f f e r e n t wavelength r a t i o  than  t o be u s e d  categories  t o be  separations  would r e q u i r e a  four  category  colour  separa-  tions . Since et  t h e d e v e l o p m e n t o f t h e lemon g r a d e r b y Powers  a l . (29) i n 1953, l i t t l e  progress  field  of electronic colour  grading  using  r e f l e c t a n c e as t h e g r a d i n g  h a s b e e n made i n t h e  of fruits  criterion.  and  vegetables  They  described  a machine c o n s i s t i n g o f a conveyor which o r i e n t e d t h e i r major a x i s p e r p e n d i c u l a r the  lemons  with  to the direction of travel. At  e n d o f t h e c o n v e y o r , t h e lemons w e r e d r o p p e d t h r o u g h an  illuminated  c o m p a r t m e n t , where t h e r e f l e c t e d  l i g h t was  9  r e c e i v e d by used  photodetectors.  The  photodetector  t o a c t i v a t e d e f l e c t i n g vanes which  lemons i n t o one  of  five  colour  ment o f e l e c t r o n i c t e c h n o l o g y of p h o t o - m u l t i p l i e r tubes, Switching but  of  circuits  details  in  literature,  the  processing  such  as  two  advance-  e a r l y 1950's.  Instead  are  of  now  in  the  ignored  sequences,  colour categories and  tubes  Some o f  systems have been timing  use.  o f vacuum  data  are  involved,  memory components  any  grading  and  system.  being  handled.  a l . (29)  w o u l d be  conveying  of  Both o p e r a t i o n s The  fruit are  i s of  that  unsuitable  f o r anything  but  for  tomatoes.  (6),  w h i c h was  single f i l e r  designed  described  o r i e n t a t i o n device  f o r d r i e d prunes would probably  The  single f i l e r  Greenwood e t a l . (13) similar  and  to that of Brantley  and  used et a l .  cucumbers,  by  Burkhardt et a l .  n o t work f o r  two  be  Brantley  tomatoes.  a t r a n s p o r t conveyor described consisted of  Powers  lemons,  not  the  tomatoes.  described  (9)  and  by  f o r sweet p o t a t o e s  h a v e some p o t e n t i a l a p p l i c a t i o n f o r The  for  o r i e n t a t i o n s y s t e m u s e d by  e j e c t mechanism, o r d e f l e c t i n g vanes c o u l d The  importance  specific  the  may  improvements the  comprised  proper  the  required.  fruit et  longer  few  result  semiconductors  triggering  Singulating in  the  s i n c e the  grading  when more t h a n of  The  integrated circuits.  of colour  simplification  .i s  no  t r a n s i s t o r s and  subtle  and  are  categorized  grades.  w h i c h h a v e b e e n made s i n c e t h e n a r e  s i g n a l s were  parallel  e t a l . (6), but  was  vee  by belts,  designed  for  10  tomatoes. and  T o m a t o e s were e j e c t e d  pneumatic  belts.  assistance  an  excellent  to  test  et  a l . (20)  ideal,  results  o f t o m a t o e s on  involving  unknown.  a d j u s t a b l e vee d e s c r i b e d by used  system  size  which  technique  Brantly  i s that  for orienting  and  The  vegetables grading sizes  multiple  belt,  cucumbers  Goodman e t a l . (12)  disadvantage  of such  A).  developed  by  available  f o r some t i m e .  i s used  A weight  in  into  The  the f r u i t  when t h e w e i g h t  of the  than  as  tomato  has  the  been  commercial that  cups, which  to preset spring-loaded dropped  fruit  onto  exceeds  a  cross-conveyor  that of  the  the  been  grader requires  i n d i v i d u a l weighing  t h e n m e c h a n i c a l l y compared m e c h a n i s m s , and  weight  for  rather  g r a d e r has  C o r p o r a t i o n , U.S.A., and  could  a grading  g r a d i n g , i . e . t h e minimum d i a m e t e r  Maximum d i a m e t e r  singulated  i n the  grading i s s t r o n g l y weighted  (Appendix FMC  assist  f o r s w e e t p o t a t o e s and  The  Mason  over holes of v a r i o u s  becomes t h e measurement c r i t e r i o n  standard  speculation  belt.  grading of f r u i t s  e t a l . (6) and  the s i z e  maximum d i a m e t e r .  be  a conveyor  grader  f o r tomatoes.  the f r u i t  fruit  of f r u i t ,  p r o m i s i n g f o r tomatoes.  favour of o v e r - s i z e  size  singulation  i n the p u b l i s h e d work.  of f r u i t  two con-  M e c h a n i c a l methods o f s i z e  the r o l l i n g  does n o t a p p e a r  be  size  the  of a f l a t  describe a vibrational  virtually  from  however, the p r o p o r t i o n o f  i s not c l e a r  Electronic  plungers  the use  i n a packing t r a y which c o u l d p o s s i b l y  orientation  is  the tomatoes  suggested  f o r t o m a t o e s w i t h no  is  fruit  to l i f t  H e r o n e t a l . (14)  veyor b e l t  using mechanical  are  11  spring  force.  Grading  tomatoes.  The  television  c a m e r a , has  for  measuring  The  d e v i c e may  a commercial  use  by w e i g h t  o f an  i s not  been r e c e n t l y areas  be more s u i t e d  size  and The  to a research instrument  colour grader combination  and/or c o l o u r grader  e t a l . (6) s i z e  grader  w o u l d r e q u i r e e i t h e r one or  products  one  size  complete  grader  just  of a size  onto  and  from  for five  A  five  size  and  the conveyor  the  tables  need  i s well  shortage automatic  conveyor  documented  grading of  (19,32).  i n the  (34),  system  ejects  The  fruits  increasing  The  packing  the  o p e r a t i o n s and  handling  and  and cost  vegeand  future f o r automatic  simplification  of  equipment f o r  increased sophistication  multiple  damage.  the  n e c e s s i t a t e d the development  h a r v e s t i n g , g r a d i n g and  equipment l i e s  graders,  appropriate packing b i n or  f o r automatic  produce  f o r example,  N  o f l a b o u r a l o n e has  agricultural  a  t h e r e i s a need f o r a  a cross-conveyor. The  and  the  to perform  c o l o u r c a t e g o r i z e s and into  grader  four size  colour graders Clearly,  has  colour grader,  sizes,  and  grader which u s i n g a s i n g l e  simultaneously fruit  than  the o p e r a t i o n of  i n tandem.  colour grader  grading operation.  size/colour  (7).  f o r tomatoes  f o u r c o l o u r s of tomatoes, i n c o n j u n c t i o n w i t h  Brantley  a  as a d e v i c e  of a g r i c u l t u r a l  a c o l o u r g r a d e r i n v o l v e s more t h a n  for  suggested  to  grader.  not y e t been developed.  grader  standard f o r  image s e n s i n g a r r a y , s i m i l a r  l e n g t h s and  A combined  size  the  grading  towards  to minimize  product  E  C  T  COLOUR  I  O  N  GRADER  C H A P T E R  1  PHYSICAL PROPERTIES OF TOMATES AS RELATED TO COLOUR  GRADING.  14  INTRODUCTION  Based it  was d e c i d e d  o n t h e work o f Powers e t a l . (29) and o t h e r s , that a ratio  o f r e f l e c t a n c e s a t two  wavelength  bands o f t h e v i s i b l e  criterion  f o r colour  spectrum would  evaluation.  determine the wavelength  among t h e f o u r c o l o u r  semi-ripe,  turning  intensities  and g r e e n —  a t each wavelength  be a s u i t a b l e  A s t u d y was c o n d u c t e d t o  r a t i o which would  separation  narrow  categories based  band.  provide —  firm  the best ripe,  on t h e r e f l e c t e d  MATERIALS AND METHODS Twenty t o m a t o e s * the study, and grouped tomatoes  each:  firm  ( v a r i e t y V e n d o r ) were c h o s e n f o r  into  ripe,  four  colour  categories  semi-ripe, turning  and g r e e n , a s  d e s c r i b e d by t h e Canada Department o f A g r i c u l t u r e (Appendix A ) .  No a t t e m p t  The g r e e n tomato group  a m i x t u r e o f m a t u r e a n d immature A spectrophotometer  photometer,  f o r t h e range  magnesium o x i d e s t a n d a r d . t o be used  (Unicam  to hold  green probably  tomatoes.  Ultraviolet Spectro-  M o d e l SP800B) was c a l i b r a t e d  (zero absorbance)  Standards  was made t o s e p a r a t e m a t u r e  f r o m immature g r e e n t o m a t o e s . included  of five  t o 100% r e f l e c t a n c e  350 nm t o 800 nm u s i n g a  Since plexiglass  t h e tomatoes d u r i n g  petri  d i s h e s were  the reflectance  tests,  t h e magnesium o x i d e s t a n d a r d was t h e n p l a c e d b e h i n d a p l e x i glass  petri  dish.  The r e f l e c t a n c e  dropped  85%  a c r o s s t h e 350 nm t o 80.0. nm r a n g e .  was  recalibrated  in  to approximately  The s p e c t r o p h o t o m e t e r  t o 100% r e f l e c t a n c e w i t h t h e p l e x i g l a s s  front of the standard. A t o m a t o s e c t i o n was c u t f r o m e a c h  the p e t r i was  dish  dish  flattened  (60 mm against  d i a X 20 mm deep) a n d t h e t o m a t o the viewed  d i s h was c o v e r e d a n d p l a c e d Several mately  2 minutes  tomato t o f i l l  samples for total  side  of the p e t r i  i n t h e sample  were scanned spectrum)  skin  d i s h . The  holder.  at a fast  (approxi-  and then a t a slow  _ A l l tomatoes used i n t h i s r e s e a r c h were o b t a i n e d from W e s t e r n G r e e n h o u s e G r o w e r s C o - o p e r a t i v e , B u r n a b y , B.C.  16 (approximately 8 minutes f o r the t o t a l spectrum)  r a t e , and  no d i f f e r e n c e was noted between the two t r a c e s . Consequently, all  subsequent scans were c a r r i e d out a t the f a s t speed. The absorbance  (A) was measured  a t 10 nm i n t e r v a l s  from 380 nm t o 800 nm f o r each o f the twenty spectrograms and c o n v e r t e d t o p e r c e n t r e f l e c t a n c e u s i n g the r e l a t i o n s h i p : R(%)  =  10  _ A  X  100% *  [1-1]  R e f l e c t a n c e r a t i o s were c a l c u l a t e d by d i v i d i n g the percent reflectances  o f 903 d i f f e r e n t wavelength p a i r s  b e g i n n i n g w i t h 380 nm/390 nm, 380 nm/400 nm f o r each tomato.  The mean r e f l e c t a n c e r a t i o o f t h e f i v e  tomatoes i n each c o l o u r permutation.  between a d j a c e n t c o l o u r  permutation.  c a t e g o r y was c a l a c u l a t e d  The d i f f e r e n c e s  semi-ripe-turning;  t o 790 nm/800 nm  o f mean r e f l e c t a n c e  categories,  i . e . firm  f o r each ratios  ripe-semi-ripe;  and t u r n i n g - g r e e n were c a l c u l a t e d f o r each  The t h r e e d i f f e r e n c e s o f mean r e f l e c t a n c e  between a d j a c e n t c o l o u r  categories  ratios  were summed t o produce a  maximum r e f l e c t a n c e r a t i o d i f f e r e n c e as suggested by Goddard e t a l . (11).  f o r each wavelength  ratio,  To i l l u s t r a t e , i f the  d i f f e r e n c e between mean r e f l e c t a n c e r a t i o s o f the f i r m r i p e and s e m i - r i p e tomatoes a t the 60 0 nm/66 0 nm wavelength r a t i o was 0.34, and the d i f f e r e n c e between s e m i - r i p e and t u r n i n g was 0.63, and the d i f f e r e n c e between t u r n i n g 0.5,  and green was  then the maximum d i f f e r e n c e between the means a t t h e  600 nm/660 nm wavelength r a t i o would be 1.51. *  See Unicam  Spectrophotomer Model SP800B Manual.  17  The l a r g e r t h e d i f f e r e n c e b e t w e e n t h e means o f adjacent the  three  colour  colour categories,  the larger w i l l  means, a n d t h e g r e a t e r  categories,  according  be t h e sum o f  the separation  between  t o Goddard e t a l . (11).  18  RESULTS AND The of adjacent ratios with  DISCUSSION  " t o p 50" maximum t o t a l  colour  are l i s t e d  the greatest  categories i n Table  d i f f e r e n c e s b e t w e e n means  and t h e i r  wavelength  1.1 i n d e s c e n d i n g o r d e r  difference.  beginning  The r e s u l t s a g r e e . w i t h  o f G o d d a r d e t a l . ( 1 1 ) , who f o u n d t h a t 540  associated  nm/680 nm w a v e l e n g t h r a t i o s  separation  f o r t h e good tomatoes  categories  from t h e o t h e r  grade  t h e 550 nm/680 nm a n d  y i e l d e d "a r e a s o n a b l y (red)  and green  accurate  tomatoes  categories".  C a r e f u l examination o f each o f the adjacent category the  mean r e f l e c t a n c e r a t i o  turning  and t u r n i n g .  and green a t t h i s  total  probably  semi-ripe  ratio  (maximum) d i f f e r e n c e . acceptable  f o r the separation  o f green  ratio  about  from  turning. separates  t h e mean t o be s m a l l ,  according  are l i s t e d  i n Table  to the p r i o r i t y  turning  f o r separating the  " t o p 5" w a v e l e n g t h r a t i o s  comparisons  from  e q u a l l y w o u l d show a p p r o x i m a t e l y  deviations  factor i n  The 550 nm/680 nm r a t i o i s  b e t w e e n t h e means o f e a c h c a t e g o r y ,  The  order  i s the predominant  wavelength r a t i o which best  categories  differences  colour  does n o t i n c l u d e t h e  from f i r m r i p e o r s e m i - r i p e The  standard  that  The l a r g e d i f f e r e n c e b e t w e e n  tomatoes, b u t i t i s n o t t h e best  colour  colour  d i f f e r e n c e between f i r m r i p e and s e m i - r i p e , n o r  between s e m i - r i p e  the  differences indicates  55 0 nm/680 nm w a v e l e n g t h r a t i o  greatest  those  a l l four t h e same  assuming t h e and e q u a l .  f o r each o f the three 1.2, i n d e s c e n d i n g  o f maximum d i f f e r e n c e b e t w e e n  19 TABLE 1.1 "TOP 50" WAVELENGTH RATIOS BASED ON MAXIMUM TOTAL DIFFERENCES BETWEEN MEANS OF THE REFLECTANCE RATIOS FOR FOUR COLOUR CATEGORIES. Total Semi Turning Green No. Ratio Difference - Firm -Semi -Turning 1 3.776 550/680 0.212 1.426 2.139 2 540/680 3. 690 0.196 1. 340 2.154 3 3.686 560/680 0.206 1.448 2. 033 4 3.501 530/680 0.160 1.128 2 . 213 5 570/680 3.458 1.421 0.220 1.817 6 3.422 550/670 0. 207 1.301 1. 914 7 540/670 1.221 3.343 0.191 1.931 8 560/670 3.340 0. 201 1. 322 1.817 9 530/670 0.156 3.173 1. 986 1.031 10 570/670 3.129 0.215 1.620 1. 294 11 580/680 3.078 0.286 1. 306 1.486 12 520/680 2. 974 0.133 0. 908 1.928 13 590/680 2. 798 0. 352 1.154 1. 292 14 580/670 2.778 0.278 1.180 1. 320 15 520/670 2.697 0.134 1.732 0.831 16 600/680 2. 588 0.390 0. 980 1. 218 17 590/670 2.512 0.341 1.028 1.144 18 550/660 2.388 1. 061 0.190 1.137 19 540/660 2.333 0.176 0.995 1.163 20 560/660 2.329 0.184 1. 078 1.067 21 600/670 2.301 0. 373 0.853 1.075 22 530/660 2.218 0.143 0. 841 1.234 23 570/660 2.175 1.052 0.197 0. 927 610/680 24 2.157 0. 350 1. 030 0. 778 25 510/680 2.139 0. 682 0.127 1.330 26 510/670 1. 939 0.124 0.622 1.1-92 580/660 27 1.913 0.256 0.944 0. 713 28 520/660 1.885 0. 676 0.124 1. 086 29 610/670 1.885 0. 326 0.656 0. 904 30 550/690 1.863 0. 941 0.749 0.173 31 620/680 1.841 0. 295 0.647 0.899 32 540/690 1.820 0.160 0. 882 0.778 560/690 1.816 33 0.168 0.956 0.692 550/650 34 1.750 0.178 0.881 0.692 35 530/690 1.7 33 0.130 0.744 0.858 36 540/650 1.710 0.825 0.721 0.164 37 560/650 1.706 0.172 0.897 0.638 38 590/660 1.701 0. 313 0.799 0.589 39 570/690 1.691 0.178 0. 581 0.931 40 530/650 1.628 0.134 0.699 0. 796 41 630/680 1.594 0.196 0. 568 0.830 42 570/650 1.585 0.183 0.870 0.531 620/670 1. 582 43 0.266 0.529 0.786 44 550/640 1. 568 0.172 0.809 0.587 45 500/680 1.560 0.118 0.540 0.902 46 540/640 1.532 0.158 0. 757 0.616 47 560/640 1.528 0.166 0.823 0. 539 48 600/660 1.508 0.341 0.631 0.536 49 580/690 1.475 0.832 0. 233 0.410 50 520/690 1.472 0. 762 0.113 0. 597  20  TABLE 1.2  "TOP 5 " WAVELENGTH RATIOS FOR EACH OF THREE COLOUR COMPARISONS ACCORDING TO PRIORITY OF MAXIMUM DIFFERENCE BETWEEN ADJACENT COLOUR CATEGORIES.  A /A, a b  Semi-Firm  PRIORITY:  Semi-Ripe -- Firm Ripe  Turning-Semi  i  Green-Turning  1 . 218  600/680  .390  600/670  .373  .980 .853  590/680  .352  1.154  1.292  610/680  . 350  .778  1.030  590/670  .341  1.028  1.144  PRIORITY:  1.075  Turning - - Semi-Ripe  560/680  . 206  1.443  2 . 033  550/680  .212  1.426  2.139  570/680  .220  1.421  1.817  540/680  .196  1.340  2.154  560/670  .201  1 . 322  1.817  PRIORITY:  Green -- T u r n i n g  530/680  .160  1.128  2.213  540/680  .196  1.340  2.154  550/680  .212  1.426  2.139  560/680  . 206  1.448  2.033  530/670  .156  1 . 031  1.986  21  the  means o f f i r m r i p e - s e m i - r i p e ;  turning-green of  The d a t a  f o r semi-ripe  to green,  530 nm/680 Although  two  colour  deviation  adjacent  colour  imply  good  t-test  colour  i n Table  means w i l l  Students'  be d i f f e r e n t  t-test The  semi-ripe  i n Table  ratio  question  levels,  i n Table  ratios f o r each 1.3, i n  o f maximum t  values  v s . t u r n i n g , and  1.3 shows t h a t s e l e c t i o n  f r o m t h e s e l e c t i o n b a s e d on S t u d e n t s '  i s probably still  equally  B a s e d on t h e v a l u e s confidence  significant  b a s e d on t h e d i f f e r e n c e s b e t w e e n  i n the d i r e c t i o n o f the i d e a l  f o r the separation  ratio will  no  standard  Comparisons o f t h e sequence o f wavelength  1.2 t o t h o s e  ratio  are l i s t e d  to the p r i o r i t y  The d i f f e r e n c e p o i n t s  wavelength  the  was u s e d t o compare t h e means,  comparisions  o f an optimum w a v e l e n g t h  length  separation,  The " t o p 5" w a v e l e n g t h r a t i o s  according  turning v s . green.  t-test.  560 nm/680nm a n d f o r t u r n i n g  f o r t h e 50 w a v e l e n g t h  firm r i p e vs. semi-ripe;  ratios  t h e 600 nm/680 nm  exists.  categories  1.1.  descending order  separation  t h e l a r g e d i f f e r e n c e s b e t w e e n t h e means o f  Students'  i n Table  and  nm.  b e t w e e n t h e means  of the three  for  with  i n e a c h g r o u p may be s o l a r g e t h a t  The  listed  t h e maximum  i s obtained  to turning,  categories  difference  of  indicates that  f i r m r i p e and s e m i - r i p e  ratio;  semi-ripe-turning;  o f the groups, but  a more r e l i a b l e i n d i c a t o r . remains,  separate  o f t i n Table i t appears t h a t  "Which s i n g l e wave-  a l l four colour 1.3 and t h e i r  categories?"  associated  any w a v e l e n g t h r a t i o  from  22  TABLE  a  1.3  "TOP 5" WAVELENGTH RATIOS FOR EACH OF THREE COLOUR COMPARISONS ACCORDING TO PRIORITY OF MAXIMUM STUDENTS t VALUES FOR ADJACENT COLOUR CATEGORIES.  b  Firm-Semi  PRIORITY:  F i r m - R i p e --  Semi-Turning  Turning-Green  Semi-Ripe  600/660  4.648**  6.751***  8 . 542***  610/680  4.366**  5.797***  7 .084***  620/680  4.234**  5.407***  7.246***  600/680  4.094**  6.313***  7.314***  610/670  3.971**  5.896***  9.074***  PRIORITY:  Semi-Ripe  --  Turning  560/640  2.932*  9.147***  7.123***  550/640  3.088*  9.146***  7.867***  540/640  3.262*  9.027***  8. 320***  570/690  2.905*  9.009***  5.627***  560/690  2.895*  8.786***  6.189***  PRIORITY:  Turning  -  Green  520/670  2.876*  6.973***  13.938***  510/670  3.198*  6.599***  13.514***  530/670  2.790*  7.346***  12.844***  520/660  3.187*  7 .068***  12.143***  510/680  3.295*  6.815***  11.964***  Significant  a t 0.1%  level  Significant  a t 1%  level  Significant  a t 5%  level  23  one  o f t h e t h r e e p r i o r i t y groups would s e p a r a t e  from t u r n i n g , and t u r n i n g from g r e e n . wavelength r a t i o s group separate level  —  firm  ripe  a t only  However, o n l y t h e  ripe v s . semi-ripe p r i o r i t y  from  semi-ripe  the wavelength r a t i o s  separate one  i n the firm  serai-ripe  a t t h e 99% c o n f i d e n c e  i n the other  t h e 95% c o n f i d e n c e  level.  two g r o u p s A c h o i c e o f any  w a v e l e n g t h r a t i o i n t h e 600 nm/660 nm t o 610nm/670 nm  group should colour  result  i n good s e p a r a t i o n among t h e f o u r  categories, but the  b e s t wavelength r a t i o would be  600 nm/660 nm, s i n c e i t shows t h e g r e a t e s t v a l u e s both  firm  the  second  ripe v s . semi-ripe largest  of t f o r  and s e m i - r i p e v s . t u r n i n g , and  value o f t f o r t u r n i n g v s . green.  24  C H A P T E R  THEORY  RELATED OF  TO  2.  THE  A COLOUR  DEVELOPMENT  GRADER.  25  INITIAL Ideally, ratio be  technique,  t o maximize t h e use o f t h e r e f l e c t a n c e  t h e same a r e a on t h e t o m a t o s u r f a c e  v i e w e d by b o t h  tions  sensing elements.  due t o c o l o u r d i f f e r e n c e s  measure o f t h e r a t i o cancels  any e f f e c t  a result by  bination  over  Initial  of incandescent  light  measured r e f l e c t a n c e size  using this  t e s t s were c o n d u c t e d  source  onto  indicating  (as  with  a com-  s o u r c e s and  housing.  to vary with  that different  Both The  tomato areas o f  sensed.  A trifurcated considered.  was f o u n d  A  i s viewed  p r o b l e m s were e n c o u n t e r e d .  housing,  t o m a t o were b e i n g  variation  i f t h e same a r e a  and f l u o r e s c e n t l i g h t  ratio  varia-  a t two w a v e l e n g t h s  intensity  s e n s i n g e l e m e n t s a l l mounted i n a m e t a l and t h e r m a l  should  t h e tomato s u r f a c e .  light  o f v a r y i n g tomato s i z e s )  geometrical  the  This minimizes  o f the r e f l e c t e d  of reflected  t h e two s e n s o r s .  two  CONSIDERATIONS  fibre  optic  a s s e m b l y , F i g u r e 2.1, was  One f u r c a t i o n w o u l d be u s e d  to direct  t h e tomato s u r f a c e , and t h e o t h e r  equal portions of the r e f l e c t e d  light  the l i g h t  two t o d i r e c t  t o each o f the photo-  detectors. The l i g h t e m i t t i n g a n d r e c e i v i n g optic  bundle  end o f t h e f i b r e  was c h o s e n s o t h a t i t w o u l d e m i t  light  through  a rectangle 1 i n (2.5 cm) X 0.063 i n (0.16 cm) with i t s lengths being perp e n d i c u l a r t o t h e movement o f t h e t o m a t o u n d e r t h e f i b r e bundle. uniform  A random f i b r e lighting  a r r a n g e m e n t was c h o s e n t o e n s u r e  o f t h e t o m a t o s u r f a c e as w e l l as u n i f o r m  26 FIGURE  2.1  TRIFURCATED  FIBRE O P T I C  ASSEMBLY  FIBRE MFD.  MOLD B Y  NO.  DOLfcN  X-7Z3 -JENN£.X  MASSACHUSETTS  27  light ted  reception.  and  The  minimum t o m a t o s u r f a c e a r e a  v i e w e d w o u l d be  l e n g t h of the  an  t o m a t o as  inch  i t passed  A p h o t o t r a n s i s t o r was over  other devices  tubes,  and  analog  applications  diode), tage  such  a high  light  t e m p e r a t u r e ) was  spectral  response  photodetector multiplier  primarily  f o r the  for  photo vol-  i n conjunction with  over  the v i s i b l e  3300°K) have l i t t l e  photo-  same lamp  phototran-  response. (350 0°K  as a l i g h t  colour  source,  r a t e o f change t h a t i s  range.  The  spectral  effect  a b l e due  t o the  sharp  specific  wavelengths. the  A  on  the shape o f  the  f l u o r e s c e n t lamp was  spikes i n i t s spectral  findings  i n Chapter  would r e q u i r e peak w a v e l e n g t h s o f Optic f i l t e r s  vary  i n their  1, 600  since  relatively  energy  Lower o p e r a t i n g t e m p e r a t u r e s  distribution.  respectively.  for a  distribu-  lamp a t 3 5 0 0 ° K f i l a m e n t t e m p e r a t u r e  shown i n F i g u r e 2.3.  B a s e d on  the  f o r use  output  curve  Most s i l i c o n  tungsten  considered  of a tungsten  filters  the  the  bundle.  a wide o p e r a t i n g  f o r use  exhibit  intensity  provides a spectral  energy  suitable  photo diodes  A high  tion  sensitivity,  i s shown i n F i g u r e 2.2.  and  uniform  c h o s e n as  fibre  over  circuits.  transistor  it  under the  (as o p p o s e d t o d i g i t a l  A typical  sistors  wide s t r i p  since i t i s designed  r a n g e a n d w o u l d be  integrated  cm)  as p h o t o d i o d e s , p h o t o  photo c e l l s ,  has  (2.5  illumina-  is  (e.g.  spectral  deemed  undesir-  distribution  the nm  ideal and  relative  660 peak  at  optic nm  28 FIGURE  2.2  RELATIVE TYPICAL  4oo  soo  RESPONSE  2.3  goo  TUNGSTEN SPECTRAL  +00  SOO  A  PHOTOTRANSISTOR  WAVELE/VGrH  FIGURE  OF  SOO  WAVELENGTH  300  700 ( N M )  FILAMENT  LAMP  DISTRIBUTION  700  (NM)  j j  QOO  29  transmissions than  and have f i n i t e  a d i s c r e t e wavelength.  lengths  for a particular  o f a h a l f bandwidth. above f i l t e r s The  peak w a v e l e n g t h  deviation  filters  or their  What e f f e c t w i l l standard  tungsten  ratio  will  1.3.  the separation  therefore, the  being t r a n s m i t t e d over must be t a k e n  What  into  i s the e f f e c t  i f t h e band w i d t h  account on t h e  o f one o r b o t h  peak t r a n s m s i s s i o n s a r e changed?  the use o f a l i g h t  source other than  lamp h a v e on t h e f i n a l  analysis of the entire system  filter  system.  relative  f o r the•  bandwidths.  o f t h e energy  when d e s i g n i n g t h e o p t i c  i n terms  t h e 600 nm o r 660 nm  decreases  I f possible,  o f the o p t i c  reflectance  expressed  by t h e d a t a i n T a b l e either  b y 10 nm g e n e r a l l y  Integration  final  from  more  o f t r a n s m i t t e d wave-  i s usually  primarily  s h o u l d have n a r r o w  the band w i d t h  encompassing  The c h o i c e o f h a l f bandwidths  between c o l o u r c a t e g o r i e s . filters  The range  filter  i s governed  d a t a shows t h a t  band w i d t h s  light  ratio  s o u r c e , sample,  a  obtained?  An  light detector  p r o v i d e a n s w e r s t o t h e s e and o t h e r q u e s t i o n s .  30  ANALYSIS OF LIGHT  SOURCE, SAMPLE, DETECTOR  An a n a l y s i s was of  light  source-sample-detector  of r e f l e c t a n c e . and  light  carried  The e f f e c t s  sources  were  out t o study  the  g e o m e t r y on t h e  of using  various  effects  measurement  optic  also investigated.  A schematic of the source-sample-detector shown i n F i g u r e  2.4.  filters,  Each o p t i c f i l t e r  l o c a t e d between t h e o u t p u t  of the f i b r e  was  system i s  conveniently  o p t i c b u n d l e and t h e  photodetector. Since transistors will currents, will  the f i n a l  be t h e r a t i o  the r a t i o w i l l  t o be o b t a i n e d  f r o m t h e photo-  o f e i t h e r two v o l t a g e s  be a d i m e n s i o n l e s s  s i m p l i f y the system a n a l y s i s through  rather  or  quantity, t h e use o f  which relative  than absolute q u a n t i t i e s . The components  Xi  ratio  o f t h e a n a l y s i s a r e as f o l l o w s :  =  peak w a v e l e n g t h o f t h e s h o r t w a v e l e n g t h o p t i c filter.  2  =  peak w a v e l e n g t h o f t h e l o n g w a v e l e n g t h o p t i c  Xx  - a =  s h o r t wavelength f i l t e r t r a n s m i s s i o n lower (at a p p r o x i m a t e l y 0.1% peak t r a n s m i s s i o n ) .  Xi  + a =  s h o r t wavelength f i l t e r t r a n s m i s s i o n upper l i m i t (at a p p r o x i m a t e l y 0.1% peak t r a n s m i s s i o n s ) .  A  2  - b =  long wavelength f i l t e r (at a p p r o x i m a t e l y 0.1%  t r a n s m i s s i o n lower l i m i t peak t r a n s m i s s i o n ) .  A  2  + b =  long wavelength f i l t e r (at a p p r o x i m a t e l y 0.1%  t r a n s m i s s i o n upper l i m i t peak t r a n s m i s s i o n ) .  A  source,  filter.  limit  A  =  r e l a t i v e energy o f the l i g h t b e t w e e n 380 a n d 800 nm.  at a given A  B  =  r e l a t i v e r e f l e c t a n c e o f a tomato, a t a g i v e n b e t w e e n 380 and 800 nm.  A  31 FIGURE  2.4  SCHEMATIC.  OF  SOURCE-SAMPLE-DETECTOR  TRIFURCATED FIBRE OPTIC ASSEMBLY  COhfVBYOR  BS.LT  SYSTEM  32  r e l a t i v e t r a n s m i s s i o n of the s h o r t wavelength o p t i c f i l t e r , a t a g i v e n X b e t w e e n 380 and 800  nm.  r e l a t i v e t r a n s m i s s i o n o f the long wavelength optic f i l t e r , a t a g i v e n X b e t w e e n 380 and 800 nm. D  r e l a t i v e response of the p h o t o d e t e c t o r , a t A b e t w e e n 3 80 and 800 nm.  E.  output of the photodetector r e c e i v i n g the s h o r t w a v e l e n g t h s o f l i g h t i n t e g r a t e d b e t w e e n ( A - a) and ( A i + a ) . x  output of the photodetector r e c e i v i n g the long w a v e l e n g t h s o f l i g h t i n t e g r a t e d b e t w e e n ( A - b) and ( A + b ) .  E.  2  2  In the r a t i o  this  analysis,  o f output  factors tance Taking  such  r a t i o E^/E2 i s  currents of the photodetectors,  current being proportional semi-conductor  the r e f l e c t a n c e  surfaces.  t o the energy T h i s energy  as t h e o u t p u t  impinging  factors  of the l i g h t  i n to account  on t h e  i s a function of source, the  o f t h e t o m a t o , and t h e t r a n s m i s s i o n s o f t h e these  each  yields  reflec-  filters.  the following  relationship: (Ai  + a) [A (A)  E  n  1  D ( A) ] dA  2  [2-1]  + b) [A ( A)  (X;  C (A)  a)  (X; (A  . B ( A)  b)  . B ( A)  C (A) 2  D ( A) ] dA  33  Approximations  f o r the  Integrals  A(A) , B ( A ) , whose d e f i n i t i o n pose be  of this  o b t a i n e d by  + a)  and  curves  (A  from  from  - b)  2  was  f o r the  s o u r c e and  collected  steps.  The  380  was  nm  and  mission Gaussian  and  2.3.  collected  filter  f u n c t i o n which  mission  characteristics  decided  that  reasonable  of  steps,  d a t a from  over  from  the  ripe  i n 10  and  nm  green  due  flexible  i n peak  the  trans-  to the c o m p l e x i t y o f  the  of this  i t was  type of f i l t e r ,  triangle  would  s e r v e as  a  f o r the t r a n s m i s s i o n curves.  = 2 half  band w i d t h  t h e band w i d t h  f o r the t r i a n g l e )  o f the t r i a n g l e , half  was  20  t h e same r a n g e firm  the  the  trans-  isosceles  and  distribution  n o r m a l l y r e p r e s e n t s the  t r a n s m i s s i o n over  peak w a v e l e n g t h ,  to  incremental  the curve r e p r e s e n t i n g  t o be  and  approximation  equal sides  a)  2.5.  relative  the  -  may  a r e a measurement.  i n 10 nm The  pur-  the  o f the p h o t o d e t e c t o r  for a typical  was  band w i d t h ,  an  nm  { X \  The  energy  t o 800  also  + b).  spectral  the a n a l y s i s ,  band p a s s  2  f o r each  tomato a r e shown i n F i g u r e  optic  (A  to  from  chosen  spectrograms  For  functions  f o r the i n t e g r a l s  functions  f o r the response  i n F i g u r e s 2.2  spectrograms  a r e complex  Approximations  curves of the  Data light  D(A)  summation o f i n c r e m e n t a l a r e a s u n d e r  A A = 10 nm  distance,  and  as e q u a t i o n s i s n o t n e c e s s a r y f o r t h e  analysis.  representative (Ai  C(A)  after  was  (where band calculated  The width from  peak t r a n s m i s s i o n ,  band w i d t h were c h o s e n  for analysis.  So  FIRM  400  SOO  600 WME.LEN6TH  j FIGURE  2.5  S P E C T R O G R A M FIRM  RIPE  A N D  OF  A  G R E E N  700 • (NM)  TYPICAL T O M A T O  RIPE.  BOO  35  Using be  t h e summation o f a r e a s , t h e i n t e g r a l s  approximated  and t h e r a t i o E ^ / ^ c a l c u l a t e d  could  using the  relationship:  fl E  -  m E A A A B A A C, A A D A A P P i p P i = 0,10,20 [2-2]  2 E A A A B A A C_ A A q q 2 q j = 0,10,20  where  D A A  q  p = A - a + i x  q = A  2  - b + j  m = 2 X h a l f band w i d t h o f t h e s h o r t w a v e l e n g t h filter n = 2 X h a l f band w i d t h filter. Various optic f i l t e r s , ting and  of the long wavelength h a l f band w i d t h s ,  lamp s p e c t r a l c u r v e s , e t c . w e r e t e s t e d t h e r a t i o E^/E^  c  a  l  c  u  l  a  t  e  d  illumina-  i n e q u a t i o n [2-2]  f o r e a c h o f t h e 20 t o m a t o e s  (Chapter 1 ) . F o r any s e t o f i n p u t c o n d i t i o n s , t h e 20 r a t i o s G = E ^ / l E ^  the largest of  (corresponding t o the greenest  was a d j u s t e d t o a v a l u e o f 1 0 , a n d s u b s e q u e n t l y  tomato)  the remaining  19 r a t i o s w e r e n o r m a l i z e d b y m u l t i p l y i n g e a c h b y t h e n o r m a l i zing  factor: F  =  10/G.  [2-3]  36  RESULTS OF The band w i d t h  effects  ANALYSIS  o f v a r y i n g p e a k t r a n s m i s s i o n and  of the o p t i c  filters  r a t i o were s t u d i e d t o e n a b l e  on  a filter  which  suited  the  requirements  tion  among  colour categories.  p r i m e c o n c e r n was t h e optimum  s t u d i e d by  at  350  nm  Effects  was  that  a t 360  o f Peak  when f i l t e r s  —  spectral  wavelength  separa-  ratio  of  p r e v i o u s l y suggested  output  of the normal tungsten nm  light  sources  curve of the  a h y p o t h e t i c a l lamp whose  was  that  as  was 3500K  0  irradiance  a t 80 0 nm;  the  o f the normal tungsten  lamp  at  Transmission 600  nm/660 nm  of equal half  categories  from  mean r e f l e c t a n c e  band widths  40  o f peak t r a n s m i s s i o n s f r o m  20%  to  a t-test  on  The  nm/660 nm  o b t a i n e d when c o m b i n a t i o n s band w i d t h s ,  used  f o r the  600  2.1.  Values  2.2.  and nm  20%  and  mean r e f l e c t a n c e  o f 20 and  660  nm  40%  nm/20 nm  ratios,  t o 40  nm/40  nm  peak t r a n s m i s s i o n s were  filters  respectively,  and  60%  H a l f Band W i d t h  600  half  shown i n T a b l e  nm  t h e means o f a d j a c e n t c o l o u r  are l i s t e d i n Table  of F i l t e r  20  obtained  and  are  of  ratios, nm  i n the a n a l y s i s ,  resulting  Effects  The  of using different the  combinations  were u s e d t  made  etc.  The  various  effect  reversing  irradiance 790  t o be  f o r maximum s t a t i s t i c a l  nm/660 nm  lamp t o p r o d u c e  nm  selection  reflectance  ratio. The  tungsten  600  the measured  half  are  of  37  TABLE 2.1  NORMALIZED REFLECTANCE RATIOS OF 600nm/660nm, FOR COMBINATIONS OF EQUAL HALF BAND WIDTH F I L T E R S AND VARIOUS % TRANSMISSIONS: VALUES OBTAINED BY INTEGRATING OVER THE BAND WIDTHS.  Half  Band W i d t h o f 600 nm F i l t e r  Half  Band W i d t h  o f 660 nm  =  20 nm 20  Filter  nm  T r a n s m i s s i o n o f 600 nm  Filter  20% t o 60%  T r a n s m i s s i o n o f 660 nm  Filter  20% t o 60%  Firm  Semi-Ripe  Ripe  Green  Turning  Mean*  2.35  3.95  7.14  9.65  S.D.**  0.13  0.80  0.67  0 .27  Half  Band W i d t h f o r 600  nm  Filter  =  40 nm  Half  Band W i d t h f o r 660  nm  Filter  =  40 nm  T r a n s m i s s i o n o f 600 nm  Filter  20% t o 60%  T r a n s m i s s i o n o f 660 nm  Filter  20% t o 60%  Firm  Ripe  Semi-Ripe  Turning  Green  Mean*  1.83  2.97  6.11  9 .61  S.D.**  0.10  0.67  0 .80  0 .51  *  Mean = A v e r a g e  **  S.D. = S t a n d a r d  o f 5 tomatoes. Deviation.  38  TABLE 2.2  STUDENTS t VALUES FOR COMPARISON OF MEAN REFLECTANCE RATIOS OF FOUR COLOUR CATEGORIES BASED ON DATA IN TABLE 2.1  H a l f Band W i d t h o f 600 nm  Filter  H a l f Band W i d t h o f 660 nm  Filter  =  20 nm 20 nm  T r a n s m i s s i o n o f 600  nm F i l t e r  20% t o 60%  T r a n s m i s s i o n o f 660  nm F i l t e r  20% t o 60%  Firm Ripe vs. Semi-Ripe  Semi-Ripe vs. Turning  4.387**  Turning vs. Green  6.806***  7.730***  H a l f Band W i d t h  f o r 600 nm  Filter  =  40 nm  H a l f Band Width  f o r 660 nm  Filter  =  40 nm  T r a n s m i s s i o n o f 600  nm F i l t e r  20% t o 60%  T r a n s m i s s i o n o f 660  nm F i l t e r  20% t o 60%  Firm Ripe vs. Semi-Ripe  Semi-Ripe vs. Turning  3.807**  6.711***  ***  Significant  a t 0.1%  level  **  Significant  a t 1%  level  Turning vs. Green 8.216***  39  shown i n T a b l e  2.3.  Table  2.4  lists  the values of t r e s u l t i n g  c o m p a r i s o n o f means o f a d j a c e n t Table  2.3.  Light  Source  c o l o u r c a t e g o r i e s shown i n  the s p e c t r a l  lamp, and t e s t i n g  analysis  the  Effects  Reversing sten  from  showed  this  new  no s i g n i f i c a n t  s e p a r a t i o n between a d j a c e n t  output  curve  of the  h y p o t h e t i c a l lamp change i n t h e  tung-  i n the  statistical  colour categories.  40  TABLE 2.3  NORMALIZED REFLECTANCE RATIOS OF 600 nm/660 nm, FOR COMBINATIONS OF VARIOUS HALF BAND WIDTHS AND TWO % TRANSMISSIONS: VALUES OBTAINED BY INTEGRATING OVER THE BAND WIDTHS.  H a l f Band W i d t h (nm) for 600nm 660nm 20  30  40  20  20  20  20  30  20  20  40  30  20  40  40  20  20  30  40  20  20  30  30  *  20  Percent Transmission for 600nm 660nm  20  40  20  Mean  =  Average  S.D.  =  Standard  40  40  40  40  40  40  40  40  40  Firm Ripe Mean* S.D.**  SemiRipe Mean S.D.  Turning Mean S.D.  Mean S.D.  2. 35  3.95  7.14  9.65  0.13  0.80  0.67  0. 27  2.42  3.94  7.13  9.66  0.13  0.78  0.68  0.27  2.52  3.94  7.11  9.66  0.12  0.75  0.69  0.26  2.42  4. 05  7.27  9.69  0.14  0.81  0.67  0.27  2.46  3.99  7.19  9.67  0.13  0. 78  0. 68  0.27  1.77  2.89  5.98  9.56  0.10  0.66  0.80  0. 54  2. 52  4. 20  7.44  9.75  0.14  0.82  0.65  0. 25  2.30  3.79  7.12  9. 58  0.12  0.73  0. 76  0.39  1.85  2. 97  6.11  9.61  0.10  0.67  0.80  0. 51  o f 5 tomatoes Deviation.  Green  41  TABLE 2.4  STUDENTS t VALUES FOR COMPARISON OF MEAN REFLECTANCE RATIOS OF FOUR COLOUR CATEGORIES BASED ON DATA IN TABLE 2.3.  Half Band Width (nm) for 600nm 660nm  Percent Transmission for 600nm 660nm  Firm-Ripe vs. Semi-Ripe  Semi-Ripe vs. Turning  Turning vs. Green  20  20  20  40  4.387**  6.806***  7 . 730***  30  20  20  40  4.293**  6.885***  7 .706***  40  20  20  40  4.177**  6.951***  7.727***  20  30  20  40  4.444**  6.866***  7.551***  30  30  20  40  4.326**  6.915***  7.563***  40  30  20  40  3.767**  6.674***  8.302***  20  40  20  40  4.511**  6.926***  7.386***  30  40  20  40  4.465**  7.075***  6.457***  40  40  20  40  3.807**  6.711***  8 .261***  S i g n i f i c a n t at 0.1% l e v e l Significant  a t 1%  level  42 DISCUSSION The indicate  t h a t t h e r e i s no  reflectance held  mean r e f l e c t a n c e  ratio  constant  and  h a l f band widths increased category any  from  600  nm  semi-ripe  t as  600  t o 40  660  nm nm  The  a t the  of the  and  two  the  660  each,  600  nm/660  o f the  1%  nm  i s not  confidence results  and  40%  of  600  nm/660 nm  combinations 40  nm/40 nm  tance  The  decreased  660  ratio  filter  analysis.  of each c o l o u r corresponding  t h e means o f a d j a c e n t  listed  nm  i n Table  2.4.  from  separation  the  lower  The  f o r the  Table  value  20  600  f o r the  nm rest  2.3.shows t h a t  nm/20 nm  to  i n t h e mean  values of t f o r the  reflec-  comparison  colour categories of Table v a l u e o f t f o r the  consistently with  width  of the  filter.  width  shows a s l i g h t  nm  and  category.  semi-ripe decreases 600  remote  ripe  were c h o s e n  produces a gradual decrease  ratios  for  Widening  firm  by  colour  2.2.  o f h a l f band widths  The of  f o r the  the  are  in integration  categories i s reflected  filter  If  are  significant  level.  T y p i c a l peak t r a n s m i s s i o n s o f 20%  the  nm  filters  filters  where s e p a r a t i o n o f  shown i n T a b l e  2.1  t h e means f o r e a c h  decrease  filters  nm  and  tomatoes i s g r e a t e s t .  between t h e s e of  nm  colour category  from  on  i n Table  t h e peak t r a n s m i s s i o n s a l t e r e d .  are decreased.  the band w i d t h  effect  listed  i f the h a l f band w i d t h s  o f the  20  ratios  the  firm  2.3  ripe  increasing  are vs.  band-  Widening the  66 0 nm  half  band-  increase i n t values  except  when i n  43  combination 20  nm  with  filter  the best  6 0 0 nm  the  combined w i t h  of t f o r semi-ripe  do  seem t o change w i t h  remain r e l a t i v e l y  vs.  half  tion  vs.  semi-ripe,  green.  b a n d w i d t h s was describes  an  pass or very  significantly  Examination  inexpensive  the  f o r the  does not  affect  gories.  The  provided  t h a t the  in  the  light  type  of  at  6 6 0 nm s h o u l d be  are  the  light  1.3  the  separa-  turning,  half  band  half  width  band w i d t h  of the i n t e r f e r e n c e  The  critical  source  than  peak t r a n s m i s s i o n o f  s e p a r a t i o n between c o l o u r  the  and  4 0 nm  beyond  nm  filter.  used i s not  c h o i c e o f one  the  cate-  critical,  filters  also  exist  Inexpensive  having  half  band  a t 6 0 0 nm  widths  and  one  acceptable.  comparison of t values  i n Table  i n d i c a t e s that analysis using equation  alter  to 40  the  vs.  to a d e t e c t a b l e degree.  common, and  The  but  (as o p p o s e d t o n a r r o w b a n d  narrow band pass i n t e r f e r e n c e f i l t e r s 2 0 nm  variations,  of effects  peak w a v e l e n g t h s o f t h e  source  of  green  colour separation i s less  c h o i c e o f peak w a v e l e n g t h .  filter  turning vs.  semi-ripe  band pass  narrow band pass)  chosen  The  affect  s i n c e a 4 0 nm  unnecessary  I n summary, t h e h a l f filter  indicates  semi-ripe.  f r o m 2 0 nm  band w i d t h  not  turning vs.  filter  -  constant.  do  ripe  and  band w i d t h  for either f i l t e r firm  ripe  6 0 0 nm  The  - 4 0 nm  t u r n i n g and  The c h a n g e s i n h a l f  of  filter.  6 6 0 nm  the  s e p a r a t i o n between f i r m  values not  - 4 0 nm  statistical  separation of  2.2  [2-2]  and  does  Table not  t h e mean r e f l e c t a n c e  44  ratios  examined.  necessary ratio  to e s t a b l i s h  a t two  w a v e l e n g t h s may  The  F  o b t a i n the [2-3]  A scale scale,  analysis  be  the  i s not  reflectance  used  as d e s c r i b e d i n  system  i s necessary,  o f 10 N,  was  will  used  produce  two  f o r the a n a l y s i s , similar  but  results.  G  =  maximum v a l u e o f E ^ / E , [2-2]  limits  convenient  calculated  f o r the greenest  photodetector  gain ratio  ratios  amplifiers.  Now,  2  g a i n / l o n g wavelength  any  factor  [2-4]  N/G  two  however,  normalizing  photodetector  =  their  the  of the  The  F  The  Reflectance  information.  gain r a t i o  from  within  analysis  s e p a r a t i o n and  o f the  following  i s the  where  so t h a t  this  complete  1.  Chapter  to  T h e r e f o r e the  amplifiers  (short wavelength  photodetector gain)  f o r a l l tomatoes w i l l 0 < E../E., _<  N.  tomato. must be  adjusted  photodetector  i s equal to t h e n be  F.  maintained  C  H  A  P  DESIGN  T  E  R  APPROACH  3  46 INTRODUCTION I t has been e s t a b l i s h e d t h a t t h e r a t i o ted  light  a t two n a r r o w w a v e l e n g t h b a n d s i n t h e v i s i b l e  spectrum w i l l present and  selection, out  be t h e c r i t e r i o n  design.  optic  of reflec-  Specific  filters  f o r colour grading  components  such  must now b e s e l e c t e d .  as  i n the  photodetectors  H a v i n g made t h e  a s i g n a l p r o c e s s i n g u n i t must be d e s i g n e d  the task o f d i v i d i n g  t h e two p h o t o d e t e c t o r  produce the r e f l e c t a n c e r a t i o ,  to carry  signals to  t o c a t e g o r i z e t h e tomato  b a s e d on t h e r e f l e c t a n c e r a t i o ,  and t o t r a n s f e r  t o an a p p r o p r i a t e e j e c t mechanism.  the signal  The m e c h a n i s m i s a c t i v a -  t e d when t h e t o m a t o and e j e c t m e c h a n i s m a r e i n j u x t a p o s i t i o n . The  signal  analog  processor w i l l  processor,  cessor handles  Signal handling  available  and vegetable  commercially  then  The a n a l o g  pro-  proceeds through the  conveying  efforts  are f l a t  belts,  s h o u l d be c o n c e n t r a t e d  conveyors,  T h i s would a l l o w as w e l l as easy  system  f o r tomatoes.  i t was d e c i d e d  Since  that a l l  towards d e s i g n i n g a tomato  w h i c h w o u l d be c o m p a t i b l e  systems.  systems a r e  a n d i t was n o t t h e a i m o f t h i s r e -  t o i n v e n t a new c o n v e y i n g  many c o n v e y o r s  grader  processor.  the  processor. Fruit  search  and t h e d i g i t a l  two s e c t i o n s —  t h e i n f o r m a t i o n up t o t h e p o i n t where c a t e g o r i -  zation occurs. digital  be d i v i d e d i n t o  with  existing  conveying  the purchase o f " o f f the s h e l f " adaptation  o r g a n i z a t i o n s w h i c h a l r e a d y had such  o f the grader f o r conveyors  i n use.  47  The and  fruit  i t s design w i l l  considered pressure  pneumatic  using a f l a t , was c h o s e n ,  it. The  be d e s c r i b e d .  s y s t e m was f o u n d conveyor,  6 feet  matte b l a c k b e l t ,  since i t provided  wavelengths r e l a t i v e  This provided  a constant  t h e most  item,  were  but a high  suitable.  i n l e n g t h , was  6 inches wide.  built  A black  belt  a low r e f l e c t a n c e a t t h e two t o t h e t o m a t o e s t r a n s p o r t e d on low r e f l e c t a n c e b a c k g r o u n d .  b e l t was c h a i n d r i v e n b y a v a r i a b l e s p e e d m o t o r , a l l o w i n g  testing  a t various conveyor I n many c a s e s ,  the  Many p o s s i b i l i t i e s  f o r moving t h e tomatoes o f f t h e b e l t ,  A test  critical  e j e c t i o n m e c h a n i s m was n o t a s t o c k  speeds.  the "ideal"  components  s y s t e m d e s i g n were n o t c o m m e r c i a l l y  Consequently, where  reasonable  necessary.  required f o r  or readily  available.  s u b s t i t u t i o n s have been i n c o r p o r a t e d  48 INITIAL Light  COMPONENT  Source  \  A Dolan-Jenner Model  light  SELECTION  source comprising  (3350°K  colour  No. 150, v a r i a b l e  intensity  a s t a n d a r d DNE p r o j e c t i o n  temperature) w i t h d i c h r o i c  lamp  r e f l e c t o r was u s e d .  Photodetectors Two FPT 120A* p h o t o t r a n s i s t o r s w e r e primarily  for their The  previously Optic  r e s p o n s e c u r v e o f t h e FPT 120A was  Filters t h e b e g i n n i n g o f t h e r e s e a r c h , b o t h t h e 600 nm  660 nm i n t e r f e r e n c e  decided 550  spectral  sensitivity.  shown i n F i g u r e 2.2.  At and  high  chosen  that  filters  t h e 600 nm f i l t e r  nm f i l t e r  were n o t a v a i l a b l e . might  w h i c h was a v a i l a b l e .  t h e two f i l t e r s  are l i s t e d  be s u b s t i t u t e d  I t was by a  The s p e c i f i c a t i o n s f o r  below:  Peak w a v e l e n g t h  550 nm  660 nm  H a l f bandwidth  20 nm  20 nm  Peak T r a n s m i s s i o n  20%  40%  Referring length  ratio  maximum t o t a l categories. colour *  ranks  t o T a b l e 1.1, t h e 550 nm/660 nm wave-  eighteenth i n the l i s t ,  b a s e d on t h e  d i f f e r e n c e b e t w e e n means o f a d j a c e n t c o l o u r The s t a t i s t i c a l  categories  using  s e p a r a t i o n between a d j a c e n t  t h e 550 nm/660 nm w a v e l e n g t h  M a n u f a c t u r e d by F a i r c h i l d View, C a l i f o r n i a .  Semiconductor  Corp.,  ratio  Mountain  49  was  studied  using  ensure t h a t stitute  this  ratio  f o rthe i d e a l  distribution 120A  the analysis described  [2-2]  tested  Table tion  3.1.  values  o f adjacent  may be e x p e c t e d .  not  colour  and t u r n i n g ,  categories  o f the  poor, using  affected.  Figure  t h a t good  f i r m r i p e and semi-  t h e 550 nm/660 nm  The 550 nm f i l t e r  was  standard  should  therefore  Families phototransistor  where t h e o u t p u t v o l t a g e ,  V , i s a function semi-  Two a m p l i f i e r s m e a s u r i n g t h e e n e r g y  through the o p t i c f i l t e r s  functions  filter  filter.  3.1 shows a s t a n d a r d  circuit  conductor area.  o f the l i g h t  from t h e tomato  t o produce the d e s i r e d  i s r e a d i l y accomplished  Operational  Amplifier  trans-  p r o d u c e two v o l t a g e s  reflected  o f t h e two v o l t a g e s  tance r a t i o  separa-  and g r e e n  i n c i d e n t r a d i a n t e n e r g y on t h e p h o t o - s e n s i t i v e  Division  categories,  however, t h e r e s t o f t h e system d e s i g n  be a d v e r s e l y  mitted  equation  are l i s t e d i n  and t u r n i n g  between  t h e FPT  The r e s u l t i n g  2  3.1 s u g g e s t s  The s e p a r a t i o n  A n a l o g and D i g i t a l  are  data  o f E^/E -  u s e d a s a s u b s t i t u t e f o r t h e 600 nm  of  data,  f o rthe four colour  i n Table  be r e l a t i v e l y  amplifying  The s p e c t r a l  the optic f i l t e r  deviations  The d a t a  combination;  sub-  and t h e s p e c t r o g r a p h i c  between s e m i - r i p e  ripe w i l l  as a r e a s o n a b l e  600 nm/660 nm r a t i o .  to generate p r e d i c t e d  the t-values  2, t o  20 t o m a t o e s was programmed i n t o  means a n d s t a n d a r d and  be u s e d  o f t h e DNE b u l b ,  response curve,  previously  could  i n Chapter  which surface.  reflec-  through t h e use o f a  (Op Amp)  circuit.  Since the  50  TABLE 3.1  NORMALIZED REFLECTANCE RATIO MEANS, STANDARD DEVIATIONS, AND STUDENTS t VALUES FOR FOUR COLOUR CATEGORIES USING A 5 50 nm/660 nm WAVELENGTH RATIO: VALUES OBTAINED BY INTEGRATING OVER THE BAND WIDTHS.  Filter  H a l f Band  Width  Peak T r a n s m i s s i o n  550 nm  660 nm  20 nm  20 nm  20 %  401  Firm-Ripe  Semi-Ripe  Turning  Green  Mean  0.458  1.193  5.329  9.646  S.D.  0.051  0.583  0.961  0.388  t - Values Firm-Ripe v s . Semi-Ripe  2.805*  Semi-Ripe v s . T u r n i n g  8.227***  Turning  9.313***  v s . Green  ***  Significant  at 0.11 l e v e l  *  Significant  at 5%  level  FIGURE 3.1 STANDARD NPN PHOTOTRANSISTOR AMPLIFIER USING AN FPT120A v  V+  O  LIGHT  51  52  dividing decided  circuit  i s an i n t e g r a l p a r t o f t h e system,  that analog  Op Amps.  signal  Modern Op Amps  which g e n e r a l l y operate The was b r o a d . TTL  on a s p l i t  speed  than  devices a r e very  electrical TTL  are available  + 15 v o l t  power  supply.  t h a t c o u l d be used  switching capability circuits  an a s s e t f o r t h i s  o f the popular  was b e l i e v e d t o be type  o f instrument.  s u s c e p t i b l e t o noise, requiring  shielding.  circuits  as i n t e g r a t e d c i r c u i t s ,  families  (Transistor-Transistor Logic)  more o f a h i n d r a n c e The  p r o c e s s i n g s h o u l d be done u s i n g t h e  choice o f d i g i t a l  The h i g h  i t was  The l o w +5 v o l t  rendered  i t even l e s s  supply  compatible  much  voltage of the with the  Op Amps. The o f CMOS  newly d e v e l o p e d  and r a p i d l y  (Complementary S y m m e t r y - M e t a l O x i d e  was f o u n d  t o be v e r y  suitable  forthis  f a m i l y h a s many a d v a n t a g e s o v e r devices w i l l highly  operate  compatible  dissipation  The CMOS T h e CMOS them  T h e i r q u i e s c e n t power  10 ^ t h a t o f T T L c i r c u i t s , a n d  switching o f small analog switches  design.  power s u p p l y m a k i n g  t h e Op Amps.  i stypically  family  Semiconductor)  TTL c i r c u i t s .  o n a +15 v o l t  with  expanding  signals  i s achieved with  unknown t o t h e T T L f a m i l y .  bilateral  The n o i s e i m m u n i t y o f  t h e CMOS d e v i c e s i s much h i g h e r t h a n  TTL l o g i c  lower  (MHz) a s o p p o s e d t o  s w i t c h i n g speed  o f 5 megahertz  30 MHz f o r T T L s was n o t a h i n d r a n c e , will  typically  be b e l o w  10H .  colour  grader.  since sorting  F o r these  f a m i l y was c h o s e n f o r t h e d i g i t a l  devices.  reasons,  The  operations t h e CMOS  processing section o f the  ELECTRONIC COLOUR GRADING SYSTEM: OVERVIEW A block diagram o f the e l e c t r o n i c of the colour grader sections the  t o the signal processor  digital  presence  processor.  ratio  signals  one  into  leaves the sensing area,  the  processor  The c a t e g o r y  attached  d o w n s t r e a m f r o m t h e s e n s i n g h e a d . When  signal  station,  a  mechanism.  i s used t o synchronize  i n t h e memory w i t h  T h e memory i s c o m p r i s e d  and t u r n i n g .  The green  the end o f t h e conveyor.  different  i t s eject  o f t h e memory w h i c h i s u s e d t o  storage  and t h e  t h e movement  t h e movement o f t h e c o n v e y o r o f three s h i f t  f o r each o f t h e three c o l o u r c a t e g o r i e s :  off  a memory  l i g h t beam c h o p p e r d i s k a n d p h o t o d e t e c t o r a r e  chopped e l e c t r i c a l  ripe  into  t h e tomato  t o t h e a x l e o f one o f t h e c o n v e y o r p u l l e y s ,  of the data  the reflec-  information i s  a n d t h e d a t a moves t h r o u g h  an e l e c t r o m e c h a n i c a l e j e c t A  senses t h e  a t the time  c a t e g o r i z e d tomato i s i n l i n e w i t h  operate  p r o c e s s o r and  under t h e s e n s i n g head. The  processor  s i g n a l appears a t t h e output  belt.  the analog  i s used t o c a t e g o r i z e t h e tomato  the d i g i t a l  as t h e t o m a t o t r a v e l s  T h e r e a r e two  and c o n t i n u o u s l y c a l c u l a t e s  of four colour categories.  entered  3.2.  processor  t h e summation o f t h e p h o t o -  as t h e tomato passes  peak r e f l e c t a n c e r a t i o  —  The a n a l o g  o f t h e tomato t h r o u g h  detector output tance  i s shown i n F i g u r e  signal  r e g i s t e r s , one  firm ripe,  t o m a t o e s were a l l o w e d Each s h i f t  semi-  to f a l l  r e g i s t e r has a  c a p a c i t y , d e p e n d i n g on t h e l i n e a l  distance  RED FlLTERl  A PHOTOTUMSISTOR  1  e  B PRE-AMR  RESET  NOTCH 6, 10W PASS FILTER D ANAtOS DIVIDER  GREEN} FILTER]  A PHOTOTRANSISW,  (LE^  DISPLAY  B PKE-AMP.  IN  E PEAK DETECTOR 1  C NOTCH & tOW PASS FILTER  L^fp)  "I  G  H LOW PASS FILTER  |Sl/MM/W6 AMP. /  TIMER  I [INVERTER  SEMI-RIPE.  N IDECODJNG  FIRM RIPE  SAffS  ——O  FIGURE  3.2  COLOUR  GRADER  Z  O  COMPARATOR  3 Ot/r  K  OUT  OUT-  SCHM/TT T/?/<5SER  DIGITAL  PROCESSOR  COMP. I IN O COMP. 2 W  OPTO-ISOLATORS & TF.lhCS  BLOCK  COMPARATOR  St/MMWfi AMP. 2  M TIMERS  SOLENOID' I >  O  J  O CTO/WP.3 W  TiM£RS LATCHES <$• MEMORIES  I  PROCESSOR  -O wi?ire w  TURNING  COMPARATOR  PEAK DETECTOR Z  ANALOG  O  DIAGRAM  SOLENOID  2  m  WRITE OUT  /?EI5£7 OUT  SKMPLE OUT  55  downstream from the station  sensing  i s located.  station will  A  head t h a t a p a r t i c u l a r  categorized  t o m a t o and  always c o i n c i d e a t e j e c t i o n time  of conveyor b e l t  s p e e d , due  eject  i t s eject regardless  t o t h e memory-conveyor  belt  synchronization. The  solenoids  s y s t e m were s t a n d a r d isolate  these  circuit  by  will  be  with  types,  from the  means o f an  i n more d e t a i l , necessity.  l l O v AC  devices  Each o f the  incorporated  and  pneumatic  i t was  voltage  eject  necessary  signal  to  processing  opto-isolator interface. blocks  respect  i n Figure to  Where p o s s i b l e , t h e  dealt with  low  i n the  separately.  3.2  will  be  function, design analog  and  digital  discussed  and processors  56  ANALOG SIGNAL PROCESSOR Divider  Circuit The  voltages and  (Box D, F i g u r e  circuit  chosen  i s shown i n F i g u r e  3.2)  to divide 3.3.  I t consists  two t y p e 741** Op Amps. The s e c o n d  a summing a m p l i f i e r , for  the d i v i s i o n  are  as f o l l o w s : (a) (b) (c)  where  z V  o f an MC1495*  741 Op Amp  w h e r e a s t h e MC1495 a n d f i r s t  operation.  The c h a r a c t e r i s t i c s  < + 10 v o l t s . x — -10 v o l t s < V < + 10 — z — V , = -10 V /V ol z' X  i s used as 741 a r e u s e d of the c i r c u i t  0 < V  volts.  =  output voltage transistor  from t h e "green"  =  output voltage transistor  from t h e " r e d " photo-  Initial saturation  t h e two p h o t o d e t e c t o r  testing  of this  circuit  photo-  showed t h a t t h e  voltage  (V , = c o n s t a n t , f o r any V , V ) was -12.5 ol x z The o u t p u t v o l t a g e r a n g e o f t h e d i v i d e r i s t h e r e f o r e J  volts.  z e r o t o -12.5 v o l t s  i fV  and V x  are positive. z  CMOS d e v i c e s  o p e r a t e f r o m z e r o t o +15 v o l t s ,  advantageous  t o a d d +12.5 v o l t s  summing a m p l i f i e r volts.  * **  Since the  c  i t was f o u n d  t o the d i v i d e r  output using a  t o c h a n g e t h e o u t p u t r a n g e o f +12.5 t o z e r o  The new e q u a t i o n f o r t h e c i r c u i t i s :  MC p r e f i x i n d i c a t e s component m a n u f a c t u r e d by M o t o r o l a Semi-conductor, Inc., Phoenix, A r i z o n a . T y p e 741 Op Amps a r e m a n u f a c t u r e d by M o t o r o l a S e m i c o n d u c t o r , I n c . (MC1741); F a i r c h i l d Semi-conductor Corp. (UA741), M o u n t a i n V i e w , C a l i f o r n i a ; RCA C o r p . (CA3741) S o m e r v i l l e , New J e r s e y ; and o t h e r s .  FIGURE  3.3  A N A L O G  DIVIDER  CIRCUIT  58  V  Q  =  2  [3-1]  From 0 £  £  0 £ V  /V  12.5  1 2 . 5 , the < 1.25.  i t may  shown u s i n g t h e  ratio  F = 1.60 will  and  on  are The  specified  shown t h a t  maintain V  f o r the  to the d i v i d e r  listed  "green"  tomatoes  i n Table  potentiometers,  limits  so t h a t  and  adjusted to approximately when V > 1.25 V . z x  must  be  2,  that  a given  /V w i t h i n the above z' x amplifier  limits.  should  Using equation  v o l t a g e s f o r the  the twenty  range  [2-4], N = 1 . 2 5 .  i n Chapter  "red" a m p l i f i e r .  are adjusted i n i t i a l l y the  [3-1]  X  analysis  t h e p r e d i c t e d mean o u t p u t  lated,  be  the g a i n o f the  X gain of the  g o r i e s based  Z  Therefore, i n equation  be  Consequently  V /V  i n p u t range  I t may  1.60  -10  be  [3-1],  four colour cate-  (Chapter  1)  were  calcu-  3.2. P^  through  P^,  the c i r c u i t  i s balanced*. - 1 2 . 5 volts  i n Figure 3 . 3 ,  operates w i t h i n  Potentiometer so t h a t V  P,. i s  2 i s zero  * See M o t o r o l a L i n e a r I n t e g r a t e d C i r c u i t s D a t a Book, 1 9 7 2 , (second e d i t i o n ) p. 7 - 3 8 7 f o r c a l i b r a t i o n p r o c e d u r e .  59  TABLE 3.2  PREDICTED MEAN OUTPUT VOLTAGES FOR FOUR COLOUR CATEGORIES BASED ON EQUATION [3-1] AND THE TWENTY TOMATOES (Chapter 1 ) .  Colour  V  q  2  (volts)  Firm Ripe  11.93  Semi-Ripe  11.00  Turning  5.82  Green  0.41  60  Phototransistor  and P r e a m p l i f i e r C i r c u i t s  The. h i g h impedance o u t p u t amplifier  shown i n F i g u r e  n o n - i n v e r t i n g type output.  reference. fiers (a)  are  the  3.1 was f o l l o w e d by a  741 Op Amp w h i c h p r o v i d e d  black  A , B , F i g u r e 3.2)  o f the p h o t o t r a n s i s t o r  The 741 Op Amp a l s o p r o v i d e s  to e s t a b l i s h  (Box  conveyor b e l t  The s c h e m a t i c s  f o r the  a fine  low-gain,  a low impedance offset  as a zero  adjustment  voltage  "red" and "green"  ampli-  r e d a m p l i f i e r may n o t  exceed  shown i n F i g u r e 3.4.  The o u t p u t  voltage  +  (input r e s t r i c t i o n  10 v o l t s  large,  firm  sensing  ripe  o f the  on V  o f the  t o m a t o was p l a c e d  h e a d , 1/2 i n (1.3 cm)  divider).  under the  A  light  from the f i b r e o p t i c bundle*, and 2  a quantum measurement o f 0.25 uE/m  s e c (micro E i n s t e i n s /  2 meter 75%  sec)  o f the  was o b t a i n e d light  through  intensity  the  660 nm f i l t e r a t  s c a l e o f the  illuminator.  -3 T h i s r e f l e c t e d quantum l e v e l i s e q u i v a l e n t t o 1.5 X 10 2 2 mw/cm ( m i l l i w a t t s / c m ). S p e c i f i c a t i o n sheets f o r t h e -3 FPT  120A do n o t  yield  i n f o r m a t i o n b e l o w 5 X 10  2 mw/cm ; current  consequently a t +15 v o l t s  quantum l e v e l s , data.  phototransistor  supply  and a l i n e a r  The r e s u l t i n g  collector  was m e a s u r e d a t v a r i o u s r e g r e s s i o n p e r f o r m e d on t h e  e q u a t i o n was:  I = 54.2 Q T h i s w i l l p r o d u c e t h e maximum v o l t a g e the red a m p l i f i e r . 1  C  *  the  ,  3  9  [3-2]  2  E  expected  for  FIGURE  3.4  RED  A N D  G R E E N  A M P L I F I E R S  RED  AMPLIFIER  t/Sv  G R E E N  AMPLIFIER  P H O T O T R A N S I S T O R  62  where  I_„ = c o l l e c t o r  current  i n uA  (micro  amps)  2 Q  = quanta,  Equation  i n uE/m  [3-2] y i e l d s  tomato. The b l a c k measured  I,„ = 7.9  conveyor b e l t  through  sec.  t h e 660 nm  uA f o r t h e f i r m  r e f l e c t a n c e was filter,  ripe  also  and found  t o be  2 0.06  uE/m  ground  sec.  using  The c u r r e n t  equation  generated  [3-2] y i e l d s  due t o t h e b a c k -  I ' „ = 1.1 yA. eh  Neglecting governing  the fine  the output  offset  adjustment,  the  equation  o f each o f t h e n o n - i n v e r t i n g  amplifier  circuits i s : 2 = + 1) V. R in R  V  o  [3-3]  L  J  1  where  2 (—  V  =  output  voltage  V\  =  input voltage  (referenced  t o ground)  (referenced  t o ground)  R  +1)= If  v  = closed  loop  gain.  R, = R„ = 10K3:, t h e n A =2, 1 2 v  value  of V  large  firm  If  A  o  =10 ripe  volts,  t h e n V. =5 in  t o R^,  then  f o rthe  results  so as n o t t o c o n t r i b u t e  the current  t r a n s i s t o r .and t h e r e s i s t o r , R^, photo input  volts  tomato.  Rg i s s u f f i c i e n t l y s m a l l  significantly  a n d i f t h e maximum  through  i s t h e same.  from t h e b l a c k  belt  only,  the photoWhen t h e  63  V. i  n  - V 3  =  c  R  1.1  uA  [3-4]  where V\  =  0  V  =  course o f f s e t adjustment  c  (zero v o l t s  f o r background) voltage  therefore, V  =  -1.1 R  [3-5]  When t h e p h o t o again is  the current  t h e same.  -  (-1.1  [3-5],  tomato, and  and t h e f i r m  R^  ripe  yields:  R,)  2. =  3  ripe  through the phototransistor  current  i n R  i s from the f i r m  Substituting  tomato photo V.  input  7.9  uA  since, V. in  = 5  volts,  therefore, R^  =  735 KX2 , o r a s u i t a b l e  R  =  750 YSl  3  Substituting V  =  c  [3-6] i n [3-5] y i e l d s -0.825  course o f f s e t  volts, be s u i t a b l e  f o r the  adjustment.  fine offset  equation:  be [3-6]  A v a l u e o f Rg = 10 KQ w o u l d  The  v a l u e would  adjustment  range  i s g o v e r n e d by t h e  64 V o f«f s e t4. =  ± V s u p p l,y  (Rc/RJ 5' 4  [3-7]  1  J  If, 4  .=  R  c  =  470 a  =  ±1.5  V « . offset  Since in  the gain r a t i o  the d i v i d e r  must be 1.60  A  4.7 Kfl, and  R  volts  F i s e q u a l t o 1.60  circuit,  as  described  the g a i n o f the green  amplifier  times the g a i n o f the r e d a m p l i f i e r ,  or  =3.20, i . e . v R  2  Rf or  R  +  1  3  '  =  2  Let R^  =  2  2.2 R-L  R^ and R^  [3-8]  f o r the green  amplifier  e q u a l R^ and  f o r the red a m p l i f i e r , i . e . R  ±  R then  3  from R  =  10 Kft, and  =  750  Ytt  [3- 8] ,  =  2  22 K0-.  The b a c k g r o u n d r e f l e c t a n c e was  measured through t h e  2 550  nm  filter  equation  and f o u n d  [3-2],  the current  phototransistor i s :  I"  C E  =  t o be 0.05  0.84  uA.  uE/m  generated  sec.  From  i n the green  65  As  i n [3-4] , V.  - V -  = 0.84  uA.  [3-9]  3  Substituting V, = 0 in R then, The to that  V  3  c  = 750  KQ  = -0.63  volts  f i n e o f f s e t a d j u s t m e n t r a n g e was of the red  amplifier.  selected  equal  66  Notch F i l t e r  and Low P a s s F i l t e r  The to  light  intensity  The  120  v a r i a t i o n s , such as those  Hz n o i s e  sharply  with  the l i g h t  two v o l t a g e  c r e a t e d by t h e  source.  p e a k s , one p o s i t i v e and one n e g a -  p e r c y c l e i n t h e 60 Hz s i n e wave p r o d u c e an  twin-T notch to  3.2)  p h o t o t r a n s i s t o r a m p l i f i e r s are very s e n s i t i v e  60 Hz s i n e wave d r i v i n g  tive  (Box C, F i g u r e  s i g n a l a t each p h o t o t r a n s i s t o r output. filter  using  LM302* v o l t a g e  c u t t h e s i g n a l a t 120 Hz.  a 24 Hz c u t - o f f f r e q u e n c y ,  behind  undesirable  the notch  filter  using  A  f o l l o w e r s was  chosen  A low p a s s a c t i v e a 741 Op Amp  to minimize other  was  filter placed  low f r e q u e n c y  noise,  s u c h as 60 Hz. The very  filter  passes a l l frequencies  narrow band o f f r e q u e n c i e s  which i n t h i s low  notch  c a s e i s 120 Hz.  frequencies  signal  amplitude  The low p a s s  need  f o r both  Since  effective  f i l t e r i n g was d e s i r e d  ,  passes a l l  continues  a t a r a t e o f 9dB/octave.  filters  follows.  Q  f , where t h e c  i s c u t b y 3dB a n d a t t e n u a t i o n frequencies,  frequency f  filter  up t o t h e c u t - o f f f r e q u e n c y ,  through the higher The  around a c e n t e r  except a  may be i l l u s t r a t e d  as  most o f t h e n o i s e was 12 0 Hz, t h e m o s t f o r that  frequency.  The  o f t h e 120 Hz  notch  "notch  d e p t h " o r maximum a t t e n u a t i o n  filter  was m e a s u r e d a n d f o u n d t o be -45dB.  filter  having  a 9dB/octave s l o p e ,  i n order  A low p a s s t o be a s e f f e c t i v e  * LM p r e f i x r e f e r s t o components m a n u f a c t u r e d by N a t i o n a l Semi-conductor Corp., Santa C l a r a , C a l i f o r n i a .  67  as  the notch  filter  a t 120 Hz, w o u l d r e q u i r e  f r e q u e n c y o f 4 Hz. sorting  operations  tomatoes/second.  This  l i m i t a t i o n would  w h i c h were e x p e c t e d Sorting rates  ents  with  t o be above 4  therefore  a c u t - o f f o f 24 Hz was c h o s e n  may be u s e d ) t o be p l a c e d  i n t e r f e r e with  above a p p r o x i m a t e l y  t o m a t o e s / s e c o n d were n o t e x p e c t e d , filter  a cut-off  a low p a s s  (standard  i n s e r i e s with  20  compon-  the notch  filter. Figure filter  circuits  3.5 i s a s c h e m a t i c o f one o f two used i n the c o l o u r  grader,  following  the red phototransistor  following  the green p h o t o t r a n s i s t o r  The  equations governing  notch  filter  f  (Figure 3.4).  r- ] 3  2  [3-11]  C  =  2C  [3-12]  For  maximum e f f i c i e n c y ,  —  x  2  resistors  should  component m a t c h i n g i s  b e 0.1% t o l e r a n c e ;  Components w i t h  these tolerances  a v a i l a b l e s o 1% r e s i s t o r s  in  o f t h e 100 Kft p o t e n t i o m e t e r t h e f e e d back  loop  capacitors were n o t  a n d 2% c a p a c i t o r s  used, r e q u i r i n g a v a r i a b l e band w i d t h adjustment use  10  R /2  tolerance.  readily  amplifier  =  2  1  1%  a m p l i f i e r , and t h e o t h e r  a r e as f o l l o w s :  ±  critical  one c i r c u i t  t h e component s e l e c t i o n f o r t h e  o = 2* l c  R  identical  were  through the  a n d t h e LM302 v o l t a g e  t o t h e j u n c t i o n o f C, a n d R . 0  follower  —If"f  FIGURE  3.5  NOTCH  AND  LOW  PASS  FILTERS '  0 0  69  Selection [3-10] t h r o u g h Let  o f components  was made u s i n g  equations  [3-12] a s f o l l o w s ' : C  now R  =  2  1  0.01 y F ,  2u f C, O 2 =  133 Kfi  R_  =  66.5 Kfi (two 133 Ktt r e s i s t o r s i n parallel)  C.  =  0.02 yF (two 0.01 yF c a p a c i t o r s i n  R  ±  parallel). The e q u a t i o n s g o v e r n i n g low p a s s  =  J  C  R_ + R. 2 /2 ir f R_ R. c 3 4  , then  [3-14]  =  J  R  3  C  =  3  4  =  Tolerances since  /2 TT f R, c 3  = 100 KQ , a n d f C  (R_ + R.) 3 4  [3-13] becomes  C,  Let  c  [3-15]  = 24 Hz, t h e n  0.094 y F , a n d  2C^  =  °'  0 4 7  y  F  f o r R^, R^,  a c u t - o f f frequency s l i g h t l y  resulting  from  [3-13]  = /2 TT f c  R^ =  s e l e c t i o n f o r the  f i l t e r are:  C-  If  component  component  The u n i t y  mismatch  * and  are not c r i t i c a l ,  above o r below  24 Hz  i s inconsequential.  gains o f the a c t i v e  filters  do n o t  70  a l t e r signal amplitude/ except at frequencies above 24 Hz, where attenuation occurs at a rate of 9dB/octave, as desired.  71  Peak D e t e c t o r  1  (Box  E,  Figure  3.2)  PEAK DETECTOR 1 i s an w h i c h s t o r e s the most p o s i t i v e The  stored voltage  schematic  allow  signal  appears a t the  o f the peak d e t e c t o r The  analog  f u n c t i o n of the  c a p i c a t o r C^  storage  circuit,  appearing  a t the  output  circuit 741  Op  to charge to the  of  the  input.  circuit.  A  i s shown i n F i g u r e  Amp  and  diodes  3.6.  i s to  i n p u t v o l t a g e , but  not  12 to  discharge.  voltage C^  put  after  zero  resulting the  of the  over  detector  no  at the  output  with  (10  switch.  goes LOW  and  will  a new  r e l a y , but and  of  out-  the to  a t the  bilateral  control  switch  since i t i s a  semi-  c a n n o t wear o u t . the b i l a t e r a l  to a zero  remain a t signal  capaci-  peak d e t e c t o r  The  c o n t r o l input causes  LM302  a t the  minimal d r i f t  moving c o n t a c t s  o  from the  (HIGH) p u l s e  to discharge  of the  appearing  R e s e t t i n g the  signal  ft)  current  voltage  a positive  voltage V  switch  potential  zero v o l t s  through  until  appears a t the  The  the  peak  input. Figure  DETECTOR 1 i n p u t ) semi-ripe  under the  by  to a small  i t has  reset pulse  and  time.  c l o s e , a l l o w i n g C^ The  little  CD4066 b i l a t e r a l  identical  reset pulse  R^.  impedance  peak i s s t o r e d ;  voltage  conductor,  to  input  i n a constant  i s accomplished  input is  high  follower, drains very  tor  stored  The  3.7a  shows t y p i c a l  signals for uniformly  tomatoes o f e q u a l  s e n s i n g head.  tomato, the  d i v i d e r output  Due  d i v i d e r output  size,  coloured  as  the  t o edge e f f e c t s  signal  is bell  firm  tomato of  (PEAK ripe  passes  the s p h e r i c a l  shaped.  If  the  to FIGURE  3.6  PEAK  D E T E C T O R  1  F I G U R E  3.7  O U T P U T FIRM (o)  V O L T A G E S  RIPE.  DIVIDER  A N D  FOR  SEMI  O U T P U T  -  TYPICAL RIPE  FOR  T O M A T O E S  U N I F O R M L Y  RIPE-  T O M A T O (b)  DIVIDER RIPE  (c)  P E A K A N D  OUTPUT  FOR  N O N  -  U N I F O R M L Y  T O M A T O D E T E C T O R (b)  O U T P U T  FOR  (a)  74  v o l t a g e was m e a s u r e d midway b e t w e e n t h e l e a d i n g  and t r a i l i n g  e d g e s o f t h e s i g n a l , t h e v o l t a g e r e a d w o u l d be t h e peak voltage detector  —  t h e maximum r e d n e s s circuit.  —  without  t h e need  f o r a peak  U n f o r t u n a t e l y , tomatoes a r e n o t always  u n i f o r m i n r i p e n e s s , i . e . o n e a r e a may b e r e d d e r t h a n Typical ripe  divider  output  f o r non-uniform  a n d s e m i - r i p e t o m a t o e s a r e shown i n F i g u r e 3.7b.  the m i d - p o i n t between l e a d i n g indicate  maximum r e d n e s s .  t o r output ripe  signals  another.  signal  tomatoes.  redness, V  r)T:  , , will Air  Now  edges does n o t  F i g u r e 3.7c shows t h e peak  f o reither  For both  and t r a i l i n g  firm  detec-  uniformly r i p e o r non-uniformly  types o f tomatoes,  be measured and s t o r e d .  t h e maximum  75  Comparators  1, 2 a n d 3 (Box F, F i g u r e  The  schematic o f the comparator c i r c u i t  shown i n F i g u r e tinuously three  3.2)  3.8.  The o u t p u t  and s i m u l t a n e o u s l y  used i s  o f PEAK DETECTOR 1 i s c o n -  present  a t the input  c o m p a r a t o r s , COMPARATOR 1, 2 and 3.  of the  Referring to  Figure  3.8 when t h e i n p u t v o l t a g e , V " , i . e . PEAK DETECTOR 1  output  voltage,  the  IN  voltage  exceeds the s e t v o l t a g e  output,  zero  volts,  fier  (typically  V  due t o t h e h i g h 200,000).  The IN914 d i o d e  clamps V range the  o  between z e r o  f r o m +14 v o l t s  open l o o p  0  four  colour  comparators  t o -14 v o l t s .  and  S  E  T  colour  separating ripe. nally an  otherwise  V  would  o  The two IN914's  initial  o r LOW  across  diodes.  f o r a comparator. three  Since  different  Two  adjust-  for setting  the cutoff  and s e m i - r i p e  voltages from  The g r e e n c u t o f f v o l t a g e , V~T?m -i , i s a d j u s t e d board,  since this  voltage  firm inter-  requires  only  s e t up. The  1)  comparator  are required.  from s e m i - r i p e ,  on t h e c i r c u i t  goes  a r e a v a i l a b l e on t h e f r o n t p a n e l o f  sorter cabinet, turning  o f each  a r e t o be s e p a r a t e d ,  m 0  ampli-  saturated  are input protection  adjustments  V  ments, V - , ™ „ and V _ „ the  a t the output a n d +14 v o l t s ,  categories  g a i n o f t h e 741  state t o the negative  i s a threshold voltage  m  f r o m +14 t o  The c o m p a r a t o r e s s e n t i a l l y  i n p u t o f each comparator V „  o f a comparator,  m  , o f t h a t comparator drops  from t h e p o s i t i v e s a t u r a t e d state.  V~„  output  (state 0).  o f each comparator  i s e i t h e r HIGH  (state  76 FIGURE  O  3.8  C O M P A R A T O R  CIRCUIT  77  The colour  output  states  c a t e g o r i e s they The  outputs  forms c o m p a t i b l e connected  o f the t h r e e comparators  r e p r e s e n t a r e shown i n T a b l e o f the comparators  are d i g i t a l  and t h e 3.3. wave-  w i t h CMOS d e v i c e s , and t h e s e o u t p u t s a r e  to the d i g i t a l  p r o c e s s o r , a s shown i n F i g u r e  3.2.  78  TABLE 3.3  Colour Category  OUTPUT STATES OF COMPARATORS 1, 2, and 3, FOR FOUR COLOUR CATEGORIES  ' COMP. 1  OUTPUT STATE COMP. 2  COMP. 3  Green  1  0  0  Turning  0  0  0  Semi-Ripe  0  1  0  Firm Ripe  0  1  1  79  Summing A m p l i f i e r 1  (Box  Rather than mechanically  G,  use  Figure  3.2)  a separate  light  a c t i v a t e d t r i g g e r , which senses  a tomato under t h e  sensing  head,  i t was  signals  a t the  d i v i d e r i n p u t c o u l d be  uniform  output  signal,  The  d i v i d e r output  since  the  red  for  r e d and  large  regardless  c a n n o t be  s i g n a l amplitude  the  and  red  s i g n a l and  the  varies with  of the  as  colour.  a  a tomato.  trigger,  The  sum  of  constant  tomato p r o d u c e s  a small  and  a green  red  drifts  large d r i f t s  at the  be  due  light  to small  a t the  output.  input The  intensity  are  drift  of two  a tomato  signal.  m a j o r d r a w b a c k i n a summing a m p l i f i e r s u c h  i s that small  additive, at the  v a r i a t i o n s or  resulting  inputs  changes  as  may  in  temperature. The  trigger  tomato i s p r e s e n t ,  voltage  reflected  from the  small  amount o f  reflected  voltage A  should  i . e . when t h e  light  black  sensing  from the  schematic diagram of  the  provided  adjusted  T  7  , and 1  The  V „ IN 2 offset T  belt,  To a  The  the  background  circuit.  output t h a t the  7 4 1 SUMMING  voltage offset  R  adjustment  no  the  offset  non-inverting  in  of V . IN to zero.  z e r o when  head sees o n l y  i n c l u d e d i n the  3.9.  sum  be  conveyor b e l t .  light  a d j u s t m e n t was  ideally  AMPLIFIER 1 i s shown i n F i g u r e the  presence t h a t the  colour  green s i g n a l ,  s i g n a l and  or  summed t o p r o d u c e  used e f f e c t i v e l y  a small  in  zero  decided  green tomatoes, s i n c e a red  The  ambient  of  the  g r e e n s i g n a l s , however, i s r e l a t i v e l y  produces a l a r g e green  this  activated,  i s adjusted  for  V  Q  is  FIGURE  3.9  S U M M I N G  AMPLIFIER  I0OK  W v — i SOK ZERO BACK&NO.' APJ;  -.  -ISv  1  81  zero output  at a given  viewing  black conveyor b e l t .  mately the  the ± 4.8  volts  affect  intensity The  with offset  as d e s c r i b e d i n e q u a t i o n  zero adjustment  adversely  light  the  due  the  signal.  head  range i s a p p r o x i [3-7].  to slow i n p u t v a r i a t i o n s  trigger  sensing  Drift  will  in  82  Belt  Background Monitor The  monitor  sate  f u n c t i o n o f t h e b e l t background  minor d r i f t  AMPLIFIER  (Box H , I , J , K , F i g u r e 3.2)  i n the i n i t i a l  o f SUMMING  f o r any d r i f t . circuit  i s comprised  filter,an  analog  AMPLIFIER  2, u s i n g 741 Op Amps.  background  inverter,  monitor The  required  circuit  low pass  tion.  Component  The s c h e m a t i c  i s shown  active  of the b e l t  i n F i g u r e 3.10.  w i t h a 10 Hz c u t o f f  frequency,  any h i g h f r e q u e n c y n o i s e p r e s e n t a t  1 output.  peak d e t e c t o r c a n r e s u l t  o f a low pass  PEAK DETECTOR 2, a n d SUMMING  filter,  t o suppress  t h e SUMMING AMPLIFIER  and  zero adjustment  i s to  1 (Box G, F i g u r e 3.2) a n d t o c o n t i n u o u s l y compen-  The  was  monitor  Noise  a t the input of the  i n an e r r o n e o u s  background  correc-  s e l e c t i o n was made u s i n g e q u a t i o n s  [3-13]  [3-14]. The  polarity  o u t p u t o f t h e low pass  as t h e output  amplifier,  having unit  SUMMING AMPLIFIER  input,  i.e.  o f SUMMING AMPLIFIER  i s o f t h e same 1.  The i n v e r t i n g  g a i n , changes t h e p o l a r i t y o f t h e  1 signal.  DETECTOR 2 w h i c h s t o r e s  filter  This signal  t h e most p o s i t i v e  t h e most n e g a t i v e o u t p u t  i s fedinto signal  PEAK  at i t s  v o l t a g e o f SUMMING  AMPLIFIER 1. SUMMING AMPLIFIER 2 sums t h e o u t p u t o f PEAK DETECTOR 2 and t h e output  o f SUMMING AMPLIFIER  voltage, V .  i s t h e same a s V  compensation.  V  q  I  N  1 t o produce  w i t h background  an o u t p u t drift  : S U M M I N G  AMPLIFIER  2  IOOK  VvV  •77  FIGURE  3.10  BELT  B A C K G R O U N D  M O N I T O R j  84  To AMPLIFIER is  illustrate,  o  viewing the b l a c k conveyor  , will  sensing from  0.5 t o 5 v o l t s , amplifier  The o u t p u t  4.5  volts.  output drops  from  a t -0.5 v o l t s ,  consequently V  (-0.5 + 0.5) = 0 v o l t s  referenced  t o zero v o l t s ,  variations  i n b e l t background  varies  -0.5 t o -5 v o l t s .  divider  i n amplitude  a n d does n o t c h a n g e w i t h  output  signal  as m e n t i o n e d  a signal  above b a c k g r o u n d .  summing a m p l i f i e r i.e.  tomato s i z e .  detected  as l a r g e  slight  previously  a c c o r d i n g t o t h e c o l o u r o f t h e tomato,,  tomatoes would n o t produce  of signal  always  reflectance.  as a t r i g g e r  problem  AMPLIFIER  t o (-0.5 + 5.0) =  and was t h e r e f o r e n o t u s e d  ted  o f SUMMING  But  t h e most  The o u t p u t o f SUMMING AMPLIFIER 2 i s t h u s  The  rapidly  f o r e x a m p l e , a n d a t t h e same t i m e t h e  input voltage; from  under t h e  o f SUMMING AMPLIFIER 1 r i s e s  t h e o u t p u t o f PEAK DETECTOR 2 r e m a i n s  2 changes  o f PEAK  a n d t h e sum o f t h e two v o l t a g e s  When a t o m a t o p a s s e s ^  head, t h e o u t p u t  inverting  belt.  be -0.5 v o l t s ,  be z e r o v o l t s .  positive  t h e o u t p u t o f SUMMING  1 h a s d r i f t e d t o 0.5 v o l t s , w h i l e t h e s e n s i n g h e a d  DETECTOR 2 w i l l V  suppose t h a t  outputs Very ones.  green  g r e a t enough t o be d e t e c -  SUMMING AMPLIFIER  amplitude  s i n c e many  variation  1 and 2 overcome t h e  with colour,  are functions of l i g h t  but the  intensity,  s m a l l t o m a t o e s may n o t be a s r e a d i l y  85  Schmitt  Trigger Circuit The  in  function  (Box L , F i g u r e 3.2) o f the Schmitt  trigger  circuit,  F i g u r e 3.11 i s t o c h a n g e t h e b e l l - s h a p e d s i g n a l  output  o f SUMMING AMPLIFIER  l e a d i n g edge i s u s e d  2 into  a square  a s an " o n " t r i g g e r  p r o c e s s o r and t h e t r a i l i n g  shown  a t the  p u l s e where t h e  f o r the analog  edge i s u s e d  signal  as an " o f f " t r i g g e r .  When'no t o m a t o i s p r e s e n t , PEAK DETECTOR 1 i s i n a r e s e t position, its  with  inverting  V' k  a t zero v o l t s  a s low a s p r a c t i c a l s u c h The o u t p u t  This w i l l  the Schmitt  fluctuations, its  v o l t s , which  due t o d i r t  13.5 v o l t s  i s compatible  clamped w i t h swing  from  trigger  The o u t p u t  a IN914 d i o d e  -0.7 v o l t s  ure .  o r unevenness i n  operation i s affected. trigger  i s about  +14  i susually  -14 v o l t s ,  which  acceptable input voltage t o o f the Schmitt  trigger i s  t o ground, r e s u l t i n g  t o +14 v o l t s .  was f o u n d more f a v o u r a b l e t h a n back  background  w i t h t h e CMOS l o g i c c i r c u i t s . T h e  below t h e lowest  t h e CMOS d e v i c e s .  o f n o i s e t o appear  on t h e c o n v e y o r  HIGH l e v e l o f t h e S c h m i t t  LOW l e v e l o f t h e S c h m i t t is  t r i g g e r w i l l go  i n p u t as a r e s u l t o f r a p i d  reflectance, before the sorting The  = 1 v o l t , and  T  a l l o w up t o 0.5 v o l t s  trigger  trigger  r e t u r n HIGH when V „ < 0.5 IN  T  at  HIGH, s i n c e  o r LOW.  that  o f the Schmitt  LOW when V „ > 1 v o l t , a n d w i l l IN volts.  trigger  two t h r e s h o l d v o l t a g e s o f t h e S c h m i t t  0*5 v o l t s .  =  t  o f the Schmitt  input i s normally  The were c h o s e n  the output  l o o p e o f t h e Op Amp, w h i c h  i n an output  T h i s clamping  placing  a diode  i s another  technique  i n the feed-  clamping  proced-  F I G U R E  3.11  S C H M I T T  T R I G G E R  CIRCUIT  87  Referring are  to Figure  3.11, t h e t h r e s h o l d  d e f i n e d as f o l l o w s : R  th  V  =  +  - V -  R  where  J  R /  (V  0  —  th  v  - V  R°+ R  r e f  I " 3  ref  v  =  second t h r e s h o l d  V  =  output  v o l t a g e when s o l v i n g f o r  =  output  v o l t a g e when s o l v i n g f o r V  2  R  threshold  L  V.^  l '  resistance values  =  In general,  V  ref  substituting V  =  equation -  0  —  R  V  _, R, a n d R ref 1 2  [3-16]  0  yields:  0  —  = 1 and V  t h  R)  ^  i n the c i r c u i t .  mus t. be d e t e r m i n e d .  +  / J  voltage  a n d V' , = 0.5 v o l t s , th  (R,  °  voltage  S i n c e V\. = 1 v o l t , th  V..  !  r 3 -171  + v  2  first  o  1 6  ^)  r  + R  V  =  V R  (V  0  "  v  R^,  voltages  t " 3  1 8  ^  = +14 i n [3-18] a n d s o l v i n g f o r  Q  gives: 13 R  i  R ,  =  "  [3-19]  ref substituting V' for  R  2  = 0.5 and V  t h  = -0.7 i n [3-17] and s o l v i n g  gives: l -±  R  R  substituting V  =  2  [3-20]  ref  =  0  ,  {  ref d p  2  V  *  i n [3-19] 5  4  v  o  l  t  s  1  }  [3-20] yields: [3-21]  88  substituting R Now, l e t R then  R  [3-21] i n [3-20]  2  ±  2  R^  =  0.035 R  =  330 Kfi  =  12 Kft  =  R^//R^*  E  £  R^ i s c o n n e c t e d  then  forV  [3-22]  error  current. by t h e u s e o f t h e v o l t a g e  R. a n d R_. 4 5 t o t h e +15 v o l t  supply  a n d R,. t o g r o u n d ,  - = 0.54 v o l t s , ref R  Choosing  = 12 Kft f o r minimum o f f s e t  i s obtained  divider,  1  If  R  '  1  input bias V  yields:  =  4  26.8 R -  s u i t a b l e values R  4  =  27 Kfi  R  5  =  1  It the  Schmitt  the  belt  [3-23]  5  of  a n d R,. g i v e s :  KR.  i s evident  that  signal drift  t r i g g e r must be c o r r e c t e d  background monitor s i n c e  a t the input to  by a c i r c u i t  a constant  0.5 v o l t s due t o d r i f t w o u l d n o t a l l o w  input  such as above  the Schmitt t r i g g e r  to turn o f f . The o u t p u t o f t h e S c h m i t t digital this  waveform  signal will  Although V to  q  compatible with  t h e CMOS l o g i c  be t r a n s f e r r e d t o t h e d i g i t a l  d r o p s t o -0.7 v o l t s a n d CMOS d e v i c e s  -0.5 v o l t s ,  the "overdrive"  _ Net  trigger circuit  parallel  resistance  i sa  d e v i c e s , and processor. are rated  may be r e d u c e d by a d d i n g a  89  current  limiting resistor  CMOS d e v i c e suitable.  input.  Any  between t h e S c h m i t t  resistor  between  1.5  trigger KQ  and t h e  and 10 Kfi i s  90  DIGITAL SIGNAL Timing C i r c u i t The which  (Box M, F i g u r e  PROCESSOR  3.2)  function of the timing  circuit,  Figure  i s a c t i v a t e d by t h e S c h m i t t t r i g g e r p u l s e ,  i s t o unlock  PEAK DETECTOR 1 f r o m i t s r e s e t s t a t e and t o t r a n s f e r category enters of  information  the viewing  the Schmitt  colour viewing  to the d i g i t a l  area  o f the sensing  t r i g g e r pulse  unlocks  c a t e g o r i z a t i o n begins. area  processor.  of the sensing  head, t h e t r a i l i n g  which allows  trailing  t o be d e c o d e d  edge o f t h e WRITE  The  timing  circuit  edge  When t h e t o m a t o l e a v e s t h e  a  The  When a t o m a t o  PEAK DETECTOR 1, a n d  t r i g g e r s the timing  comparator outputs  colour  head, t h e l e a d i n g  Schmitt t r i g g e r pulse 210 us WRITE p u l s e ,  3.12,  edge o f t h e  circuit  the information  and s t o r e d  pulse  resets  t o produce a t the  i n t h e memory. PEAK DETECTOR 1.  i s c o m p r i s e d o f f o u r NOR  gates  (1-CD4001)* two o f w h i c h o p e r a t e  as a m o n o s t a b l e m u l t i v i b r a t o r .  The  to the f i r s t  1.5 Kfl r e s i s t o r  current to  a t the input  protection resistor,  10 ma, maximum.  to the gate  the input  gate i s a  gate  current  The p r o t e c t i o n was a d d e d t o p r e v e n t  i n the event that  d r o p p e d t o -15 v o l t s , trigger  limiting  NOR  the Schmitt t r i g g e r  due t o d i o d e  damage  voltage  failure  i n the Schmitt  (Figure  3.12) a t i n p u t  circuit. The  10 Kft d e l a y  resistor  * CD p r e f i x r e f e r s t o CMOS d e v i c e s S o m e r v i l l e , New J e r s e y .  m a n u f a c t u r e d by RCA  Corp.,  i_r  I.SK  o — v w  SCHMITT TRI66ER  IHPilT  to  0 . 0 / ILF  O-OlpF  —\{  O  IS  IO K  AA/V  WRITE.  OUT  PEkK DETECTOR RESE.T OUT  DELAY  Lo SAMPLE.  FIGURE  3.12  TIMING  CIRCUIT  OUT  I  92  #2* o f t h e f i n a l signal in  that  will  input  line.  i s used t o compensate at input  Without delay  a p p e a r a t t h e RESET o u t p u t ,  the Schmitt  widths. of  gate  delay which occurs  The of  NOR  RESET o u t p u t trigger  The RESET o u t p u t  t h e CD4066 b i l a t e r a l The  trigger  pulse  SAMPLE  compensation,  one o f w h i c h  switch,  Figure  be d i s c u s s e d  to circled  points  i s equal  pulses  t o t h e sum pulse  to the c o n t r o l input 3.6.  later  i n figure.  gate  i s i n error.  i s t h e complement o f t h e  * # refers  two  a n d t h e WRITE s i g n a l  i s connected  output  and w i l l  #1 due t o t h e e x t r a  pulse width  pulse  f o r the  Schmitt  i n Section I I .  93  Decoding Gates The  (Box N, F i g u r e 3.2) outputs  of the three  comparators  COMP. 2 a n d COMP. 3) c h a n g e c o n t i n u o u s l y PEAK DETECTOR 1 r i s e s tomato. the  three  the  colour category  to  comparator outputs  the s h i f t  for a particular  has been r e a c h e d and i s s t o r e d ,  remain r e l a t i v e l y  information  register  as t h e o u t p u t o f  t o i t s maximum v a l u e  Once t h e peak v o l t a g e  (COMP. 1,  i s ready  c o n s t a n t , and  t o be t r a n s f e r r e d  memories, which a r e s y n c h r o n i z e d  to  t h e movement o f t h e b e l t . Since to  travel  register  i t was d e c i d e d  t o t h e end o f t h e conveyor b e l t , memories were r e q u i r e d  semi-ripe  i s decoded  COMP. 3, v i a t h e t h r e e  voltage Figure less is  —  3.13.  Turning  NOR g a t e s ,  3.8.  ripe,  than V  g  E  T  2  -  one f o r  input  s t a t e s o f COMP. 2 a n d  NOR 1, NOR 2, a n d NOR 3,  i s less  than V - ™  Separation  by t h e o u t p u t  o f these  f o r COMP. 2,  0  two c o l o u r  o f COMP. 1, w h i c h  a green tomato i s b e i n g  i n a LOW o u t p u t  appears a t t h e other  categories  t o be w r i t t e n  3.13.  sensed, the output  voltages  i s LOW f o r a l l  information  t h e memories t h r o u g h NOR 4, F i g u r e  signal  T h e memory  Note t h a t g r e e n tomatoes a l s o produce  HIGH, r e s u l t i n g  is  one f o r f i r m  shift  t o m a t o e s a r e c a t e g o r i z e d when t h e i n p u t  except green tomatoes, p e r m i t t i n g  if  three  from t h e output  o f t h e comparators  controlled  into  only  a n d one f o r t u r n i n g t o m a t o e s .  information  Figure  t h a t t h e g r e e n tomatoes were  F o r example, o f COMP. 1 i s  a t NOR 4 e v e n when t h e WRITE  input  t o NOR 4.  No  t r a n s f e r r e d t o t h e memory t h r o u g h NAND g a t e s ,  information NAND 1,  94 FIGURE  JL  3 . 1 3  D E C O D I N G  G A T E S  95  NAND 2, a n d NAND 3, a n d t h e g r e e n of  the conveyor  as though  i t was n e v e r  tomato c a t e g o r i e s , t h e o u t p u t ing  sensed.  from  transferred  t o the outputs  WRITE p u l s e d u r a t i o n .  width result  i n double  the data first  category The  go LOW f o r t h e  i t i spossible  f o r more  o f t h e WRITE  i n PEAK DETECTOR 1 w h i c h  categorization  for  I n t h e o r y , a l l t h r e e NAND  t o be l o w f o r a f r a c t i o n  latches, w i l l  t o be  o f NAND 1, NAND 2, a n d NAND 3,  In p r a c t i c e  due t o m i n u t e d r i f t  allow-  o f NOR 4, a n d t h e  n o r m a l l y b e HIGH, a n d o n l y o n e w i l l  t h a n one o u t p u t  For a l l other  t h e NOR 1, NOR 2, a n d NOR 3 o u t p u t s  t h e d u r a t i o n o f t h e WRITE p u l s e . gates w i l l  t o t h e end  o f COMP. 1 i s LOW, t h u s  t h e WRITE p u l s e t o a p p e a r a t t h e o u t p u t  information  the  tomato t r a v e l s  o f one t o m a t o .  A  pulse  will circuit,  be d e s c r i b e d l a t e r w h i c h a c c e p t s  only  signal received.  1.5 Kft r e s i s t o r s  are c u r r e n t p r o t e c t i o n  a t t h e i n p u t s t o t h e NOR g a t e s  resistors.  96  Light  C h o p p e r and P h o t o d e t e c t o r The  light  (_Box  small holes, regularly  ference.  For the  s p a c i n g and  size  1/2  The conveyor  disk diameter  t h e d i s k and light  and  disk.  As  inch  (1.3  d i s k was  pulleys,  and  spaced,  of conveyor  belt  was  t o - c e n t e r d i s t a n c e between t h e approximately  the  source on  the  light  and  light  with  one  output,  cycle  The  frequency  the  conveyor  past  a fixed  f o r each of t h i s  belt  constant with  as  t h a t the equal  centerto  belt.  one  side,  of  the  side of  so t h a t  the the  beam i s t r a n s m i t t e d as  the h o l e s  pass,  t h e a r e a between the h o l e s .  the  belt  1/2  inch  digital  speed, but  moves, i s a d i g i t a l (1.3  cm)  signal w i l l  of belt be  signal  determined  length of conveyor  The  movement.  each c l o c k c y c l e w i l l  respect to the  by  remain  belt  moving  point.  The  photodetector  tive  operational amplifier,  used  i n shown i n F i g u r e  a photo diode t h e CA3062 c a n due  the  the hole centers of  the d i s k t o the p h o t o d e t e c t o r i s b l o c k e d by  circum-  a x l e o f one  the other  circular  used,  p l a c e d on  d e t e c t o r were a l i g n e d w i t h the d i s k r o t a t e s ,  pulley  of conveyor  m o u n t e d on  a light  the  s m a l l h o l e s was  cm)  a photodetector  photodetector  3,2)  near  c h o s e n so  through the  Figure  chopper disk, i s a t h i n , m e t a l ,  disk with  hole  P,  c h o s e n was and  3.14.  the Other  a CA30 62  schematic  light  of the  photodetectors,  sensicircuit  such  o r p h o t o t r a n s i s t o r c o u l d have been used, be w i r e d  easily  as  a Schmitt  to i t s h y s t e r e s i s c h a r a c t e r i s t i c  trigger,  makes t h e  as  but  which,  photodetector  FIGURE  3 . 1 4  LIGHT  C H O P P E R  P H O T O D E T E C T O R  A OUT  98  circuit  very  CA3062 w i l l  stable.  The d i g i t a l  be r e f e r r e d  output  t o a s CLOCK A.  signal  of the  99  Divide-by-3  Circuit  The  (Box Q, F i g u r e 3.2)  function o f the divide-by-3  divide  t h e CLOCK A f r e q u e n c y  output  now r e p r e s e n t s  every in  a memory  by 3, s o t h a t e a c h c y c l e a t t h e  planned  one s h i f t  T h i s would r e q u i r e  ( e . g . a f i r m r i p e memory)  downstream t h a t . t h e  eject station  belt.  t h a t t h e CLOCK A s i g n a l be  the.memory i n f o r m a t i o n  clock cycle.  i s to  1 1/2 i n (3.8 cm) o f c o n v e y o r  I t was i n i t i a l l y used t o s h i f t  circuit  location  (bit)  a b i t t o be a v a i l a b l e f o r every  i s located.  s t a t i o n was l o c a t e d 24 i n (61 cm) d o w n s t r e a m  1/2 i n (1.3 cm) The l a s t  eject  from t h e s e n s i n g  h e a d , t h u s r e q u i r i n g a 48 b i t s h i f t  capability.  of  r e g i s t e r s had 4 o r 8 b i t  the c i r c u i t  storage  design,  capability,  common s h i f t  and f o r t h e t h r e e memories needed,  14 i n t e g r a t e d c i r c u i t s  would have been  I t was b e l i e v e d t h a t memory than  information  A t t h e time  was s p a c e d  about  required.  fewer b i t s  c o u l d be u s e d i f  1 1/2 i n (3.8 cm) a p a r t  rather  1/2 i n (1.3 c m ) . T h i s means t h a t a n y two t o m a t o e s must be a minimum  of  1 1/2 i n (3.8 cm) a p a r t  i.e.  greater  than  i s not l i m i t i n g , that  size.  on t h e b e l t  from c e n t e r  3/4 i n (1.9 cm) i n d i a m e t e r .  since small  This  tomatoes a r e g e n e r a l l y  The number o f s h i f t  register bits  t o center, factor  double  c a n t h u s be  r e d u c e d by a t h i r d .  Figure and  The  divide-by-3  circuit  schematic  3.15.  The c i r c u i t  i s comprised  a CD4018 p r e - s e t t a b l e d i v i d e - b y - " N "  i s shown i n  o f CD4011 NAND counter.  gates  Two NAND  F I G U R E  3.15  D I V I D E - B Y - 3  100  CIRCUIT  o CLOCK A INPUT  CLOCK A OUTPUT  CLOCK 3 OUTPUT  101  gates  a r e employed  counter,  since  t h e CLOCK A r i s e  us, which i s c l o s e time up"  as p u l s e shapers  a t the input t o the  and f a l l  time  i s a r o u n d 10  t o t h e maximum a l l o w a b l e r i s e  o f t h e CD4018 c l o c k  input.  the clock pulse transistion  and f a l l  T h e two NAND g a t e s  "speed  f r o m HIGH t o LOW, a n d LOW t o  HIGH. Two  o f t h e o u t p u t s o f t h e CD4018 a r e c o n n e c t e d t o  t h e i n p u t s o f a CD4011 NAND g a t e , inverted This  a n d f e d b a c k t o t h e " d a t a " i n p u t o f t h e CD4018.  i s a standard c i r c u i t configuration  function  for a divide-by-3  u s i n g t h e CD4018. The  to  the output o f which i s  CLOCK A f r e q u e n c y d i v i d e d - b y - 3 w i l l be r e f e r r e d  a s CLOCK B.  Section I I .  T h e CLOCK A o u t p u t w i l l b e u s e d  later i n  102  Data L a t c h e s ,  Timers  and Memory C i r c u i t s  Data cannot  be e n t e r e d  into  (Box R, F i g u r e  the s h i f t  register  memories a t a n y t i m e , n o r c a n t h e d a t a be r e t r i e v e d Certain and  c o n d i t i o n s must be met b e f o r e d a t a  consistently (a)  (a HIGH o r LOW  goes  (nanoseconds) b e f o r e  The s t o r a g e o f t h e d a t a  LOW,  changes s t a t e  o r LOW  register  from  of  used,  level,  the s h i f t  the clock  the data storage  f o r each s h i f t storage  location  no more d a t a  register  latches,  HIGH t o a LOW  a  c a n be e n t e r e d  the next  cycle  F i g u r e 3.16,  f o r the colour category into  the s h i f t  a t the output  output.  data  register.  be one c y c l e  until  Maximum  o f CLOCK B.  As  o f one o f t h e d e c o d i n g  ( F i g u r e 3.13), i t s c o r r e s p o n d i n g  normally  until  either  starts.  i n the l a t c h w i l l  soon as a p u l s e o c c u r s gates  transition.  r e g i s t e r memory) i s t o a c t a s a  c a n be t r a n s f e r r e d time  a HIGH t o  s o t h e i n p u t d a t a must n o t  The f u n c t i o n o f t h e d a t a  temporary  either  t o HIGH d e p e r i d i n g on t h e s h i f t  HIGH o r LOW  latch  as t h e c l o c k  Once t h e c l o c k i n p u t h a s r e a c h e d  into  at least  the clock input  occurs  change s t a t e d u r i n g c l o c k  (one  register  high.  signal  (c)  can s u c c e s s f u l l y  s t a t e ) must be p r e s e n t  the input to the s h i f t  700 n s  (b)  a t anytime.  be s t o r e d .  The d a t a at  3.2)  latch  changes  from  a  F I G U R E  3 . 1 6  L A T C H I N G  CIRCUIT  IT  ~r r O  TURNING OUTPUT  ~i_r O  SEMIRIPE OUTPUT  i__r O  FIRM  RIPE OUTPUT  104  The or gates  change i n s t a t e  out signals  arriving  b e c a u s e o f t h e CD4023 3 - i n p u t set  latch  i s reset  are simultaneously The  data  two t i m e r s  l a t c h e s a r e used  pulse.  The s e t - u p  the r e s e t  pulse width  that occurs  positive  SET  data  in  order  going  from  HIGH t o LOW,  and a r e s e t  of data  to invert  CLOCK B  CLOCK B  t i m e r , a 14 us edge o f t h e  t h e RESET t i m e r i s RESET p u l s e .  on t h e n e g a t i v e  on t h e p o s i t i v e  into  going  Since the  edge o f  the s h i f t  register  edge o f t h e c l o c k p u l s e , i t (CLOCK B) f o r t h e s h i f t Similarly,  latches requires a negative  used  A l l three  ( f r o m HIGH t o LOW)  As t h e t r a i l i n g  u s i n g two CD4011 g a t e s .  two g a t e s  c a n any  as 6us.  at the input o f the set-up  RESET p u l s e was a l s o The  state  t o p r o d u c e a " s e t up" t i m e  CLOCK B, a n d t h e t r a n s f e r  the  a f t e r the  ( F i g u r e 3.17) a s s o c i a t e d w i t h t h e  UP t i m e r i s t r i g g e r e d  registers  HIGH o u t p u t  t o p r o d u c e a 6 us p o s i t i v e  was n e c e s s a r y  Only  and t r a n s f e r r e d .  pulse i s produced.  (CD4015) o c c u r s  latches,  reset.  negative  14 us p u l s e c h a n g e s triggered  NAND g a t e s .  blocks,  t i m e was c h o s e n a s a m o d e s t 14 u s , a n d  At every pulse  instantly  a t t h e o t h e r two  to i t s normally  more i n f o r m a t i o n be a c c e p t e d latches  o f one l a t c h  resetting of  going p u l s e , so the  i n v e r t e d (RESET) u s i n g two CD4011 g a t e s .  f o r e a c h i n v e r s i o n were w i r e d  to increase their Both the data  (LATCH OUT) a r e n o r m a l l y  current drive  input  in parallel  capabilities.  (DATA IN) a n d l a t c h  HIGH, a s shown i n F i g u r e  output 3.18.  The  F I G U R E  3 . 1 7  D A T A  _n_n_  L A T C H  105  TIMERS  ~i_n_r  CLOCK B  INPUT  RESET  TIMER  106 FIGURE  CLOCK  3.18  / 72 IN. CONVEYZR TRAVEL  J  B  D A T A  L A T C H W A V E F O R M S  BELT  \  RESET  DATA  IN  < LATCH  DATA  to <  LATCH  OUT  IN  .1  OUT  f I  107  shift and  register  memory, t h e r e f o r e , s e e s a c o n s t a n t  s t o r e s a "1" e v e r y  HIGH s t a t e .  t i m e CLOCK B c h a n g e s  When t h e d a t a  i n p u t g o e s LOW  tomato has been c a t e g o r i z e d ) the  shift  case  as soon as t h e n e x t  occurs.  The most d i f f i c u l t  w h i c h must be c o n s i d e r e d ,  C a s e 1:  WRITE p u l s e w i d t h RESET  a HIGH s t a t e ,  shown i n F i g u r e the  latch  i n p u t LOW pulse. will  occurs  less  the  latch  output  transition, has  been  C a s e 2:  and t h e d a t a 3.18.  CLOCK B LOW situation, during  than  arrives.  i s always equal  u n t i l the returns  the l a t c h  output  into  t o HIGH i . e . worst  t h e SET UP  time:  output  f r o m a LOW  is still  HIGH, a s  i s s e t LOW  before  The d u r a t i o n o f t h e l a t c h t o t h e l e n g t h o f t h e WRITE short, the l a t c h  RESET p u l s e HIGH.  changed  input  occurs,  A t the next  output  a t which positive  time CLOCK B  i s HIGH, a s n o r m a l , a n d t h e d a t a  lost. WRITE p u l s e w i d t h g r e a t e r t h a n and  RESET  The  difference  t h e sum o f SET UP  times. between Case (the data  2 and Case 1 i s t h a t i n latch  t h e sum o f t h e SET UP a n d RESET t i m e s  when t h e RESET p u l s e f r o m LOW  that a  t h e sum o f SET UP a n d  latch  i s very  C a s e 2 t h e WRITE p u l s e w i d t h than  latch  The d a t a  I f t h e WRITE p u l s e  be s e t LOW  to a  times.  RESET p u l s e pulse  f r o m a LOW  (indicating  S u p p o s e t h a t CLOCK B h a s a l r e a d y to  input,  a "0" must be t r a n s f e r r e d  register  transition  HIGH  appears, the data  input)  i s greater  ( F i g u r e 3.18).  latch  output  Now,  changes  t o HIGH f o r t h e d u r a t i o n o f t h e RESET p u l s e , a n d  108 returns LOW.  t o a LOW  The LOW  signal w i l l  be t r a n s f e r r e d  on t h e n e x t p o s i t i v e  t h e RESET p u l s e  and f i r m firm  shift  latch  r e m a i n LOW  The  The  the data  output w i l l  register  ripe  since  The l a t c h  pulse.  which  state  resets  the next  into  the s h i f t  register, with  used  f o r turning,  o f one CD4015 d u a l  t h e two 4 b i t s h i f t  to follow  prised  o f one a n d a h a l f  an8 b i t s h i f t .  memory o f two CD4015's  semi-  (16 b i t s ) .  memory" i s e q u i v a l e n t  of  c o n v e y o r b e l t movement.  (12 b i t s ) A shift  t o one c l o c k The f i r m  information  registers  wired i n  and t h e t u r n i n g o f one b i t  cycle,  "down  o r l 1/2 i n (3.8 cm)  r i p e memory i s t h e r e f o r e  12 i n (30 cm) d o w n s t r e a m  the  s e n s i n g h e a d , where t h e i n f o r m a t i o n was f i r s t  the  memory.  Similarly,  4 bit  The s e m i - r i p e memory i s com-  CD4015's  the  the  after  c l a s s i f i c a t i o n s a r e shown i n F i g u r e 3.19.  series  tion  RESET  the latch.  r i p e memory i s c o m p r i s e d  capable of s h i f t i n g  until  is still  t r a n s i t i o n o f CLOCK B,  t h r e e memory c i r c u i t s ripe  input  from  stored i n  t h e s e m i - r i p e memory s t o r e s  informa-  f o r 18 i n (46 cm) d o w n s t r e a m f r o m t h e s e n s i n g h e a d , a n d turning  memory f o r 24 i n (61 cm).  t o be l o c a t e d  Eject  stations  willhave  12 i n (30 cm), 18 i n (46 cm) a n d 24 i n (61 cm)  downstream from t h e s e n s i n g head, o t h e r w i s e t h e s h i f t registers  will  have t o be l e n g t h e n e d o r s h o r t e n e d .  When t h e i n f o r m a t i o n shifted register  entered  t h e maximum number o f s h i f t s , changes s t a t e  (in this  case  cycle,  i n a memory h a s b e e n  the output o f the s h i f t f r o m HIGH t o LOW) f o r  the  d u r a t i o n o f t h e one c l o c k  i . e . the output  goes  LOW  f o r 1 1/2 i n (3.8 cm) o f t h e c o n v e y o r b e l t movement.  109 F I G U R E  3 . 1 9  TURN INS INPUT  SEMI-RIPE INPUT  —r—  IS- '/zCD+0/5 I  IS  FIRM RIPE INPUT  JUL o — — CLOCK B INPUT  VzCDtOlS I  '/ZCD40/3\  E  M  c  1 IS  M  7 IO Vz CD40/S 9  c  1 7  IO  VZ.CD4-0IS  9  =3= '/2CD+0/S I0\ 9  X  O  R  Y  C I R C U I T  IS 2 '/ZCD40I5 I  1 5  '/ZCD40/S 2 /  =1=  7 '/2.CD-&IS lo\  TURNING, OUTPUT  ~L_r — o SEMI-RIPE OUTPUT  FIRM RIPE OUTPUT  110  Opto-Isolators  and T r i a c s  If  t h e LOW o u t p u t  t o an e l e c t r o m e c h a n i c a l hydraulic 1  signal  device,  solenoid valve,  f r o m a memory i s c o u p l e d  such as a pneumatic o r  the device w i l l  1/2 i n (3.8 cm) o f b e l t movement.  coupling  a shift  for  less  having (3.8  than  device,  unless  the device  must be  1 1/2 i n (3.8 cm) o f b e l t movement.  2 i n (5.1  probably  t i m e r s were u s e d  f o r example, t h e second F o r these  reasons,  the electromechanical  b e t w e e n low power d e v i c e s  i n the past  devices  were u s e d  i n the colour grader  be and  like  However, r e l a y s h a v e  o p t o - i s o l a t o r s and t r i a c s .  the optic  t o CMOS d e v i c e s coupler  Common s o l e n o i d s a r e  through  The o p t i c  The o p t i c c o u p l e r s  The l a t t e r  b y 110 v o l t provide  between  couplers can  t h e use o f a t r a n s i s t o r ,  c a n a l s o d r i v e a 110 v o l t  operated  by semi-  t o a c t as t h e c o u p l e r s  CMOS memories a n d t h e s o l e n o i d s . connected  devices.  such as t r a n s i s t o r s , and  such as s o l e n o i d s .  conductor  eject  no  t o a c t a s an  m o v i n g p a r t s a n d h a v e b e e n r e p l a c e d i n many c a s e s  the  Two  i s e j e c t e d by a d e v i c e  a l s o be e j e c t e d .  have been used  power d e v i c e s  timer  normal o p e r a t i o n s .  cm) o f b e l t ,  t o operate  Relays  A  c o l o u r c a n b e s p a c e d by as l i t t l e a s  1/2 i n (3.8 c m ) , a n d i f t h e f i r s t  o p e r a t i n g over  operated  t h e t i m e r e q u i r e d f o r 1 1/2 i n  i n t e r f e r e with  tomatoes o f d i f f e r e n t  high  i s no a d v a n t a g e t o  t o a timer which operates the  cm) o f b e l t w i l l  interface  There  output  a d u r a t i o n g r e a t e r than  tomato w i l l  be a c t i v a t e d f o r  register  electromechanical  1  (Box S, F i g u r e 3.2)  AC  AC t r i a c .  sources.  complete  isolation of  Ill  the  CMOS d e v i c e s  triacs.  This  110 vAC l i n e disrupt  f r o m t h e 110 vAC l i n e  voltage  i s most d e s i r a b l e s i n c e n o i s e must n o t f e e d  normal  present  common  back i n t o t h e l o g i c  on t h e  c i r c u i t r y and  operation.  A s c h e m a t i c o f t h e o p t o - i s o l a t o r and t r i a c is  shown i n F i g u r e  drive  the l i g h t  isolator. the  3.20.  emitting  When t h e LOW  shift  o f t h e LOW  signal.  diode  as l o n g  s i g n a l i n a memory r e a c h e s  The t r i a c s  as t h e g a t e  conveyor b e l t  signal,  ± 15 v o l t  t h e end o f  conduct  equivalent  line  The 110 vAC l o a d  i s i n series with the of the  t o 1 1/2 i n (3.8 cm) o f  This  that  power s u p p l y  e n s u r e s maximum n o i s e a n d t h e low power  —  not the  isolation  IC c i r c u i t r y .  e x i s t s i s b e t w e e n t h e LED a n d p h o t o -  o f t h e MOC1003, a n d t h e i s o l a t i o n  between t h e two i s t y p i c a l l y  L2001L5 t r i a c s  t h e 110 vAC  i s active f o r the duration  o p e r a t e on a s e p a r a t e  coupling  The  t o the  t h e p h o t o t r a n s i s t o r s which d r i v e the gates  IC s u p p l y .  transistor  f o r the duration  are coupled  i s conducting.  b e t w e e n t h e 110 vAC c i r c u i t only  opto-  travel.  Note t h a t the t r i a c s  will  e j e c t mechanism)  and thus t h e l o a d  memory o u t p u t LOW  The  (LED) o f t h e MOC1003  The p h o t o t r a n s i s t o r s  (the e l e c t r o m e c h a n i c a l  of  A 2N3638 PNP t r a n s i s t o r i s u s e d t o  o f t h e MOC1003's c o n d u c t c u r r e n t  gates o f the t r i a c s .  triacs,  circuit  r e g i s t e r , t h e LED's a r e a c t i v a t e d a n d t h e p h o t o -  transistors  current  a t the  maximum c u r r e n t  resistance  1 0 ^ ohms. handling  i s 1 ampere, and l o a d s  capability will  of the  have t o be  F I G U R E  O O  3 . 2 0  O P T O - I S O L A T O R S  A N D  TRIACS  r^/ ns v •tlS  UNREGULATED  O  a A/363 3  IC GND.  113  maintained  below t h a t the  level.  capacitor  across  triac  inductive  l o a d when t h e  The  470ft r e s i s t o r  dissipates stored  triac  i s suddenly  and  energy  O.luF in  turned o f f .  an  114 Display  Timers The  directly is  display  timer c i r c u i t  t o the sorting  to light  grader  (Box T, F i g u r e 3.2) does n o t c o n t r i b u t e  f u n c t i o n o f the grader.  one o f t h r e e LED's o n t h e f r o n t  c a b i n e t , thus  identifying  panel o f the  the colour category  which a tomato has been p l a c e d by t h e machine. used  to identify  firm  ripe  and a green  f o r t u r n i n g tomatoes.  required  no d i s p l a y ,  primarily voltage  m  A r e d LED was  The green  semi-  tomatoes  T h e d i s p l a y s were  up t h e c o m p a r a t o r  (V-,_ ) .  into  t o m a t o e s , a n o r a n g e LED f o r  by e l i m i n a t i o n .  i n setting  settings  ripe  Its function  used  (Box F, F i g u r e 3.:2)  F o r e x a m p l e , a t o m a t o w o u l d be  bill  visually  selected  as a s e m i - r i p e such  w o u l d be c l a s s i f i e d  as f i r m  ripe.  that anything  The t o m a t o was p a s s e d  under t h e s e n s i n g head and t h e comparator v o l t a g e on  the front  panel  the tomato passed The  until  o r a n g e LED w o u l d  a n d t h e r e d LED s t a r t e d  flash.  the machine w i t h o u t activated. colour  F i g u r e 3.21.  data 3.16.  flashing  to flash  after  instead.  r e t u r n e d t o a p o i n t where t h e  T h i s method e n a b l e d  The"same m e t h o d was u s e d  category  adjusted  rapid  s e t up o f  w a i t i n g f o r t h e e j e c t mechanism t o be i n setting  the other  comparator v o l t a g e s .  A schematic in  t h e o r a n g e LED s t o p p e d  c o m p a r a t o r v o l t a g e was t h e n  redder  o f the d i s p l a y  The c i r c u i t  latch circuit  timer c i r c u i t  i sbasically  i s shown  t h e same a s t h e  d e s c r i b e d p r e v i o u s l y , a n d shown i n F i g u r e  The i n p u t s t o NAND g a t e s , NAND 1, NAND 2 a n d NAND 3  are connected  directly  t o the outputs  o f the decoding  gates  115 FIGURE  3.21  D I S P L A Y  TIMER  CIRCUIT:  116  (Figure buffers  3.13).  The l a t c h  to drive  provides  t h e LED's.  up t o 7 s u c h  resistors  outputs  output  transistors.  Q  latched is  a n d Q becomes  a n d Q i n a LOW s t a t e . output w i l l  As l o n g as Q  light.  three Q outputs  has  a r e connected  3 i n p u t NAND g a t e , NAND 4.  LOW, t h e n o r m a l l y is  inverted  LOW o u t p u t  through  When one  about  20 ms.  o f the Q outputs  together.  T h i s HIGH  As t h e o u t p u t  a HIGH s t a t e  comprised  a t the output  o f NAND 5 o f NAND 6  o f NAND 6 f o r  A s t h e o u t p u t o f NAND 6 r e t u r n s LOW, t h e mono-  stable multivibrator  consisting  triggered  a HIGH RESET p u l s e o f a b o u t  t o produce  pulse  i s inverted  latch  outputs.  are used  goes  t h e t h r e e i n p u t NAND g a t e , NAND 5, w h i c h  a l l three inputs t i e d  NAND 7 p r o d u c e s  to the inputs o f  o f NAND 4 goes HIGH.  goes LOW, t h e m o n o s t a b l e m u l t i v i b r a t o r and  As s o o n a s o n e  g o e s LOW, t h e o t h e r two l a t c h e s a r e g a t e d o u t . The  one  The Q o u t -  i s f e d b a c k t o t h e i n p u t s o f t h e o t h e r two  l a t c h e s v i a t h e CD4023 t h r e e i n p u t NAND g a t e s . Q output  i s normally  When one o f t h e i n p u t s g o e s LOW,  HIGH, t h e LED a t t h e l a t c h  put o f a l a t c h  resistors.  a t the S(set) input t o the latch  i n a HIGH s t a t e ,  array  The 33 Kft a n d 390 ft  ( F i g u r e 3.21) o f a l a t c h  LOW, a n d Q i s n o r m a l l y h i g h . a LOW a p p e a r s  to transistor  T h e CA3081 NPN t r a n s i s t o r  are current limiting The  a r e connected  through  o f NAND 10 a n d NAND 11 i s  NAND 12, w h i c h  The two NAND g a t e  as pulse shapers,  HIGH t o LOW o f t h e o u t p u t  resets  inverters,  t o speed  20 u s . T h e a l l of the  NAND 8 a n d NAND 9  up t h e t r a n s i t i o n  p u l s e a t NAND 6, w h i c h  from  i squite  slow  117  due  t o c a p a c i t o r C^. One  20  ms  LOW.  o f t h e t h r e e LED's w i l l  d e p e n d i n g on w h i c h one  light  o f the three  for  inputs  approximately first  goes  118  POWER SUPPLIES The based  d e s i g n o f a ± 15 v o l t  r e g u l a t e d power  on t h e t h e o r e t i c a l , c u r r e n t consumption  described  board  Instead,  t h e s y s t e m was t e s t e d u s i n g a t e s t  and e x p e r i m e n t a l  c o n s u m p t i o n was m e a s u r e d . circuits  of the c i r c u i t s  s o f a r w o u l d r e q u i r e many l o n g a n d u n n e c e s s a r y  calculations. circuit  supply  was a r o u n d  power s u p p l y  and t h e c u r r e n t  Maximum c u r r e n t f o r t h e i n t e g r a t e d  100 ma.  A ± 15 v o l t  r e g u l a t e d power  s u p p l y k i t (RAE 1510 K I T ) was a v a i l a b l e w h i c h was c a p a b l e o f delivering to drive  ± 500 ma.  the IC's.  to maintain  Voltage  + 15 v o l t  in  Figure  in  theopto-isolators  3.22, was d e s i g n e d  transistor  collector, capable  for  this  to drive  ( F i g u r e 3.20).  power s u p p l y ,  o f t h e system. power s u p p l y . lead.  Maximum c u r r e n t p e r o p t o -  A transformer,  and r e c t i f i e r allowing  at the diodes further  No v o l t a g e r e g u l a t i o n was r e q u i r e d The s u p p l y  The s e p a r a t e  isolators  and t r i a c s  sensitive  integrated circuits AC l i n e s .  shown  the phototransistors  i s g o v e r n e d b y t h e 1.5 Kft r e s i s t o r  a n d i s 10 ma.  115 vAC COMMON  115 v o l t  unregulated  integrated circuits.  o f h a n d l i n g 1 ampere w e r e c h o s e n t h u s  expansion  adequate  r e g u l a t i o n was d e s i r a b l e i n o r d e r  stable operation o f the linear  A separate  isolator  T h e power s u p p l y was more t h a n  assures  GROUND i s c o n n e c t e d power s u p p l y  maximum i s o l a t i o n  to the  f o r the optobetween t h e  and t h e e l e c t r i c a l l y  noisy  FIGURE  3 . 2 2  P O W E R  SUPPLY  CIRCUIT  FOR  T R I A C S  120 MECHANICAL HANDLING SYSTEM As m e n t i o n e d objective tomato  i n the i n t r o d u c t i o n ,  of the present research  handling  veyor b e l t  t o d e s i g n a new t y p e o f  system, b u t r a t h e r  to transfer  t o use a t y p i c a l  t h e tomatoes  eject  stations.  The p r o b l e m  fruit  on c o n v e y o r b e l t s  i n the United  ejection  f o r t h e tomatoes  system  studied  States.  c l a s s i f i c a t i o n was n o t o f p r i m e  and d e v e l o p e d t o a  to test  c o u l d be employed  o f an  from t h e conveyor b e l t concern e i t h e r .  the e l e c t r o n i c  i n a large  s u c h as  The p e r f e c t i o n  was t h e d e s i g n o f a r e a s o n a b l e c o n v e y o r and e j e c t c o u l d be u s e d  con-  and c e n t e r i n g o f  r e a s o n a b l e d e g r e e by l a r g e m a n u f a c t u r i n g c o m p a n i e s FMC C o r p o r a t i o n  flat  t o t h e s e n s i n g head and  of singulating  has been  i t was n o t t h e  design,  scale prototype.  after  Of i m p o r t a n c e system  features  which  o f which  121  The  Conveyor  System  The  conveyor  black  6 inch  (15 cm)  about  6 feet  (2.44  rollers,  one  system c o n s i s t e d of a f l a t ,  wide b e l t  cm).  The  o f w h i c h was  m o t o r and v a r i a b l e s p e e d Conveyor  belt  The frame w i t h 1/3  o f t h e way  belt,  system  a plywood  f e e d end  assembly  the b e l t  3.2 3a.  E2M2  Industries, Inc.).  continuously  from  zero  cm/sec).  sensing  mounted on a m e t a l h e a d was  slightly,  a t the e j e c t  The  light  mounted on t h e i d l e r  i s shown i n F i g u r e  tilted  two  mounted  about  from t h e f e e d end o f t h e c o n v e y o r , a c r o s s  After passing was  a Z e r o Max  (Zero-Max  and m o t o r was The  length of  s t r e t c h e d between  adjusted  (152  top.  as shown i n F i g u r e  photodetector  b e l t was  gearbox  inches/sec  belt  a working  c h a i n d r i v e n by  s p e e d c o u l d be  t o more t h a n 60  having  matte-  copper d i s k  the  and  p u l l e y a t the  3.23b.  underneath the sensing  to a s s i s t stations.  head,  the  i n the removal o f tomatoes  belt from  122 FIGURE  3.23  (a)  S E N S I N G  (b)  LIGHT  HEAD,  CHOPPER  A N D ASSEMBLY  123  Eject  System Of  method c h o s e n  t h e many p o s s i b l e ways o f e j e c t i n g to test  the e l e c t r o n i c  s y s t e m was  desired  o p e r a t i n g speed  tomatoes  the  pneumatic  ejection. The neighbourhood system large  o f 5 tomatoes per second.  operating at that  speed would  u n d e s i r a b l e impact The  obtained  f r o m a 1 1/2 3  subject  H.P.  Jaccuzzi  (0.028 m  3  ) surge  tank  i n (3.8  operated  62.5  (61 cm/sec) b e l t  Canada  The  surge  secondary  tank surge  (510  ) was  constructed of  Since the solenoids  cm)  speed  cm  of conveyor  belt,  are  then  a s o l e n o i d w o u l d be  at  active  DGD101 ( D e v i l b i s s (Canada) L t d . ) 5 2 a i r b o o s t e r n o z z l e s a 15 p s i g (10 newtons/m g) d r o p was m e a s u r e d a c r o s s t h e ASCO ( A s c o e l e c t r i c L i m i t e d ) 8262C90 s o l e n o i d 5 2 v a l v e a t 100 p s i g ( 6 . 9 X 10 newtons/m g) i n l e t p r e s s u r e . For 3 3 a 62.5  ms.  (3.8  was  3  galvanized pipe. in  system  (Jaccuzzi  a secondary  s o l e n o i d s were mounted.  f o r o n l y 1 1/2  a 2 ft/sec for  cm)  eject  tank.  supplied  t a n k , h a v i n g a volume o f 0 . 0 1 8 f t 1/2  eject  the tomato t o  Compressor  3  1  mechanical  a i r f o r the pneumatic  T h i s main s u r g e the e j e c t  Any  i n the  stresses.  compressed  Ltd.) having a 1 f t  on w h i c h  o f t h e s y s t e m was  ms  depletion v o l u m e was solenoids  Using Devilbiss  duration,  this  o f the primary surge tank. more t h a n c o u l d be  three times  this  The  (142  secondary  by  the time  tank.  Devilbiss  required  cm  )  surge  tank  volume, hence t h r e e  o p e r a t e d s i m u l t a n e o u s l y f o r 62.5  determined The  r e p r e s e n t s a 0.005 f t  ms  at a  t o recharge the secondary  DGD101 n o z z l e s a r e r a t e d  rate  surge  at a delivery  of  124  11  f t  (0.31  3  m)  of air/min  3  at  80  psig  A r o u g h measurement c o n f i r m e d a b o u t 5 2 85 p s i g (5.9 X 10 newtons/m g). Since solenoid gories the  four colour  valves  fourth category The  was  12  in  pipe  (30 was  is  cm)  allowed  sensing  to connect  nozzles  the  together.  shown i n F i g u r e  were s p a c e d  head.  to catch  belt  pneumatic  about 8 i n and  (20  cm)  the  A photograph of  the  t o m a t o e s as  system.  i n t o the  tomatoes would not o f an  to both guide the their  fall. The  were a l l o w e d the  belt.  (Refer  end  (15  three  cate-  of  cm)  first  the  and  the  con-  apart  was 1/4  located in  (0.6  secondary  The  three  they  cm)  surge  e j e c t mechanism  b i n due  A  test  cloth  conveyor  [In a  was  from  polyurethane  tomatoes.  tomatoes i n t o the to Figure  were e j e c t e d  to the  need to drop t o the inch].  compartments,  t o m a t o e s were f o r c e d t o  c o m p a r t m e n t s were h e a v i l y p a d d e d w i t h  than a f r a c t i o n  of  6 in  solenoid valves,  m i n i m i z e m e c h a n i c a l damage t o t h e the  the  at  3.24.  constructed the  tomato  Galvanized  A r e c e i v i n g bin, c o n s i s t i n g of  by  sorted,  conveyor b e l t ,  to drop-off  g).  2  3 m /min)  (0.34  of the  the  4 memory b i t s ) and  from the  used  t a n k and  movement o f  newtons/m  5  c a t e g o r i e s were t o be  solenoid valves  (4 CLOCK B c y c l e s o r  X 10  3 f t /min  12  were u s e d t o e j e c t t h r e e  t r a n s v e r s e l y to the  veyor.  (5.5  the drop  design  to  prototype,  r e c e i v i n g u n i t more  p o u c h was  also  b i n compartment  constructed and  break  3.24).  tomatoes which r o l l e d to drop i n t o a packing  o f f the box  end  of the  j u s t below the  conveyor level  125 FIGURE  3.24  PNEUMATIC  EJECT  MECHANISM  C H A P T E R  SYSTEM TESTING  127 MATERIALS AND METHODS (I)  E l e c t r o n i c System The  to  separate  ability  tomatoes  o f the e l e c t r o n i c colour into different  t e s t e d by g r a d i n g  and r e g r a d i n g  ranging  from green  i n colour  comparator  grading  colour categories  was  t h e same g r o u p o f t o m a t o e s ,  to firm ripe,  s e t t i n g s and o b s e r v i n g  a t various  the r e s u l t s .  V^,., , bb 1  drop o f f t h e end o f t h e conveyor. adjusted OT7  ,  on t h e f r o n t p a n e l  determine the borders  m  I  3 . 8 ) was s e t so t h a t t h e g r e e n t o m a t o e s w o u l d  (Figure  V  system  semi-ripe,  and s e m i - r i p e Field  testing  Vg  a E T  2  n  ^ sET  3  v  o f the instrument.  v  w  gET  always e  r  2  e  a n c  ^  o r c u t - o f f s between t u r n i n g and  and f i r m r i p e , r e s p e c t i v e l y . a t t h e Western Greenhouse  Co-operative  Warehouse was a l s o c o n d u c t e d , a n d t h e a u t o m a t i c a l l y p r o d u c e was j u d g e d b y f e d e r a l g o v e r n m e n t g r a d e r s  graded  a n d members  of the co-operative. (II)  Eject  System  The  p n e u m a t i c e j e c t s y s t e m was a d j u s t e d  so t h a t t h e  t o m a t o e s w o u l d be e j e c t e d t r a n s v e r s e l y f r o m t h e c o n v e y o r into  their  appropriate  storage  setting  the a i r pressure  nozzles  t o optimum a n g l e s  at  a given  desired.  bins.  The a d j u s t m e n t  belt  involved  r e g u l a t o r and a d j u s t i n g t h e a i r with  respect  t o the b e l t  so t h a t  c o n v e y o r s p e e d t h e t o m a t o e s w o u l d be e j e c t e d a s The maximum  was a l s o e s t a b l i s h e d .  operating  speed o f t h e e j e c t mechanism  128  RESULTS AND (I)  A voltage V _ „ &£J 1  , = 0.77 I  m  separate This  predicted 0.41  V  SET  2  Figure vely  as  ^  suggested  from  sufficient  the t u r n i n g  4.1.  high  3  a  r  e  s  n  o  w  I f both V g  (Figure into  b o t h V_,„  4.1a)  t  n  photographs  e  S E T  are  3  and  relati-  categorized  ripe.  was  V  SET  2  =  5  -  2  5  v  o  l  t  '  s  a  n  d  S  shown i n F i g u r e 4.1c. predicted  turning  shown i n T a b l e the  and  3.2,  split  ET  3  V  ,  oi:irT  green  =  0  E T  3  w o u l d be  but V-,™  volts,  but  may  be  e x p l a i n e d by  for  the p h y s i c a l  for  the p r e s e n t t e s t s .  physical  less  expected than  0  extremes  ,  2  5  v  falls  The  o  l  t  s  '  a  firm  s  between  i s much l o w e r  the  than  f o r the s e m i - r i p e . g r e a t e r than  volts].  The  studies  than  and  used  those  tomatoes used  the green  11  difference  s t u d i e s were p u r p o s e l y i n both  as  obtained with  the d a r k e r r e d tomatoes  properties  properties  include  t o be  11.93  8  4.1b),  voltages previously  p r e d i c t e d mean o f 11 v o l t s  [Vg  to  V  be  (Figure  t h e n m o s t o f t h e t o m a t o e s c a n be A reasonable colour  in  s e m i - r i p e groups.  are lowered  0  voltages,  a l l tomatoes can  the t u r n i n g m  3.2.  and V "  2  then  „ and V„„  m  E T  n  the  tomatoes,  the comparator ^  n  to  group.  favourably with  i n Table  of changing  ^SET  categorized If  tomatoes  found  v o l t a g e compares  effects a n <  was  mean v o l t a g e f o r t h e g r e e n  volt,  The  volts,  the green  cut-off  DISCUSSION  used  i n the chosen firm  ripe  129  130  categories. The  field  test  very promising.  results The  a t t h e c o - o p e r a t i v e were  graded  tomatoes  a c c e p t a b l e by b o t h t h e f e d e r a l co-operative (II)  Preliminary  involving  a lateral  belt  as i t p a s s e d t h e e j e c t  to  pulled The  a n g l e o f about  the e f f i c i e n c y  incline, start  system.  found adequate  2.5  (76 c m / s e c ) .  ing  5 i n (13 cm)  i n (3.8 cm)  corresponding  organization at  Ejection  (8.9 cm)  The  This  operating  g)  pneumatic  speeds  of the  up  Allow-  p e r tomato, i . e . plus  be  sufficient  f o r an  Greenhouse C o - o p e r a t i v e based  on  1975  yield  B).  v a l v e s were f o u n d t o f a i l  frequencies  the  i s approximately 5  r a t e would  (see Appendix  to  large  f o r the tomato  s u c h as W e s t e r n  solenoid  gravity  s e p a r a t i o n between tomatoes,  t h e peak h a r v e s t p e r i o d ,  predictions  required  a t h i g h e r speeds.  grading rate  tomatoes/sec.  2  at conveyor  of conveyor b e l t in  only  a f t e r which  newtons/m  became d i f f i c u l t  a maximum o f 3.5 1.5  s y s t e m was  With  belt.  5  s y s t e m was  tomatoes  conveyor  of the e j e c t  the pneumatic  p s i g ( 6 . 9 X 10  1 0 ° on t h e  showed  greatly  the tomato o f f the  ft/sec  the  nozzles,  the tomato r o l l i n g ,  100  g r a d e r s and  t h e e j e c t mechanism  that  the  judged  members.  tests  improved  were  above  10  cycles/sec.  at The  131  maximum g r a d i n g will  be  flow  is sufficient  belt.  10  rate a t t a i n a b l e with  tomatoes/sec, provided  Grading  air  flow  the  solenoids  to e j e c t the  rate  obtainable are  active.  the  system  t h a t the  tomatoes  i s presently during  this  limited  air  from by  short period  the  the that  132  S E C T I O N  II  S I Z E AND COLOUR GRADER  C H A P T E R  5  PHYSICAL PROPERTIES OF TOMATOES RELATED TO S I Z E GRADING  134  INTRODUCTION The of  fruits  most common c r i t e r i a  for size  and v e g e t a b l e s a r e d i m e n s i o n  and w e i g h t .  industry s t a n d a r d i n B.C. f o r t o m a t o s i z e based  classification The  classification is  on t h e m e a s u r e o f t h e maximum d i a m e t e r o f t h e f r u i t  (Appendix A ) .  Usually,  this  perpendicular to the polar  maximum d i a m e t e r  axis  formed  i s i n a plane  by t h e b l o s s o m and  c a l y x ends o f t h e t o m a t o . The designing  shape  o f the f r u i t  a machine t o s i z e  d i a m e t e r measurement. p o s s i b l e need  physical  for orientation  properties  Sphericity, f o r m i t y based the  grade  Variations  Dimensionless q u a n t i t i e s , in  i s o f utmost  according to a i n shape  o f the f r u i t  will  single d e t e r m i n e any  have b e e n  (25) t o d e s c r i b e  on t h r e e d i a m e t e r s , was o f l e s s  used  fruit  a r e l a t i v e measure o f s p h e r i c a l  design of the size  when  b e f o r e measurement.  s u c h as s p h e r i c i t y  analyses  importance  shape. uni-  importance i n  grader than the absolute d i f f e r e n c e s  between t h e d i a m e t e r s . In  the present investigation  related  to size  studied  to establish  before based  t h e need,  was  orientation  The c a l c u l a t i o n  of area  on two d i a m e t e r m e a s u r e m e n t s , a n d t h e c a l c u l a t i o n o f on t h r e e d i a m e t e r s w i l l  the use o f composite  tion.  properties  between d i a m e t e r s  i f any, f o r f r u i t  t h e diameter i s measured.  volume b a s e d to  grading, the d i f f e r e n c e  of physical  be d i s c u s s e d w i t h r e g a r d  v a l u e s as c r i t e r i a  f o r size evalua-  S i n c e t h e o n l y known c o m m e r c i a l l y a v a i l a b l e  size  135  graders  f o r tomatoes  u s e w e i g h t as t h e s i z e c r i t e r i o n , i t  was  also  of i n t e r e s t to investigate  the r e l a t i o n s h i p  the  maximum d i a m e t e r and t h e w e i g h t o f t h e  fruit.  between  136  MATERIALS AND METHODS The the  ellipsoid  was c h o s e n a s t h e a p p r o x i m a t i o n f o r  shape o f a tomato, as s u g g e s t e d  by M o h s e n i n  (25),  having  a p o l a r a x i s f o r m e d b y t h e c a l y x a n d b l o s s o m ends o f t h e tomato.  The t h r e e d i a m e t e r s ,  maximum  (major) d i a m e t e r  the minor diameter,  D I A . l , DIA.2, a n d DIA.3 a r e t h e  measured a t t h e e q u a t o r i a l  p e r p e n d i c u l a r t o D I A . l , measured a t t h e  equatorial  plane;  at  a plane  perpendicular to the equatorial plane.  is  equal  the  a n d t h e maximum p o l a r d i a m e t e r  t o DIA.2 a n d DIA.3 i s l e s s  tomato approximates  DIA.3 a r e e q u a l approximates  plane;  than  i s g r e a t e r than  When  DIA.l  D I A . l , t h e shape o f  an o b l a t e s p h e r o i d .  and D I A . l  measured  When DIA.2 a n d  DIA.2, t h e s h a p e  a prolate spheroid.  The  three diameters,  D I A . l , DIA.2, a n d DIA.3, a n d  t h e w e i g h t o f e a c h o f 153 t o m a t o e s were m e a s u r e d a n d r e c o r d e d . The (3.63  i n size  cm) t o 3.85 i n (9.78 cm)  category ranged  samples ranged  standard  from  from  (which  from  D I A . l = 1.43 i n  covers  the federal  size  s m a l l t o e x t r a l a r g e ) and w e i g h t s  0.92 oz (26.4 g) t o 10.82 o z (309.1 g ) . The a r e a  of  the equatorial  of  an e l l i p s e :  p l a n e was e s t i m a t e d  AREA The approximation  =  J  using the approximation  (DIA.l X DIA.2).  v o l u m e o f t h e t o m a t o was e s t i m a t e d  using the  o f an e l l i p s o i d : VOLUME = J  ( D I A . l X DIA.2 X D I A . 3 ) .  137  Correlations weights, well  as  and  the  of  regressions  three  correlations use  the  c a l c u l a t e d areas  linear  each of  among  and  measured weight  c a l c u l a t e d area  regressions  a s i n g l e diameter, DIA.l,  and  v o l u m e s were o b t a i n e d  f o r the  diameters, linear  and  measured d i a m e t e r s  as  and  as  versus  volume.  The  were u s e d t o j u s t i f y  the  a measure o f  the  fruit  size. The size  data  categories,  difference each of  a t the  would imply  that  zero  be  s u g g e s t an  of  equatorial  large.  the The  the  A difference of the  tomato  circular zero shape  a difference greater  the  approximation.  DIA.2 was  than  The  used to e v a l u a t e  s i z e measurement a t  in  the  the  the  category  data,  since  was  treated  the  shape o f  separately, the  fruit  rather seemed  size. The  size  into  plane.  than p o o l i n g with  and  as  t o m a t o o r i e n t a t i o n on  Each s i z e  vary  a circle;  ellipse  extra  a measure o f  e q u a t o r i a l plane  d i f f e r e n c e between D I A . l effect  as  e q u a t o r i a l plane. i n the  grouped  c a l c u l a t e d f o r each tomato  categories  a p p r o x i m a t e d by  would  t o m a t o e s was  - DIA.2] was  four size  uniformity  could  153  s m a l l , medium, l a r g e and  [DIA.l  the  f o r the  mean d i f f e r e n c e s o f  categories  were d e t e r m i n e d  were compared f o r the  and  [DIA.l 951  - DIA.2] b e t w e e n  confidence  differences within  each  intervals category.  to  138  RESULTS The  c o r r e l a t i o n matrix of DIA.l,  weight, c a l c u l a t e d area lated Five the in  volume i s shown linear  three  diameters,  descending order  The  as w e l l  differences  categories.  o f weight versus each o f  as a r e a  and v o l u m e a r e  to their  o f [DIA.l  - DIA.2] w i t h i n  The d i s t r i b u t i o n o f / D I A . l - DIA.2  t r a n s f o r m e d by s q u a r i n g  them.  root  The means,  i n t e r v a l s f o r the d i f f e r e n c e o f [DIA.l  are  i n Table  5.2  T h e r e was  large  categories.  small,  itself,  f o r the small,  The s t a n d a r d  DIA.l  deviations  and l a r g e  f o r the extra  correlation the  - DIA.2]  of  categories  [DIA.l were  coefficient  large  medium  i n size,  and DIA.2 remained  the  relatively  con-  - DIA.2] f o r t h e  [DIA.l  - DIA.2]  tomatoes, represented  o f 0.7393.  and  small.  A c o r r e l a t i o n d i d e x i s t between and  a n d 95%  categories.  As t h e t o m a t o e s increased  between D I A . l  medium  size  and t h e  no c o r r e l a t i o n b e t w e e n t h e d i f f e r e n c e  - DIA.2] a n d D I A . l  difference stant.  f o r a l l four  was  confidence  basis,  confidence  [DIA.l  a size  a skewed d i s t r i b u t i o n f o r a l l  i n t e r v a l s were c a l c u l a t e d on t h e s q u a r e  listed  listed  correlation coeffic-  f o u n d t o be more n o r m a l , h e n c e t h e means a n d 95%  results  samples.  5.1.  c a t e g o r y were f o u n d t o f o l l o w size  and c a l c u -  5.1, b a s e d on t h e 15 3  equations  according  2 (r ) i n Table  ients  i n the e q u a t o r i a l plane,  i n Table  regression  DIA.2, DIA.3,  In t h i s  l a r g e r t h e t o m a t o , t h e more e l l i p t i c a l  size  by a  category  i t i s i n the  139  TABLE 5.1  DIMETER-WEIGHT CORRELATIONS AND LINEAR REGRESSION EQUATIONS  DIA. 1  DIA. 2  DIA. 3  WEIGHT  , AREA  DIA. 1  1.0000  DIA. 2  0.9762  1.0000  DIA. 3  0.8544  0.8928  1.0000  WEIGHT  0.9836  0.9798  0.8895  1.0000  AREA  0.9940  0.9863  0.8575  0.9926  1.0000  VOLUME  0.9822  0.9820  0.8992  0.9985  0.9920  VOLUME  1.0000  WEIGHT it 0.150)oz = (0.599 + 0.003) VOLUME - (0.015 + 0.024) 2 = 0.9971 r  [5-1]  WEIGHT it 0.337)oz = (1.32 + 0.012) AREA  - (1.10 + 0.063) 2 = 0.9852 r  [5-2]  WEIGHT it 0.499)oz = (4.15 + 0.062) DIA. 1 - (5.70 + 0.159) 2 0.9675 r  [5-3]  WEIGHT it 0.553)oz = (4.89 + 0.081) DIA. 2 -(6.82 + 0.195) 2 = 0.9600 r  [5-4]  WEIGHT it 1.26 )oz= (6.56 + 0.274) DIA. 3 -(10.11 + 0.622) 2 = 0.7913 r  [5-5]  where AREA = J- (DIA. 1 X DIA. 2) inch  2  and VOLUME = J (DIA. 1 X DIA. 2 X DIA. 3) inch'  140  TABLE 5.2  Size Category  MEAN DIFFERENCES BETWEEN DIA.l AND DIA.2, AND 95% CONFIDENCE INTERVALS FOR FOUR SIZE CATEGORIES.  Mean IDIA.1-DIA.2], inch, (cm)  0.Q45  Small  (0.114)  0.073  Medium  (0.185)  0.096  Large  (0.244)  Extra  large  0.271 (0.688)  95%  Confidence Interval [DIA.1-DIA.2], inch (cm)  0.000 to 0.165 (0.111)  (0.419)  0.015 to 0.175 (0.038)  (0.445)  0.011 to 0.263 (0.028)  (0.668)  0.016 to 0.834 (0.041)  (2.118)  141  equatorial  plane.  As a r e s u l t ,  the standard  [ D I A . l - DIA.2] f o r t h e e x t r a l a r g e c a t e g o r y that  of the other three c a t e g o r i e s .  lation of for  this  standard  versus  DIA.l  than  Because o f t h e c o r r e -  DIA.l  and DIA.2 t h a t one w o u l d  tomato i n t h e e x t r a l a r g e  A linear  i s greater  d e v i a t i o n does n o t r e p r e s e n t t h e r a n g e  d i f f e r e n c e between a single  deviation of  expect  category.  r e g r e s s i o n p e r f o r m e d on  [ D I A . l - DIA.2]  f o r the e x t r a l a r g e tomatoes, produced the  equation: [ D I A . l - DIA.2] ± 0.149 = DIA.l where  DIA.l r  2  The DIA.l  =  0.00 or whereas  t o 3.00 in <  interval  [5-6]  0.399 cm <  a  [ D I A . l - DIA.2] < 0.411 i n [ D I A . l - DIA.2] < 1.044  a tomato w i t h  in <  f o r a tomato w i t h  i n (7.62 cm) w o u l d b e :  a DIA.l  w o u l d h a v e a 95% c o n f i d e n c e  or  (1.86 ± 0.091)  0.5466.  0.00 cm <  0.157  ± 0.299)  and DIA.2 a r e i n i n c h e s , a n d  95% c o n f i d e n c e  equal  (0.659  equal  cm  t o 3.50 i n (8.89 cm)  interval:  [ D I A . l - DIA.2] < 0.741 i n [ D I A . l - DIA.2] < 1.882  cm  142  DISCUSSION The that be  c o r r e l a t i o n m a t r i x shown i n T a b l e 5.1  t h e maximum d i a m e t e r a t t h e e q u a t o r i a l  u s e d as an i n d i c a t i o n  of the weight  minor  diameter, perpendicular  plane  i s closely  plane, DIA.l,  o f the tomato.  to DIA.l a t the  between a s i n g l e  third  The that  at  i s that  second  largest  o f v o l u m e b a s e d on  i s an e l l i p s o i d ,  coefficient  largest  results  f o r weight.  correlation  coefficient  m i n a t i o n o f a l l t h r e e d i a m e t e r s , and  best  measurement w h i c h DIA.2 o n l y ,  and  includes  only  diameter, DIA.l,  third  best  results  second b e s t .  of area i n the  includes  the  the c a l c u l a t i o n be  ideal  deterof  i f the  A system o f  o f a r e a b a s e d on t h e  be  be  largest  f o r weight.  desired.  d i a m e t e r s , would  would  the  assumption  the determination of DIA.l  the c a l c u l a t i o n  the l a r g e s t  corre-  correlation  calculation  the t h r e e diameters would  c o r r e l a t i o n w i t h w e i g h t was  the  i n the  The  A system o f measurement which  v o l u m e b a s e d on  best  i s t h a t o f DIA.2, and  t h e e q u a t o r i a l p l a n e b a s e d on an e l l i p s e  second  The  the  o f DIA. 3..  calculation  t h e tomato  correlation  The  a s s o c i a t e d with weight  largest  The  d i a m e t e r m e a s u r e m e n t and w e i g h t i s  that of DIA.l versus weight. coefficient  may  equatorial  t o D I A . l , whereas DIA.3,  correlated  p o l a r d i a m e t e r i s more i n d e p e n d e n t o f D I A . l . lation  indicates  A system which  and two  measures  a t the e q u a t o r i a l plane,  as an e s t i m a t e o f t h e t o m a t o ' s  weight. 2  The  regression  e q u a t i o n s and  their  associated  r  143  values area,  shown i n T a b l e and  volume a r e  5.1  indicate  linearly  t h a t D I A . l , DIA.2,  related  to the  DIA.3,  tomato's  weight. The was  third  obtained  largest  correlation  f o r the weight versus  A system which measures o n l y D I A . l estimate  the weight of a As  shown i n T a b l e  5.2,  small to extra large.  circular tion  as  the  between  medium and vals  for  size  category  smallest largest 95%  applies  l a r g e tomato has interval,  The  95%  ial  largest.  correla-  inter-  3.00  F o r example,  in in  (5.72  0.011  t o 0.263 f o r  5.2  be  shape o f the  plane w i l l  no  confidence  =  i n the  i n t e r v a l may  The  95%  DIA.l  confidence  given DIA.l  confidence  The  D I A . l = 2.25  (7.62  the  cm)  and  the  cm),  and  the  [DIA.l -  interval  f o r the  does not  apply  [ D I A . l - DIA.2] i n c r e a s e s w i t h any  T h e r e was  less  DIA.2],  tomatoes.  t o m a t o e s shown i n T a b l e  For  becomes  f o r the s m a l l e s t tomato i n a  f o r the  l a r g e t o m a t o has  plane  DIA.l w i t h i n the s m a l l ,  categories.  as w e l l a s  of  size categories,  equatorial  increases.  [ D I A . l - DIA.2] a p p l y  f o r both  could therefore reasonably  increasing  [ D I A . l - DIA.2] and  confidence  regression equation.  t h e mean d i f f e r e n c e s  The  tomato s i z e  large size  DIA.l  0.9675,  tomato.  [ D I A . l - DIA.2] i n c r e a s e w i t h from  coefficient,  determine  DIA.l  extra large  since  in this  size  extra large category, calculated  category. the  using equation  tomato, e s p e c i a l l y  i n the  the need f o r o r i e n t a t i o n  of  95% [5-6]. equatorthe  144  tomato,  before  spherical, DIA.3. to  DIA.l  c a n be m e a s u r e d .  no o r i e n t a t i o n i s r e q u i r e d ,  I f t h e tomato i s an o b l a t e  rest with  the polar  axis  I f t h e tomato i s since  spheroid,  perpendicular  DIA.l  = DIA.2 =  t h e tomato  t o t h e p l a n e on  which  i t r e s t s , a n d no f u r t h e r o r i e n t a t i o n i s r e q u i r e d ,  DIA.l  = DIA.2.  orientation  I f t h e tomato i s a p r o l a t e  i n the polar  plane w i l l  spheroid,  be r e q u i r e d ,  I f t h e tomato i s an e l l i p s o i d ,  polar  and e q u a t o r i a l  axis  ellipsoid and  tomatoes a r e g e n e r a l l y  DIA.3 i s  stable  since  usually  the extra  the smallest,  plane w i l l The  [DIA.l  therefore  mean d i f f e r e n c e s  be  making  i n the e q u a t o r i a l  w o u l d be [ D I A . l in  - DIA.2J.  the equatorial  DIA.l, equal  and o n l y t o [DIA.l  equatorial greater  plane  than It  the error Only  t h e tomato most  intervals  i f the tomatoes  plane,  i . e . o f DIA.2 was  i n t h e measure o f D I A . l  one o r i e n t a t i o n o f t h e t o m a t o  p l a n e p r o d u c e s no e r r o r  i n t h e measure o f  one o r i e n t a t i o n p r o d u c e s a maximum - DIA.2].  i nthe  5.2 i n d i c a t e t h e w o r s t  were n o t o r i e n t e d  of DIA.l,  tomatoes,  required.  t h a t w o u l d be e x p e c t e d  instead  large  Orientation  measurement e r r o r  measured  be  The  a n d 95% c o n f i d e n c e  - DIA.2] shown i n T a b l e  A l l other orientations  error i nthe  produce d i a m e t e r measurements h a v i n g  zero but l e s s than i s concluded  that  DIA.2  o r i e n t a t i o n of the  be r e q u i r e d .  i f r e s t i n g on one o f i t s p o l e s .  equatorial  of  plane w i l l  since  no  = DIA.3, h o w e v e r , o r i e n t a t i o n o f t h e D I A . l a x i s w i l l required.  tends  [DIA.l  errors  - DIA.2].  o r i e n t a t i o n o f t h e tomato f o r  145  the  accurate determination o f DIA.l w i l l  for  the l a r g e r  tomatoes than  measurement e r r o r tomato  size.  be more  important  the s m a l l ones, s i n c e the  due t o l a c k o f o r i e n t a t i o n  increases with  146  C H A P T E R  SIZE  DETERMINATION SCHMITT  USING TRIGGER  6  T H E COLOUR PULSE  GRADER  147  INTRODUCTION The grader  Schmitt  trigger  centered  i s travelling  Schmitt  trigger  studied  at a fixed  chapter,  pulse width  trigger  diameter  o r the conveyor diameter  t h e r e l a t i o n s h i p between t h e and v a r i o u s tomato s i z e s w i l l  conveyor b e l t p u l s e , such  "limit  head d e s i g n w i l l  speed. as b e l t  F a c t o r s which  be  affect  speed, and m i s a l i g n -  respect to the f i b r e  optic  sensing  of detection" of the present  sensing  be d i s c u s s e d .  The l i m i t  of detection i s the  o f a t o m a t o w h i c h i s t o o s m a l l t o be d e t e c t e d , a n d  thus  does n o t produce a S c h m i t t  tion  of the instrument  diameters  be a f u n c t i o n o f a  a l s o be e x a m i n e d . The  diameter  will  head,  speed, the  a t a v a r y i n g s p e e d , an e r r o r i n t h e  ment o f t h e t o m a t o w i t h head w i l l  respect to the sensing  result.  In t h i s  Schmitt  I f t h e tomato i s  I f t h e tomato i s n o t c e n t e r e d  measurement w i l l  the  s e n s i n g head.  t h a t t h e tomato  i s moving a t a c o n s t a n t  t r i g g e r pulse width  the tomato.  belt  optic  on t h e c o n v e y o r b e l t w i t h  the conveyor b e l t  Schmitt of  of the colour  i s p r o p o r t i o n a l t o t h e l e n g t h o f time  spends under t h e f i b r e  and  pulse width  trigger  pulse.  The r e s o l u -  i s t h e s m a l l e s t d i f f e r e n c e b e t w e e n two  w h i c h c a n be d i s c r i m i n a t e d .  148  MATERIALS AND Size  Standards I t was  tomato s i z e tangible  e v i d e n t from  versus  size  Schmitt  l o n g term  shelf  life  testing.  The  life green  a t room t e m p e r a t u r e  Three size  t r i g g e r pulse width  shelf  m a k i n g them u n s u i t a b l e as  as  white  s t a n d a r d s , one  respectively.  sphere,  so t h a t  b e l t with  the  realistically represented and  the  flat the  the  The  in  spheres  styroball  divider  the  same, t h e d i v i d e r o u t p u t  was  approximately  slightly The  spheres  medium, and  (5.1 cm),  2 volts.  2.5  in  i n the  longest ripen,  chosen  large. cm)  and  c u t from  p l a c e d on as  were  (6.4  the  each  conveyor  approximating flat  more  side  The  three diameters,  D I A . l , DIA.2  are  listed  6.1.  o f the  and  i n Table  c o l o u r g r a d e r was  since their  v o l t a g e f o r each  of the  This voltage rendered  red r e g i o n than  s t y r o b a l l s were t h e r e f o r e s u i t a b l e  as  measured  c o l o u r s were a l l  " t u r n i n g " i n c o l o u r , i . e . the s t y r o b a l l s more l i g h t  the  one  A segment was  c o u l d be  output  the three s t y r o b a l l s ,  as  tomatoes, w i t h  s h a p e o f a t o m a t o , where t h e  for  balls  w h i c h makes them u n d e s i r a b l e  s i d e down, a s w e l l  c a l y x end.  DIA.3 o f e a c h  some  c h a n g e c o l o u r as t h e y  s m a l l , one  2.9  cm)  that  of  tomatoes, were r e q u i r e d .  textured styrofoam  w e r e 2.0  (7.4  study  standards.  Their diameters in  the beginning of the  standards, other than  Tomatoes h a v e a f i n i t e for  METHODS  i n the  three  the  styro-  reflected green  standards.  region.  149  TABLE 6.1  D I A . l , DIA.2, and DIA.3 o f THREE STYROBALL SIZE STANDARDS  Styroball Sni"z e_  _  Small  Medium  Large  DIAMETERS,  i n c h (cm)  D — I—A ••.-1 1 l » D I A . 2  DIA.3  2.00  2.00  1.63  (5.08)  (5.08)  (4.14)  2.48  2.48  2.01  (6.30)  (6.30)  (5.11)  2.85  2.85  2.35  (7.24)  (7.24)  (5.97)  150  P u l s e Width  Measurement  The the  black  adhesive  flat  Technique  s i d e o f each  conveyor b e l t  s t y r o b a l l was a t t a c h e d t o  f o r a l l tests,  tape, and the S c h m i t t t r i g g e r  g r a d e r was m e a s u r e d u s i n g a T e k t r o n i c s Model  Since directly  Frequency  t h e f r e q u e n c y o f CLOCK A  proportional  measure o f b e l t  to  pulse of the colour  t o the rate  speed.  CLOCK A f r e q u e n c y v e r s u s b e l t A Tektronics  Frequency  (Figure  of belt  An a p p r o x i m a t e  give  conversion scale of  used  speed  i n subsequent  will  tests.  P u l s e Width  s t y r o b a l l was c e n t e r e d a n d t a p e d t o t h e c o n -  veyor b e l t  surface-  the b e l t  The b e l t was s e t i n m o t i o n ,  s p e e d d e t e r m i n e d by m e a s u r i n g t h e  CLOCK A f r e q u e n c y . to  DC 503 was  The CLOCK A f r e q u e n c y  E f f e c t o f S t y r o b a l l S i z e on S c h m i t t T r i g g e r a t F o u r C o n v e y o r B e l t Speeds  and  an a c c u r a t e  s p e e d i s shown i n T a b l e  m e a s u r e t h e CLOCK A f r e q u e n c y .  The l a r g e  3.15) i s  movement, t h e  Counter, Model  be q u o t e d a s t h e m e a s u r e o f b e l t  A.  Counter,  Speed  m e a s u r e o f t h e CLOCK A f r e q u e n c y w i l l  6.2.  sided  DC 503.  Measurement o f B e l t  the  using double  The s t y r o b a l l  the conveyor allowing  remained  a Schmitt t r i g g e r  attached pulse  w i d t h measurement t o be o b t a i n e d e v e r y t i m e t h e styroball  p a s s e d under  eliminating measurement.  recentering  t h e s e n s i n g head, of the s t y r o b a l l  thus f o r each  151  TABLE 6 . 2  THE COLOUR GRADER CLOCK A FREQUENCY VERSUS APPROXIMATE CONVEYOR BELT SPEED.  CLOCK A F r e q u e n c y (Hz)  Speed,  20  Conveyor B e l t inch/sec (cm/sec)  10  (25)  40  20  (51)  60  30  (76)  80  40 0  100  ' (102)  50  (127)  120  60 (15 2)  152  B.  Thirty.Schmitt obtained 50,  C.  trigger  p u l s e w i d t h measurements  f o r each o f f o u r b e l t  medium a n d s m a l l  i n A and B was  Each o f the three to  the conveyor b e l t ,  of  off-center  of a Styroball  styroballs  one a t a t i m e ,  The measurement indicate  deliberately 5/8 to  inch  off-set  (1.6 cm).  was  centered  Ten S c h m i t t t r i g g e r  obtained  as t h e s t y r o b a l l  e a c h 1/4  inch  (0.64 cm)  taped  effects  optic  ( i f any) f o r c e n t e r i n g  A belt  s p e e d o f 40 Hz sensing  h e a d was moved  in five  the  by t h e f i b r e  head  from the c e n t e r o f the b e l t The s e n s i n g  and  p r o d u c e d by s u c h o f f -  The f i b r e o p t i c  t h e movement o f t h e b e l t ,  intervals.  error  t h e need  t o m a t o e s on t h e c o n v e y o r b e l t . f o r the t e s t s .  f o r the  on t h e  to establish  viewing of the s t y r o b a l l  center viewing w i l l  repeated  styroballs.  E f f e c t of Off-Center Viewing Measured Diameter  chosen  s p e e d s - - 30, 40,  a n d 60 Hz.  The p r o c e d u r e d e s c r i b e d  s e n s i n g head.  were  1/4  inch  by  was  was about  transversely (0.64  cm)  p u l s e w i d t h measurements were  p a s s e d under t h e s e n s i n g head, f o r  interval.  153  RESULTS AND  DISCUSSION  E f f e c t o f S t y r o b a l l S i z e on Width a t Four Conveyor B e l t The of  the  Table  The  passing  the  through the  t o m a t o and  on  trigger pulse  i s linear with Practically,  exceeded b e f o r e  the  widths speeds  the  the  o f view b e f o r e  experience  with  speed.  The  A tomato, o r area  the  colour grader,  the  i n Figure  curves  asymtote around cm)  circuit of  be  the  view  fibre  curves  1.5  inches  inches  threshold (3.8  6.1  are  (3.8  appear q u i t e  cm).  must  pulse widths  standard f o r the  deviations of  three  styroballs  the  Based  relates The  extrapolated  cm).  Above  linear.  at  Schmitt  be  optic  Resolution The  a  indepen-  i t i s d e t e c t a b l e above background.  p o r t i o n s o f the  (6.4  field  styroball,  i n the  dotted  inches  the  threshold w i l l  1.5  to a probable  trigger  r e f l e c t a n c e d i f f e r e n c e between  conveyor b e l t .  conveyor b e l t  and  a l l lines  Schmitt  t o a tomato d i a m e t e r o f about  2.5  in  a reflectance  This threshold i s a function of  l a r g e enough t o o c c u p y s u f f i c i e n t field  listed  p l o t t e d f o r four b e l t  6.1,  origin.  s e n s i n g h e a d and  dent of  associated  r e l a t i o n s h i p between p u l s e w i d t h  shown i n F i g u r e  responds. the  their  errors  6.1.  t h r e s h o l d must be  at  standard  speeds are  Schmitt  diameter are  Ideally, diameter  the  Pulse.  d e v i a t i o n s , and  for four b e l t  means o f  styroball  Figure  Trigger  t r i g g e r p u l s e w i d t h s and  diameters,  6.3.  versus in  means, s t a n d a r d  Schmitt  styroball  Schmitt Speeds  trigger  four b e l t  speeds  154  TABLE 6.3  Styroball Dia.,inch  MEANS, STANDARD DEVIATION, AND STANDARD ERRORS OF SCHMITT TRIGGER PULSE WIDTHS FOR THREE STYROBALLS AT FOUR CONVEYOR BELT SPEEDS.  (cm)  Mean  PULSE WIDTH (ms) S.D.  S.E.  B e l t Speed: 30 Hz 2.00 (5.08)  153.7  2.935  0.545  2.48 (6.30)  199.4  1.634  0.298  2.85 (7.24)  224.3  1.509  0.276  2.00 (5.08)  117.1  0.888  0.165  2.48 (6.30)  150.4  1.180  0.215  2.85 (7.24)  169.9  1.093  0.200  2.00 (5.08)  93.3  1.241  0.230  2.48 (6.30)  120.6  0.828  0.151  2.85 (7.24)  137.8  1.300  0.237  2.00 (5.08)  79.0  0.883  0.164  2.48 (6.30)  102.7  1.037  0.189  2.85 (7.24)  118.2  1.210  0.221  B e l t Speed: 40 Hz  B e l t Speed: 50 Hz  B e l t Speed: 60 Hz  155 FIGURE  6.1  M E A N  SCHMITT  STYROBALL BELT  AT  PULSE FOUR  WIDTH  VS.  C O N V E Y E R  SPEEDS  40-| 1 O  TRIGGER  DIAMETER  1 /  1  1 2.  1  1 3  D i A M E T E f ? ^/NCH)  1  -*  f-  156  as  listed  tion is  deviations are probably  conveyor  conveyor Table  belt  belt.  6.3 i s 2.935 ms  converted  variation  i n size The  greater  than  standard of  worst  be:  i n Table  true  o f t h e mean, a n d  interval ± 0.075  f o r a given  (0.19 cm).  This  negligible.  resolution  (0.16 cm).  i s therefore Typically,  be 0.023 i n c h  ± 0.045 i n c h  will  styroball  slightly  however, t h e  (0.058 cm)  ( t h e mean  as a p e r c e n t o f t h e  (0.11 cm).  be w i t h i n 3/64 i n c h  interval Therefore  (0.12 cm) o f  size. The  worst  belt  speed  d e s i g n w o u l d be a p p r o x i m a t e l y increase  (5.08 cm)  6.3) and t h e 95% c o n f i d e n c e  the diameter  o f the  d e v i a t i o n i s 0.038 i n c h  deviations expressed  of the diameters  their  case  1/16 i n c h  the standard  will  i s probably  width  deviation listed i n  As a p e r c e n t a g e  the diameter  deviation will  diameters,  95%  be:  "squirming"  standard  to inches, the standard  will  pulse  due t o n o n - u n i f o r m i t y o f  cm) a n d t h e 95% c o n f i d e n c e  diameter  trigger  f o r t h e 2.00 i n c h  speed.  of the r e s o l u -  The m a g n i t u d e s o f t h e  s p e e d , and l a t e r a l  The l a r g e s t  t h e 30 Hz b e l t  (0.10  i f the Schmitt  as a measure o f d i a m e t e r .  standard  at  6.3 g i v e some i n d i c a t i o n  o f the instrument  used  the  i n Table  the r e s o l u t i o n .  variation 4%.  f o r the present  Better regulation  would  157 S c h m i t t T r i g g e r P u l s e Width v e r s u s Speed f o r Three S t y r o b a l l S i z e s For a given s t y r o b a l l pulse width frequency) expect,  and  conveyor  i s constant.  diameter,  speed  and  6.0  and  styroballs,  length.  6.9  cycles,  respectively,  the product  The  cycles  t h a t one  are the  p r o d u c t s were  f o r the  of  (measured as t h e CLOCK A  occupies a certain  t h e number o f CLOCK A  measure o f b e l t  Belt  T h i s i s the r e s u l t  since a given s t y r o b a l l  of b e l t ,  4.7,  belt  Conveyor  length same  approximately  s m a l l , medium and  calculated  from  would  large  the data i n Table  6.3. E f f e c t of Off-Center Viewing Measured Diameter The of the  1/4  mean o f t h e  inch  (0.64  cm)  moved a c r o s s t h e c o n v e y o r  of a Styroball  on  the  ten pulse widths  obtained for  each  intervals  s e n s i n g head  was  b e l t was  plotted  bolic  s h a p e , i t s maximum c o r r e s p o n d i n g t o t h e o n - c e n t e r  caused  a decrease Using  curve due  as  the  D e v i a t i o n s to the  " t r u e " measure o f the  was  122.5  the  1/4  inch ms.  inch  right  t h e maximum p u l s e w i d t h  maximum p u l s e w i d t h a t 1/4  c o u l d be f o r the  (0.64 The  (0.64  c u r v e was  i n the measured p u l s e  to o f f - c e n t e r i n g  and  resulting  against the-dis-  t h e h e a d was  styroball.  The  the  tance  of the  moved.  as  cm)  of  predicted.  size,  F o r example, 126.5  i n the diameter  viewing  the  the  t h e maximum t h e p u l s e  off-center  view  center  o b t a i n e d from  s m a l l s t y r o b a l l was  from  para-  width.  styroball  measurement e r r o r cm)  or l e f t  of  i s thus:  error the ms,  width due  to  158 Error = =  2  ; ? 12 6.5 Q  C  X  h  ms  The e r r o r v a l u e s The  conveyor b e l t  (126.5 - 122.5) ms (0.16 cm).  e r r o r s were c a l c u l a t e d i n 1/8  cm) i n t e r v a l s f r o m z e r o  center.  t o 5/8 i n c h  are l i s t e d  (or the center  error, (5.08 device  (0.64  i n Table  6.4.  A 1/4  inch  of the  head) does n o t  (0.64 cm) o f f s e t r e s u l t s  0.025 i n c h  (0.064 cm)  f o r the  (7.24 cm) d i a m e t e r s t y r o b a l l o r a 0.9% measurement  a n d a 0.063 i n c h  (0.16 cm) e r r o r  cm) d i a m e t e r s t y r o b a l l , on t h e f e e d  to center  (1.6 cm) o f f -  of the sensing  a measurement e r r o r o f a b o u t  2.85 i n c h  inch  o f f s e t o f the s t y r o b a l l from the c e n t e r  seem t o be t o o c r i t i c a l . in  n  0.063 i n c h  Similarly, (0.32  i  c  tomatoes  f o r t h e 2.00  o r a 3.2% e r r o r .  A  centering  end o f t h e conveyor b e l t s h o u l d (especially smaller  cm) o f t h e b e l t c e n t e r  ones) w i t h i n  w i t h o u t much  inch  be  able  1/4  difficulty.  inch  159  TABLE 6.4  Off-Center Distance i n c h (cm) 0  1/8  1/4  3/8  1/2  5/8  (0)  (0.32)  (0.64)  (0.95)  (1.27)  (1.59)  APPROXIMATE DIAMETER MEASUREMENT ERROR AT VARIOUS OFF-CENTER DISTANCES FOR THREE STYROBALLS, RELATIVE TO THE ONCENTER MEASUREMENT.  Small Styroball  ERROR (inch) Medium Styroball  Large Styroball  0.000  0.000  0.000  (0.000)  (0.000)  (0.000)  0.016  0.016  0.008  (0.041)  (0.041)  (0.020)  0.063  0. 039  0.025  (0.160)  (0.099)  (0.064)  0.103  0. 078  0.059  (0.262)  (0.198)  (0.150)  0.174  0.132  0.110  (0.442)  (0.335)  (0.279)  0.245  0. 202  0.170  (0.622)  (0.513)  (0.432)  160  SUMMARY The the  tests  colour  conducted  grader Schmitt t r i g g e r using the s t y r o b a l l  a f u n c t i o n o f the diameter the  conveyor  width  belt.  and t h e b e l t  size  of the s t y r o b a l l  standards, i s and t h e speed o f  The p r o d u c t o f t h e S c h m i t t t r i g g e r speed  pulse  (when m e a s u r e d as t h e f r e q u e n c y o f  CLOCK A) f o r a g i v e n d i a m e t e r  i s constant.  between t h e w i d t h o f t h e S c h m i t t t r i g g e r ball  pulse width f o r  The r e l a t i o n s h i p  p u l s e and t h e s t y r o -  diameter  i s quite  linear  down t o a b o u t  a 2 inch  (5 cm) d i a m e t e r , where t h e s t r a i g h t  line  rolls  balls  o f f to a limit  measurement e r r o r  c e n t e r placement increases creases  as t h e s t y r o b a l l  size.  the b e l t  results  (0.16 cm)  ball  a n d as l i t t l e  inch  (7.24 cm) d i a m e t e r  a s 0.025 i n c h  increases  f o r a given from t h e c e n t e r  (5.08 cm) d i a m e t e r  styro-  (0.064 cm) f o r t h e 2.85  capable of reasonable alignment of belt,  i t appears  pulse width  diameter, provided that  0.063  styroball.  tomatoes on t h e c o n v e y o r  resolution  belt  The e r r o r i n -  (0.64 cm) o f f s e t  f o r t h e 2.00 i n c h  With a system  The  a given o f f -  on t h e c o n v e y o r  distance  Styro-  be d e t e c t e d .  i n a measurement e r r o r o f about  inch  Schmitt t r i g g e r  from  decreases.  speed)  (3.8 cm).  cannot  resulting  size  A 1/4 i n c h  1.5 i n c h limit  of the s t y r o b a l l  as t h e o f f - c e n t e r  styroball  the  o f about  h a v i n g d i a m e t e r s below t h i s The  of  (for a constant belt  the b e l t  feasible  t o use  as a measure o f t h e tomato's speed  i s relatively  obtainable with the instrument w i l l  be  constant.  161  primarily speed. be  about  a function  of the r e g u l a t i o n  For the p r e s e n t d e s i g n , 3/64  inch  (0.12  cm).  of conveyor  t h e r e s o l u t i o n was  belt found to  C H A P T E R  DESIGN  APPROACH  7  163  INTRODUCTION  A combined incorporating grader  the  size  Schmitt  and  c o l o u r g r a d e r was  t r i g g e r pulse with  d e s c r i b e d i n S e c t i o n 1.  Schmitt  trigger  manner s i m i l a r grader.  generated  output  A number o f c o m p a r a t o r s  limits  were u s e d  to generate  stored  i n a memory a l o n g w i t h  and  to  processed  the  in a  v o l t a g e of the c o l o u r  p r e s e t to the s i z e  a digital the  by  the c o l o u r  A voltage proportional  p u l s e w i d t h was to the d i v i d e r  designed  category  s i g n a l which  colour category  was  informa-  tion. Since gories  exist,  f o u r c o l o u r c a t e g o r i e s and  twenty combinations  of s i z e  five and  T h i s w o u l d r e q u i r e a minimum o f n i n e t e e n s h i f t memories. green all  decided that  t o m a t o e s and  sizes  gory,  I t was  and  of green  due  to the  low  size  colour  (4 s i z e s ) w o u l d be  a l l c o l o u r s o f below s m a l l tomatoes  w o u l d be  i n another.  This reduced  required  to t h i r t e e n , with  of those  tomatoes which r o l l e d  the  arise.  register percentage  below s m a l l tomatoes g e n e r a l l y tomatoes  cate-  of  encountered*  i n one  cate-  (3 c o l o u r s )  t h e number o f m e m o r i e s  fourteenth category o f f t h e end  comprised  o f the b e l t  - a l l  t o m a t o e s w h i c h were b e l o w s m a l l . Not  o n l y can used  the Schmitt  colour  g r a d e r be  timing  p u l s e s common t o b o t h  trigger pulse of  i n the s i z e / c o l o u r graders  grader, but  c a n be  the other  drawn f r o m  the  * P e r s o n a l c o m m u n i c a t i o n w i t h W e s t e r n G r e e n h o u s e Co-op. members  164  colour  grader. The components  colour grader,  t o be u s e d  will  i . e . l i n e a r IC's w i l l  signal  p r o c e s s i n g , and CMOS I C ' s w i l l  signal  processing.  match t h o s e  be u s e d be u s e d  of the  f o r analog for digital  165  THEORY  I t was diameter  and  Schmitt  approximation cally,  decided  trigger  f o r the  may  be  would  shown i n F i g u r e  threshold effect,  would a l l pass through  line  relationship  pulse width  curves  n e g l e c t i n g the  l i n e s w o u l d be  that a linear  the o r i g i n ,  and  the the  a f u n c t i o n of conveyor b e l t  represented  between  suffice  6.1.  as  an  Theoreti-  straight  lines  slopes of speed.  the  Any  one  by:  D  =  Kt  [7-1]  D  =  diameter  K  =  constant  t  =  pulse width  D  =  where (volts)  (sec)  or  An voltage start  (K)  of the  integrating output  Kdt  integrator circuit, and  Schmitt a t the  trigger  end  integrates a integrating  p u l s e , a t t = 0,  and  at  the  to  stop  o f the p u l s e would produce a u s e d as  a measure  constant  final  of,the  diameter. For a fixed  v o l t a g e may  and  which  i s t r i g g e r e d to begin  v o l t a g e w h i c h c o u l d be  tomato's  decided  [7-2]  be  chosen.  belt For  speed, a constant the present  t h a t a range o f o p e r a t i n g b e l t  t h a t the  v o l t a g e t o be  integrating  t e s t model i t s p e e d s was  i n t e g r a t e d , E , w o u l d be  was  desirable, directly  166  proportional  t o conveyor b e l t  speed.  conversion  was t h e r e f o r e n e c e s s a r y .  conversion  may be a c h i e v e d  constant over  height  a fixed  Frequency  by g e n e r a t i n g  and w i d t h and t h e n  sampling  A frequency  time.  to voltage  to voltage  a short pulse of  integrating  the pulses  Therefore,  n = E - e. A t i=l  E  [7-3]  1  where e^  = pulse  height  (volts)  At = p u l s e w i d t h ( s e c ) n  = number  Since height stant  of pulses  = f T = frequency  X sampling  time.  e^, and t h e w i d t h  At, of the pulse  a r e con-  then, E  =  n e. A t l  [7-4]  E  =  f e. A t T  [7-5]  or  Due t o power s u p p l y desired e^  value  limitations,  o f E i s 10 v - s e c .  t h e maximum  I f the pulse  height,  = 15v, t h e n , f  At T  =  The 5 ft/sec  2/3 conveyor b e l t  s p e e d was assumed n o t t o e x c e e d  (152 cm/sec) o r 120 Hz CLOCK A f r e q u e n c y ,  t h e maximum v a l u e A t  [7-6]  max  =  therefore  o f At i s  ISFT  [ 7  '  7 ]  167  The so  sampling  t h a t many p u l s e s  equation  [7-7]  (25  are  T,  should  integrated.  be  as  If T =  l o n g as 1 sec,  possible  then  becomes,  At  =  At  time,  5.56  ms  [7-8]  a slow conveyor b e l t  cm/sec) o r  20.Hz CLOCK A  speed, o f  frequency,  10  inch/sec  equation  [7-5]  becomes, E  =  20  X  E  =  1.67  15  and  a t 20  sampling  t i m e may  E can  s t o r e d f o r the  be  For integration with and  respect  120  Hz  be  20  3  X  1  T = 1 sec,  pulses  sampling  are  120  pulses  The  to a point, provided  that  period with  negligible  produces a l i n e a r  Substituting E f o r the  are  integrated.  s p e e d , E remains- c o n s t a n t .  constant  to time.  pulse,  10~  and  i n c r e a s e d up  i n t e g r a t i n g from zero  trigger  Hz  only  a given b e l t  o f the  X  v-sec.  Note t h a t the integrated  X 5.56  ramp  the  The  voltage  for K i n equation  length of  loss.  [7-2]  Schmitt  produces:  rP D  =  A  Edt  [7-9]  0 or D  =  A E p  D  =  v o l t a g e r e p r e s e n t i n g the the tomato  E  =  integrating voltage  [7-10]  where diameter  of  168  p  =  Schmitt t r i g g e r by t h e t o m a t o  A  =  constant.  If diameter  the l a r g e s t  of 4 inches  pulse width was c h o s e n  i s about  pulse width  produced  t o m a t o t o be e n c o u n t e r e d  (10 cm), t h e n a t 20 Hz b e l t p = 400 ms.  a s 12.5v, t h e r e f o r e ,  The maximum solving  has a speed, t h e  value of D  f o r A i n equation  [ 7 - 1 0 ] , we g e t , A Note t h a t or  =  19.  [7-11]  f o r t h e same d i a m e t e r ,  i f the b e l t  speed  = 60 Hz,  30 i n c h e s / s e c (76 c m / s e c ) , E  =  5.00  p  =  133 ms  A  =  19.  By  converting the b e l t  quency, t o a v o l t a g e ,  and i n t e g r a t i n g  length o f the Schmitt t r i g g e r to the Schmitt t r i g g e r  speed,  i . e . CLOCK A  fre-  the voltage f o r the  pulse, a voltage D proportion  pulse i s generated.  trigger  pulse i s a function  Chapter  6, t h e r e f o r e D i s p r o p o r t i o n a l  The S c h m i t t  o f tomato d i a m e t e r ,  a s shown i n  t o diameter.  169  ELECTRONIC S I Z E AND  COLOUR GRADER:  OVERVIEW  A size signals size  from  g r a d e r was d e s i g n e d  the c o l o u r grader  category  signals.  were c o m b i n e d w i t h one  signal  u s i n g some o f t h e  ( S e c t i o n 1) t o p r o d u c e  The s i z e  category  the colour category  f o r each o f t h e d i f f e r e n t  digital  signals  digital  signals  t o produce  size/colour  category  combinations. A block diagram o f t h e s i z e grader circled from  digital  processor  i s shown i n F i g u r e  inputs i n the diagram a r e s i g n a l s  the colour grader The  pulse generator  t h e CLOCK A s i g n a l ,  which  which allows t h e generated  over  a fixed  signal belt of  circuit  speed  every  cycle belt  t o be s t o r e d by t h e i n t e r -  begins  a t the output  SAMPLE i n p u t f r o m trigger  takes  place  1 s e c , a f t e r which the s t o r e d anew.  and a v o l t a g e , E, which  i s obtained  plement o f the Schmitt  t o be i n t e g r a t e d  ( B ) . The i n t e g r a t i o n  p e r i o d , about  i s monitored  The  is  pulses  i s updated and the i n t e g r a t i o n  speed  belt  time  (A i n F i g u r e  a l s o p r o d u c e s an INTEGRATE a n d a n UPDATE  of the integration  and s t o r a g e  directly  i s t h e measure o f conveyor  signal,  grator  obtained  h e i g h t and w i d t h  The c i r c u i t  the r e s u l t  7.1. [The  and timer c i r c u i t  speed.  and  and s i z e / c o l o u r  described i n Section 1].  7.1) p r o d u c e s a p u l s e o f u n i f o r m of  grader  i s a function  of (B).  the colour grader pulse  t h e measure o f t h e tomato d i a m e t e r .  Thus t h e  i s t h e com-  ( s e e F i g u r e 3.12) a n d The v o l t a g e , E , i s  /PEAK ( DETECTOR  I)  MS  ESf T INJ  COMP. (SAMPLE  COMP.S INTEGRATOR AND STORAGE.  PROCESSOR  (COLOUR A)  O—  PULSE  A  GENERATOR ANO  (COMP.  INPUTS  l)  ,  O  TIMER (LATCH  COM PA  INPUTS)  SEMI-KlPe.  RESET)  SJZE  SIZE/COLOUR  SHIFT  DECODER  REGISTER MEMORIES  i. Arts.a  INPUTS  /SEMI  S M A L L / F I R M  DECODING S A T E S  K.IPE  C K T R K LAUGr./sCMl-  O-  COMP.^O C O M A 61 COMP. 7 <  OUT  PROCESSOR  D/S/TAL  (CLOCK  OOT  RAMP GENERATOR AND STORAGE  C  ANALOG  4  IN)  LA&GC/FIRM  AMD TRIACS  RlPE.  R I P E .  ISICCHU^/FIP'I  LATCHING CIRCUIT  OPTOISOUAJORS  PIPE. mrB.  e x r * A l A W t / f l R M RIPE  . Ait  FIGURE  7. 1  SIZE  GRADER  SIXES/G&EEH  A N D SIZE/COLOUR  DIGITAL P R O C E S S O R  BLOCK  SOLENOICH IS  GRADER  DIAGRAM  ,  O  171  integrated final  f o r the duration  voltage  D i s obtained  tomato d i a m e t e r . generator  This  and s t o r a g e The  as  D, i s t h e n p r o c e s s e d  voltages  corresponding  by t h e c o m p a r a t o r c i r c u i t s  digital  s i g n a l i s decoded (F).  information  i s then combined w i t h  the size  one  Thirteen  "drop-off"  shift  t h e tomato g e t s  r e g i s t e r output,  to  colour grader,  data  in a shift  to i t s eject  (G)  register  t o store the station.  register  appears  i t i s used t o c o n t r o l a  pneumatic s o l e n o i d t o e j e c t t h e tomato. the  category  r e g i s t e r memories a r e u s e d a n d  When a s i g n a l s t o r e d i n a s h i f t the s h i f t  category.  category  a t t h e end o f t h e conveyor b e l t ,  until  signal  The c o l o u r  a single size/colour signal i s stored  information  at  (D), and t h e o u t -  (E) a n d s t o r e d  i n a latching circuit  (H).  D is  to size  form a 4 - b i t d i g i t a l  temporarily  memory  i n t h e same way  f r o m 0000 t o 1111 d e p e n d i n g on t h e s i z e The  and  i n t h e ramp  s i g n a l o f the colour grader.  puts o f t h e four comparators ranging  place  c i r c u i t (C).  compared t o f o u r p r e s e t limits  and t h e  which i s a f u n c t i o n of the  i n t e g r a t i o n takes  voltage,  the d i v i d e r output  category  o f t h e SAMPLE p u l s e ,  As was t h e c a s e f o r  o p t o - i s o l a t o r s and t r i a c s  i n t e r f a c e t h e low power d i g i t a l  (I) were  used  I C ' s t o t h e 115 v o l t  AC  solenoids. Rather than b u i l d more s o l e n o i d s ability  and o t h e r  a long  c o n v e y o r and p u r c h a s e t e n  h a r d w a r e , i t was d e c i d e d  o f the system t o b o t h s i z e  and c o l o u r grade  that the tomatoes  172  could with  be t e s t e d u s i n g the three  three  solenoids  t h e t h i r t e e n memory  o p t o - i s o l a t o r and t r i a c of the colour  s y s t e m c o u l d be u s e d a s w e l l . for  size  and c o l o u r  group would c o n t a i n  a l l other  and c o l o u r  only  three  conveyor  Tomatoes c o u l d  could  "drop-off"  size/colour categories.  be r e g r a d e d , b u t t h e s o l e n o i d s  be t e s t e d t h i s  This wired  A l l permutations of  way t h r o u g h t h e u s e o f  f i n a l prototype  size  and c o l o u r  mounted on a l o n g  conveyor system.  construction o f the f i n a l prototype  fulfill  t h e n be g r a d e d  and t h e  t h i r t e e n o p t o - i s o l a t o r s and t r i a c s ,  solenoids that  The same  solenoids. A  contain  and t h e  o t h e r s h i f t r e g i s t e r memories.  size  together  circuits  i n groups o f t h r e e ,  r e m a i n i n g group c o u l d to three  grader.  circuits  present  objectives.  grader  would  and t h i r t e e n I t was  believed  was n o t n e c e s s a r y t o  173  Pulse  G e n e r a t o r and Timer C i r c u i t s A  cuits  schematic o f the pulse  (Box  A, F i g u r e 7.1)  generator and timer  i s shown i n F i g u r e 7.2. A period  s a m p l i n g o f a b o u t one s e c o n d was c h o s e n  o v e r w h i c h t h e b e l t s p e e d w o u l d be m o n i t o r e d . the to  pulse  generator  120 Hz.  result large  A sampling p e r i o d  errors, since  ft/sec  increases  with  (A b e l t s p e e d o f l e s s  than  stored  integration  of the clock  letting and  T  then R  x  =  1.4 R-j^ C  =  0.1 y F  =  0.1 s e c  =  714 KQ  adjustment o f t h e p e r i o d .  *  generated  components  a n d C^. The  signal i s defined as: [7-12]  1  [7-13]  R^ was c h o s e n a s a 1 Meg  which m a i n t a i n s The  result.  s i g n a l o f 0.1 s e c p e r i o d w a s  NAND 1 a n d NAND 2 a n d t i m i n g  inputs,  incurring  o v e r s e v e r a l s e c o n d s w o u l d r e s u l t i n t o o much  T  tor,  could  (30 cm/sec) w o u l d p r o d u c e t h e same e r r o r s ) .  A clock  period  f r o m a b o u t 24  24 p u l s e s ,  the integration error  i n thepreviously  using  The i n p u t t o  o f l e s s t h a n one s e c o n d  number o f p u l s e s .  Integration drift  i s CLOCK A, w h i c h v a r i e s  i n an i n t e g r a t i o n o f l e s s t h a n  decreasing 1  cir-  R  i s an i n p u t  stability,  sampling  #1* i n F i g u r e  # refers to circled  clock 7.2.  potentiometer  t o allow  protection  and i s g e n e r a l l y  resis-  t w i c e R^.  i s g a t e d v i a one o f t h e NAND 1 The s a m p l i n g  points  c l o c k must b e  i n the figure.  174 FIGURE 7.2 PULSE GENERATOR AND TIMER CIRCUITS  N0R6)O—<J lo)  O  INTEGRATE SWITCH  TO UPPATE. SWITCH  TO  AWAiOS  INVERTER PRECEDING, WTEGRATOR  R > IOOK z<  175  synchronized with  t h e CLOCK A f r e q u e n c y  so t h a t  number o f p u l s e s a r e a l w a y s b e i n g i n t e g r a t e d . zation  i s ensured  through  o f NOR 1 a n d NOR 2.  t h e same The s y n c h r o n i -  t h e u s e o f t h e R/S l a t c h  The s a m p l i n g  clock operates  comprised  o n l y when  #1 i s HIGH. The  sampling  decade c o u n t e r  having  c l o c k output,  t e n decoded o u t p u t s .  o f t h e CD4017 i s n o r m a l l y  low, m a i n t a i n e d  CLOCK A a t i n p u t #3 o f t h e l a t c h . #4, g o e s HIGH f o r 100 ms a f t e r T = 800 ms. ms a f t e r  8 sampling  9 sampling  clock.  goes HIGH, t h u s  resetting  c l o c k does n o t s t a r t  a t i n p u t #3.  tion  signals.  o f t h e two c l o c k  circuit*  comprised  CLOCK A s i g n a l about  LOW.  t o zero.  stopping the  positive  i s a monostable  goes LOW, a s h o r t p o s i t i v e  NOR 3 a n d a p p e a r s  As s o o n a s  a t #6.  input  The s a m p l i n g  This assures  o f NAND 3 a n d NAND 4.  A t = 658 us i s p r o d u c e d  through output  pulse generator  low, thus  t h e next  CLOCK A p u l s e a p p e a r s  The  clock pulses, or  t h e CD4017 r e s e t  the counter  again u n t i l  output,  #5, g o e s HIGH f o r 100  #1 g o e s  A t t h e same t i m e ,  input  by t h e p r e s e n c e o f  c l o c k p u l s e s , o r T = 900 ms. output  a CD4017  The r e s e t  T h e "8" d e c o d e d  T h e "9" d e c o d e d o u t p u t ,  #5 goes HIGH, t h e l a t c h sampling  #2, i s f e d i n t o  going  synchroniza-  multivibrator  Every  time t h e  going pulse o f  This pulse i s inverted  a t t h e i n p u t t o NOR 4, #7.  The  o f NOR 4, #8, i s t h e complement o f #7 o n l y when #4 i s I f #4 i s HIGH, t h e n  * The component s e l e c t i o n  #8 i s a l w a y s LOW. of this  circuit  As p r e v i o u s l y  i sdescribed  later.  176  mentioned,  #4 i s LOW f o r 800 ms t h u s  the pulse generator at  (Box  The  of the integrator controlled  UPDATE t i m e r o u t p u t ,  through signal  appears  chosen, the  updating  #4 a n d w h i c h  LOW, t h e r e f o r e t h e NOR 5 a n d a g a i n  As s o o n as #4 goes HIGH, t h e i n v e r t e d t h e UPDATE t i m e  T h e 66 ms t i m e  and i s n o t c r i t i c a l .  integrator  thus  i n v e r t e d through  a t #11 goes LOW, t r i g g e r i n g  66 ms p u l s e a t #9.  circuit  o f NAND 5 a n d NAND 6.  #9, i s n o r m a l l y  first  NOR 6 a t #10.  and storage  by o u t p u t  t h e UPDATE t i m e r c o m p r i s e d  #4 s i g n a l  The p u l s e s  t o be i n t e g r a t e d .  B, F i g u r e 7.1) i s  triggers  a  t o a p p e a r a t #8 f o r 800 ms.  #8 a r e t h e p u l s e s Operation  allowing the pulses o f  The p u l s e  t o be t r a n s f e r r e d the storage  p e r i o d was allows  arbitrarily  the output o f  t o the storage  information.  t o produce  circuit,  The o u t p u t  o f NOR 6,  #10, h a s n o t c h a n g e d d u r i n g t h e 66 ms p e r i o d , s i n c e t h e f o r mer " 1 " , "0" c o n d i t i o n s a t i n p u t s #11 a n d #9 h a v e to  "O", " 1 " , r e s u l t i n g  still  b e i n g LOW.  Only  updated, i . e . a f t e r thus  resetting  reset  HIGH a p p e a r i n g  i n t h e i n t e g r a t o r p u l s e a t #10 after  the storage c i r c u i t  The s a m p l i n g  t o zero.  appearing  starts  again  a t #3.  The i n t e g r a t o r  c l o c k i s then  a t #5, a n d i s t h e n  signal  has been  t h e 66 ms h a s e l a p s e d , d o e s #10 go HIGH,  the integrator  f o r 34 ms.  reversed  restarted  stopped  remains  by a  by t h e CLOCK A  I n t e g r a t i o n o f t h e 658 y s p u l s e s  f o r a p e r i o d o f 800 ms.  177  Integrator  and S t o r a g e The  Figure  7.3.  grator,  and s t o r a g e  The e q u a t i o n  governing  comprised  where  referring  =  =  3  and  of the i n t e -  , C^, i s :  dt  ±  [7-14]  [7-5]j [ f e. A t T ] .  to maintain  [7-15]  s m a l l r e s i s t a n c e and c a p a c i -  c h o s e n a s 1W, a n d C  3  as 0.1  yF.  Now  =  - 10  [ f e. A t T] .  [7-16]  t o s t a y w i t h i n t h e o p e r a t i n g v o l t a g e r a n g e , f , e^,  divide  be d i v i d e d  A t by 10.  A t  max  At  max  reason,  by 10.  Therefore  I t was  equation  found  advantageous  [7-7] becomes:  IMOT  =  and s i n c e T = 800 ms  circuit  the output  shown i n  voltage  -  was  is  [7-15] becomes:  order  For t h i s  e  7.1)  3  output  =  A t , o r T must now to  C  3  E  E In  R  input voltage  order  values, R  equation  -  e^ =  E  tance  circuit  o f t h e 741 Op. Amp.  to equation  In  (Box B, F i g u r e  integrator  E  or  Circuit  t " 7  (integration  =  time),  [7-17]  n  d  C  2  w  e  r  ]  becomes  694 y s . a  1 7  [7-18] J  e  chosen i n the p u l s e  generator  t o p r o d u c e a p u l s e c l o s e t o 694 y s , w h i c h t u r n e d o u t  178 FIGURE  7.3  INTEGRATOR  AND  STORAGE  C I R C U I T  179  to  be A t = 658 y s , when s t a n d a r d  were u s e d .  (Refer t o F i g u r e 7.2). Resetting  through  o f the i n t e g r a t o r t o zero  t h e u s e o f a CD4066 b i l a t e r a l  the b i l a t e r a l undesirable suggested the  c a p a c i t o r s and r e s i s t o r s  switch operates  [7-16] .  i n t e g r a t o r were f i r s t  amplifier,  thus A  integrator  on a +15 v o l t  f o r the i n t e g r a t o r output  by e q u a t i o n  f o r zero  across  C^. S i n c e  supply,  i t was  t o go n e g a t i v e , a s  The p o s i t i v e  input pulses to  i n v e r t e d u s i n g a u n i t y g a i n 741  making e^ n e g a t i v e ,  standard  switch  i s accomplished  offset  circuit  drift.  and E p o s i t i v e . was u s e d t o a d j u s t t h e  The IN914 a t t h e i n t e g r a t o r o u t I  p u t was u s e d t o e n s u r e across  either  protection  o f t h e two b i l a t e r a l  v o l t a g e would  appear  R. i s a current 4  switches.  resistor. The  information follower. of  t h a t no n e g a t i v e  second b i l a t e r a l  to the high  s w i t c h c o n t r o l s t h e UPDATE  i m p e d e n c e i n p u t o f t h e LM302  The i n t e g r a t o r o u t p u t  t h e LM302 f o r t h e l a s t  allowing  i s connected  to the input  66 ms o f i n t e g r a t i o n  time,  t o c h a r g e t o t h e new i n t e g r a t o r o u t p u t  When t h e b i l a t e r a l  switch  i s reopened a f t e r  voltage  thus  voltage.  t h e 66 ms  dura-  12 tion,  the capacitor discharges  t h e LM302 and t h e 1 0 Very  little  p e r i o d which  charge  1 2  through  t h e 10  ft  input of  ft " o f f " r e s i s t a n c e o f t h e CD4066.  i s lost  over  follows i n i t i a l  t h e 800 ms  storage.  integration  The LM302  output  remains r e l a t i v e l y c o n s t a n t f o r a g i v e n c o n v e y o r b e l t s p e e d . The o u t p u t o f t h e LM302 was m e a s u r e d f o r s e v e r a l  180  conveyor  belt  calculated  speeds,  using equation  The  the  =  15  At  =  658  ys  T  =  800  ms.  theoretical  and  i n Table  7.1.  theoretical  [7-16] by  e. l  and  listed  and  values  were  letting  volts  experimental  values  are  181  TABLE 7.1  CLOCK A Freq. (Hz)  THEORETICAL AND MEASURED INTEGRATOR OUTPUT VOLTAGES AT VARIOUS CONVEYOR BELT SPEEDS.  Theoretical E (volts)  Measured E (volts)  30  2.4  2.3  40  3.2  3.1  50  3.9  4.0  60  4.7  4.8  70  5.5  5.5  120  9.5.  x  9.2  182  Ramp G e n e r a t o r  and S t o r a g e  A schematic circuit  Circuit  o f t h e ramp g e n e r a t o r  i s shown i n F i g u r e 7.4.  integrator  (Box C, F i g u r e  as s u g g e s t e d  and s t o r a g e  The ramp g e n e r a t o r  by e q u a t i o n  7.1)  i s an  [7-9]:  •P D  =  A  [7-9]  Edt .0  The  equation  f o r the i n t e g r a t o r i s :  D  Therefore  =  -  i n [7-9],  R  A  and  C  5  =  E  e  R  =  ±  dt  [7-19]  5  5  C  5  - e.. x  From  [7-11]  A  =  19  =  0.05  =  0.05 uF  =  0.047 y F .  /  Therefore Letting  R  5  A suitable  value As  i n p u t was  C  o r  forC  5  i n the case first  order to maintain prevent  5  [7-20]  R<- = 1 Mft then  the  C  f o r the i n t e g r a t o r  inverted with  a positive  a negative voltage  bilateral  switch.  against negative  a unit  g a i n 741 Op Amp, i n  ramp g e n e r a t o r  from  appearing  The IN914 a l s o  ( F i g u r e 7.3),  output,  and t o  a c r o s s t h e CD4066  a c t s as a p r o t e c t i o n  v o l t a g e s a t t h e ramp g e n e r a t o r  output.  183 FIGURE  7.4  RAMP  G E N E R A T O R  A N D  S T O R A G E  SAMPLE INPUT  +SSv  INPUT  , '  CIRCUIT  184  The (Figure  SAMPLE s i g n a l f r o m t h e c o l o u r  3.12) i s t h e m e a s u r e o f t h e t o m a t o d i a m e t e r .  controls  t h e two b i l a t e r a l  switches,  tomato i s under t h e s e n s i n g therefore SW2  SW1  i s open  i s closed.  voltage,  sorter  and SW2.  While a  h e a d , t h e SAMPLE i s HIGH, and  (due t o t h e NAND g a t e i n v e r t e r ) a n d  The ramp g e n e r a t o r  E, f o r the d u r a t i o n  same t i m e c h a r g e s  SW1  It  integrates  the incoming  o f t h e SAMPLE p u l s e ,  t o t h e ramp g e n e r a t o r  When t h e SAMPLE s i g n a l goes LOW,  t h u s r e s e t t i n g t h e ramp g e n e r a t o r .  the  ramp g e n e r a t o r  i s separated  output  SW1 d i s c h a r g e s  Cg,  and a t t h e voltage.  capacitor  A t t h e same t i m e  from C  c  a s SW2  i s opened,  D  l e a v i n g Cg c h a r g e d . by  t h e PEAK DETECTOR 1 RESET p u l s e  and  i s therefore  plus 210  The b i l a t e r a l  LOW  switch,  SW3,  from t h e c o l o u r  f o r the d u r a t i o n  the stored  comparator c i r c u i t s until  the next  voltage  grader,  o f t h e SAMPLE s i g n a l  t h e 210 y s WRITE s i g n a l f r o m t h e c o l o u r ys a l l o w s  i s controlled  grader.  t o b e compared  a f t e r w h i c h C^ i s d i s c h a r g e d  tomato a r r i v e s under t h e s e n s i n g  The  i n the t o ground head.  185  Comparator  4, 5, 6, a n d 7 (Box D, F i g u r e 7.1) The  size  the c o l o u r grader  grader  comparator  comparator  circuit  circuit,  except  comparator has been added t o i n c l u d e f i v e of only four. cuit  The s c h e m a t i c  i s shown i n F i g u r e 7.5.  numbered  from  comparator  circuits  colour grader,  adjusted  of the colour  function  (3.8 c m ) .  (3.8 cm) d i a m e t e r  output  o f COMP. 4 r e m a i n s  greater be  from  size  the outputs categories  V _, 0  m  t o be c o n s i d e r e d , i n  HIGH, a s n o r m a l ,  less  an o u t p u t output  t h a n 1.5  thus  inhibiting Tomatoes o f  a t COMP. 4, a n d d a t a may  t h e memories a c c o r d i n g t o t h e c o n d i t i o n s a t  7.2.  states  The p o t e n t i o m e t e r s  t o allow ready  access  i n the colour sorter, clamping compatible  diode with  The s i z e  o f t h e f o u r comparators a r e  a r e mounted o n t h e f r o n t  As  tor's  ^ internally  T  under t h e s e n s i n g head, t h e  a LOW o u t p u t  and t h e o u t p u t  colour grader  and  E  o f COMP. 5, COMP. 6, a n d COMP. 7.  l i s t e d i n Table and  g  t o COMP. 1 o f  e n t e r i n g any o f t h e m e m o r i e s .  produce  entered into  the three  grader.  When a t o m a t o  passes  cir-  have been  o f COMP. 4 i s a n a l a g o u s  inches  information  categories instead  them f r o m  i n t h a t COMP. 4 h a s V  inches  an e x t r a  o f t h e comparator  f o r t h e s m a l l e s t tomato s i z e  t h i s c a s e . 1.5  that  The c o m p a r a t o r s  4 to 7 to distinguish  The the  diagram  i s similar to  for V „ 0  m  _, V_,_  m  p a n e l o f t h e s i z e and and adjustment. input protection  a r e used  diodes  t o keep t h e compara-  t h e CMOS d e v i c e s .  186 FIGURE  7.5  C O M P A R A T O R  CIRCUIT.,  187  TABLE 7.2  Size Category  OUTPUT STATES OF COMP. 4, COMP. 5, COMP. 6, and COMP. 7 FOR FIVE SIZE CATEGORIES.  COMP. 4  COMP. 5  COMP., 6  CULL  1  0  0  0  SMALL  0  0  0  0  MEDIUM  0  1  0  0  LARGE  0  1  1  0  EXTRA LARGE  0  1  1  1  COMP  188  Since a l l green one  location,  the output  alone i n combination information decided  o f COMP. 1 o f t h e c o l o u r g r a d e r  w i t h t h e WRITE p u l s e a c t e d as t h e i n p u t  f o r t h e GREEN s h i f t  that  diameter,  t o m a t o e s were t o be e j e c t e d a t  a l l tomatoes  less  register than  memory.  1.5 i n c h e s  size/colour  o f f t h e end o f t h e conveyor b e l t grader design.  T a b l e 7.3.  remaining  o f COMP. 4  i n the  T h i s l e a v e s COMP. 2, COMP. 3,  COMP. 5, COMP. 6, a n d COMP. 7 t o p r o d u c e o u t p u t the twelve  (3.8 cm)  r e p r e s e n t e d by no c h a n g e i n t h e o u t p u t  would r o l l  I t was  colour categories,  states f o r  a s shown i n  189  TABLE 7.3  OUTPUT STATES OF COMPARATORS 2,3,5,6,7 FOR TWELVE SIZE/COLOUR CATEGORIES.  CATEGORY Size Colour  COMP.2  OUTPUT STATES COMP.5 COMP.3 COMP.6  COMP.7  Turning  Small  0  0  0  0  0  Turning  Medium  0  0  1  0  0  Turning  Large  0  0  1  1  0  Turning  Extra  0  0  1  1  1  Large  Semi  Ripe Small  1  0  0  0  0  Semi  R i p e Medium  1  0  1  0  0  Semi  Ripe Large  1  0  1  1  0  Semi  Ripe E x t r a  1  0  1  1  1  Firm  Ripe Small  1  1  0  0  0  Firm  R i p e Medium  1  1  1  0  0  Firm  R i p e -Large  1  1  1  1  0  Firm  Ripe E x t r a  1  1  1  1  1  Large  Large  190  Decoding Gates  (Box E , F i g u r e 7.1)  A schematic Figure is  7.6.  similar  that  The f u n c t i o n  output  fora specific  main d i f f e r e n c e decoding  gates  and d e s i g n o f t h e decoding  gates  and is  combination  gates i n  o f c o m p a r a t o r o u t p u t s . The  between t h e c o l o u r g r a d e r and s i z e i s that  the l a t t e r  T h e 3 - i n p u t NOR g a t e  i n order t o minimize  uses  grader  3 - i n p u t NOR g a t e s , o f t h e two i n p u t  I C , a CD4025, c o n t a i n s 3 g a t e s  package count,  t h e i n v e r t e r NOR 5  a 3 - i n p u t g a t e , a n d NOR 6 a c t s a s a 2 - i n p u t g a t e ,  two o f t h e i n p u t s t i e d The grader,  with  together.  WRITE i n p u t p u l s e i s o b t a i n e d f r o m  inverted  gates  i s LOW f o r t h e d u r a t i o n o f t h e WRITE  NOR 1, NOR 2, NOR 3, a n d NOR 4, i n s t e a d gates.  i s shown i n  t othat o f the c o l o u r grader decoding  a single  pulse  o f the decoding  through  NOR 5 a n d g a t e d  w h e n e v e r t h e o u t p u t o f COMP. 4 i s LOW.  through  the colour NOR 6  This enables t h e  o u t p u t s o f NOR 1, NOR 2, NOR 3 a n d NOR 4 t o b e t r a n s f e r r e d to the outputs  o f NAND 1, NAND 2, NAND 3, a n d NAND 4.  191 FIGURE 7.6  DECODING GATES  IMPUTS  IL WKITE  1  —  l.SK  N0R6)  o-VvV  O-AA/VCOMP.S  NOR l  l.SK NORZ  COMP- 6  l.SK  CM/vV COMP. 7  N0R.3 LARGE.  192  Latching  Circuit  (Box F , F i g u r e 7.1)  A schematic Figure is  7.7. The d e s i g n a n d f u n c t i o n  similar  t o the colour grader  differences instead  are that  of  of this  latching  t h e new c i r c u i t  o f 2 - i n p u t NAND g a t e s  uses  latching  circuit  The main  4 - i n p u t NAND  gates  h a v e b e e n r e p l a c e d by a  output  the colour grader  NAND 1 goes LOW the output  a r e f e d i n t o NAND 1.  (indicating of the latch  a green  comprised  directly  The  latch  into  t h e green  i s reset,  category  a s a r e t h e CD40 44  RESET p u l s e o b t a i n e d f r o m  both  I f the output  appears,  tomato).  NAND 2, a n d NAND 3, t o a HIGH s t a t e . fed  latches.  o f COMP. 1 a n d t h e WRITE i n p u t ,  COMP. 1 i s HIGH a n d a WRITE s i g n a l  sets  i s shown i n  circuit.  I C , a CD4044 w h i c h c o n t a i n s 4 s u c h The  from  circuit  o f 3 - i n p u t NAND g a t e s , a n d t h e l a t c h e s w h i c h were  comprised single  o f the latching  the output o f The LOW  signal  o f 2 - i n p u t NAND g a t e s , The l a t c h  shift  output i s  register  memory.  l a t c h e s by t h e LATCH  the colour grader.  193 FIGURE  7.7  LATCHING  CIRCUIT  OUTPUTS TO DECODER  INPUTS  IS V4CD4044 SMALL  IS  —o  V2JZD40IZ.  SMALL  TT IS  MEDIUM  —o  MEO/UM  TT LAR&E.  to  '/ZCD+OIZ  LARGE.  '/4C04044  IS  SXTRA LAK<S£  VZCD4-0/Z  EXTRA LARGE.  IT. LATCH  COMP.  RESET  I IN  o WRITE IN  SL SRCLS.AI OUTPUT TO MEMORY  194  Size/Colour  Decoder  The gates  used  s i z e / c o l o u r decoder  t o decode t h e c o l o u r  comparator outputs particular The  g r a d e r and s i z e  i n t o a s i n g l e output  size  grader  corresponding to a i n Table  7.3.  i s shown i n  gates w i l l  and c o l o u r  be p r e s e n t  input  inputs  signals are  one s i z e  a t the decoder  o n l y one o f t h e o u t p u t s  go HIGH. The  category  F o r any s i n g l e t o m a t o , o n l y  signal will  Consequently,  to  i s a series of  7.8.  signals.  colour  circuit  o f the s i z e / c o l o u r decoder  Both LOW  7.1)  s i z e / c o l o u r c a t e g o r y , as d e s c r i b e d  schematic  Figure  (Box G, F i g u r e  a n d one  inputs.  o f the twelve  NOR  ^ t o t h e 2 - i n p u t NOR  the outputs o f the s i z e  gates  are connected  grader  latching  circuits,  Figure  7.7, a n d t h e c o l o u r g r a d e r  latching  circuit,  Figure  3.16.  The t w e l v e  the inputs o f the s h i f t  outputs register  are connected memories.  directly to  195 FIGURE  7.8  SIZE/COLOUR  DECODER  INPUTS SIZE  COLOUR  SMALL  Q_ TURNING  CIRCUIT  OUTPUTS SIZE/COLOUR. SMALL/TURNING  MEDIUM  MEDIUM/TURNING  LARGE  LARGE./* TURN/MS  EXTRA LARGE  X L /  TURNING  -O SMALL/ SEA4IRlPZ  = 3 > ; = L >  SEMIRIPE  -O  MEDIUM/SEMIRIPE.  -O  LARGC/SEMIK/PE  -O XL/S£Af/RIPE  -O FIRM RIPE  SMfiLL/FIRM RIPE  -O  MEDIUM/FIRM RIPE  -O  LARGE/FIRM RIPE.  -O  XL/FIRM «IP£  196  Memory C i r c u i t The similar  (Box H, F i g u r e design  to that  o f t h e s i z e / c o l o u r memory c i r c u i t i s  of the colour  each s i z e / c o l o u r category (no.  from the sensing  g r a d e r memory c i r c u i t  shift  of b i t s ) corresponding  size/colour  7.1)  register i s of a  to a lineal  category  i s located.  downstream  The f u n c t i o n o f e a c h  i s t h e same a s f o r t h e c o l o u r  category  information  s t a t i o n , a t which  electromechanical  grader  —  shift  to store  f o r a tomato as t h e tomato t r a v e l s  downstream from t h e s e n s i n g  veyor  length  h e a d where t h e e j e c t s t a t i o n f o r t h a t  register  eject  distance  i n that  time  device  head, u n t i l the stored  i t reaches i t s s i g n a l t r i g g e r s an  t o e j e c t t h e tomato from t h e c o n -  belt. The  main d i f f e r e n c e between t h e c o l o u r  grader  memory and t h e s i z e / c o l o u r memory i s i n t h e t y p e o f s h i f t register  used.  The s h i f t  were o f t h e d u a l storage  4 - b i t type  capability  during  the design  at  a length  g r a d e r was b e i n g  o f the s i z e / c o l o u r grader available.  f r o m 1 t o 64 b i t s ,  t h e s i x programmable  were i n c o r p o r a t e d their  a maximum  designed,  r e g i s t e r s were n o t a v a i l a b l e .  became c o m m e r c i a l l y for  (CD4015) h a v i n g  versatility.  grader 8 bit  per IC.  When t h e c o l o u r grammable s h i f t  r e g i s t e r s used i n the c o l o u r  inputs.  pro-  However,  t h e MC14557  The MC14557 c a n b e programmed d e p e n d i n g on t h e c o n d i t i o n s T h e s e new s h i f t  registers  i n t o the s i z e / c o l o u r grader because o f  197  The s i x p r o g r a m m a b l e shift  register  rocker  l e n g t h , were  switches.  bank o f s e v e n  The r o c k e r  switches  inputs which c o n t r o l the  connected switch  14 p i n IC s o c k e t , m a k i n g  design.  The s c h e m a t i c  circuits  used  7.9.  programmable these  ideal  f o r the present shift  i n t h e s i z e / c o l o u r memory c i r c u i t up" r e s i s t o r s  making t h e i n p u t  HIGH u n l e s s  i s shown i n  a r e used  a rocker  switch  between  inputs i s  7.4.  N o t e t h a t t h e DATA i n p u t i s a p o s i t i v e of the negative  colour grader.  be LOW  i n order  going  pulse  The o u t p u t s  to activate  a Q output,  same s t a t e a s t h e d e s i r e d o u t p u t  has  two o u t p u t s ,  size/colour gorized, output  LOW.  This allows  HIGH o r n o r m a l l y  decoder outputs  —  LOW  pulse  must  The CD4015  t h e i n p u t t o t h e memory must  a Q a n d a Q.  be o f  The MC14557  a choice of  output.  Since the  go HIGH when a t o m a t o i s c a t e -  t h e HIGH may be s t o r e d i n t h e MC14557 and t h e Q  u s e d t o f e e d a LOW  circuit.  registers  the opto-isolators.  the  going  i n the. CD4015 o f  of the s h i f t  only  a normally  thus  used  has  either  i s closed,  the length of the s h i f t  and t h e c o n d i t i o n o f t h e programmable  shown i n T a b l e  the  at the  LOW.  The r e l a t i o n s h i p  instead  register  i n p u t s , L I , L2, L4, L8, L16, and L32, t o keep  inputs normally  register  .i t  into a  f o r one o f t h e t h i r t e e n  S i x 1 Mft " p u l l  SPST  assembly c o n s i s t e d o f a  w h i c h c o u l d be p l u g g e d  standard  Figure  to s i xminiature  signal  to theopto-isolator  198 FIGURE  7.9  O N E IN  OF  THE  13  SHIFT  REGISTER  SIZE/COLOUR  +/5V  CLOCK  0  IN  CIRCUITS  MEMORY  CIRCUIT  USED  199  TABLE 7.4  INPUT L8 L4  SHIFT REGISTER LENGTH AND INPUT CONDITIONS AT THE SIX PROGRAMMABLE INPUTS.  SHIFT REGISTER LENGTH  L32  L16  0  0  0  0  0  0  1  Bit  0  0  0  0  0  1  2  Bits  0  0  0  0  1  0  3  Bits  0  0  0  0  1  1  4  Bits  0  0  0  1  0  0  5  Bits  L2  LI  •  1  0  0  0  0  0  33  Bits  1  0  0  0  0  1  34  Bits  •  •  •  •  • •  •  1  1  1  1  1  0  63  Bits  1  1  1  1  1  1  64  Bits  200  The registers,  CLOCK B s i g n a l i s u s e d t o a d v a n c e t h e s h i f t  a s was t h e c a s e  CLOCK B s i g n a l i s o b t a i n e d latch  timer  circuit,  The  Q outputs  pins  7.10.  a 64 b i t s t o r a g e  distance station  For simplicity shift  c a n be l o c a t e d i s 8 f e e t  t h e CLOCK, DATA  register.  A l l other  a s shown i n F i g u r e 7.9. (3.8 cm) o f  head t h a t a e j e c t  (244 c m ) .  With  6 inches  I f greater  may be c a s c a d e d  to obtain  can store data  sensing  up t o 16 f e e t  DATA i n p u t s  shift  length  i s connected  Two s h i f t  t o the  registersi n  (488 cm) d o w n s t r e a m  o f the f i r s t  connected t o the outputs  from  12 s h i f t r e g i s t e r s  o f the s i z e / c o l o u r decoder  The t h i r t e e n t h s h i f t  register  stores  s i z e s o f g r e e n t o m a t o e s , a n d i t s DATA i n p u t  directly  between  head.  The  circuit.  the s h i f t  of the f i r s t  DATA i n p u t o f t h e s e c o n d a n d s o o n . series  spacing  l o c a t i o n s i s d e s i r e d , any number o f MC14557  r e q u i r e d , where t h e o u t p u t  t o output  NAND 3, F i g u r e are  data  movement p e r CLOCK B c y c l e , t h e maximum  downstream from t h e s e n s i n g  registers  all  only  c a p a c i t y a n d 1.5 i n c h e s  t h e 13 s t a t i o n s r e q u i r e d .  eject  are  grader  cm) b e t w e e n e j e c t s t a t i o n s , i t i s p o s s i b l e t o accommo-  date  the  The  F i g u r e 3.17.  a r e shown f o r e a c h  conveyor b e l t  (15  from t h e c o l o u r  o f e a c h MC14557 a r e c o n n e c t e d  With  grader.  s c h e m a t i c o f t h e c o m p l e t e memory c i r c u i t i s  shown i n F i g u r e and  i n the colour  connected  of the latch  7.7.  the data f o r i s connected  c o m p r i s e d o f NAND 2 a n d  A l l Q t o the output o f t h e r e g i s t e r s  t o the opto-isolator c i r c u i t .  FIGURE  7.10  S I Z E / C O L O U R  M E M O R Y  INPUTS SIZE  J  OUTPUTS OPTO-ISOLATOR COLOUR  MCI45S7 -I DATA  CLOCK  SMALL/TURNING  MCI4S57  -2  DATA  Q" CLOCK  MEDIUM/TURNING  MC/4SS7  -3  DATA LARGE]'TURNING  <? CLOCK  -4  MCI+SS7  DATA XL j TURNING)  Q C/.OCK  MCI4S57  -  //  DATA LARGE/FIRM RIPE  Q CLOCK  1 MC14-557-  IZ  DATA  X L / FIRM RIPE  Q CLOCK  MC 14-557-  13  DATA ALL (FROM  SIZES/'GREEN LATCHING  CIRCUIT)  o CLOCK  B  CIRCUIT';  IN  Q CLOCK  z z n —  TO S  202  Opto-Isolator The the  opto-isolator  size/colour  grader. three  g r a d e r was  The s i z e / c o l o u r  a t a time.  circuit of  and T r i a c C i r c u i t  13 r a t h e r  isolator  and t r i a c  i s the c u r r e n t  volt  unregulated  unit  (Figure  3.20)  the current  unit,  i s 32 ma  capable o f supplying supply  shown The  volt  through  solenoids  a 470ft  416 ma  requirement  used  115v AC power c o n s u m p t i o n  unit  a n d t h e +15 drain per  resistor.  circuitry.  The  In each  f r o m t h e +15v  due t o t h e 1.5  Kft r e s i s t o r i n  The u n r e g u l a t e d  3.22, w o u l d be  g r a d e r u n i t w o u l d be a b o u t  consist  f o r t h e 13 u n i t s ,  s u p p l y must be  The t r i a c  power  adequate.  i n the c o l o u r  16.7 w a t t s e a c h , a n d i f t h e same s o l e n o i d s the  triac  from each o f the  IC s u p p l y ,  a minimum o f 130 ma.  i n Figure  tested  3.20.  by t h e o t h e r  circuit.  colour  of the opto-  i n each u n i t  i s 10 ma,  phototransistor  comprised  to supply  demanded  supply  and  The maximum c u r r e n t  t h e maximum c u r r e n t  unregulated  were t h e r e f o r e  i n t h e d e s i g n o f t h e 13  t h e +15  supply.  used t o t e s t  p r o t o t y p e would  i n Figure  drain  s u p p l y must be a b l e  plus  the  —  7.1)  i n the  opto-isolator  size/colour  prime concern  two power s u p p l i e s  IC  categories  shown  circuit  t h e same one u s e d  than the 3 u n i t s  Of circuit  and t r i a c  The p r o p o s e d  f o r the f i n a l  (Box 1, F i g u r e  grader were  f o r the e n t i r e  2 30 w a t t s maximum.  consumed  employed,  size/colour  203  MECHANICAL  The was i d e n t i c a l solenoids, Recommended section.  size/colour to that  pneumatic  used  HANDLING  SYSTEM  grader mechanical h a n d l i n g system i n the colour grader.  s u p p l y and c o n v e y o r were  improvements w i l l  be d i s c u s s e d  The same  used.  in a  later  H A  P  SYSTEM  T  E  R  TESTING  8  205  INTRODUCTION  Testing around  the  t e s t s had  Chapter  4.  of  evaluated  the  the by  category size  s e c t i o n of  V  f o r s i z e and  controls  grader  of  i n a given  included.  impossible, relatively  since with  Consequently,  large,  large, The  the  the  g r a d e r was  with  the  categories The was  Both o v e r s i z e  and  over-  to  e j e c t mechanisms were  t o m a t o e s was  virtually  conveyor b e l t system, stay only  on the  the  the  flat  extra  categories.  tomato c o l o u r  equal  in  t o m a t o e s w h i c h were  tomatoes would not  investigated but  colour  l a r g e g r o u p , where no  present  medium s i z e  of d i f f e r e n t c o l o u r  colour  t e s t s were c o n d u c t e d on  e f f e c t of  outlined  M i s c l a s s i f i c a t i o n s due  small  spherical small  belt.  by  of  as  since  i n the m i s c l a s s i f i e d  extra  exists.  Testing  and  grader,  comparators.  s i z e category.  i n a l l except the  concentrated  tomatoes a c c u r a t e l y  number o f  tomatoes were i n c l u d e d  classification  the  to c l a s s i f y  mechanical problems a s s o c i a t e d not  the  been conducted e a r l i e r ,  examining the  misclassified undersize  s i z e / c o l o u r g r a d e r was  L i m i t s were s e t  adjusting  ability  the  s i z e category  grading  by  of  on  the  s i z e measured  to e s t a b l i s h whether s i z e w o u l d be  size  tomatoes  graded  differently. The ripe  and  colour  turning.  the  time of  the  tests.  categories  The  t e s t i n g was  t e s t e d were f i r m r i p e , s e m i -  number o f too  small  green tomatoes a v a i l a b l e t o be  included  i n any  of  at  206  MATERIALS AND  The  tomatoes used  grader v a r i e d i n size colour  from t u r n i n g  The  i n t e s t i n g the  firm ripe.  e f f o r t was center  of  generally  made t o p l a c e the  deliberatly  sensing  offset  the  either.  DIA.  parallel  t o the Tests  belt tor  speed, or settings, V  40 E  Hz T  1 #  CLOCK A V  g  a relatively  uniform  three  categories,  colour  would r e s u l t .  with  the  t o m a t o e s were  not  i n the  The  E  T  2  a t 20  and  numerical  V  S  E  green/turning  DIA.  inches/sec  T  split  firm ripe,  differences  turning/semi-ripe  semi-ripe/firm  split  ripe split  was  was  3  The  was  E  T  S E T  3  compara-  were c h o s e n so samples  semi-ripe  at V" g  roughly  cm/sec)  colour  of the  split  at V  1  (51  and  at V „ 0  bhi  the  large,  line.  frequency.  ,  equatorial  unusually  t o m a t o e s were o r i e n t e d w i t h  were c o n d u c t e d  S  in line  2 were c o n s i d e r e d  center  this  No p a r t i c u l a r  e x c e p t where t h e  conveyor b e l t  manually.  down, s i n c e  most s t a b l e .  Orientation  b e t w e e n DIA.  which case the  end  head, however, the  neglected,  in  calyx  in  feeding  c a r r i e d out  tomatoes e x a c t l y  planewas g e n e r a l l y 1 and  l a r g e , and  S i n g u l a t i o n and  c o n v e y o r b e l t was  t o m a t o e s were u s u a l l y p l a c e d  o r i e n t a t i o n was  size/colour  f r o m medium t o e x t r a  to  o f tomatoes onto the  METHODS  2  =  4.8  =  9.3  in  that the  turning m  1  , =  1  volt;  JL  volts; volts.  the  207  Size was  classification  b a s e d on t h e f o l l o w i n g  DIA. 1 r a n g e s ; large  2.250 i n (5.72 cm) < l a r g e  < 3.000 i n (7.62 cm)  The SET  i n A p p e n d i x A,  3.000 i n (7.62 cm) < e x t r a  1.875  V  as o u t l i n e d  4' S E T  i n (4.76 cm) < medium  size  comparator  5' S E T  V  V  6'  a  n  d  V  _< 2.250 i n (5.72 cm)  s e t t i n g s were made  SET  V.  T  h  e  P  r  o  c  e  d  u  r  e  using f  o  r  a d j u s t m e n t was a s f o l l o w s : a)  A tomato w i t h a  b)  size  DIA. 1 = 3.00 i n (7.62 cm) was c h o s e n a s standard.  _ was a d j u s t e d consistently  c)  V __ 0  was d e c r e a s e d /  V „ 0  t o m a t o was  i n the large  category.  until  the standard  t o m a t o was c o n -  classified  i n the extra  large  enough s o t h a t  the  _ was i n c r e a s e d  m  the standard  classified  far, l  sistently d)  so t h a t  just  category. standard  SET / t o m a t o was a g a i n  consistently classified  S t e p s a) t h r o u g h d) were r e p e a t e d tomatoes  (5.72 cm) t o m a t o was u s e d t o a d j u s t  S  E  T  small  V , o c  t o m a t o e s were n o t i n c l u d e d  ^ was a d j u s t e d  arbitrarily,  Once t h e c o m p a r a t o r v o l t a g e s  below V  g  size/colour categories  circuit  inputs,  Figure  at  E  were s e t ,  a time.  m  c  .  i n the T  ,.. the  t o m a t o e s , 193 i n a l l , were g r a d e d b y t h e s i z e / c o l o u r three  A  V „ „ _ ,, a n d faJiJ. b  (4.76 cm) t o m a t o was u s e d t o a d j u s t  Since V  standard  c  1.875 i n c h  tests,  different  f o r each o f t h e V „ _ adjustments r e m a i n i n g .  2.250 i n c h a  using  as l a r g e .  grader  The o p t o - i s o l a t o r  3.20, were c o n n e c t e d  to three  outputs  208 of the  s i z e / c o l o u r memory, F i g u r e  placed  s e q u e n t i a l l y on  the  tomatoes which b e l o n g e d  and  conveyor b e l t .  to the  u n d e r t e s t were e j e c t e d by size/colour  7.10,  three  the  a l l tomatoes Only  size/colour categories  pneumatic system;  c a t e g o r i e s were c o l l e c t e d  at the  c o n v e y o r . The  s o r t e d t o m a t o e s were s e p a r a t e d  mainder.  three  to  three  and  the  The other  s i z e / c o l o u r category  (except,  the  o f a tomato a f f e c t s on  graded i n t o  the  pared  using  and  from the  of  re-  connected  the  memory,  of  the  those  conveyor  been t e s t e d  green c a t e g o r i e s ) . whether the  i t s size.  category  was  carried  means i n e a c h s i z e  An  category  analysis  been  out.  colour  machine The  were com-  F-test. nine  three  machine g r a d e d three  size  s i z e / c o l o u r c a t e g o r i e s were  categories —  extra large,  medium. Each s i z e  ripe,  the  regrading  made t o e s t a b l i s h  same s i z e  colour category  grouped i n t o  of  c o l o u r c a t e g o r i e s w h i c h had  three  The  end  t h e measurement o f  three  an  at the  s m a l l and  a t t e m p t was  of variance  end  by  s i z e / c o l o u r c a t e g o r i e s had  of course, An  large,  outputs  above t e s t i n g p r o c e d u r e c o n t i n u e d  a l l of the  a l l other  o p t o - i s o l a t o r i n p u t s were t h e n  t o m a t o e s w h i c h were c o l l e c t e d until  those  semi-ripe,  categories, t o m a t o e s was  the  and  category  contained  t u r n i n g tomatoes.  number  recorded.  tomatoes which f e l l  now  outside  the  size  of  In each o f the  (or p e r c e n t a g e ) o f Misclassified  a mixture  firm size  misclassified  t o m a t o e s were a l l category  boundaries  209  stated the  previously.  tomato i n  l a r g e c a t e g o r y w o u l d be any t o m a t o h a v i n g ' a DIA. 1  greater than  than  or equal  category  3.000 i n c h e s  (7.62 cm) o r h a v i n g  t o 2.250 i n c h e s  h a s no u p p e r l i m i t ,  classified of  F o r example, a m i s c l a s s i f i e d  (5.72 cm). and thus  as o v e r s i z e i n t h i s  the m i s c l a s s i f i e d  group.  a DIA. 1 l e s s  The e x t r a l a r g e  no t o m a t o e s c a n b e The s t a n d a r d d e v i a t i o n  tomatoes around a g i v e n s i z e  cut-off  limit  was u s e d  ability  to accurately size  category  as t h e measure o f t h e machine's grade  tomatoes.  210  RESULTS AND  A.  T h e o r e t i c a l Size Category Experimental Limits The  (Figure  7.3)  for a belt  f o r the Schmitt  D which  Limits  voltage generated speed  (51 c m / s e c ) , i s E = 3.1 v o l t s E  DISCUSSION  by t h e i n t e g r a t o r  (Table 7.1).  t r i g g e r pulse width  be p r e d i c t e d f o r any d i a m e t e r  and  a theoretical Recall  where  produces  D  =  A  =  p Substituting 20 i n / s e c  R  diameters,  =  =  5  C  Schmitt t r i g g e r given diameter,  pulse width f o r a i n seconds. and E = 3.1 a t  speed, i n t o  [7-10]  yields  3.30 d  [8-1]  i n inches.  the c r i t i c a l  v a l u e s o f D,  i n Table The  than  = 0.047,  5  c a t e g o r i e s were c a l c u l a t e d  listed  7.4)  5  [8-1], the t h e o r e t i c a l  including  experimental  speed,  calculated.  (Figure  1  where d = 20p = d i a m e t e r Using  at a given b e l t  width  [7-10]  (51 cm/sec) b e l t D  The p u l s e  A E p  = 1 Mft, C  5  the v o l t a g e  that,  R  less  Integration of  i s t h e measure o f tomato d i a m e t e r .  value of D  circuit  o f 40 Hz o r 20 i n / s e c  may  are  versus  voltages f o r various  cut-offs  and a r e l i s t e d i.e. V  S  E  T  5  , V  g  separating i n Table  E  T  g  ,  and V  size  8.1. The g  E  T  ?  8.1.  experimental  the t h e o r e t i c a l  v a l u e s o f D were values, suggesting  consistently that the  211  TABLE 8.1  THEORETICAL AND EXPERIMENTAL VALUES OF D, FOR VARIOUS DIAMETERS.  D Diameter, 1.500  inch  (cm)  Theoretical  (volts) Experimental  4.95  (3.810)  1.875  6.18  4  7.42  6.30  (V  S E T  9.89  9.30  (V  S E T  (4.763) 2.250  '  6  5  ( S E T 5> V  ,)  (5.715) 3.000 (7.620)  3.500 (8.890)  11.54  y  )  212  tomatoes appeared size.  The  to  the  grader  d i f f e r e n c e between  the  t h e o r e t i c a l and  mental values suggesting  smaller  a p p e a r s t o be  that  the  than t h e i r  is  that  the  a straight line  l a r g e r the  tomato, the  t h e o r e t i c a l curve of passing  through  i n c r e a s i n g d i f f e r e n c e between the mental values Table  8.1,  of  D as  suggests that  curvilinear.  The  probably  same as  pulse  should  and  E f f e c t of  three  three  The  of  F values  not  T  equal.  categories  4  ,  V  S  to  E  the  diameter  [8-1],  as  the  experishown i n  is  shown i n F i g u r e 5  Size  (DIA.  ,  V  S  E  T  and  g  the  large  the  three  increased  the  redness of  and  colour  1)  of  are  E  T  The  ?  opposed  to  large the  tomatoes i n each f o r each of of  listed and  three  medium  categories  the  g  6.1.  Measurement  analysis  i n the  as  V  trigger  t h e o r e t i c a l values.  were compared  using  diameters of as  T  the  mean d i a m e t e r s o f In  origin  outlined previously,  indicate that, the  D versus  D versus diameter  F i n each s i z e c a t e g o r y  categories, are  E  mean d i a m e t e r s  size categories,  values  S  Tomato C o l o u r on  colour  diameter.  r e l a t i o n s h i p between S c h m i t t  cut-off voltages  The the  as  true  the  relationship is  s t y r o b a l l diameter,  c a r r i e d out  the  actual  size,  more c l o s e l y  diameter decreases, the  the  the  to  t h e o r e t i c a l and  r e l a t i o n s h i p of  adjustments of V be  setting B.  the  width  voltage  the  experi-  inversely proportional  machine-measured d i a m e t e r approaches the Recalling  actual  of  the  variance. i n Table  The 8.2.  medium s i z e colour  categories  categories,  the  consistently  tomato i n c r e a s e d .  The  mean  TABLE 8.2  VALUES OF F RESULTING FROM A COMPARISON OF MEAN DIAMETERS OF THREE COLOUR CATEGORIES IN A GIVEN S I Z E CATEGORY.  Size Category  F  Extra large  1.6t  Large  2.9*  Medium  5.8**  Significant  a t 1% l e v e l  *  Significant  a t 5% l e v e l  t  Not  s i g n i f i c a n t a t 5% l e v e l .  214  d i f f e r e n c e b e t w e e n t h e mean o f t h e m e d i u m / t u r n i n g and  t h e medium/firm r i p e  Although  statistically  c a t e g o r y was 0.14  significant,  inch  category  (0.36 cm).  the difference  i s only  7% o f t h e mean d i a m e t e r  i n t h e medium c a t e g o r y , w h i c h i s  probably  practically.  insignificant,  size with by  increasing  the fact  output  "red" a m p l i f i e r given size, and  o f t h e t o m a t o may be e x p l a i n e d  t o the r e d wavelengths.  v o l t a g e i s i n most c a s e s  t h e sooner  The  The less  "green" than the  v o l t a g e , s o t h e more r e d i n a t o m a t o o f a  the longer w i l l  analysis  will  i t be d e t e c t e d by t h e g r a d e r ,  i t be s e e n  assumption  by t h e s e n s i n g  head.  w h i c h must be made i n t h e u s e o f  o f v a r i a n c e i s t h a t t h e p o p u l a t i o n s whose means a r e  being  compared  are normally  distributed.  date,  the s i z e  distribution  o f a l l tomatoes c o l l e c t e d  grower a r e p r o b a b l y size.  each category  with C.  distributed  i s no l o n g e r n o r m a l l y  the F values  this  fact  colour  listed  i n Table  Ability  from  ability  o f the s i z e / c o l o u r  i n F i g u r e s 8.1,  c , shows m a c h i n e g r a d e d  8.2  For this  s h o u l d be c o n s i d e r e d  Grader  grader  t o s i z e and  r e p r e s e n t e d by t h e  a n d 8.3.  a  size categories,  distributed. 8.2  harvest  a b o u t some mean  of the Size/Colour  grade tomatoes i s p i c t o r i a l l y  photographs  At a given  i n mind.  Size Grading The  and  normally  When t o m a t o e s a r e s u b - d i v i d e d i n t o  reason,  mean  that the p h o t o t r a n s i s t o r p r e - a m p l i f i e r c i r c u i t s  a r e most s e n s i t i v e amplifier  redness  The i n c r e a s i n g  Figure  extra large/firm  8.1 a , b ,  ripe,  215  FIGURE 8. 1 MACHINE GRADED FIRM RIPE TOMATOES (o) EXTRA LARGE / (b) LARGE (c) MEDIUM  216 FIGURE  8.2  MACHINE (a) E X T R A  G R A D E D SEMI-RIPE LARGE  (b) L A R G E Ic) M E D I U M  TOMATOES  218  large/firm Figure  r i p e , and m e d i u m / f i r m  8.2 a, b , a n d c shows m a c h i n e  large/semi-ripe,  large/semi-ripe,  tomatoes, r e s p e c t i v e l y . graded e x t r a  Figure  large/turning,  tomatoes, r e s p e c t i v e l y . tomatoes which size, the  r i p e tomatoes, r e s p e c t i v e l y .  fall  graded  extra  and medium/semi-ripe  8.3 a, b , and c shows  large/turning  and m e d i u m / t u r n i n g  Each s i z e / c o l o u r category  within  machine  contains  the s p e c i f i e d boundaries f o r  a n d some t o m a t o e s w h i c h f a l l  outside  these  limits  —  m i s c l a s s i f i e d tomatoes. The p e r c e n t a g e o f m i s c l a s s i f i e d t o m a t o e s i n a  given the  size category,  s i z e grading  deviation limits, size  alone,  accuracy  does n o t r e a l i s t i c a l l y  represent  of the s i z e / c o l o u r grader.  The  o f t h e m i s c l a s s i f i e d tomatoes  h o w e v e r , does  from t h e i r  show t h e d e g r e e o f o v e r l a p  cut-off  between  categories. Since  colours  only  one s i z e c u t - o f f i s u s e d f o r a l l  o f tomatoes, i t i s reasonable t o pool  misclassified colour.  a l l o f the  tomatoes around a s i z e c u t - o f f , r e g a r d l e s s  of  A t e a c h c u t - o f f , i . e . a t 1.875 i n (4.76 cm),  2.250 i n (5.72 cm), and 3.000 i n (7.62 cm), i t may be assumed t h a t exists. there  are  To i l l u s t r a t e ,  will  oversize  a normal d i s t r i b u t i o n o f m i s c l a s s i f i e d tomatoes a t t h e 3.00 i n (7.62 cm)  be some t o m a t o e s w h i c h a r e m i s c l a s s i f i e d , b e i n g  f o r the large  category,  m i s c l a s s i f i e d , being  category.  cut-off,  a n d some t o m a t o e s  undersize  f o r the e x t r a  The a s s u m p t i o n made h e r e ,  i s that  which  large  the o v e r s i z e  219  and  undersize  tributed (7.62  t o m a t o e s when g r o u p e d w i l l  a b o u t a mean w h i c h  cm) c u t - o f f .  i s close  be n o r m a l l y  dis-  t o t h e 3.000 i n  A s i m i l a r d i s t r i b u t i o n i s expected a t  each o f the other  two c u t - o f f  may be c a l c u l a t e d  f o r each o f t h e d i s t r i b u t i o n s , and a  statement  limits.  Confidence  intervals  made on t h e m a g n i t u d e o f t h e s i z e  measurement  The  of the m i s c l a s s i -  error.  fied  means a n d s t a n d a r d  tomatoes around  t h e 2.250 i n (4.76 cm) c u t - o f f a n d  3.000 i n (7.62 cm) c u t - o f f data  are l i s t e d  only half  95% c o n f i d e n c e  was  Table  a standard  1.875 i n (4.76 cm) c u t - o f f , lower  limit  undersize diameter. that  cut-off  o r a mean  less  listed i n  o f 0.082 i n (0.208 cm) a t  t h e 95% c o n f i d e n c e  tomatoes were g r e a t e r t h a n suggest  (the u n d e r s i z e  are also  deviation  o f 1.714 i n (4.35 cm).  T h i s may  included,  i n t e r v a l f o r each m i s c l a s s i f i e d  and t h e r e s u l t s  Assuming  The  available.  g r o u p was c a l c u l a t e d 8.3.  8.3.  i s not  o f t h e normal d i s t r i b u t i o n  f o r t h e medium c a t e g o r y ) The  a  i n Table  f o r t h e 1.875 i n (4.76 cm) c u t - o f f  since half  deviations  A l l o f t h e medium 1.714 i n (4.35 cm) i n  a smaller standard than  i n t e r v a l has  deviation  1.875 i n (4.76 cm)  at  f o r that  group. An value  F-test  o f F = 1.295  a t t h e 95% c o n f i d e n c e ( f o r 8 and 6 degrees  n u m e r a t o r and d e n o m i n a t o r , distributions  of Table  8.3.  respectively)  level  yielded  a  o f freedom i n t h e f o r t h e two n o r m a l  The v a r i a n c e s were t h e r e f o r e  220  TABLE 8.3  MEANS, STANDARD DEVIATIONS AND 95% CONFIDENCE INTERVALS FOR MISCLASSIFIED TOMATOES AROUND THE 2.250 INCH (5.715 CM) AND 3.000 INCH (7.620 CM) CUT-OFFS.  Cut-off, inch (cm)  Mean inch (cm)  Standard Deviation,inch (cm)  2.250  2.204  0.092  (5.715)  (5.598)  (0.234)  3.000  3.021  0.082  (7 .620)  (7.673)  (0.208)  95% Confidence I n t e r v a l , inch (cm)  mean +  0.180 (0.457)  mean +  0.161 (0.409)  221  assumed e q u a l . three  cut-off  possible The  I t i s proposed limits  to apply  standard  that  are equal.  Consequently,  one s t a n d a r d  deviation  mean o f t h e s t a n d a r d  the variance a t the  deviation  selected  for this  deviations  listed  i t is  t o each  cut-off.  p u r p o s e was t h e  i n Table  8.3,  n a m e l y , s = 0.087 i n (0.22 cm). The in  percentages  each s i z e category,  of oversize  as graded  and a r e l i s t e d  in  8.4 a n d s y i e l d s t h e f o l l o w i n g If  as a)  outlined,  tomatoes a r e graded  tomatoes  by t h e m a c h i n e , w e r e  recorded Table  i n Table  and u n d e r s i z e  8.4.  Combining  the data  prediction:  w i t h V,,^ a d j u s t m e n t s e t  then,  6.5% o f t h e medium t o m a t o e s w i l l these w i l l  be w i t h i n  be o v e r s i z e ;  68% o f  0.087 i n (0.22 cm) o f  2.250 i n (5.72 cm) o r < 2.337 i n (5.936 cm) i n diameter. b)  9.7% o f t h e medium t o m a t o e s w i l l these w i l l  be w i t h i n  be u n d e r s i z e ;  68% o f  0.087 i n (0.22 cm) o f  1.875 i n (4.76 cm) o r > 1.788 i n (4.54 cm), i n diameter. c)  5.9% o f t h e l a r g e these w i l l  tomatoes w i l l be w i t h i n  be o v e r s i z e ;  68% o f  0.087 i n (0.22 cm) o f  3.000 i n (7.62 cm) o r < 3.087 i n (7.84 cm) i n diameter, d)  and so on. It  i s d i f f i c u l t to assess  the a c c e p t a b i l i t y o f  222  TABLE 8.4  PERCENTAGE OF OVERSIZE AND UNDERSIZE TOMATOES FOR EACH SIZE CATEGORY AS GRADED BY THE SIZE/COLOUR GRADER.  S i z e Category  Percent Oversize  Percent Undersize  T o t a l No. o f Tomatoes i n each s i z e c a t e g o r y  Medium  6.5  9.7  62  Large  5.9  7.4  68  -  4.8  63  E x t r a Large  223  the  size  g r a d e d c a t e g o r i e s above s i n c e t o l e r a n c e s  ranges are  not  given  i n the  standpoint,  the  oversize  undersize  cantly  and  from t h e i r It  tomatoes are size  cut-off limit.  specifications,  boundary. category  The can  increased be  be  9.7%  a t the  The  i f the decrease  insignifi-  percentages  undersize limit  to the  of undersize  around a  may  be  a given  high  or  in  low  i n the  (4.76  The  limits  s i d e of  optimum o v e r s i z e / u n d e r s i z e  ratio.  be  to  the  medium cm)  undersize  should  given  percentage  tomatoes i n the 1.875  of  adjusted  expense o f a g r e a t e r p r o p o r t i o n o f oversize.  are  boundaries.  that equal  The  size  practical  tomatoes which  such t h a t o n l y  either  decreased  slightly.  tomatoes b e i n g an  category  necessary  fall  From a  are b e l i e v e d to deviate  g r a d e d o v e r s i z e and  tomatoes w i l l  will  machine graded  size  i s not  category  required of  few  standards.  for  limit  is  percentage small  adjusted  for  SUMMARY  Experimentally  obtained values  category  cut-off  deviated  somewhat f r o m t h e  a  linear relationship  deviation Schmitt  from the  trigger  not  linear.  out  using  V  limits,  S  E  d i a m e t e r has the  of  effect  of  g  ,  correlation,  misclassified  misclassified (0.22  of  on  will  cm)  of' t h e  of  The that  the  are  the  measurement I t appears  68%  their  the  and overall  deviations  small.  misclassified  tomatoes  were g r a d e d  cm) of  undersize  t o m a t o e s was  was  applied  these w i l l  category  cut-off  misclassified  tomatoes  from the  considered  of  that  in  were g r a d e d u n d e r s i z e . (0.22  is  carried  between c o l o u r  t o m a t o e s , and  thus  the  values.  size  c a t e g o r y b o u n d a r i e s was  the  from  i t s machine-measured  misclassified  t o m a t o e s , and  ,  fact  i n s i g n i f i c a n t since  0.087 i n  ?  than a d j u s t i n g  i f any,  c a t e g o r y , where 4.8%  standard deviation  T  the  voltage  percentage of  smallest percentage of  E  l i m i t s s h o u l d be  category boundaries  greatest  S  origin.  to  rather  larger  V  size  values obtained  medium c a t e g o r y , where 9.7%  large  and  the  diameter r e l a t i o n s h i p  tomato c o l o u r  The  deviation  T  i s due  theoretical  i n the  0.087 i n  E  through the  standards,  was  extra  S  cut-off  tomato, the  size The  V  line  s i z e measurement i s p r o b a b l y  from t h e i r  ,  c l e a r l y been e s t a b l i s h e d .  The  percentage of  5  theoretical  the  their  not  d i a m e t e r be.  T  pulse width versus  to  redder the  E  passing  t o m a t o e s as  The  S  straight  Setting  controls  T  V  for  practically  the A  to a l l  be  limit.  within The  size  insignificant  225  FINAL  A tions 1.  SUMMARY  summary o f t h e m a j o r f i n d i n g s o f t h e i n v e s t i g a -  reported  Physical  here a r e l i s t e d  i n point  form  below.  P r o p e r t i e s o f Tomatoes as R e l a t e d  to Colour  Grading. -  The w a v e l e n g t h  r a t i o which i s a s s o c i a t e d  maximum r e f l e c t a n c e r a t i o greenest the  and r e d d e s t  two  colour  Students'  - Ratios the  tomatoes,  separation  f o r the best  o f tomatoes  i n t o more  than  600 nm/660 nm m a x i m i z e s  t between  green colour other  i s not necessarily  categories.  - The w a v e l e n g t h r a t i o ,  and  d i f f e r e n c e between t h e  i d e a l wavelength r a t i o  statistical  with a  than  firm ripe,  semi-ripe,  turning  categories.  600 nm/660 nm may be u s e d , b u t a t  e x p e n s e o f optimum s e p a r a t i o n  between  categories. 2.  Physical Properties  o f Tomatoes a s R e l a t e d  to Size  Grading. -  The maximum d i a m e t e r o f a t o m a t o , i n t h e e q u a t o r i a l plane,  correlates well with  the weight o f the  tomato. -  The s m a l l e r  t h e tomato, t h e s m a l l e r  the d i f f e r e n c e  between t h e major and minor d i a m e t e r s , equatorial  plane .  i n the  226  - O r i e n t a t i o n o f tomatoes on a conveyor b e l t making a d i a m e t e r  before  measurement i s more c r i t i c a l  f o r l a r g e r t h a n s m a l l e r tomatoes. - The  d i f f e r e n c e between the major and minor  diameters  i n the e q u a t o r i a l p l a n e i s c o r r e l a t e d w i t h the major d i a m e t e r  i n o n l y the e x t r a l a r g e s i z e  category. 3.  C o l o u r Grader  Design.  - Photodetector  a m p l i f i e r d e s i g n can o n l y be  carried  out i f t h e c h a r a c t e r i s t i c s o f t h e l i g h t o p t i c f i l t e r s and p h o t o d e t e c t o r s  source,  a r e known.  - D e t e c t i o n o f t h e p r e s e n c e o f a tomato can be out u s i n g the a l g e b r a i c sum d e t e c t o r s i g n a l s as the  o f the two  carried  photo-  trigger.  - Reasonable c o l o u r s e p a r a t i o n i s a c c o m p l i s h e d  by  c o n t i n u o u s l y c a l c u l a t i n g the r a t i o o f v o l t a g e s from two p h o t o t r a n s i s t o r s s e n s i n g  reflected  l i g h t and ^comparing the peak v o l t a g e t o p r e s e t values. - C o m b i n a t i o n o f the s t o r e d peak v o l t a g e and the o f the sum  use  o f t h e two p h o t o d e t e c t o r v o l t a g e s  as  the s e n s i n g t r i g g e r , overcomes d i f f i c u l t i e s a s s o c i a t e d w i t h s y n c h r o n i z a t i o n of  separate  s e n s i n g and t r i g g e r i n g systems. - W i t h o u t background m o n i t o r i n g , s m a l l d e g r e s s of i n the r e f l e c t a n c e o f the conveyor b e l t  can  drift  detrimentally and  affect  triggering  Conveyor b e l t  both  of the s i g n a l  processors.  background monitoring  plished  through  follows  t h low f r e q u e n c y  but  s e n s i n g o f t h e tomato  may be accom-  t h e use o f a c i r c u i t  not the high  drift  frequency  which  o f the background,  of the sorting  operation. Storage  o f category  synchronized guarantees  i n f o r m a t i o n i n a dynamic  with  memory  t h e movement o f t h e c o n v e y o r ,  that at the e j e c t i o n  time,  the e j e c t  mechanism and tomato a r e i n j u x t a p o s i t i o n , regardless ize  Grader  o f conveyor b e l t  speed,  Design.  D i a m e t e r measurement o f a t o m a t o c a n be through  the conversion  Schmitt  trigger pulse  paring Since  o f the colour into  of conveyor b e l t  values.  t r i g g e r pulse width  must be p r o v i d e d w h i c h m a i n t a i n s f o r a given  of  speed.  belt  Category  i s a function  speed, a compensating  voltage  a  i n f o r m a t i o n c a n be p r o c e s s e d grader.  circuit  constant  tomato d i a m e t e r ,  manner a s i n t h e c o l o u r  grader  a v o l t a g e , and com-  the voltage t o preset  the Schmitt  accomplished  regardless  i n t h e same  228  5.  Test Results. - Colour  grading  the  present  less  than  grading and  be  satisfactorily  design  accomplished  f o r a l l tomatoes except  or equal  diameter, - The  can  to about  1 1/2  in  s i n c e d e t e c t i o n becomes  rate of  5 tomatoes/sec,  size/colour  the pneumatic  are  l i m i t e d by  eject  with  those  (4 cm)  in  difficult.  f o r both the  colour  capacity of  mechanism employed  i n the  tests. - The  electronic design to  - The  20  sorting  s h o u l d be  o p e r a t i o n s u s i n g the  capable  o f the  size  measurements, appears  - The  95%  confidence  effects the  diameter  above 2 i n  categories  up  t o 1/4  (5  undersized  0.045 i n  s e n s i n g of the  on  styroball  (0.11  in  on  at  (0.64  cm)  on  styroball  for  at  off-set  diameters  cm). on  tests  no  more t h a n  10%  t o m a t o e s i n any  conducted  the present  on  be w i t h i n 0.087 i n  (0.22  9  design,  o v e r s i z e d and  10%  category.  u n d e r s i z e o r o v e r s i z e t o m a t o e s , 68%  boundary,  cm)  tomato  insignificant  of tomatoes, w i t h  should y i e l d  10%  t o be  based  measurement, b a s e d  S i z e / c o l o u r grading, based  the  grader,  are p r a c t i c a l l y  distances  - Of  up  level.  of off-center  studies,  -  a t speeds  tomatoes/second.  resolution  the  of grading  present  cm)  for a l l categories.  of  the  will  category  229  RECOMMENDATIONS  Recommendations w i t h tion  o f the present  size/colour procedures present 1.  grader  design,  and O p t i c a l  In the present  the  System  design,  Design.  t h e r e may be a few  These redundancies  for  use w i t h  and  testing  600  nm/660 nm w a v e l e n g t h  light  conducted  a long  be e l i m i n a t e d  s h o u l d be  redesigned filters,  u s i n g t h e optimum  optic  ratio. s e n s i n g h e a d c o u l d be  t o i n c r e a s e t h e amount o f i n c i d e n t  and r e f l e c t e d  signal  should  600 nm a n d 660 nm o p t i c  o f the f i b r e  increased,  o u t over  design.  - The p h o t o t r a n s i s t o r a m p l i f i e r s  - The w i d t h  redundancies  due t o t h e m o d u l a r d e s i g n o f  s y s t e m w h i c h was c a r r i e d  the f i n a l  version of the  i n p o i n t form below.  are necessary  period. in  i n the manufacture o f a complete  o u t on a m o d i f i e d  are l i s t e d  which  applica-  f o r t o m a t o e s , as w e l l a s f u r t h e r t e s t i n g  t o be c a r r i e d  Electronic -  design  respect to the future  to noise  light,  ratio  thus  i n c r e a s i n g the  o f the p h o t o t r a n s i s t o r  amplifiers. - Background b e l t  r e f l e c t a n c e should  a minimum w i t h  r e s p e c t t o a l l tomatoes so t h a t  tomatoes s m a l l e r than sensed.  be m a i n t a i n e d a t  1 1/2 i n (4 cm) may b e  230  -  I f a t o m a t o i s l a r g e enough diameter) in  the s h i f t  enter  two b i t s  register,  two c o n s e c u t i v e  memory. be  t o occupy  (> 2.5 i n (6.4 cm) area  i t may be p o s s i b l e t o "eject"  Consequently  o f storage  signals  the e j e c t  i n t o the  s o l e n o i d would  a c t i v a t e d f o r 3 i n (7.6 cm) o f c o n v e y o r  belt,  as o p p o s e d t o o n l y  would p r o b a b l y  1.5 i n (3.8 cm).  increase sorting  speed  This  consider-  ably. 2. M e c h a n i c a l  Handling  - The e l e c t r o n i c  System.  system d e s c r i b e d should  a different  conveying  system, p r e f e r a b l y a u n i t  which a u t o m a t i c a l l y feeds, the  tomato, i n o r d e r  A s i n g l e Vee b e l t  I t may be n e c e s s a r y capacity orifice  may  suffice  in  operate  conveyors  order  tomato.  storage  tank o r the  time,  two s o l e n o i d s i n  p r o p o s a l w o u l d be c o n -  expensive.  from t h e conveyor b e l t  cross  are considered.  t h e tomato a t e j e c t i o n  The l a t t e r  s i d e r a b l y more - The d r o p  surge  be t e s t e d  of the solenoids to increase the  i f necessary,  parallel.  misclassification.  to increase the r e l a t i v e  flow o f a i r across or,  and o r i e n t s  and s h o u l d  systems  o f the secondary size  centers  to minimize  b e f o r e more c o m p l i c a t e d -  be t e s t e d w i t h  should  to the storage  be m a i n t a i n e d  t o minimize mechanical  bins or  a t a minimum,  damage t o t h e  231  CITED REFERENCES  1.  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U.S. P a t e n t No. 3 , 7 8 1 , 5 5 4 , p a t e n t e d December 25, 1973.  19.  M a n f r e , B.L. 1968. -- f o r p r o f i t .  20.  M a t s o n , G.D. and N.N. M o h s e n i n . 1973. Mechanical o r i e n t a t i o n and p a c k i n g o f a p p l e f r u i t . Trans. ASAE 1 6 ( 6 ) : 1190-1193.  21.  M c C l u r e , W.F., R.P. R o h r b a c h , L . J . Kushman and W.E. Ballinger. 1973. The B e r r y m a t i c : An a u t o m a t i c f r u i t s o r t i n g m a c h i n e . ASAE P a p e r No. 7 3 - 6 5 2 5 .  22.  M c C l u r e , W.F. and P. U.S. P a t e n t No. 1973.  23.  M c C l u r e , W.F., R.P. R o h r b a c h , L . J . Kushman and W.E. Ballinger. 1975. Design o f a h i g h speed f i b e r optic blueberry sorter. T r a n s ASAE 1 8 ( 3 ) : 4 8 7 - 4 9 0 .  The m e c h a n i c a l h a r v e s t i n g o f t o m a t o e s T r a n s . ASAE 1 1 ( 3 ) : 3 5 6 - 3 5 9 .  Rohrbach. 1973. Blueberry sorter. 3 , 7 7 3 , 1 7 2 , p a t e n t e d November 20,  233  24.  M e h r a , H.K., N.R. B u l l e y a n d L.M. S t a l e y . . 1 9 7 2 . Some p h y s i c a l and r h e o l o g i c a l p r o p e r t i e s o f s t r a w b e r r i e s . Can. A g r i c . E n g . 1 4 ( 2 ) : 8 5 - 8 8 .  25.  M o h s e n i n , N.N. ( e d . ) 1 9 7 0 . P h y s i c a l P r o p e r t i e s o f P l a n t and A n i m a l M a t e r i a l s . Volume I . P u b l i s h e d by G o r d o n § B r e a c h , S c i e n c e P u b l i s h e r s I n c . , 150 F i f t h A v e n u e , New Y o r k , N.Y. 1 0 0 1 1 .  26.  O ' B r i e n , M. a n d S.C. S a r k a r . 1 9 7 3 . C o m p u t e r i z e d g r a d i n g o f t o m a t o e s by o p t i c a l t r a n s m i s s i o n c h a r a c t e r i s t i c s . ASAE P a p e r No. P C - 7 3 - 0 9 .  27.  O ' B r i e n , M. a n d S.C. S a r k a r . 1 9 7 4 . S y s t e m f o r o p t i c a l transmission c h a r a c t e r i s t i c s f o r computerized grading tomatoes. Trans. ASAE 1 7 ( 2 ) : 1 9 3 - 1 9 4 .  28.  Palmer, J . 1961. E l e c t r o n i c s o r t i n g o f p o t a t o e s and c l o d s by t h e i r r e f l e c t a n c e . J . A g r i c . Eng. Res. 6: 1 0 4 - 1 1 1 .  29.  P o w e r s , J . B . , J . T . Gunn a n d F.C. J a c o b . 1953. E l e c t r o n i c c o l o u r s o r t i n g o f f r u i t s and v e g e t a b l e s . A g r i c . Eng. 34: 1 4 9 - 1 5 4 , 1 5 8 .  30.  R o h r b a c h , R.P., W.F. M c C l u r e , L . J . Kushman a n d W.E. Ballinger. 1973. Developments i n a u t o m a t i c l i g h t transmission difference soring of blueberries. ASAE P a p e r No. 7 3 - 6 5 2 8 .  31.  S a r k a r , S.C. a n d M. O ' B r i e n . 1 9 7 5 . M e a s u r e m e n t o f power s p e c t r a f o r o p t o e l e c t r o n i c sorting o f tomatoes. T r a n s . ASAE 1 8 ( 1 ) : 1 7 7 - 1 8 0 , 184.  32.  S t e p h e n s o n . K.Q., R.K. B r y l e r a n d M.A. W i t t m a n . V i b r a t i o n a l r e s p o n s e p r o p e r t i e s as s o r t i n g f o r tomatoes. T r a n s . ASAE 1 6 ( 2 ) : 258-260.  33.  S t e p h e n s o n , K.Q. 1974. C o l o u r s o r t i n g system f o r tomatoes. T r a n s ASAE 1 7 ( 6 ) : 1 1 8 5 - 1 1 8 6 .  34.  T r a u b , L.G., P.L. W r i g h t a n d H.L. S t e e l e . 1971. Machine h a r v e s t i n g tomatoes. Amer. V e g . G r o w e r . , S e p t . 18-20, 47, 49.  35.  Wood, R.A. 1973. Apparatus f o r s o r t i n g p r o d u c t s . U.S. P a t e n t No. 3 , 7 7 6 , 3 8 1 , p a t e n t e d December 4, 1 9 7 3 .  1973. criteria  234  36.  W o r t h i n g t o n , J . T . , D.R. M a s s i e and K.H. N o r r i s . 1973. Light transmission technique f o r p r e d i c t i n g ripening t i m e f o r i n t a c t g r e e n t o m a t o e s . ASAE P a p e r No.73-6526.  37.  Y e a t m a n , J.N. and K.H. N o r r i s . 1965. Evaluating internal q u a l i t y o f a p p l e s w i t h new a u t o m a t i c f r u i t s o r t e r . Food T e c h n o l . 1 9 ( 3 ) : 1 2 3 - 1 2 5 .  235  GLOSSARY OF  band p a s s  category  central  filter  information  wavelength  - with reference to o p t i c a l f i l t e r s , an i n t e r f e r e n c e f i l t e r h a v i n g a h a l f bandw i d t h g r e a t e r t h a n 5% o f t h e c e n t r a l wavelength. -  a d i g i t a l s i g n a l , e i t h e r HIGH o r LOW, o r c o m b i n a t i o n o f s i g n a l s , g e n e r a t e d when a tomato i s c a t e g o r i z e d e l e c t r o n i c a l l y , which r e f e r s s p e c i f i c a l l y to a colour or size/colour category.  - with reference to o p t i c a l f i l t e r s , the wavelength a t the m i d p o i n t o f the h a l f bandwidth. - C o m p l e m e n t a r y Symmetry Oxide Semiconductor.  CMOS  dB,  TERMS  decibel  division  Metal  - may be e x p r e s s e d a s 20 l o g V /V.. where ^ o V = output voltage V? = i n p u t v o l t a g e .  1  - with reference t o analog s i g n a l s , the a l g e b r a i c operat i o n c o n d u c t e d on two v o l t a g e s . - with respect t o d i g i t a l signals, the i n t e g r a l d i v i s i o n o f a frequency. - r a t i o of output input voltage.  gain  gain  ratio  half  bandwidth  -  voltage to  r a t i o o f t h e g a i n o f one a m p l i f i e r to the gain o f another a m p l i f i e r .  - with reference to o p t i c a l f i l t e r s , t h e w i d t h o f a band m e a s u r e d a t h a l f peak t r a n s mission.  236  - w i t h reference to analog s i g n a l s , a d e v i c e whose i n p u t a n d o u t p u t v o l t a g e s a r e d i f f e r e n t by algebraic sign only.  inverter  - with reference to d i g i t a l s i g n a l s , a d e v i c e whose o u t p u t i s t h e complement o f i t s i n p u t i . e . i f t h e i n p u t i s LOW, t h e o u t p u t i s HIGH, and v i c e v e r s a . memory  - a d i g i t a l storage area comprised o f one o r more s h i f t r e g i s t e r s .  NAND g a t e  - a d i g i t a l d e v i c e whose o u t p u t i s LOW o n l y when a l l o f i t s i n p u t s a r e HIGH.  n a r r o w band p a s s  NOR  filter  - with reference to o p t i c a l f i l t e r s , an i n t e r f e r e n c e f i l t e r h a v i n g a h a l f bandwidth between 1% and 5% o f c e n t r a l w a v e l e n g t h . - a d i g i t a l d e v i c e whose o u t p u t i s HIGH o n l y when a l l o f i t s i n p u t s a r e LOW.  gate  octave  - doubling  Op Amp, o p e r a t i o n a l a m p l i f i e r  - a h i g h - g a i n dc a m p l i f i e r t h a t has a d i f f e r e n t i a l i n p u t and a s i n g l e ended o u t p u t .  open l o o p  - t h e g a i n o f a n Op Amp when no n e g a t i v e feedback i s used.  optic  gain  filter  of a  frequency.  - an i n t e r f e r e n c e f i l t e r capable of t r a n s m i t t i n g a wavelength band o f t h e v i s i b l e s p e c t r u m , and b l o c k i n g o t h e r s .  peak w a v e l e n g t h  - with reference to o p t i c a l f i l t e r s , w a v e l e n g t h a t maximum transmission.  percent  - the h a l f bandwidth expressed as a p e r c e n t i l e o f c e n t r a l wavelength; i . e . 0.1% f i l t e r a t 440 nm h a s a h a l f b a n d w i d t h o f 0.4 4 nm.  (%) b a n d w i d t h  237  phototransistor  - s o l i d state device s i m i l a r to an o r d i n a r y t r a n s i s t o r e x c e p t t h a t l i g h t i n c i d e n t on t h e pn j u n c t i o n c o n t r o l s the response of t h i s device; offers builti n g a i n and g r e a t e r s e n s i t i v i t y than photodiodes.  reflectance  - r a t i o of r e f l e c t e d energies at two w a v e l e n g t h s when t h e i n c i d e n t e n e r g i e s a t t h e two wavelengths are equal.  ratio  singulate  - to arrange i n s i n g l e  TTL  - Transistor-Transistor integrated c i r c u i t .  very  narrow  wavelength  band p a s s  ratio  filter  file. Logic  - with reference to o p t i c a l f i l t e r s , an i n t e r f e r e n c e f i l t e r h a v i n g a h a l f bandwidth b e t w e e n 0.1% and 1% o f c e n t r a l wavelength. - r a t i o o f two w a v e l e n g t h s ; r e f l e c t e d e n e r g y a t one o f t h e s e w a v e l e n g t h s d i v i d e d by the r e f l e c t e d energy a t the other wavelength produces the reflectance ratio.  238  APPENDIX A F e d e r a l * and I n d u s t r y * * G r a d i n g S t a n d a r d s f o r G r e e n h o u s e I.  F e d e r a l and  Tomatoes  I n d u s t r y C o l o u r G r a d e s and S t a n d a r d s * * * Canada  N o . l Grade  7 1 . ( l ) ( d ) a r e , i n any i n d i v i d u a l  p a c k a g e , one o f t h e  following  s t a t e s of development: "mature", " t u r n i n g " , "semir i p e " or " f i r m  ripe".  7 3 . ( 1 ) ( a ) " m a t u r e " means, (i)  except f o r f i e l d  t o m a t o e s grown i n B r i t i s h  C o l u m b i a and M a n i t o b a , t h a t definite in  t h e t o m a t o shows a  t i n g e o f p i n k a t t h e b l o s s o m e n d , and  the case of f i e l d  t o m a t o e s grown i n B r i t i s h  C o l u m b i a and M a n i t o b a , t h a t t h e t o m a t o i s developed, well  filled  fully  out, gives a feeling  s p r i n g i n e s s when p r e s s u r e  i s applied,  of  i s bright  waxy i n a p p e a r a n c e , h a s s e e d s t h a t a r e w e l l d e v e l o p e d and seed c a v i t i e s consistency,  of a  and  ( i i ) n o t more t h a n 25% o f t h e f i e l d *  jelly-like  tomatoes  by  Canada A g r i c u l t u r a l P r o d u c t s S t a n d a r d s A c t , F r u i t and V e g e t a b l e R e g u l a t i o n s , Queen's P r i n t e r , O t t a w a 1 9 6 8 , C a t a l o g u e No. YX79-1955-27-1968. ** C o u r t e s y W e s t e r n G r e e n h o u s e C o - o p e r a t i v e , B u r n a b y , B.C. *** G r e e n h o u s e t o m a t o g r a d e s and s t a n d a r d s a r e t h e same as f i e l d tomato g r a d e s and s t a n d a r d s .  239  (ii)  CONTINUED count are t u r n i n g in  British  i n the case o f tomatoes  Columbia  and M a n i t o b a , and n o t more  t h a n 101 o f t h e f i e l d turning  "turning"  means  (i)  the f i e l d  that  tomatoes  i n t h e case o f tomatoes  than i n B r i t i s h  grown  by c o u n t a r e grown o t h e r  Columbia and M a n i t o b a ;  tomato  shows f r o m a t i n g e t o  25 p e r c e n t p i n k o r r e d c o l o u r , and (ii)  n o t more t h a n 10% o f t h e f i e l d count a r e mature  "semi-ripe" (i)  that  tomatoes  by  or semi-ripe;  means  the f i e l d  tomato  shows f r o m 25 p e r c e n t  t o 75 p e r c e n t p i n k o r r e d c o l o u r , a n d (ii)  n o t more t h a n 10 p e r c e n t o f t h e f i e l d by c o u n t a r e t u r n i n g o r f i r m  "firm (i)  ripe"  ripe;  tomatoes  and  means  that the f i e l d  tomato  shows f r o m 75 p e r c e n t  t o 100 p e r c e n t p i n k o r r e d c o l o u r , and (ii)  n o t more t h a n 10 p e r c e n t o f t h e f i e l d by c o u n t a r e s e m i - r i p e .  tomatoes  240  II.  Federal Size Standards Canada No.1  Grade  7 6 . ( l ) ( g ) h a v e a minimum d i a m e t e r o f 1 1/2 (h)  inches;  h a v e , when i n a p a c k a g e , w i t h t h e e x c e p t i o n o f one s p e c i m e n , a maximum v a r i a t i o n 1 inch  i n diameter of  i n t h e c a s e o f t o m a t o e s w i t h a minimum  d i a m e t e r o f 2 i n c h e s , and a maximum v a r i a t i o n i n d i a m e t e r o f 1/2 i n c h i n a l l o t h e r 78.  Notwithstanding anything  cases;  i n these Regulations, i n the  g r a d i n g o f g r e e n h o u s e t o m a t o e s n o t more t h a n (a)  5 p e r c e n t o f t h e g r e e n h o u s e t o m a t o e s by c o u n t may be b e l o w t h e minimum  (b)  size;  10 p e r c e n t o f t h e p a c k a g e s , when t h e g r e e n h o u s e t o m a t o e s a r e i n p a c k a g e s , may c o n t a i n tomatoes t h a t  III.  exceed the p e r m i t t e d  I n d u s t r y S i z e Grades (1)  in British  greenhouse  size  variation;  Columbia  Greenhouse tomatoes a r e grouped i n t o  five  size  categories: (a)  "cull", less  (b)  a l l t o m a t o e s h a v i n g a minimum d i a m e t e r  t h a n 1 1/2  inches,  " s m a l l " , a l l t o m a t o e s h a v i n g maximum d i a m e t e r s b e t w e e n 1 1/2 i n c h e s a n d 1 7/8  inches,  241  III.  CONTINUED ( c ) "medium", a l l t o m a t o e s h a v i n g diameters  maximum  b e t w e e n 1 7/8 i n c h e s a n d 2 1/4  inches, (d) " l a r g e " , a l l t o m a t o e s h a v i n g diameters  between  maximum  2 1/4 i n c h e s a n d 3 i n c h e s ,  (e) " e x t r a l a r g e " , a l l t o m a t o e s h a v i n g maximum diameters (2)  greater than  3 inches.  Federal Standards apply t o general t o l e r a n c e s .  242  APPENDIX B GRADING RATE AT PEAK OF GROWING SEASON FOR B.C. LOWER MAINLAND BASED ON 1975 YIELD PREDICTIONS, MEAN WEIGHT OF TOMATOES IN EACH SIZE CATEGORY, AND APPROXIMATE DISTRIBUTION OF SIZE CATEGORIES* Size Category  Mean Tomato Weight ( l b s )  No. o f Tomatoes per 20 l b box  Small  0.107  187  Medium  0.163  123  Large  0.346  58  Extra large  0.495  40  Maximum B.C. 1975 y i e l d i n one week = 20,000 boxes a t 20 l b s ea. Maximum Lower Mainland 1975 y i e l d i n one week = 70% X 20,000 = 14,000 boxes  Size D i s t r i b u t i o n  % of Total  No. o f Boxes/week  4  560  Medium  23  3220  Large  54  7560  Extra large  11  1540  Small  . No.2 Grade  8  1120 (hand sorted)  T o t a l without No.2's = 1,000,860 tomatoes/week Based on a 6 day work week, a t 8 hours/day Grading rate = 5.8 tomatoes/sec  Based on a 7 day work week, a t 8 hours/day Grading rate =5.0 tomatoes/sec *  Courtesy o f Western Greenhouse Co-operative, Bumaby, B.C.  

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