Driving More than one SSR

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Andy Dean
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Driving More than one SSR

Post by Andy Dean » Tue Sep 05, 2017 5:25 am

Is it possible to drive more than one SSR from a single output by wiring them in series or parallel?

If so what is the maximum current load on a single Dout? The spec sheet for the SSRs I use state the control side current draw is <13ma, I don't think I will be going to drive more than two from one output.

Any help much appreciated.

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JonW
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Re: Driving More than one SSR

Post by JonW » Tue Sep 05, 2017 10:32 am

The outputs are rated for 20mA. 13mA is a little high for an SSR. Most I've seen are around 7-8mA draw, which would easily allow driving two (in parallel).

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Re: Driving More than one SSR

Post by Andy Dean » Wed Sep 06, 2017 5:24 am

Cheers, it does say <13mA on the spec sheet, so it may be down sub 10mA. I'll get a multimeter out and measure the current through one to make sure, that's the way to be certain I guess.

I take it overloading the output will damage it?

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oakbarn
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Re: Driving More than one SSR

Post by oakbarn » Wed Sep 06, 2017 1:23 pm

You could use a relay board to trip a replay and have that drive the two SSRs. That is what I do when I need more than a single SSR to trip on an asserted Out. The Relay Boards are fairly cheap on Amazon or Ebay. You do need a Power supply but I have those just lying around.

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Re: Driving More than one SSR

Post by Andy Dean » Mon Sep 11, 2017 5:37 am

Cheers Oakbarn! I was thinking that might be a better way to do it. I have one of those relay boards in my panel at the moment from Audiowind on eBay, that I use to control pumps and valves, I see they do a low load SSR board too which I might give a shot.

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Re: Driving More than one SSR

Post by clearwaterbrewer » Mon Nov 27, 2017 6:42 am

A good way to do this might be to put a transistor and a few resistors in a section of shrink tube and be done with it..

Look at the schematic (in the documents section)this project, remove all but R1, R2, and Q2, and you could drive several SSR's, the 2N3904 transistor can do 200mA (and it will work with 5 or 12 v, which is good for most BCS users)

https://www.sparkfun.com/products/retired/10684 (this project is not currently available, but you don'w want the project, you want the schematic)

schematic:
https://cdn.sparkfun.com/datasheets/Wid ... rd-v10.pdf


disclaimer - I ran my three homebrew elements with 2 SSR's each (one for each leg) for 5 years on the BCS without issue... I removed one set to lower the heat created in the panel.. oh, and electricity can KILL YOU...

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Re: Driving More than one SSR

Post by Andy Dean » Thu Dec 07, 2017 5:39 am

I Looked at the loading curve for the SSRs I use and sure enough its about 13ma at 5V. In the end I got a small Schneider electric SSR controlled by the BCS to feed 12v to the control side of the two power SSRs. Haven't tried it yet but it should work :P

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