help with motion sensor

Discussion in 'The Projects Forum' started by salai ezhil Mathi, May 13, 2017.

  1. salai ezhil Mathi

    Thread Starter New Member

    Jan 24, 2017

    I am buying a motion seensor module from Aliexpress. I do not know how to connect a LED light to make it work.

    I will supply the module with 12V DC how much voltage will I get at the output end ?

    my LEd lamp is rated 12V dc and 6 watts. it has its own resistor circuit. I just have to connect + and -. Please let me know how to connect the lamp to the module.
  2. Wingsy


    Dec 18, 2016
    You can't just connect your LED to the motion sensor and have it work. Here's why:

    1. The circuit is powered from 3.3v via voltage regulator IC1. This regulator is rated for 30ma, so getting 6W out of the thing isn't possible.

    2. The output signal from U4, pin #2 passes through a 1k resistor before you get your hands on it, further limiting the power you can draw.

    3. There are other reasons, but 2 is enough.

    What you will need to do is to use the output signal (it goes to 3.3v momentarily when motion is detected) to drive a transistor to turn on your LEDs. A quick search turned up an IRF3708 as a suitable type. (Connect the Source lead of the transistor to the negative of your 12v supply, the Gate lead to pin #2 of the MS connector, the Drain lead to the cathode (-) of your LED, and the anode (+) of your LED to your 12 positive supply. You also need to have the negative lead of the 12v supply connected to pin #1 of the MS connector (Ground).)

    Are you comfortable in doing this?
  3. salai ezhil Mathi

    Thread Starter New Member

    Jan 24, 2017
    No problem. Could you please put it in a diagram so that I can make the circuit better.
  4. bertus


    Apr 5, 2008

    Here are two datasheets of the used chip.
    That way you might get a better view on how the chip works.