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Simple one shot connection on timer

Discussion in 'Electronic Design' started by [email protected], Nov 4, 2007.

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  1. Guest

    I need to activate a machine in x hours after turning on a timer.
    The machine has tip-touch buttons so I guess I can use the 2 poles of
    the start-button while leaving the original circuits connected.

    Does anybody know what circuit I need for this application?

  2. Jamie

    Jamie Guest
  3. Frank Buss

    Frank Buss Guest

    This depends on the maschine, but maybe it is possible, e.g. with a
    transistor, parallel to the button.
    If you have power supply, too, you can use an oscillator and some HC4040 or
    other counters. With a LM555, which generates a 100Hz signal, you can delay
    more than 40 hours. This is the no-programming solution and useful, if you
    have already the counters and an oscillator.

    Another nice one-chip solution, but more complicated, is to use a MSP430 or
    PIC microcontroller, which are available with integrated oscillator. I
    think the assembler program can be written in less than 10 lines. With some
    more external components you could implement an adjustable delay, e.g. with
    a potentiometer and the integrated ADC of some microcontrollers, or with a
    standard digital GPIO by measuring the time needed for charging and
    discharging a capacitor with a potentiometer.
  4. Frank Buss

    Frank Buss Guest

    This could work, if the relay is used for switching the buttons, but looks
    a bit expensive and is not necessary, because the mains power needs not to
    be switched.
  5. Tolstoy

    Tolstoy Guest

    You have a style more minimalist than the redacted Raymond Carter.

    Unclear whether
    A) You want a timer circuit, or
    B) You already have a timer, and you want to know how to connect it to
    your machine.

    If (A), you don't have to spend a lot of money, or do a lot of circuit-
    building (unless you want to).
    The surplus houses like, electronics goldmine
    ( etc. often have digital or mechanical timers
    in stock. Like the digital timer from a Mr. Coffee machine
    allelectronics had for 5 bucks a while back. People that want to turn
    on a bathroom heater before they wake up or something like that often
    will use such surplus timers.

    If (B), you should give more information. We know nothing about this
    machine of yours. Is the "tip-touch" button one of those things that
    works by capacitance sensing? You might not even have to connect your
    timer to the button itself, you know. It isn't the button you want to
    turn on, it's the machine. Anything's possible, until you give us a
    post with some meat in it.
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