When I was starting the design of my brew rig, I went looking for a way to control my electric boil kettle without buying another PID. I came across this website.
I thought to myself. This should be easy. I have built PWM circuits before and I probably have enough spare parts laying around to make it. So that is what I did.
Well yesterday i finally got around to testing the circuit properly. So Plugged a DC motor into the SSR output and turned on the power. I started turning the potentiometer knob expecting to see the speed slow down. Nothing.......... Well that is strange. I tried a few combinations of wiring on the knob. Nothing. It just turns the motor off at certain spots when you turn it down. So now what?
I get out my volt meter and connect it. 12v when turned all the way up. Fine. Start turning the knob "down", and still 12v. I hesitate for a moment and the power goes off. I wait a few more seconds and the power goes back on. So i keep turning the knob and counting the second between on and off. Sure enough it changes when I turn the knob.
This is the first time I have come across a PWM circuit like this. It turns the output full on, or full off for set amounts of time. No variance in voltage and no quicker or slower pulsing that I am used to.
So I guess my question to all of you is and others who may go this route. Would a normal PWM still work? I am thinking that a normal PWM circuit might kill a SSR if it pulsed on/off too fast.
Also if anyone is interested in one of these circuits. I have an extra one that I built. I can also make more boards pretty easy. I could make them in two different configurations. All in a box complete with dial and inputs, or just the board and terminal blocks like the picture below.