Parallax PIR sensor problem

Discussion in 'The Projects Forum' started by djole, Jan 21, 2010.

  1. djole

    Thread Starter New Member

    Oct 19, 2008
    2
    0
    Hi guys,
    I am working with Parallax PIR sensor and I have a problem. It works with 3.3VDC and when it detects motion output voltage is 1.7V and that is not enough to trigger the interrupt on the microcontoler side. I've tried with pill-up resistor but that is not working. Anybody have any idea how it can be solved?

    Thanks for helping.
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    If you are working with a 5 volt microcontroller, you can power the PIR sensor from 5 volts, so the outputs will match your uc's logic levels.....
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Otherwise...a 10K pullup resistor on the μcontroller's interrupt pin, the collector of a 2N3904 to the μcontroller's interrupt pin, the 2N3904's emitter to common, and a 100K resistor between the 2N3904's base and you PIR's output. Interrupt will be a low.

    Ken
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    This all depends if the op has the PIR's output selected as active high, the module's output is jumper selectable to be either Active High or Active Low.... the op never mentioned which configuration they are using.... I used the same exact module for my Pic32 B.U.M. System and it works just fine to interrupt the uc...... Also if the op is using 5 volts for the uc, and 3.3 volts for the PIR, then he should tie the pullup resistor on the output of the PIR to the 5 volt rail, so when it triggers it would be at the 5 volt ttl level....

    My .02
     
  5. djole

    Thread Starter New Member

    Oct 19, 2008
    2
    0
    Hi Ken, I've tried that and it works very well. I am going to try to use PNP transistor and make interrupt high. Thank you very much for your help once again!

    One more thing,I have to use only 3.3VDC because that are project demands.
     
    Last edited: Jan 22, 2010
  6. savingaurora

    New Member

    Jan 11, 2010
    8
    0
    I've done something similar with a PIC project (12F615) but the way that I did it was using an analog to digital converter and set a range in my program. Set the interrupt code by hand. But if yours is working stick with it.
     
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