Hello everybody :)
I have two questions about the quite popular HC-SR501 PIR Infrared Motion Sensor:
does the sensor reveal motion even if the person is behind a thin wall?
is it possible to hack the sensor in order to get a smaller sensing angle, maybe around 30 degrees? The angle with the original lens is around 120 degrees. I was wondering if would be possible to remove the lens and replace it maybe with a cone o something similar in order to get a more directional sensor