555

Discussion in 'The Projects Forum' started by ht systems, Aug 21, 2011.

  1. ht systems

    Thread Starter Member

    Aug 2, 2011
    71
    1
    can i use an ac voltage as an input to 555 circuit ?
     
  2. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    yes
    .......
     
  3. ht systems

    Thread Starter Member

    Aug 2, 2011
    71
    1
    thank you , i guess i have to try it
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    The powersupply of the 555 MUST be DC.
    What input do you mean?
    The trigger input may NOT go negative and above the DC voltage of the powersupply.

    Bertus
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, no - it can't use AC directly as an input, as AC implies that the signal goes above and below the 0v reference; the negative voltage would burn up the 555 timer.

    It might use rippled DC input, as long as the rippled DC did not exceed the limits of the timers' power supply rails.

    Rippled DC can resemble AC (as a sine wave), but isn't centered around the 0v reference.
     
  6. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    Good point, wookie. I missed that. Or did I assume ht knew that? It's so hard to guess the intellectual level of a person when you've only seen him make one sentence.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Always assume the worst. And ask for a schematic.
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Could use clipping diodes to VCC & GND with current limiting, also capacitive couple input.
     
  9. JingleJoe

    Member

    Jul 23, 2011
    185
    10
    Sometimes I feel like I am the only person who can see this thread.
     
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