High trigger monostable 555 timer with IR motion sensor

Discussion in 'General Electronics Chat' started by vedrit, Apr 27, 2013.

  1. vedrit

    Thread Starter New Member

    Apr 27, 2013
    3
    1
    I'm trying to put together a circuit with a 555 timer in monostable with an IR motion sensor acting as trigger. The vast majority of circuits for the 555 in monostable require a low trigger, but the IR sensor is a high trigger.
    The few circuits that have a high trigger don't work. The IR sensor puts out a 5vDC and the overall circuit is 13vDC.
    I apologize in advance, I don't have a circuit drawn up since I've pulled it apart, and I've been basing it off of pre-designed circuits.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Use an npn transistor to invert the trigger signal, with a 10K resistor to the Base, collector to pin 2 of the 555 with a 10K resistor to pin 8.
     
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    Last edited: Apr 27, 2013
  3. vedrit

    Thread Starter New Member

    Apr 27, 2013
    3
    1
    I was hoping not to need a transistor, but if I need one I need one. Thanks
     
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