solid state relays

ehall · Jul 13, 2009

I have an application that may need solid state relay and am looking for information. Basically what I've got a switched circuit with a light on it that I want to reuse to activate another circuit. This doesn't work with a traditional relay since the coil passively consumes the current on the circuit but does not draw any current on its own. So put incandescent bulbs in the circuit and they draw good current, but the coil in the relay consumes it all by producing a bigger and bigger magnetic field until nothing is left to drive the bulb filament. With LEDs it's the exact opposite--they do not need draw hardly any current, so there is not enough juice to charge the coil, even though the lights are on.

Can I use a solid state relay in this application so that the lights would draw current without the relay consuming it all.

alex22 · Jul 13, 2009

If by "solid state relay" you mean a transistor than it would work. I did a few labs using a transistor to turn a LED on in Electronics class.

jeeperjohn · Jul 13, 2009

There's good info to be had here:
http://www.opto22.com/

You need a relay that can be triggered with the very small current of a LED. If you can be more specific about what you are trying to do I can help you design a circuit for it.

panzerjeep · Jul 14, 2009

Put the led on the relay output (30 or 87) and energize the relay directly by the switch and battery.

RCP Phx · Jul 14, 2009

ehall said:
I have an application that may need solid state relay and am looking for information. Basically what I've got a switched circuit with a light on it that I want to reuse to activate another circuit. This doesn't work with a traditional relay since the coil passively consumes the current on the circuit but does not draw any current on its own. So put incandescent bulbs in the circuit and they draw good current, but the coil in the relay consumes it all by producing a bigger and bigger magnetic field until nothing is left to drive the bulb filament. With LEDs it's the exact opposite--they do not need draw hardly any current, so there is not enough juice to charge the coil, even though the lights are on.

Can I use a solid state relay in this application so that the lights would draw current without the relay consuming it all.

That doesnt make any sense at all !!!

brycexj · Jul 14, 2009

I'm going to ask a stupid question but I hope you have the coil of the relay wired in parallel with the the light bulb. If you have it wired in series this may explain the problem you are having. But if this is not the case a solid state relay will draw less current and most likely solve your problem.

old_man · Jul 14, 2009

I'll second that not making any sense. I'm an electrical engineer. Just for your info, a SSR only works for switching AC. They can be powered by either DC or AC or current, depending on the model.

Draw a schematic (picture) of what your existing circuit looks like, then show what you want to add.

ehall · Jul 14, 2009

I got it figured out now thanks

I wasn't aware that SSRs were AC output only that's interesting

solid state relays

ehall

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alex22

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jeeperjohn

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panzerjeep

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RCP Phx

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brycexj

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old_man

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ehall

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