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use a PIR sensor as a light sensor switch

Discussion in 'Sensors and Actuators' started by beerzinnss, Sep 26, 2016.

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  1. beerzinnss


    Sep 26, 2016
    I have this light/motion sensor to turn on my flood light outside: ;
    My question is - would it be possible to use it as a switch for another lamp outside? So that when it's dark the lamps turn on, and turns off when ambient light level increases (not using the motion detection for the second circuit).
    I couldn't find a circuit diagram for this sensor and I'm also not sure it's ok to add a relay somewhere in a circuit like that.
    Maybe anyone has done something similar, or can help me in any way? If needed, I can open it up and take some pictures.

  2. davenn

    davenn Moderator

    Sep 5, 2009
  3. beerzinnss


    Sep 26, 2016
    Thanks for the answer,
    This one has a dark/light sensor inside as well, so that the flood light turns on only when it's dark (and someone's walking by).
    You can see the two knobs for setting the brightness and time in the users manual (attached) from the manufacturers web site.
    My intention is to use the LDR inside the sensor (and its circuit), to turn on and off another pair of lamps (with a relay? transistor?).
    I thought that maybe someone here has opened up these sensors or tried something similar with them

    Attached Files:

  4. Bluejets


    Oct 5, 2014
    The LDR is used as a conditional section of the pir complete if dark enough then....... Hacking into this is just not practical given the number and cost of basic LDRs which will do the job for about $15
  5. beerzinnss


    Sep 26, 2016
    Well, opened it up- couldn't resist :D
    turns out it is controlled by this chip:
    Yes, a dark/light sensor costs around 5euros where i live, just wanted to try out modifing what I already have where I need it.
    Now I see it's nearly impossible, as the voltage through LDR goes in to the IC, rest is done digitally.
    Thanks anyway!
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