RE: [CAD_CAM_EDM_DRO] Relay question about diodes across the coil

AC relays can broadcast quite a bit of energy if you open the circuit while
the current is flowing. I have seen them take out an unattached laptop
about 8 feet away. A snubber circuit will stop this if you are switching
the coil with a contact like a switch or another coil. If you are switching
the coil with a triac then there is no chance to broadcast energy since the
current only stops flowing at a zero crossing.

Greg

-----Original Message-----
From: washcomp [mailto:jeff@...]
Sent: Saturday, January 10, 2004 8:06 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Relay question about diodes across the coil


Back when I was a kid learning about relay circuits on the job
(1960's), most of the control circuits I got involved in used low
voltage A.C. and I don't ever remember seeing a diode. I just found
out that it's good practice to put a diode across the coil of relays
to keep them from chattering due to the current stored in the coil
inductance. Question is: Only on D.C. relays or is this supposed
to be done on A.C. relays as well?

Jeff




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