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Fail-Safe Latching Relay

Discussion in 'General Electronics Discussion' started by eaztridah247, May 6, 2015.

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  1. eaztridah247


    May 6, 2015
    I am looking to use a latching relay that also includes a fail safe state if power is loss. I know normal latching relays remain in the state they currently are in if power is lost, but I am looking for one that fails to a certain state upon loss of power.

    I have searched for a component that does this but have come up empty. Does anyone have any ideas?

  2. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    Tell us what your trying to achieve and maybe we could be of help.
    Maybe a latching relay is not necessary.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    An ordinary SPST relay with normally-open contacts performs as you describe. You wire the contacts between one end of the coil and the power lead to the coil. The other power lead goes to the other end of the coil. Until power is applied, the relay coil remains de-energized and the contacts are open. If power is applied to the coil, the normally-open contacts will close and continue to apply power to the coil, thus latching it on. If power is lost, the coil de-energizes and the normally-open contacts open. This is fail-safe operation. If you don't want the relay to re-energize when power is restored, the coil must be initially and momentarily energized from a normally-open switch wired in parallel with the relay contacts.
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