I am trying to use a HC-SR501 motion sensor to control outdoor lights. While it works perfectly indoors, outdoors it detects even minor movements of leaves, even at minimum sensitivity. Is there any way to decrease the sensitivity even more?
A PIR sensor can't detect leaves.
It can only detect objects of different temperature in different facets of it's fresnel lens (dome).
Warmer/colder pockets of wind can activate PIR sensors.
How/where the sensor is mounted can minimise false alarms.
Black paint (nail polish) or tape on certain facets of the lens can block detection areas.
That sensor has a control for 'sensitivity', but it does not control 'sensitivity'.
It's a delay adjustment before the alarm output goes high (trigger inhibit timing control).
That might also help to stop false triggers.
If you want to change gain of the amplifier inside, Google for the datasheet of the BISS0001 chip.
Leo..
If it's not the leaves that cause it to trigger, I have no idea what does. I installed two motion sensors. One has mostly concrete pavement, walls and some windows in sight, while the other has plants after a few meters of concrete pavement. Then, at around the same distance as the other one, a window. The one which has plants in sight triggers a false alarm every few minutes, the other one does not. Both trigger when I walk in their range.
I thought maybe it's the street that causing the false alarms, but the traffic is too low for it.
Birds or cats maybe?
It seems to be that it's related to wind. In highly windy weather, both gets false positives, but especially the one near the street (which also has plants nearby). If there is no wind, I get no false positives.
That's possible as well - at least it was an issue some 30 years ago with those sensors, they occasionally would react to movement of plants. Plants do tend to be at slightly different temperature than the air around them.
Is it possible that if a plant is in front of a window, the moving of that is detected by the sensor?
See #5.
wvmarle:
That's possible as well - at least it was an issue some 30 years ago with those sensors, they occasionally would react to movement of plants. Plants do tend to be at slightly different temperature than the air around them.
30+ years ago we used ultrasound and radar movement sensors.
They sensed doppler of the reflected waves.
They detected anything moving.
I doubt IR PIR sensors can detect moving plants.
Leo..