Review on DAOKI 5PCS Human Motion Sensor HC-SR505 Mini Infrared PIR Detector Module For Arduino Body Sensor Switch With Dupont Cable Female To Female by Ben Boulanger

They are inexpensive. Unfortunately it's too cheap. During the "on" time, they stay on for a few seconds even if no more events are detected. This is normal and quite normal for PIR sensors. With the HC-SR505, this "on" time cannot be set. When I ordered, the time fluctuated: two devices had a minimum switch-on time of around eight seconds. The third device had a minimum switch-on time of about eleven seconds. The fourth device never signaled a change. ever (dead). The fifth block signals the change and then never turns off (dead). Failure rate 40%. this is a REALLY terrible quality. remember that you have to test each device yourself. and expect a VERY long turn on time. I won't buy them again.