I've installed a mains-switching infrared sensor unit, Cybertech LFMS-WH. It doesn't say passive sensing anywhere, but I think it is passive. The lamp switching part of the circuit works properly and the detection part is problematic.
The sensor is on the wall of a exterior corridor that opens onto a public sidewalk six meters away. The goal is for it to light up when someone enters the corridor, not when someone walks by outside. I get the impression that heat doesn't reflect off surfaces, but I do wonder if the shape of the corridor is related to the problem. It's under an overhang, so the sensor location is darker than the area of the motion.
The device has two levers of adjustment: its aim and the sensitivity ("RANGE") control. In my tests it behaved the same aimed downwards in any direction, even away from the street. With a tiny turn at around 20% of the adjustment range the device goes from seeing nothing at all to seeing me out on the sidewalk. The circuit lights up way too often. I have tried mounting an aluminum shield on its side to block the street angle, but the problem persisted.
Is this hopeless? Should I switch to a ultrasonic sensor?
Best Answer
The problem is simple. These are residential motion detectors. Yours probably ran you somewhere between $20 to $30 dollars. Manufacturing costs on this was probably $7 - $8 material inclusive, let's say 50%. You can't expect a highly sophisticated piece of electronic equipment that you can calibrate to spec from these things. They are what they are, a basic low grade and inexpensive motion detector for general residential use.
Many years ago we added these things in our no warranty list with light bulbs and ballasts due to the fact that most people were disappointed in their results. Even though they selected them and they were performing, just not the way they wanted them to. We were completely able to supply them with a more sophisticated motion detector, but most people considered it cost prohibitive.
In short it's a cheap product and it performs in a cheap manner.