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555 timer

Discussion in 'Electronic Basics' started by tt, Sep 23, 2004.

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  1. tt

    tt Guest

    I am trying to construct a simple device for turning on and off three lights
    (one at a time). I have a traffic light that was blown down during a recent
    hurricane (obtained from the road dept.). It's frame was too damaged to put
    back up, but the lights work great. I would like each light to come on for
    a period then go out and the next light come on. I was thinking of using a
    555 timer because several years ago I managed to construct a wavemaker
    device for my fishtank that alternates power to two pumps creating a nice
    water current. That device is still working like a champ today.

    I looked at the plans for that wavemaker and I don't think it will do
    because I am trying to activate three items and not two. Can anyone suggest
    a solution?
  2. You can make the 555 pulse into 3 separate pulses using a 4017 chip. The
    datasheet shows how to set it up so when the third pulse ends, it starts
    over again.

    You probably will need some kind of power transistor to power the
    lights; the 4017 won't power them. However, the fishtank thing probably
    had the same issues, so this may not be a problem for you.

    Bob Monsen
  3. A 555 and a three digit shift register. each pulse of the 555 shift the
    output by one.

  4. Rich Grise

    Rich Grise Guest

    Actually, either 3 x 555 in a daisy-chain, or a counter and some selector
    logic, so that it'll be green for, say, 10 seconds, yellow for 1.5, and
    red for 15, and so on.

    Just have the falling edge of each 555's output trigger the next one,
    with the third looped around to the first.

    You would need some kind of startup logic and "forbidden state" prevention,
    but it sounds like a fun project. :)

    Good Luck!
  5. THREE 555s (plus associated RC sections etc) to light three lamps!?

    Bob's 555 (or any other simple clock generator) plus 4017 approach
    seems the obvious solution. Not only cheap and simple, but also
    flexible. It could allow gaps if desired between lighting, and/or
    different durations of the three colours, within the limit of 9 active
  6. P.S: Can you guess how many harpsichord sonatas are known to have been
    written by Scarlatti?
  7. BTW (straying slightly OT), can you guess how many harpsichord sonatas
    are known to have been written by Scarlatti?
  8. Sheesh! 555.

  9. Correct - you win the prize!

    In fact, I'm able to pass on this one to you, which I was proud to
    receive a few days ago:
  10. Rich Grise

    Rich Grise Guest

    None that are known by me. ;-)
  11. Thanks, Terry. I can see you were _fishing_ for just such an opportunity, too!

  12. If you started now and listened to one a day, I reckon you'd finish on
    1st April 2005 <g>.
  13. Rob Paisley

    Rob Paisley Guest


    For a 555 timer solution have a look at

    A suitable driver will be needed for the lamps as well.

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