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problems with 555 timer.

Discussion in 'Electronic Design' started by [email protected], Aug 14, 2006.

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  1. Guest

    Hello, everyone. This is my first electronics project, and all I'm
    trying to do is get a light to blink. I looked up schematics on about
    10 different websites, all which have failed.

    I have a 9 volt battery, the proper resistors, capacitors, etc. It's
    driving me nuts.

    Generally, the problem is all the schematics call for pin 1 to be
    connected to ground, and pin 8 connected to V+. I don't know exactly
    what this means, so I connect pin 1 to the negative current, and pin 8
    to positive current. When I do this, I feel like it's shorting out or
    something, because nothing else on the breadboard (like an LED in
    parralel to the 555 circuitry) will work, and the battery starts to get
    really hot.

    But besides that, I do everything exactly as in the schematics, and
    everytime nothing works.

    I'm getting really frustrated at this thing because I set up everything
    exactly as in the schematics, plug it in, and nothing happens. I would
    really appreciate your help, as I've pretty much exausted every 555
    timer website on the net for help.

    Thanks for your help,
  2. Guest

    Post a link to your schematic, if possible (on a personal website).

    Try building this circuit to test your 555 (maybe it's burned out?)

  3. Then there is something wrong with the 555. As long as you have
    correctly identified pin numbers 1 and 8, then applying power should not
    result in a large current draw.

    Check here:
    Try another 555.
  4. Donald

    Donald Guest

    Please send us your schematic.

    Not the web site schematic, the schematic of the thing _you_ wired.

    PS: maybe your in the wrong hobby.
  5. Mark Fortune

    Mark Fortune Guest

    Very little information to go on, but i'll give it a shot..

    It does sound like something is shorting out. what schematic are you
    working from exactly? also make sure you have the capacitors connected
    the right way around as specified in the schematics.
    If you do have a picture of how you've wired it all together too, and
    can post it on the web somewhere that would be very helpful.

    What light are you using (the one you want to blink) as its possible
    it's drawing too much current. A 1KOhm resistor in series with an LED on
    the output draws very little current and is a good indicator of wether
    it's working.

    Is the chip the right way around, and also is your understanding of the
    pin layout correct, it should be as follows:
    [1]| u |[8] (+)
    [2]| |[7]
    output==[3]| |[6]

    there's a very basic circuit on my site for a 555 astable timer,
    although you've probably come across the design before (it's quite
    popular as a beginners model)
    </blatent advertising>

    Although the schematic states 12V, the circuit should operate at any
    voltage in the range +5v to +15v

    a good starting point is to use a 220uF capacitor for C1 and R1 and R2
    as a 2KOhm resistor for R1 and a 5KOhm resistor for R2, that should give
    you an on time of about 1 second and an off time of about 0.7 seconds.

    If all else fails, your 555 chip could be dead. do you have a spare to
    try it out with?

  6. Tim Wescott

    Tim Wescott Guest

    Naa, if your response to seemingly insurmountable, unexplainable
    problems is to keep trying then you're definitely cut out for electronics.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  7. Mark Fortune

    Mark Fortune Guest

    Mark Fortune wrote:

    I put the (-) terminal in the wrong place. Should be:
    also notice the little notch at the top of the chip

    My bad!

  8. Guest

    This is the schematic... the basic astable 555 that I know and hate.

    Maybe I shorted it out somehow, today I'm going to buy another 555 and
    try it again.

    For now.. can you guys tell me if this should happen?

    (-) 1 | u | 8 LED (+)

    negative to pin 1, pin 8 to LED to positive. Nothing else is connected

    The LED turns on very bright... is this proof my 555 is toast?

    Thanks for the help... if I have more trouble I'll post pics.

  9. Luhan

    Luhan Guest

    Since you probably cannot read a schematic, could you post a link to a
    close up photo of what you have built?

  10. Mark Fortune

    Mark Fortune Guest

    Why are you connecting the LED to pin 8 (+)?

    pin 8 should be the +v source for the 555 and should be connected direct
    to the +9v supply. If you put the LED where you said you have then the
    555 is probably not getting enough power to start up, and if you've not
    got a resistor in series with the LED chances are the LED should have
    burnt out by now.
  11. It's a very good site BUT it's far too comprehensive for a beginner.

    Look at Figure 5, that is the thing to build. You can study all the rest
    AFTER you've got Figure 5 to work.

    Yes, your 555 may be dead. They are difficult to kill, but it can be
  12. Guest

    Mark, this wasn't part of my schematic... I was wondering if this
    proves that my 555 is broken or not.

    I am in fact new to electronics, but I don't expect the below schematic
    to magically cause an LED to blink.

  13. The proper newsgroup for questions like this is sci.electronics.basics

    Besides, if you are asking about timers here, the proper solution is
    generally a microprocessor.

  14. Probably, but without knowing how you have connected the other pins, we
    can't be sure.
    You are getting some rather abrupt responses, which don't help much.
    This is because you are really in the wrong newsgroup. You should be in

    However, now you ARE here, we will try to help. Have you built that
    Figure 5 circuit? If so, tell us what happens.
  15. Oh, no! Not another one. 555 timer, what, 50 cents all up? Time to first
    blink 30 minutes maximum, if you don't goof.

    Microprocessor timer 10 cents for the chip, USD100 for the development
    system and four weeks to learn to program it.
  16. Tim Wescott

    Tim Wescott Guest

    But then you can make it blink in Morse code!

    I use both, but each in it's appropriate spot. If _all_ you need is
    blinky, a 555 is the way to go.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  17. Not to mention that this "to 555, or not to 555" question may lead to
    a life-changing decision for a promising, heroic electronics designer
    eventually slipping away into the evils of software programming and
    the corrupting influences of its dark minions. ;)


  18. If you were really good, you could make it flash in Morse code with
    some 555s! ;-)

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida

  19. You're right! When will people learn that you really do have to add
    some bleach when they wash their minions? ;-)

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  20. John Fields

    John Fields Guest

    Please bottom post or in-line post where necessary.
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