What is a solid state relay?

[Bronze]

A relay to me is a purely mechanical device. Is this another name for an SCR?

 

[jserrano]

The solid state relay (SSR) is the electronic equivalent of the electromechanical type.

Take a look at this picture and it will seem clearer.

http://www.ifirobotics.com/images/ssr_600w.gif

 

[Brian Brown]

A relay to me is a purely mechanical device. Is this another name for an SCR?

A solid state relay is a pre-packaged electronic module that can take the place of a traditional mechanical relay.

Typically the input feeds an optocoupler which, depending on the load, controls a Triac, SCRs, MOSFET, or IGBT. Sometimes there's extra circuitry to handle transient suppression.

Note that solid state relays are for AC or DC, but not both.

Brian.

 

[Nelson Pass]

Also, don't even Think of sending an audio signal through one.

 

[Brian Brown]

Also, don't even Think of sending an audio signal through one.

Yikes!

It never even occured to me that somebody might want to try that!

But now you've got me thinking about it.

 

[Havoc]

There are some small opto-coupled SSR's that can be used for audio. You do not use a 10A relay for audio do you?

Something to consider when using them: they do not provide galvanic separation like "real" relays do. You always have a leakage.

 

[peranders]

Also, don't even Think of sending an audio signal through one.

Nelson, this is not so crazy as you think. I'm not totally sure but I have a vague memory of a solid state relay with double MOSFET's. But still it's pretty crazy....