LED driver circuit

Discussion in 'The Projects Forum' started by Z.K., Jun 13, 2010.

  1. Z.K.

    Thread Starter New Member

    Jun 13, 2010
    I am trying to use a 555 timer to drive a CD4510 which then goes to a 4543 to drive a common anode 7-segment LED.

    I would post a schematic, but I can't find a schematic program that has all the components. The closest I can come is at this address

    I used mostly the same circuit though I did not use the code conversion circuit and wired the 4510 directly to the 4543 chip and I wired the go button directly as well. There is a square wave coming out of the 555 though it looks quite crappy on my scope.

    I have a feeling the circuit is not meant to be a counting circuit the way it is wired up. If I toggle the go line the value does change though it gives random values form 0 to 9.

    What I want is somehow to get the 4510 to act like a count up or count down timer. I want the display to start at 0, to to 9, reset to 0 and start over again.

    I was wondering if someone could give me a hand. I know I could probably use a PIC, but I wanted to get it to work this way before I move on to PIC programming.

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    A CD4510 is a BCD up/down counter, so it should work very well for you. A data sheet is invaluable, as it tells you what each pin function is.

    One problem causer is in not having every input pin tied to Vcc or to ground. If any are left floating, they will go to a level where they will cause oscillations and prevent the rest of the IC from working.

    One way to make a schematic is to draw it by hand (rulers are good) and scan to an image file (PNG is very good).
  3. Wendy


    Mar 24, 2008
    Emphasis on input pins.
  4. Z.K.

    Thread Starter New Member

    Jun 13, 2010
    I figured it out. The timer circuit was way too slow. So, I changed the values and added a electrolytic 10uF cap. Now, it works. I counts from 0 to 9, resets and starts over. Thanks though.