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PIR Sensor

william chanwilliam chan Posts: 1,326
edited 2009-04-16 16:50 in Accessories
I find that the Parallax PIR sensor could sometimes be too sensitive when running at 3.3v
It may sometimes trigger about once in 30 minutes for no apparent movements.
Not all units exhibit this behavior.
Is there a way to reduce it's sensitivity?

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Comments

  • william chanwilliam chan Posts: 1,326
    edited 2009-03-26 08:20
    Could it be that a blinking green led might cause the PIR sensor to trigger?

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    www.fd.com.my
    www.mercedes.com.my
  • P!-RoP!-Ro Posts: 1,189
    edited 2009-03-26 19:47
    william chan said...
    Could it be that a blinking green led might cause the PIR sensor to trigger?

    Probably, if it emits IR. Try covering it up and post the results. If that doesn't do it, you're probably going to have to post a little more info before anyone can help you.

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    PG
  • JDJD Posts: 570
    edited 2009-03-27 22:55
    William Chan,

    ·Is there anything that could be moving from an unexpected source; for example an A/C or heater turning on causing a breeze, a window open, or something similar? How are you tracking that there is movement? Can you post the code you have?

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    Respectfully,


    Joshua Donelson
    www.parallax.com
  • william chanwilliam chan Posts: 1,326
    edited 2009-03-27 23:18
    Dear Joshua,

    There is not much to the code as it just detects whether the output pin from the PIR is high or not.

    Yes,

    Sometimes the PIR sensor is about 2-3 meters away from a Air Cond. Will the A/C cause problems?

    The other suspect I can think of is the noise from the boost regulator from 3v to 3.3v
    I have been adding tantalum capacitors near the PIR sensor supply rails but it doesn't seem to help.

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    www.fd.com.my
    www.mercedes.com.my
  • JDJD Posts: 570
    edited 2009-03-27 23:57
    William,

    There has been an event where the PIR unit would detect the A/C unit turning on; but it was because it was moving a sign which triggered the PIR sensor. Is the pattern consistent for false triggers? Does it always seem to wait 30 minutes?



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    Respectfully,


    Joshua Donelson
    www.parallax.com
  • pranaypranay Posts: 2
    edited 2009-04-16 10:47
    IS THERE PERFORMANCE DIFFERENCE IF WE POWER THE PIR SENSOR WITH 3.3V OR 5V.

    i TOO OBSERVED A SLUGGISH RESPONSE FROM THE SENSOR.
  • JDJD Posts: 570
    edited 2009-04-16 15:51
    Pranay,

    There should not be any difference in operation; the sensor can take up to a minute to adapt to the surroundings at first, is that that you are referring to? Or do you mean the triggering seems sluggish? Also, what trigger setting do you have the sensor set to; H or L?

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    Respectfully,


    Joshua Donelson
    www.parallax.com
  • pranaypranay Posts: 2
    edited 2009-04-16 16:42
    I meant if there was difference in sensitivity(higher at 3.3v) due to variation in voltage. As there was a little self triggering(though i need to test more)

    Also the response was a bit sluggish. I tried both the settings (H and L) . I felt that it took some time to respond or change the signal in L mode.
  • JDJD Posts: 570
    edited 2009-04-16 16:50
    Pranay,

    I have not come across that with the PIR sensors that I have used; which have been with the BASIC Stamp (+5 VDC)·and the Propeller (+3.3 VDC). Which controller are you using with the PIR sensor?


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    Respectfully,


    Joshua Donelson
    www.parallax.com
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