I have a project with 3 PIR sensors that worked great for it's first weeklong installation but the second time I installed it...one segment simply behaved irrationally. PIR seemed not to be communicating with the Arduino UNO though the other 2 communicated fine with their respective Unos (3 total) and each runs the exact same program. The power to that one set seemed to be erratic too but it was still getting power. Power was supplied to all 3 sets through the same wall wart and only 1 seemed problematic. I replaced the PIR and Uno with new ones and then it didn't work at all.All contacts had continuity and the wall warts tested fine too. I reloaded the program repeatedly, turned power on and off, tested continuity on everything, and still no results. Exhausted my limited knowledge base and had to leave the project only partially functioning. Not sure what else to do...could it be the Arduino? The fact I used a switching type power supply? I learned enough to build it, but I don't know enough about electronics to figure it out how to solve unexpected behaviors! Any suggestions about what went wrong?

 

if the power is eratic, as you said, there is no way to predict how the thing will work. clean up the power.

 

Does the PIR module have any settings? Some do and some don't. I have found them to be a bit erratic around 3 or 3.5 volts. Try to keep them above 4 volts and they work OK. Remember that they are mass produced and you could get some bad ones from some places. China often does not test for quality, just quantity but that's where most are coming from..

The output is not very good from the sensor itself, modules use a chip to make the output logic on or off. I'd use a transistor to connect it to a logic device. I have used a PNP transistor to to turn off when the PIR sent out voltage to it. That seemed to work OK, but I never tried driving an NPN with one yet.

 

alfacliff,
Thank you in advance for your patience with my limited knowledge! Can you elaborate on how to "clean up" the power? I know how to test the continuity and test the power the wall wart is providing to the board, but not much more.
Thanks,

 

Ted, thank you also for your reply. Here is a little more info. I am using the Parallax #555-28027-RT from Radio Shack which I guess must be a "module" as it is attached to a little circuit board which has a chip on it. It has jumper select sensitivity for 15 ft vs 30 ft and uses a 3 pin header. I have a 35 ft 3 wire cable going from the box containing the pcb to the sensor itself which is fastened to the ceiling pointing down. The section of the board that supplies the PIR is hooked up to a 9v 3 amp wall wart which supplies all 3 PIR's via jumpers plugged into the 3 Arduino Unos simultaneously. As I mentioned, both of the other 2 work fine with this setup, so it must not be the cord length or program. A transistor would be another component to add to the board? What does a transistor do in this instance? I appreciate your patience with my naivety!

 

Can you swap a working one with that unit? I'd think that there was a wiring problem somewhere if it just happened. It would not take much to miss the voltage signal.

Also make sure that there is nothing else blocking it of a heat source is nearby.
I have a PIR light switch and it even goes out sometimes when I don't move enough. The PIR should come on at power up for the duration it is set to to warm up.