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Auto polarity changer

Discussion in 'Electronic Design' started by Bill, Sep 11, 2007.

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  1. Bill

    Bill Guest

    I need a circuit to automatically change output from a high to low, every
    time I remove power. How about like a 555 chip or some type of flip/flop
    that gives you a high output when triggered when you first apply power?
    After you shut the system off and turn it back on the output is low. Next
    time power off then when back on, the output of the chip is high.
    IOW alternate highs & lows each time the system is turn on. I hope my
    explanation is OK.

  2. Eeyore

    Eeyore Guest

    Here's a little conceptual snag for you. If you're going to *remove* the power,
    how is the circuit going to 'remember' which state to start up in each time ?

  3. Tim Dunne

    Tim Dunne Guest

    Google 'impulse relay' for a little conceptual enlightenment. They're used
    for duty cycling pumps, compressors and the like. Each powerup reverses and
    mechanically latches the state.

  4. Gary Tait

    Gary Tait Guest

    4013 with 9v cell, a few AAs, or a lithium cell to continually power the
  5. PIC12Fxxx (with EEPROM), a couple of TO-92s or 3-pin SMT devices
    (regulator and reset), a bypass cap, and a MOSFET/diode to drive a
    DPDT relay. 6 parts, thru-hole if you like. You would also need to
    write a (very) small program.

    Best regards,
    Spehro Pefhany
  6. Phil Allison

    Phil Allison Guest


    ** Hey fuckwit.

    Your Q requires the device to have a ** memory ** .

    Simple enough with a mechanical switch or similar.

    But ONLY a permanently powered electronic device or one fitted with
    special non-volatile memory can do that pony trick.

    Get real - you PITA wanker.

    ...... Phil
  7. D from BC

    D from BC Guest

    Posted so far I think was:
    uC with mem (ex: flash mem)
    logic + battery

    Here's my short term idea...CMOS logic + Supercap!

    D from BC
  8. neon


    Oct 21, 2006
    like the man said no power then what? but if you want use a couple of AND gates output to input as a latch. these guys have a forbiden state so use a cap on one input to condition the latch. good luck.
  9. Fred Bloggs

    Fred Bloggs Guest

    But when you read a lot of science fiction anything is possible. You
    specialistic nerds just need to tell him how to do it!
  10. Rich Grise

    Rich Grise Guest

    Mechanical latching relay. When power is applied, it pulls in in state 1.
    When power is released, it drops out, flipping the pawl. Then it's
    energized again, it pulls in in state 2, and so on.

    I don't know how common they are, or how you'd find one other than a
    google search, but when I was a kid the reversing button on our toy
    train just cut off power for a moment, and the train would back up,
    then, interrupt the power again, and it'd go forward again.

    Good Luck!
  11. Rich Grise

    Rich Grise Guest

    I thought we had a new rule here: No "use a PIC" posts without a
    full schematic, code, and link to the development system. ;-)

  12. Sure, and no ASCII schematics without complete parts lists, sources
    with price and availability, and worst-case calculations for
    tolerance, temperature variations and MTBF of every part.

    Best regards,
    Spehro Pefhany
  13. John Fields

    John Fields Guest

  14. Phil Allison

    Phil Allison Guest

    "Spehro Pefhany"

    ** Asinine false analogy.

    Grow up, pedant.

    ........ Phil
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