A suggestion to reduce the relay release time when using a diode across the
coil: add a zener diode in series with the diode in connected across the
relay coil. This will dissipate the stored energy in the relay's magnetic
field faster (disappated as heat mainly in the zener). Make sure the zener
(5 to 15 or more volts -- something the other diodes can handle in PIV) is
connected the right way or not much will be gained.
Ed Guzis, W9TW
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Larry Kayser wrote:
Re: TopBand: Remote Beverage Switching
To: <topband@contesting.com>
Date: Sunday, December 29, 1996 4:52 PM
Bill wrote about back emf from a relay as the voltage is removed...
>I once ran some scope tests on suppressed vs. unsuppressed relay coil
>transients. The results were startling - an unsuppressed 28 vdc
>hermetically sealed aircraft relay can easily generate 600 volt spikes
>at the coil terminals. The addition of a back-biased diode across the
>coil nearly eliminates the spike.
This is not without a penalty however. The relay will be MUCH MUCH slower
in release time with the diode across the coil terminals.
Larry
va3lk / wa3zia
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