Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    berkeman

    User Avatar

    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

    dlgoff

    User Avatar
    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.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook