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Simple Seven Segment Counter Project Help?

  1. May 9, 2013 #1
    Hello Guys,

    I am trying to do a simple digital electronics project where I put two seven segment displays and once I connect the voltage source, the displays start counting automatically from 00 to 99.

    Here is a video of exactly what I want to do:

    My group and I found the attached schematic which we think is what we need to build to make the circuit in the video.

    We built it, but the displays just show two values which sort of look like "A", and it doesn't change.

    I was wondering, could someone tell me if that particular schematic does what I want to do?

    What is the use of the timer? Is that what increments the values from 00 to 99??

    What is the use of the potentiometer? To adjust frequency?

    Thank you all very much!

    Attached Files:

    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. May 9, 2013 #2


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    The 555 timer chip supplies pulses to pin 1 of the units counter 4026 the output on pin 5 is carried over to pin 1 of the 10's 4026 counter

    its possible that you have the 555 oscillating too fast and its counting to 100 in a second or so.
    ie. too fast for you to observe the count
    first determine how fast the 555 is pulsing, look at its pin 3 output on an oscilloscope and adjust the trimpot R2 so that its pulsing at say ... once per second

    Last edited: May 9, 2013
  4. May 9, 2013 #3
    This is not really a schematic. It is a wiring diagram. I'd have to look up the data for the chipsto knw if it would work. That should be your first step. Download the data sheets and read them

    Yes that 555 chip is an oscillator. the very first debugging step is to make sure it is oscillating and at the desired frequency. Do you have a 'scope. It not

    Remove the LEDs and the counter chips and get the 555 to oscillate and maybe simply blink a LED. Then build the counters and LEDs and get it to count a bush button. It should increment at each push. Next combine the two circuits
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