False positives in modified 3.3v PIR (SOLVED)

  • Hello, I have a problem with my modification of the PIR sensor to 3.3v , I followed tutorials and have bridged the pin welding H.

    Vera works but every so often false positives sends me , I've tried changing the sensitivity does not work , any suggestions?

  • Mod

    @rabeliyo I assume you're using the HC-SR501 sensor?
    These things are very sensitive to variations in power supply. When powered below 3V (e.g. from batteries) the sensor seems to work but reports false positives. When powered from the wrong step-up converter same things happen. See also http://forum.mysensors.org/topic/1088/battery-powered-pir
    So, how are you powering it?

  • Yeah!! is a HC-SR501 I 'm power the system with a lithium battery that gives me a discharge of between 4.10 and 3.8 volts constantly .
    The arduino mini pro is at 3.3v

    I have observed that even if you remove the power cables leaving only the signal , I get false positives

    Will I need put a capacitor at the output of the battery?

  • Mod

    @rabeliyo That supply level should be OK and stable.
    What happens if you disconnect the sensor completely and tie the signal coming from the sensor to GND (don't leave it floating!) ?

  • ok i disconnect the sensor and bridge the signal to arduino with a gnd pin and nothing happens.
    but I have observed that even if you remove the all the wires, get random positives

    i don´t know how i do wrong X(

  • Mod

    @rabeliyo when you just remove all wires the input pin will be disconnected. This is called floating and might cause the input to randomly switch between high and low quickly.
    Either connect the pin to gnd, or leave it floating and configure the pin in your sketch as INPUT_PULLUP.

  • I connected the pin to GND and has stopped giving positive for the last 10 hours .
    I guess then the sensor will be problem , I would like to not have to put a step up but if there is no choice ...

  • Already it resolved, in the end it was my mistake .
    had the power connected to the distributor of the lipho battery which has voltage variations (3,4 - 3,9V)

    When I connected the VCC and GND to the power outputs of the Arduino mini pro , it works perfectly .

    Thank you very much for the help.

    By the way, that way I can stabilize the energy that comes from the battery to the dealer to be constant?
    With a capacitor?


Suggested Topics