Mini PIR motion sensor

Other Hardware General Electronics
1

This is the sensor I'm using
Sensor
The sensor has no sensitivity adjustment
The data pin will go high (3.4V) even in an empty room with no lights, no windows in line of sight. Is it defective or is there a way to reduce sensitivity? If I put a black cap over the sensor it will not go off Its 3.5 volts that's supplied from Uno

2

Did you read about the PIR sensor? "Like the other passive infrared sensors we carry", means it responds to IR, meaning heat, meaning anything hotter or cooler than the ambient room temp will give a response, that includes your body.
Paul

3

If I swap it for this one I don't have the problem.

I also use one of these mini sensors a few years ago didn't have this problem. I need the mini for size

4

I have taken the cover off the sensor and placed a black peice of electrical tape and I get 3.27v every 10 seconds or so on the out or data pin. Pretty sure there is something wrong with the sensor

5

But not all IR is created equal. I highly doubt a PIR sensor is responsive to long-wave/far infrared.

6

That's exactly what they are sensitive too, so they can detect warm things moving around in pitch dark. 5--15µm wavelength range or so is typical.

Long range IR only passes through a few materials, polythene is one, germanium is another - both materials are used for prisms and lenses for PIR detectors and thermal cameras.

7

Your sensor seems too small to have speed and sensitivity adjustments - its probably wise to always choose a module with these adjustments, so you can tune for fewest false-positives and false-negatives.

One thought - is the power supply to the module stable? It needs to be stable and clean enough to prevent false triggers - maybe try 470uF decoupling cap or so and see if that makes any difference.

8

Was using 3v from Uno. Im using the 470uf cap and I think thats solved my problem
Thanks

9

Probably noise triggering the internal circuit - PIR sensors work by detecting very small voltage changes and they need stable power.

10

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