Solid state relay receiving 120 volts Dimmer switch

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1

I’m new here and not sure if this is in the right area so feel free to move it if not.

I’m asking a question for a friend he has a solid state relay receiving 120volts would it be ok to place a dimmer switch before the relay. Would there be any adverse effects. Thank you in advance for any response.

2

I’m not sure I’m entirely understanding the situation but if the relay is turning the 120 on/off prior to the the dimmer, it’s just like any switch and so there shouldn’t be any adverse effect.

3

No he wants to put the dimmer switch in before the relay so it would be straight 120 out to dimmer then from dimmer to relay.

4

Here is a little better explanation of what hes trying to accomplish from a post he made on another site.

I have 4 sets of lights controlled by 4 solid state relays. I’d like to dim them all with one standard household AC dimmer.Ideally, I’d wire this dimmer inline before the AC power reached the relays. However, I’m not sure this is healthy for the relays. Does anyone have a definitive answer on this?Otherwise, I could place four separate dimmers after each of the relays in the circuit, but this is more expensive, awkward, and would make hit harder to get them all dimmed at the same level.So, can I place the dimmer in front of the SSRs with no consequence?Thanks for your time!

5

The way I understand it… The relay is a dry set of contacts… No matter what the modulation is before the relay is its going to switch it. As long as your not over powering the relay… (Which I’m sure your not by dimming it.). With a dry set of contacts it basically will just create continuity regardless of how you modulate it. Hope this helps:smile:

6

thomas_ambers:
So, can I place the dimmer in front of the SSRs with no consequence?Thanks for your time!

I'm not sure. There are two types of dimmers commonly used, those that chop off the leading edge and those that chop off the trailing edge. (see below)

http://sound.westhost.com/lamps/dimmers.html

The latter shouldn’t present any problems for the SSR. Unforetunately they seem to be the least common. The chopped LE dimmers could present a couple of problem that I can see. First the chpped LE waveform presents a higher dV/dT to the SSR than is normal and I could forsee a case where that results in unexpected turn ons of the SSR when it’s supposed ot be off. And because the turn on is abnormal, there will be higher losses in the SSR and thus a potential for overheating.

Secondly I wonder what happens if the SSR is intended to be turned on at the zero crossing to reduce it’s internal losses and heating. If a zero crossing SSR is presented with a chopped LE waveform, will that lead to overheating ? And if it does, will the load presented by the set of lights be heavy enough to cause a problem ? With out knowing the specifics I can’t say for sure but some caution seems warranted. If he cares to, run the dimmer with just 1 SSR circuit and monitor it’s case temp when both on and off. It would be a good idea to e-mail the manufacturer and ask the question above.