Re: Relay Arc Supression Circuit
- From: "John_H" <johnhandwork@xxxxxxxx>
- Date: Tue, 14 Mar 2006 17:57:55 GMT
<richard.bair@xxxxxxxxxxxxx> wrote in message
news:1142357646.913735.237980@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hmmm, I'm no expert at all. That said, enlighten me! I thought the
rule of thumb was to target a zener voltage near the realy coil voltage
(5Vdc). I think the gist is that this will effectively start the
magnetic collapse sooner and provide a path for a 5.1 + 0.7 amount on
energy absoprtion back to the rail. If you go to high, it never
activates as the zener knee voltage is not met. If you go too low you
don't get the benefit of the zener and it acts more like a solo diode.
When both are in play, this aids in releasing the armature more
quickly. The load on the contact side of the realy is another realy
coil which drives an inductive laod.
Thanks for your time!
By using a 3.3V Zener instead of 5.1V, you have a Zener + Diode reverse
voltage maximum of about 5V instead of your measured 7.5V. The Zener plus
diode at highest current gives you the max reverse voltage for your LED.
If you want to use the Zener because you feel the reduced holdup is
important, consider a higher voltage zener and either 1) a diode reversed
across the LED or 2) a cap across the LED that just needs to keep the
reverse voltage from getting to 5V during the coil discharge.
.
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