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Controlling octocoupler with pwm

mikeggg

New Member
I am trying to Use PWM fan to trigger an Optocoupler relay to run a 115v compressor on lg refrigerator .. however when I use the signal feed it cycles the relay I've tried to use a capacitor to smooth out the line with no luck and when I use the 12v and the ground it trips the fan circuit I suspect from load of relay .. can someone help me out here
 

mikeggg

New Member
In using and isolation relay from 115v source but I'm trying to trigger the relay with pwm fan so the compressor cuts off when the refrigerator makes temp and fan slows ... the refrigerator won't trigger the defrost until it senses a temp drop
 

crutschow

Well-Known Member
Most Helpful Member
You could try adding a diode in series to the capacitor so the capacitor will charge to the peak value of the PWM signal, regardless of the PWM duty-cycle.
Using that should trigger the relay anytime there's a PMW signal.
Is that what you want?
 

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