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555 timer

  1. Jan 29, 2009 #1
    Can you tell me what is wrong with my timer. I want it to make a relay open and shut periodically. For some reason it's not working.

    Attached Files:

  2. jcsd
  3. Jan 29, 2009 #2


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    Staff: Mentor

    You show your output directly shorted to ground. Is that correct, or a typo?
  4. Jan 29, 2009 #3
    Nope, that's how I made it.

    If I disconnect the output/diode junction from ground, would it sink the current?
  5. Jan 29, 2009 #4


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    Science Advisor
    Gold Member

    If you do the calculation from the numbers you give, the sink current would be about 11ma, so the 555 should be able to sink that.
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