TIme delays using 555 timers

Discussion in 'General Electronics Chat' started by kaz21, Aug 30, 2012.

  1. kaz21

    Thread Starter New Member

    Jun 11, 2011
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    I am trying to make a delay using a 555 timer. The delay should be 20second off and 1us on!!i tried all the calculation but i couldn't get the output from the multisim oscilloscope!!can some one please help me with this??
    thank you!!:D
     
  2. Adamf001

    Member

    Sep 5, 2011
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  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Not brillian, or tried, but maybe simple: A 555 one shot can give a positive 20 sec. pulse, but maybe you could differentiate trailing edge with .001 cap & 1k resistor, cleaning up neg spike with an inverting schmitt trigger or a comparator.??
     
    Last edited: Aug 30, 2012
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  4. crutschow

    Expert

    Mar 14, 2008
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    How square and accurate does the 1μs pulse need to be?
     
  5. #12

    Expert

    Nov 30, 2010
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    A 20 million to one ratio with resistors and capacitors? I expect to learn something from this one!
     
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  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    As I said : .001 & 1k into a 40106 and out came a flat topped 1.2μs + pulse. It was sure a skinney little thing tacked onto end of 21 m + pulse.
     
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