555 and 4017 circuit?

Discussion in 'The Projects Forum' started by altontoth, Mar 14, 2010.

  1. altontoth

    Thread Starter New Member

    Apr 11, 2009
    I'm trying to come up with a circuit for a Scout leader, to trigger a starting light tree for a pinewood derby. The trigger signal from the computer is up to 0.5sec duration high. I want that signal to trigger a countdown of the lights (4 sets of yellow and one set of green), starting up at the first set of yellow in it's 'default' state, then sequencing through the other 3 sets of yellows at .5sec intervals or so (with a .25sec gap in between lights), then going green, and staying there until reset.

    My automatic thought was to go straight to a micro controller (that's how I happen to work), but I'm SURE that there has got to be a discreet components way to do this. The pulse signal coming from the serial port CANNOT be made longer than .5sec, so anything happening in the electronics needs to be able to 'latch' off that, or something.

  2. whatsthatsmell

    Active Member

    Oct 9, 2009
    What else has to happen when the light goes green? Does the circuit need to start a timer or trip a gate to release vehicles? Or is the green light just a visual queue? What happens when there is a false start (or in drag racing, a red light)?
  3. Wendy


    Mar 24, 2008
    I'll help you modify my schematics to your basic ideas. I've done similar in the past.

    Have you read this?

    LEDs, 555s, Flashers, and Light Chasers

    Pay special attention to Chapter 9.

    What current do your LEDs need? It would also be possible to put a piezo or buzzer in the circuit, if you'd like.
  4. altontoth

    Thread Starter New Member

    Apr 11, 2009
    Buzzer I don't need. I was planning on driving transistors to be able to either power led clusters or to drive relays for 120V lamps.

    Ultimately when the light goes green, a solenoid will also be triggered for a gate release.

    Typically with these starting lights, red lights are displayed at the end of the race (after 10sec or when all cars finish), for a couple seconds while reporting is done and the system resets.

    However, since this would be a 'dummy' connection to the rest of the system, I wasn't planning on trying to catch an end of race command or anything (I don't know the commands for the timer system in question), and was therefore going to just omit the red indicators (unless there is a way to do it).

    I will totally read up on your link; I wanted to post a reply here first.