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
    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
    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
    I was hoping not to need a transistor, but if I need one I need one. Thanks