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2 pir motion sensors Help!

Discussion in 'Sensors and Actuators' started by NickHammer, Mar 8, 2017.

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  1. NickHammer


    Mar 8, 2017
    Hello, i have 2 SR 501 pir motion sensors, im looking for a circuit that could work like this:

    both sensors have to be active(listening for motion) when one of them detects motion then it has to trigger my raspberry GPIO input but also it has to make the other sensor stop detecting motion.

    About a week ago i asked in yahoo answers and one guy told me to use a bc547. He said;
    "Use a BC 547 to supply power to the motion sensor A, by keeping V+ at collector and taking output from emitter to power the motion sensor A when a signal is sent to the base of the BC 547 each time motion sensor B is active."

    I made a schematic of how i understood what he said. Is right here

    Can someone help me to make the circuit i need or advice me about the circuit that i stated above? Thanks
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Your schematic follows the advice you've been given and is basically correct.
    However, the advice was not good. Using an NPN transistor to switch the positive supply is not a good idea as the emitter voltage will be always 0.6 V ...0.7 V less than the positive supply. This can make a difference.

    Look in our ressources section how it is done the riight way.
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