Would this PWM controller work with SSR?

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This popped into my head from the PWM stir plate thread.

I'm just wondering if one of these would work for firing an SSR that controls an element. I realize they are just a fancy 555 timer. *EDIT* from the picture, the second one looks like it might be a 556.

I was going to build a 555 for my boil, but for the price of these, way easier. On the first one, I'd probably relocate the potentiometer so the whole thing doesn't need to be mounted to the panel. It would not need to be done on the second one. First one handles 10A, second one is just 3.2, but both should work driving an SSR.

Now something else just popped in, either one would also be able to drive a 12v/24v March pump...hmmm, instead of throttleing down with a valve, throttle down with pump speed.

Any input?

You do not even need the 3A to drive an SSR, the 555 can drive the SSR directly... you can fit the 555 cap and res on the back of the potentiometer and hot glue them in place..
I have a circuit diagram and a video on this thread: https://www.homebrewtalk.com/f170/pwm-show-us-how-221301/index5.html

I like the DC pump speed control idea..

So how fast are these going to switch? My understanding of using a PWM for an SSR to control a boil kettle would be to change the frequency of the pulse. This makes switches the SSR more slowly thus making it last longer.

I suppose if you use the 10A version you could control up to that amount before needing to use an SSR and therefore wouldn't need an SSR.

So if you use either one you should consider determining how to change the frequency. I like your idea of throttling a pump. Might be a good idea to run that by Walter at March Pumps.

clearwaterbrewer said:

You do not even need the 3A to drive an SSR, the 555 can drive the SSR directly... you can fit the 555 cap and res on the back of the potentiometer and hot glue them in place..
I have a circuit diagram and a video on this thread: https://www.homebrewtalk.com/f170/pwm-show-us-how-221301/index5.html

I like the DC pump speed control idea..

Click to expand...

That was my plan to drive the SSR directly from the 555, no MOSFET needed, but both of those links had them, so why not? I guess just one more component to fail.

I like that circuit, much more simple than the other 555 PMW circuits I've seen, they usually have more caps and diodes, if it's that easy, awesome. I'll read through that thread some more.

For sure on the pump control. I haven't purchased electronic hardware for my build yet, so I could easily go with either a 12 or 24 volt transformer. Then just get the stuff I need to match. I'll be using low voltage contactors hooked to HOA switches to kill power to the elements totally, plus the planned 555 timer, so why not make the pump low voltage as well. The March 809-PL-HS-C draws 3.5A @ 12v and 1.8A @ 24v.

stlbeer said:

So how fast are these going to switch? My understanding of using a PWM for an SSR to control a boil kettle would be to change the frequency of the pulse. This makes switches the SSR more slowly thus making it last longer.

I suppose if you use the 10A version you could control up to that amount before needing to use an SSR and therefore wouldn't need an SSR.

So if you use either one you should consider determining how to change the frequency. I like your idea of throttling a pump. Might be a good idea to run that by Walter at March Pumps.

Click to expand...

I'm not to familiar with PWM and it's effect on the SSR's longevity. The frequency is controlled by one of the capacitors in the system right? And duration is controlled by the potentiometer, if I understand correctly. I guess if you don't like the frequency, you'd need to figure out which cap on those boards to replace and which way to go.

Event the 10A version is only rated at 12-60v, so you couldn't direct fire a heating element off of it, I don't think.

Good idea running this by Walter. I'll shoot him a PM.

I talked to Walter, he said that would work just fine.

This is officially on my build plans now. Problem is, the 24v March pump is about $80 more than it's 120v counterpart. So, I might have to weigh options when it comes time to pull the trigger.