Connect with us

555 Flashing LED

Discussion in 'LEDs and Optoelectronics' started by Grex, May 24, 2012.

  1. Grex

    Grex

    7
    0
    May 24, 2012
    Whats up guys,

    So I hooked up an LED with a 555 timer and am trying to get the LED flashing.

    http://www.555-timer-circuits.com/flashing-led.html

    I built the circuit based off the schematic shown in the link above, but my LED will turn on and remain on. I'm using 9v power supply and a 47 micro-farad capacitor instead of the 1micro-farad cap he recommends using. If anyone has any idea as to why this is happening hit me back.

    Thanks,
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Do you have the 555 around the right way?

    have you connected everything up correctly?

    Do you have the correct value components?

    These are the three common mistakes.
     
  3. Grex

    Grex

    7
    0
    May 24, 2012
    555 is in right way. Pin 2-6 & 4-8 connected... Values of components should be ok. I found that I didn't have pin 1 connected to ground now that its grounded, the light doesnt come on at all. Now I'm really confused haha
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Picture?
     
  5. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    I don't see the capacitor.
     
  7. Grex

    Grex

    7
    0
    May 24, 2012
  8. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    I didn't either but figured it could be hiding behind the resistor and black wire due to the bad angle and jpeg compression at such a low resolution...
     
  9. Grex

    Grex

    7
    0
    May 24, 2012
    Yeah sorry, just uploaded a new pic.

    Should there be an additional capacitor going from pin 5 to ground or is that optional?
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Yeah, you should be able to get away without that other capacitor.

    Is it possible you have the capacitor around the wrong way (or have had)? It looks like a tantalum and connecting it backwards can increase the leakage current dramatically (and permanently). If you can measure the resistance of this capacitor and it stabilises at 2M or more then you're probably safe. Alternatively, try another capacitor.
     
  11. Grex

    Grex

    7
    0
    May 24, 2012
    Forgot the tantalum's were polarized ... I flipped the cap now the light comes on an stays on. I don't have a multimeter on me to measure the cap though, unfortunately.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    It is possible that the leakage is high enough that the capacitor never charges.

    I presume you've left it powered for 30 seconds or more? The time constant is around 15 seconds for these values, but the first time its powered up the initial delay could be 50% or so longer.

    If you have another capacitor, try that. or try reducing the value of the 470k resistor.
     
  13. Grex

    Grex

    7
    0
    May 24, 2012
    Alright, I managed to find a 1micro farad electrolytic cap... I put it in and still no luck. Also tried switching to lower resistance but no go...
     
  14. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Jiggle all the wires and twist the chip a bit... I hate stab lock boards and have wasted a great deal of time banging my head due to poor connections over the years when using them...
     
  15. Madmax3zero

    Madmax3zero

    6
    0
    May 26, 2012
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-