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astable 555

Discussion in 'Electronic Design' started by [email protected], Jun 13, 2007.

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  1. Guest

    I am trying to trigger an astable 555 oscillator using another 555 in
    the monostable mode. Everything I see says that the astable 555 is
    free-running. Is there a way to trigger it using the monostable?
     
  2. homermandoh

    homermandoh Guest

    Do you mean you want to syncronize the astable somehow? The astable
    555 shouldn't need a triger to start working.
     
  3. John Fields

    John Fields Guest

    --- _____
    Connect the output of the monostable to the RESET input of the
    astable. The astable will run while the monostable's output is
    high.
     
  4. Guest

    I have a board that inputs 8 pulses to a counter and after the 8th
    count it is to trigger a one-shot 555 which will start a delay for
    about a min. Then the one shot needs to trigger the oscillator after
    the delay.
     
  5. Your description is fully unclear (to me).
    What do you mean by "trigger the oscillator"?
    Is the oscillator is supposed to run until the monostable starts and run
    again when the monostable has timed out? If not, what will stop the
    oscillator and when?

    petrus bitbyter
     
  6. Guest

    The monostable is acting as a delay of approximately one minute. The
    astable should be off until the delay is up. Then I want the astable
    to start oscillating.
     
  7. John B

    John B Guest

    So at the third attempt you have almost managed to tell what you are
    actually trying to do. I assume this is homework and needs to be
    completed by the end of the week.

    What you are describing is a 'Gated Oscillator'. Read the words I have
    just written then go back to your lecture notes and look for 'AND
    Gates' amongst your material on 'Digital Logic'. If your lecturers have
    done a half reasonable job you will find what you need to know.

    If you still cannot make sense of it go to sci.electronics.basics and
    someone will answer your question there. After that I suggest you give
    up trying to be an electronics design engineer and try journalism.
     
  8. As far as I'm informed now, you should make the monostable trigger a
    flipflop which in turn can start the oscillator.

    BTW. Your understanding of electronics looks like very minimal to me. You're
    apparently a newbie rather then a designer. You still did not answer my
    questions, even don't seem to understand why I asked them anyway. Better
    post in sci.electronics.basics next time.

    petrus bitbyter
     
  9. Jasen

    Jasen Guest

    you can use the reset pin to stop or start it.

    Bye.
    Jasen
     
  10. Fred Bloggs

    Fred Bloggs Guest

    Sure:
    View in a fixed-width font such as Courier.


    ..
    ..
    ..
    .. ___
    .. ENABLE/RST>-----------------.
    .. |
    .. |
    .. --------------
    .. | RST |
    .. V+ | |
    .. from mono | | DIS OUT |----.
    .. --------- | | | |
    .. | | [10K] | | |
    .. | | | | | |
    ..--- ->-||-[1K]-+---| THR/TRIG | |
    .. 0.1u | | | |
    .. [10K] -------------- |
    .. | |
    .. --- |
    .. |
    .. -------------- _ _
    .. | RST | | | | | ..
    .. | |- - -
    .. V+-[1K]-+--| DIS OUT |-------->
    .. | | |
    .. [Rt] | |
    .. | | |
    .. +--| THR/TRIG |
    .. | | |
    .. Ct | --------------
    .. ===
    .. |
    .. |
    .. ---
    ..
     
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