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Best method for remote control of a PSU

Discussion in 'Electronic Basics' started by Hammy, Aug 24, 2007.

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  1. Hammy

    Hammy Guest

    What is the best method for remote control of a PSU just to control
    switching it on and off? I was looking at data sheets for relays DPDT
    but they all seem to require a holding current in the coil. Is there a
    relay that latches on for a single pulse and will stay latched until a
    second pulse is delivered? No coil holding current required from the
    battery operated control signal (see schematic).Or is there an
    alternative solution?

    This is the schematic. The transformers load is a 1.5W LM317

    Thanks for any suggestions.
  2. Guest

    Yes. They are called latching relays. Just about any large
    electronics supplier sells these (see Newark Electronics, Digikey,
    Mouser Electronics, etc.)

  3. ehsjr

    ehsjr Guest

    To begin with, eliminate NTC1, NTC2 and SW2.
    You don't need a DPDT relay - single pole
    is fine. And yes, there are latching relays
    that are pulse operated and do not require
    holding current.

  4. Rich Grise

    Rich Grise Guest

    Use the pulse to energize the relay, but then get power to hold
    the relay in from whatever it is you're powering. You'd need a little
    circuitry to turn it off, say a gate where if power is on, then when
    a pulse comes in, it gets inverted and interrupts the power to the
    relay, turning it off.

    Good Luck!
  5. Hammy

    Hammy Guest

    Thanks all for your suggestions.

    I think I may have found a suitable latching relay at Digikey (not
    much selection). I've noticed that they must be derated 75% for
    non-resistive loads. The largest current carrying capacity is two amps
    resistive load and 0.5A non-resistive.

    I have a 14VAC 4.4VA Transformer coming next week hopefully Monday; I
    can take some measurements to see if 0.5A_rms is adequate for sure
    with safety margin. The LM317 is for 12V @ 0.125A.
  6. neon


    Oct 21, 2006
    WHY DON'T YOU GET TO THE LM317 AND SHUT IT OF WITH A TRANSISTOR. leave the power input as is. which has to much protection for a lm317 regulator. protect the lm317 from the secondary not from the primary. i ruther think that you don't have 35 v dc on the secondary in that case why the overkill in move protection and what not.
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