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TIDA-00489: Temporary false motion detection

Slev1n
Genius 5680 points
Part Number: TIDA-00489

Hello everybody,

we are basically using the TIDA 00489 hardware setup. Testing the motion detection behavior of our modules after fabrication in QM we noticed some strange behavior for a minority of our sensos (2-3 out of 100). In the following I am only describing the behavior of this "malfunctioning" sensors.

We put the sensors into a box where no motion (or IR radiation variation) can stimulate the sensors. However, the sensors in average detect about 20 motions, i.e. about 20 interrupts are triggered within 5mins. When we open the box and stimulate the sensors intensively (150 interrupts in 5mins) and close the box afterwards, those "false" detections do not occur anymore and no interrupts are triggered anymore when the senors are in the closed box. The following image illustrates this case in more detail.

Note that each point represents the accumulated number of interrupts within 5mins.

We did not change anything within the hardware parts from sensor, over comparator to the chip.

Any idea what could cause this behavior? In this thread I described my definitions for the HWI pins.

best wishes

Slev1n

  • 0
    TI__Prodigy 600 points

    Hello,

    We have not witnessed the behavior where the sensor recovers after being stimulated on the TIDA-00489 design.  We have, however, witnessed cases where the sensors false trigger on initial power up like you are showing.  Since we built a limited amount of these, I don't have good statistics to compare to yours.  On our failing units, we were able to replace the sensors with fresh ones and boards worked, so we attributed those to either bad or damaged PIR sensors.

    The only theory I have to offer is that maybe there is residual charge accumulated inside of the PIR sensor after fabrication.  The intense stimulation could be getting the sensor to its correct operating point and so afterwards, you see normal behavior.  Just curious but have you observed a different sensor output voltage (DC) between good and bad units after fabrication or on bad units before and after the intense stimulation?

  • 0 in reply to David Stout
    Genius 5680 points

    Hello David,

    thank you for your answer.

    David Stout said:
    Just curious but have you observed a different sensor output voltage (DC) between good and bad units after fabrication or on bad units before and after the intense stimulation?

    Unfortunately, we do not have the opportunity to investigate this behavior after final fabrication, since the boards get encapsulated.

    We will think about further tests for early detection of such devices during fabrication.

    Best wishes

    Slev1n