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Using a PIR to turn a light OFF

Discussion in 'LEDs and Optoelectronics' started by AndyC, Oct 10, 2017.

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  1. AndyC

    AndyC

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    Oct 10, 2017
    Hi!
    I'm trying to find a "reverse PIR" (for want of a better description)! In other words, one where the light is permanently on, then when the PIR detects motion, it turns the light off, then after a fixed period the light automatically comes back on again. Anyone know where I can buy such a thing? I've googled it extensively, but - as you'd expect - all searches end up on pages talking about using PIRs in their normal switching-stuff-on role.
    Failing that, anyone know how to make one? I'm an absolute electronics novice, but happy to try to follow a set of instructions! :)
    Cheers,
    Andy
     
  2. vijaykrishna

    vijaykrishna

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    3
    Sep 9, 2017
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,449
    2,809
    Jan 21, 2010
    Connect the pir to a relay and use the normally closed contacts to drive the load. When the pir activates, the relay is pulled in, turning the light off.
     
    vijaykrishna likes this.
  4. vijaykrishna

    vijaykrishna

    35
    3
    Sep 9, 2017
    nice, i never taught of that.
     
  5. AndyC

    AndyC

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    Oct 10, 2017
    Cheers guys! Shall ponder the relay option - that sounds like a possibility. Ta!
     
  6. duke37

    duke37

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    769
    Jan 9, 2011
    There may be a changeover relay in the PIR or you may be able to fit one.
     
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