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Needed - a simple Opto switch circuit

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BO NONN

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I need to track the motion of a 24-slot chopper wheel running at up to 100 rpm (~40 Hz maximum). I've got a Fairchild H22A1 slotted optical switch and a 5 VDC supply. What is the simplest circuit that I can build which will link to a Keyence Visual KV16 PLC?
The only circuit I've come across so far is a honeybee counter by David Johnson (attached). How much can this be simplified for my needs?
 

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philba

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A lot. I assume your PLC can count pulses and isn't picky about duty cycle. I'd just wire up the opto - power to led w/current limiting resistor, phototransistor pulled high and output to a schmitt trigger and then into the PLC. This diagram is for an optoisolator but the principle is the same. the ST is to avoid noise giving false pulses when there is noise.
 

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Hero999

Banned
What's the maximum frequency the PLC can count?

You might need to add a frequency divider to reduce it to a more PLC-friendly level like 5Hz.
 

philba

New Member
by the way, has any one ever tried building Dave Johnson's circuits? I've tried to build several and they never worked the way they were supposed to. At first I though it was something i was doing wrong but then I spiced a few of them and got significant differences.
 

BO NONN

New Member
Thanks very much indeed. By various indirect methods I was approaching your simple design. I appreciate your confirming that I was on the right track.
Thanks again,

bo
By the way, we did try to build Dave Johnson's bee counter, but couldn't get it to detect a sheet of black paper, much less a bee. But I could have screwed up somewhere.
 

BO NONN

New Member
Luckily this particular PLC brags of having a pair of 24-bit, 30kHz counters. So I think I'm ok there.

Thanks,

bo
 
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