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555 Timer Circuit

Discussion in 'General Electronics Discussion' started by wheelbrace, Nov 13, 2017.

  1. wheelbrace

    wheelbrace

    3
    0
    Nov 12, 2017
    Hi,

    Just wondering if I could get some help with my problem.

    I have a simple 555 time circuit that powers a flashing LED.

    This is for the inside of a car.

    When I connect the circuit to the battery with a short power lead it all works fine.

    However, when I put the circuit on a longer cable to be able to place the circuit inside the car the LED flashes once and then the circuit then stops working leaving the LED with a very faint glimmer.

    I have no idea why this happens.

    Thanks

    Dave
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,296
    1,886
    Nov 17, 2011
    There are a few possibilities:
    • Do you have the stabilizing capacitor from pin 5 (CTRL) to ground in place?
    • Do you have a bypass capacitor from Vcc to ground in place?.
    • What kind of wire are you using? A long thin wire may have excessive resistance.
     
  3. wheelbrace

    wheelbrace

    3
    0
    Nov 12, 2017
  4. Bluejets

    Bluejets

    3,488
    706
    Oct 5, 2014
    What is the LED you are using?

    When you say "connect to THE battery" ....which battery? The one in the diagram or the car battery?

    Length of the cable you are using should make no difference as the circuit only draws a few milliamps.

    Have you checked all your connections when you move to the car supply?

    Show a pic of your final arrangement in the car with as much detail as possible.
     
  5. wheelbrace

    wheelbrace

    3
    0
    Nov 12, 2017
    Ok,

    Thanks to both for your replies.

    The only battery I used is the car battery. I was messing around for ages checking for loose connections with no luck as I only have this assembled on a breadboard at the moment.

    However, I just connected a 10nf capacitor between pin 5 and ground and it now works!

    Thanks to both for your help and advice.

    Cheers

    Dave
     
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