HiLetgo 3pcs HC-SR501 PIR Infrared Sensor Human Body Infrared Motion Module for Arduino Raspberry Pi

Try starting with the sensitivity adjustment dial turned completely counter-clockwise and the delay dial completely clockwise. I found it a lot easier to tweak and troubleshoot at these settings and fine tune at the end. Also change the jumper on the underside unless you want repeat trigger mode. The component itself is durable enough and effective at the right settings.

Works as advertised.

Once you can figure out how these are supposed to work, they do the job well. There are differing opinions (documentation) on how long the delay time is supposed to run; I read anywhere from 30 mins to 3 mins (mine have measured about 2.5 to 3 mins). The sensitivity doesn't seem to change much. The trigger once / repeat trigger jumper is a nice feature, and makes it possible act as either a digital switch, or an on as long as an infra-red delta is detected. If the input voltage drops to about 4.7v, the sensor misbehaves, and makes it appear as if other parts are failing, because the data output line switches on and off erratically; however, what can you expect with incorrect input voltage.

At first I thought these were defective, but I found that when using it with a Raspberry Pi 4, it requires an extra diode before the V-in pins, otherwise some voltage instabilities from the Pi will cause false triggers very regularly on 60-second cycles (actually 59.75 seconds if you measure it out for a long enough time).After a lot of testing, including using it to drive an LED (no output to the pi itself), I was almost ready to give this a bad review, before I found some suggestions online for other HC-SR501 sensors regarding their behavior under power instabilities.I do not believe this issue was due to outside EM interference, as I tried it at multiple locations.Other than that, happy with the product and price.

Two of them functioned fine. The third did not work at all. For the price, it wasn't worth going through a return, so maybe buy one extra. Making fun small projects gets expensive in time and gas if you have to do a lot of returns.

I had some trouble with these initially but it turned out to be due to a sufficient lack of power. I had loaded too many sensors onto my board and was getting a steady stream of false positives until I removed some sensors or added a capacitor.With Esphome these are very easy to integrate into my home automation. I've been slowly replacing my commercial Z-Wave and Zigbee motion sensors with these for the added flexibility and sensitivity.

I got these because I had some from ali that started having issues.These worked fine and it was nice to be able to control the time out and sensitivity.

This PIR connected to a ESP32-CAM inside a 3d printed box with a single 16550 battery to power it. PIR senses motion, fires up the ESP32-CAM which snaps a picture, connects to WiFi and sends via text a picture of my mail being delivered. Low power draw and ideal for any PIR project