Example Description
The warehouse manager needs to count the items stored each day: when the number of items reaches 150, the green light in the warehouse monitoring room lights up; when the number of items reaches 200, the red light in the warehouse monitoring room flashes at a frequency of 1 second and triggers an alarm.
Analysis Process
(1) The analysis of this example is as follows: a counting detection device is required, and a sensor should be set at the warehouse entrance to detect whether items are entering the warehouse; a counter is needed to count the items; the red light alarm flashing at a frequency of 1 second is controlled by a special auxiliary relay M8013.
(2) The I/O wiring diagram of the FX3U PLC is shown in the figure below, using a photoelectric sensor with a source-type connection, that is, connecting OV to S/S. Similarly, the button SB also needs to use a source-type connection.
Define Input/Output I/O Table
(3) Warehouse Item Statistics Ladder Diagram
Question:
When connecting to the FX3U PLC, there are often two types of sensors encountered. How should they be connected?
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