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PIR

Discussion in 'General Electronics Discussion' started by Electric-T, Aug 20, 2017.

  1. Electric-T

    Electric-T

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    Jun 4, 2017
    Can the output on a PIR sensor be solid? I need it to power an npn transistor to switch a relay. But i cant have it pulsing and interupting the transistor therefore flipping the relay on and off. Once triggered i need it to stay on.
     
  2. Electric-T

    Electric-T

    212
    9
    Jun 4, 2017
    Ill post a schematic so you can see my dilemma
     
  3. Bluejets

    Bluejets

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    706
    Oct 5, 2014
    Most $10 pir's have a timer output for around 30 minutes max. If you need more, add another timer.
     
  4. Electric-T

    Electric-T

    212
    9
    Jun 4, 2017
  5. Bluejets

    Bluejets

    3,489
    706
    Oct 5, 2014
    The units I was referring to are exterior mount 220v. What you have is a pir module which will need additional circuitry or equipment. Might be a good idea for you to check the specs. I did, in the link you provided. See how you go then....
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    9,296
    1,886
    Nov 17, 2011
    Use an S-R flipflop. You can build it from discrete components or use an integrated logic circuit. Teh PIR sensor would be connected to e.g. the SET input such that after the first pulse from teh sensor the output of the flipflop is active and stays active regardless of the input.
    You'll have to think about how the flipflop is to be Reset, otherwsie it will be on forever (at least as long as the power supply lasts).

    If you want the output of the circuit to be active for some time only, use a monostable multivibrator. A very simple circuit is e.g. based on the venerable 555 timer ic.
     
    Electric-T likes this.
  7. Electric-T

    Electric-T

    212
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    Jun 4, 2017
    Thank you ill look into it
     
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