Identification and Sorting of Defective Products using PLC Ladder Program example
Control Purpose:
Sorting of Defective Products using PLC Ladder Program example
Detecting the defective products (taller than normal dimension) on the conveyor belt by photoelectric sensor and pushing them into the recycle box at the 5th position. The pushing
pole will be reset when the falling of defective product is detected. When errors occur, the disorder memory can be cleared and the system can be restarted by pressing RESET
Devices:
Device
Function
X0
Photoelectric sensor for detecting defective products
X4
Photoelectric sensor for monitoring the cam
X5
Photoelectric sensor for detecting the falling of defective products
X6
RESET
Y0
Electromagnetic valve pushing pole
PLC Program :
Program Description:
Every time the cam rotates once, the product will be moved from one position to another position. X4 will be
activated to execute SFTL instruction once. The content in M0~M4 will be shift to left for one bit and the state of X0 will be sent to M0.
When X0 = ON (defective products detected), the value “1” will be sent to M0 and achieve the 5th position after
4 times of shift. In this case, M4 = ON and the electromagnetic valve Y0 will be ON to push the defective product into the recycle box.
When the falling of the defective product is detected, X5 will be activated to execute [RST Y0] and [RST M4]
instructions. Y0 and M4 will be reset. The electromagnetic valve will be OFF till next defective product is detected.
When RESET is pressed, X6 will be activated to reset M0~M4, so as to ensure that the system restart the detecting
process when the memory which records defective products is in disorder.
