Introduction to Industrial Automation

10.22   Color-Based Separation of Plastic Balls

Figure 10.22 shows a mechanism that separates plastic balls depending on their color and packs them 

inside boxes in quantities of 6 or 12 pieces, depending on the position of the selector switch SS. The 

color sensor S

C

 detects the color of a ball (yellow or green) by measuring the light rays emitted by the 

motionless ball. The recognition time of a color from the S

C

 is 1 s. The activation of coil 1 happens after 

the S

C

 signal and allows the ball to drop. After the last pass from the proximity switch S

P

, coil 1 is deac-

tivated in order to stop the next ball in front of the sensor S

C

. Coil 2 sets where each ball will fall accord-

ing to its color, and the movable bearing has the position shown in the figure when coil 2 is deactivated.

When the chosen quantity is completed in every box, the corresponding indication is activated, 

and remains on until the next ball of the same color falls. The mechanism comes into operation 

(or pause) via the switch RS

0-1

. The removal of the filled boxes is automatically handled by another 

machine and is not part of this application. Write the required PLC program in Boolean language.

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  Introduction to Industrial Automation

+24 V 

DC

+24 V 

DC

ST

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TS

TO

P

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0 

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Normal sp

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Hig

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C

1

C

2

C

3

C

4

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40 cm

50 cm

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,)

PC

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Q2.0

Q3.0

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Di

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Analo

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