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Motion Sensor Circuit

Discussion in 'Sensors and Actuators' started by Spiderspartan, Oct 12, 2009.

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  1. Spiderspartan


    Oct 12, 2009
    I need help with my circuit design for this motion sensor circuit. Independently the components all work fine, but when I put them together the relay never triggers. The motion sensor datasheet says this about the output function, "Connects to an I/O pin set to INPUT mode (or transistor/MOSFET)". Can anyone help point me in the right direction here? Thanks.
    Here's a URL to an image of the circuit since I'm new to the forum I can't include it in my post.

    Last edited by a moderator: Oct 20, 2009
  2. Resqueline


    Jul 31, 2009
    The datasheet gives the answer; connect to transistor/mosfet, and you connected it to a relay (that draws way more current). You'll have to do what the datasheet says, and use a transistor as a buffer between the PIR and the relay.
  3. raniamit110


    Oct 20, 2009

    Genrally the pir sensors give a small sine wave when ir falls on i suggest you to place a signal amplifier using opamp and the use a zero crossing detector and then u can drive your relay!
  4. Resqueline


    Jul 31, 2009
    I suppose you are referring to the internal sensor itself, and that the OP was referring to a complete detector with circuits (like you describe) and a digital output.
  5. neon


    Oct 21, 2006
    the regulator is connted to the power of the next circuit where is the input the regualtor 5 voltsa does not change that is why is say regulator. 13v in 5 v out where is the input to the relay?
  6. kint98


    Nov 5, 2009
    Try putting a protection diode on your relay terminals with the cathode side to the V+ and the anode side to the gnd. This way the relay will not have a spike voltage when energized.

    Have a nice day...
  7. Dominik


    Sep 24, 2009
    Have you solved your problem?
    If not, could you please specify which PIR motion sensor you are using?
  8. srgrimm


    Dec 20, 2009
    I think Resqueline has it....there may not be enough output current/voltage to trip the relay. You're probably using the radio shack pir sensor...I didn't see a part url, anyway, you need to increase the signal coming out of the pir. You can use the transistor as stated, or you can go back to radio shack and pick up a small spst 5vdc relay and hook that up between the pir output and the final relay. It will work. Cheap and fast
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