Controlling octocoupler with pwm

[mikeggg]

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

 

[Nigel Goodwin]

I wouldn't have thought you could run a compressor like that?, speed control of motors is quite complicated, and entirely dependent on the type of motor.

 

[mikeggg]

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

 

[MaxHeadRoom78]

Conflicting details, Controlling the compressor? or just the Fan??
Opto-coupler & PWM for what?

 

[crutschow]

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?

 

[mikeggg]

Sorry to be clear I'm trying to use the signal from the pwm evap fan to trigger a isolation relay to power the compressor of the refrigerator

 

[mikeggg]

I have tried using a capacitor before and it helped as I was on the right track however I didn't try a diode .. I'm gonna see if that helps

 

[ChrisP58]

Posting a schematic of what you're doing would make it much easier for us to help you.