How to use S7-200 ordinary point count pulse number (non-high speed counting) - Database & Sql Blog Articles

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GSX-200

SMD aluminum electrolytic capacitor

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Q: I want to make a small device for detecting the movement of an object. I want to use a groove type photoelectric switch and a wheel with several small holes drilled on the side to form the detection device. The wheel is vertically installed in the middle of the slot type photoelectric switch. When the wheel touches the surface of the moving object, the small hole on the rotating side will cause the photoelectric switch to produce continuous ON and OFF pulses. The number of generated pulses will be 30 in 1 second. If the pulse generated within 1 second is less than 30, the alarm will be given. This function is implemented by non-high speed counting.

How can the above functions be implemented on the S7-200 program, and does the plc parameter need to be set?

A: Method 1:

When your program's sweep frequency (the reciprocal of the period) is greater than twice the maximum switching frequency of the photoelectric switch. You can safely write programs using general programming methods.

Method 2:

When your program scan speed does not guarantee the above conditions. However, if the frequency of the photoelectric switch is less than 500 Hz, that is, the high level is 1 millisecond and the low level is 1 millisecond. In this case, the interrupt can be interrupted by 1 millisecond. In the interrupt program, the input state is read by the instant input command, and the sampling of the higher frequency is performed.

Method 3:

When the frequency of the photoelectric switch exceeds the upper limit of 500 Hz, it reaches n Hz (I don't know. Why is it not clear later). The hardware can be used to time the time base – high speed pulse output. Pulses are sent every 100 microseconds, and the number of pulses is not limited. Then, the pulse is used to complete the interrupt and the next pulse is sent, and the input state is read by the above method 2, and the highest order is counted. This can be sampled every 100 microseconds and can be sampled to a 5 kHz pulse.

I believe that Method 3 is already the highest ability that plc can handle. (only refers to non-high speed input)

This method is the actual procedure of my "IQ question." Ideas.
Finally, don't forget to adjust the input filter time of the system block to the appropriate value.