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AC delayed off relay

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AC delayed off relay

Postby jack mcleod » Sun Feb 14, 2016 5:42 am

A ½ - ¼ sec. Delayed off of a 120v AC relay is needed. With a DC coil the cap goes in parallel. Can the delay be accomplished on an AC coil using a diode & a cap? If not how?
Thanks, Jack
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Re: AC delayed off relay

Postby KMoffett » Sun Feb 14, 2016 10:45 am

The short answer is no. DC relays depend in the coil resistance to limit the current. AC relays depend on the coil impedance at line frequency the limit the current. Applying DC to an AC relay will cause a much larger current to flow. which may cause excessive heating. And, even if that were tolerable, would require a much bigger cap to create any delay.
What are you switching on/off? Is powered hot and neutral still available at your switch after your load is turned off? There commercial Delay-off modules.

Ken

Ken
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