Help me to understand the two potmeters on my PIR sensor.

My PIR sensor has two yellow potmeters both labeled 105. Just like this:

The right one seems to kind-of change the sensitivity. If it’s rotated 100% clockwise it seems to work as expected. The out pin is high when movement is detected. Rotating the potmeter just a tiny bit back counter-clockwise makes the sensor to sensitive, the out pin is always high no matter what.

This doesn’t make much sense to me.

I have no idea what the other potmeter does. Seems to do nothing really.

One is a "time" pot. It controls the time that the sensor outputs a "high". Fully anti-clockwise is a few seconds. Fully clockwise is about 7 minutes. It will re-trigger, so it you set it for 5 minutes, and the sensor detects any movement, it's on 5 minutes again. Best to set that time pot fully anti-clockwise (shortest "on" time), and let the Arduino control the delays.

The other pot is sensitivity, but not what you might think. It's not sensitivity as in distance, but sensitivity as in how much movement is needed to activate the sensor. Leave it in the middle.

Test the sensor with a common red LED connected to the output (no resistor, no Arduino). Just 5volt (4-12volt) and a LED. Leo..

Wawa: One is a "time" pot. It controls the time that the sensor outputs a "high". Fully anti-clockwise is a few seconds. Fully clockwise is about 7 minutes. It will re-trigger, so it you set it for 5 minutes, and the sensor detects any movement, it's on 5 minutes again. Best to set that time pot fully anti-clockwise (shortest "on" time), and let the Arduino control the delays.

The other pot is sensitivity, but not what you might think. It's not sensitivity as in distance, but sensitivity as in how much movement is needed to activate the sensor. Leave it in the middle.

Test the sensor with a common red LED connected to the output (no resistor, no Arduino). Just 5volt (4-12volt) and a LED. Leo..

If I leave the sensitivity pot in the middle it always outputs HIGH even if there is nothing in front of it moving. And the time pot doesn't show the behavior you describe. Fully clockwise it outputs high do a few seconds. Everything other than fully clockwise it outputs randomly HIGH and LOW. Doesn't seem like there is any logic it is using.

I have many of these sensors in my house. Sensitivity in the middle and time fully anti-clockwise should work.

How do you supply the sensor.

Are you sure nothing is triggering it. They are very sensitive. Leo..

Rotating the potmeter just a tiny bit back counter-clockwise makes the sensor to sensitive, the out pin is always high no matter what.

You could have a defective module.