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7 segment display driver and counter

Discussion in 'General Electronics Discussion' started by Jordy Dominicus, Apr 12, 2016.

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  1. Jordy Dominicus

    Jordy Dominicus

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    Apr 12, 2016
    Hello,

    I have a problem with my circuit and I don't know why it happens.

    I have a IC (CD4518BE) that counts like this: 0-1-2-3-4-5-6-7-8-9-0-1-2-3...

    The binary signals from my counter go into a 7 segment display driver.

    Whenever I connect all the outputs (a to g) to a red 3 mm LED and a 560 ohm resistor (one for each output ofcourse), my counter IC skips number 1 (0001).

    So it counts like this: 0-2-3-4-5-6-7-8-9-0-2-3...

    When nothing is connected to the outputs, it counts normally.

    Does anyone know why this happens and how to solve this?


    image.jpeg
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    Hello and welcome to E.P. Can we see your circuit diagram if you have one?
    Adam
     
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    First thing I would try is adding some supply de-coupling and support. Add as close to the IC as possible a 100 nF across each ICs power supply pins. Also add a 2.2 uF- 10 uF Tant or electrolytic capacitor ideally across each ICs power pins (observe correct polarity) but if you can't do that then add at least one. Make sure the voltage rating of the capacitor is at least double your supply voltage.
    Adam
     
    Jordy Dominicus likes this.
  4. Jordy Dominicus

    Jordy Dominicus

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    0
    Apr 12, 2016
    It's not the best drawing, I know.
    I'm creating a digital signal with a single supply opamp. (Covering the LDR creates a low voltage and exposing it to light creates a high voltage). The output of the opamp is connected to the clock of the counter. The 4 outputs of the counter are connected to a 7 segment display driver. image.jpeg
     
  5. Jordy Dominicus

    Jordy Dominicus

    5
    0
    Apr 12, 2016
    Wow, thanks, this actually worked ! This is my first year in school and I keep learning every day ! So these capacitors prevent a sudden voltage drop ?
     

    Attached Files:

  6. Arouse1973

    Arouse1973 Adam

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    1,081
    Dec 18, 2013
    Just a lucky guess :). Glad you have it working now.
    Adam
     
  7. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    Yes you are correct!
    Adam
     
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