Re: Relay Arc Supression Circuit
- From: "John_H" <johnhandwork@xxxxxxxx>
- Date: Tue, 14 Mar 2006 17:03:54 GMT
<richard.bair@xxxxxxxxxxxxx> wrote in message
news:1142352768.820768.256560@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I have the following circuit:
<snip>
I'm concerned about reverse bias on the LED when the realy lets go. I
measure about 7.5 Vdc across the LED when the relay lets go. I think
the zener and the diode act as a good method to handle the coil
magnetic field collapse and ensure fast armature motion but I do
violoate the 5 Vdc LED reverse bias voltage. Any comments or
suggestions for this circuit? I need to maintain the LEDs for
visibility and troubleshooting. I'm hoping this thread discusses some
general techniques for realy arc supression and addresses the LED in
this specific example.
Thanks!
Do you feel the Zener voltage is important? I only ever used simple diodes
across the relay coil. The voltage is quite a bit smaller to collapse the
magnetic field, but how long do you believe that collapse will take driven
into 0.7V? If the zener is removed, the LED is protected. If you change to
a 3.3V zener, your reverse voltage will hit about 5V - on the edge, but
better. If you feel strongly that the zener is needed, I like Ian
Stirling's idea of the doide across the LED which also gives you a snubber
resistor.
.
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