LED unexpected sudden BLINK

Discussion in 'The Projects Forum' started by amcutp, Dec 25, 2011.

  1. amcutp

    Thread Starter New Member

    Dec 25, 2011
    4
    0
    Here is my friend's project about traffic light.
    The 5-bit counter using 74LS163 worked well since we can see the 5 LED indicated.

    BUt when deal with 3 types of light (RED: 25s, Yellow: 2s, Green: 5s), the problem comes since the RED light suddenly blink.

    I helped him to check the K-map n circuit but still can find the problem.
    So, I post it here n would like to ask from your suggestions.

    Thank you.
    (Refer to the attach file: junction1.ms11 : using Multisim 11)
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Can you post the schematic in .png format?
    Not all have multisim over here.

    Bertus
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You may have mistakenly purchased a blinking-type red LED. Once power is applied to them, they start blinking every 1-2 seconds.

    Use a multimeter to test the output voltage, or substitute another LED to see if that is the problem.
     
    amcutp likes this.
  4. amcutp

    Thread Starter New Member

    Dec 25, 2011
    4
    0
    here it is.
     
  5. amcutp

    Thread Starter New Member

    Dec 25, 2011
    4
    0
    I tried replacing with most of the available probe in Multisim 11. But, the same problem still comes.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, of course your red LED is flashing.

    You have the left 74LS163 being clocked, and the output goes to the yellow wire, which is ORed into the red LED.

    Didn't you expect that?
     
  7. amcutp

    Thread Starter New Member

    Dec 25, 2011
    4
    0

    The 3 RED, YELLOW, GREEN lights on the right hand side are results of logic combination of outputs from 2 IC 74LS163.

    Anyway, I think I don't get exactly what you really mean.

    My guess is is it the problem comes from using logic gates instead of IC for those AND n OR gates. I'm afraid of the speed problem.
     
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