Diode Needed For Solid State Relays?

[5artist5]

Diodes are commonly used to dissapate the high voltage feedback that is created when the magnetic field collapses after a relay or solenoid is de-energized.

I have been working under the assumption that solid state relays do not need this.

Is that correct?

[pshort]

Yes, it is correct.

[5artist5]

Oh good!
Thanks.

[4nntt]

Ha, disregard my original post, I missread the first post.

[pshort]

Disregard this post, it was the result of a misunderstanding.

[4nntt]

No, you're right. I didn't see the word "not" in there when I read it the first time, so I thought you were telling him he needed to add a diode. After re-reading, I went back and edited my post.

[hpropman]

Yes that is correct a standard relay needs the diode because it uses an electromagnet to pull the metal contact from pole to the other. when that magnetic field collapses after the power is removed from the relay it can cause damage to the driving transistor. That is why the diode is installed backwards because the current flows in the opposite direction when the field collapses. Solid state relays do not use an electromagnet. they use a triac that is optically isolated from the control signal.