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serial port powered relay.

Discussion in 'Electronic Basics' started by Jasen Betts, Sep 2, 2010.

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  1. Jasen Betts

    Jasen Betts Guest

    Serial port powered relay.

    DTR ----------------o----.
    | |
    | / 10K
    100nF === \
    | / RL 50 Ohms
    / | || ______
    Z0107AM __|>|______o__||____| |___
    | |<| || |______| |
    | || |
    | 100uF 16V latching |
    | bipolar relay |
    GND ---------o-------------------------------'

    I just threw it toogether and it worked, i'm not sure if the
    values chosen are optimum.

    I was able to commutate a 25A 250VAC rated relay
    with a 7.5V, 50 ohm coil

    the only down sidea are you need to wait 10s for the
    capacitor to charge before it'll switch and the
    slightly oddball parts.
  2. Wim Lewis

    Wim Lewis Guest

    Looks to be a small triac from Philips/NXP. The -AM is the package suffix,
    maybe just a typo for Z0107MA, which is a SOT54 aka TO92 package.
  3. Jamie

    Jamie Guest

    I think that is one of those ratchet relay's..
  4. Jasen Betts

    Jasen Betts Guest

    yes, that's the one. sorry about the bad label.
  5. Jasen Betts

    Jasen Betts Guest

    Set the oposite voltage on the input.

    PC serial port has a high resistance (about 1K2) and an open circuit voltage of
    about +/- 11v

    So if you model the input labeled DTR as a slow bipolar 11V square wave
    through a 1K2 resistor you'oull see that the circuit works by charging
    the big capacitor through the 10K resistor and then discharging it in
    a surge through the triac when the input changes polarity.

    Then you have to wait for it to charge up again.

    ¡spuÉÉ¥ ou 'Éꟽ ÊžooꞀ

    --- news:// - complaints: ---
  6. is it not the same!? output and input? off course, there's a differency
    in resistance ;-)
  7. :) I can't measure in electronics with you John Fields, yet. I have
    had luck...

    Thanks for the link!
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