Q1. The requirement to sense glass bottles leaving an automatic washer on a production line conveyor belt has been notified to you. The output from sensor is to be of binary form, that is, logical 1 when the part is present and logical 0 when no part is present. It is as well essential to make sure that a change of sensor state takes place closer to the sensor when a bottle approaches than when it moves away. The switching distance will lie between 5 and 20 mm. The production line is for food products and environment is clean and maintained at a temperature of 15°C. Bottles will pass the sensor at a rate of every 10 second. There is no need for the protection from contact with objects however it must be proof against the water drips.
Propose an appropriate sensor and justify your recommendation. Sketch a diagram which shows the functional blocks in the sensor and describe each function.
Would the suggested sensor be appropriate if a change was made from glass to the plastic bottles?
Q2.
a) In which kind of memory is the executive program that controls the PLC positioned?
b) How is loss of the loaded program prevented whenever the PLC is switched off?
c) Is opto-coupling found just on the inputs to a PLC?