Timer 555- variable delay

Discussion in 'Homework Help' started by donJuan85, Feb 7, 2014.

  1. donJuan85

    Thread Starter New Member

    Feb 7, 2014
    3
    0
    hi,
    I need help to build simple circuit, using timer 555 or something similar.
    Most important for me is that output signal has to appear in variable delays.
    it's mean that once signal is sent with 2sek delay, next time with 5sek, another time delay= 3sek. Hope you will understand :)

    [​IMG]

    thank's
     
  2. kkazem

    Active Member

    Jul 23, 2009
    160
    26
    Well this is quite easy. Use the 555 app note for the basic one-shot or astable multivibrator. Next use a pot if you want adjustment over a range of delays or use a multi position switch with different res values if you want a few specific time delays. You should be able to get it from here. Regards, Kamran Kazem.
     
  3. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi don,
    Do you mean automatically increment/decrement after each pulse.?
    2sec > 5sec > 3sec

    E
     
  4. donJuan85

    Thread Starter New Member

    Feb 7, 2014
    3
    0
    It's exactly what I mean, outgoing signal has to be "mystery" for me.
    Of course, 3 different periods (3sec;5sec;2sec) will be completely enough.

    Kamran Kazem, does your suggestion will be suitable for my assumptions above?

    Regards,
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    How about a standard 555 delay circuit, but rather than charging the timing cap from the supply, it charges from the output of very slow free running triangle wave, or ramp generator?
     
  6. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi Don,
    You could configure a 555 timer that clocked a 4017 counter/decoder.
    Use the 10 possible states of the 4017 outputs to select different 555 charge rate resistors.
    Look for 'School Bell' 555 timing circuits on the web.
    If you cannot find a suitable one, let me know.
    E
     
  7. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    This is what I was thinking for random time delays.
    I don't understand what you circuit needs for reset or output.
    This is my idea for a random one-shot.
     
  8. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi inwo,

    I 'think' the OP is trying to build a fixed repetitive 3 group of fixed time periods, rather than random periods, for some sort of 'guess' game.?:confused:

    OP, we need more details of what you are trying to do.
    E
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Sounds random to me. The number of periods seems immaterial.

    It's a mystery to me.:D
     
  10. donJuan85

    Thread Starter New Member

    Feb 7, 2014
    3
    0
    hi again,
    my friend told me to use AVR, it's different way but i can try.

    i'm trying to build start machine for training.




    let's simplify, when i push "ready to race" button i need to be focused when the green led light up. The time between pushing the button and light signal has to be unknown for me.
    that's the idea:)

    br
     
  11. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    That's what I thought.

    Not sure I want to build it. (posted circuit) Maybe someone could simulate it and set the RCs to your times.
    (and fix any mistakes):D
     
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