ST SHILLEHTEK HC-SR501 PIR Motion Sensor Module Blue for Raspberry Pi, Arduino, and Other Microcontrollers

It just works. If you like to tinker and have some spare PCB boards around, throw this on. It's low power draw and sensitivity is great. I've put a little motion sensor together to automate some lights with Home Assistant. Good price; you can find cheaper, but it's not going to arrive with the Amazon-backed 30-day return if you get a dud. If there's an issue, I usually want to address it and get back to tinkering quickly, so I'm willing to pay a bit more.

The pins on the back were exposed. I am surprised it didn't get damaged in shipping. That said, the unit arrived fine and is working as expected. Very easy to use and isn't any different from many, many other same sensors by different manufacturers. The library support is great online and easily found.The GND pin label is hidden so look up exactly where it is. I am using it with Raspberry Pi 4 and no special drivers are needed. Its a simple ON/OFF sensor and no digital modulation. For simple projects, it does the job 10/10.

As a few other reviewers have noted, a software controllable adjustment would be an improvement but would increase the cost. So, you need to provide access to the pots if you need to change the sensitivity. The delay you can do similarly programmatically but that means the device may not be able to sleep as much if you're running on battery.

This PIR sensor is exactly like the other dozen clones out there. Very easy to use. Outside pins are for 5v VCC and GND, middle pin goes HIGH/LOW. 2 pots to adjust sensitivity and timing, and a jumper pin to switch trigger modes (when/how the timer restarts). Since the GND/VCC pin labeling is covered up, look it up or just remember GND is closest to the switch trigger selection jumper. The big dome is just a lense to widen the field of view, so if it's too wide for your application, it's not usually an issue to partially cover it up for a narrower cone of sensitivity.There's a couple "hidden" features on these: there's a couple solder pins on the bottom to hook up a couple more sensors to help with accuracy. One is for a thermistor, the other for a photoresistor. Adding an LDR (photoresistor) is probably the one most people would choose to use because it helps avoiding triggers when the lights turn on or off. The other is to help with temp-related trigger issues -- it is sensitive to IR, after all.You're paying for convenience since it's basically plug'n'play, but even then, this is a little on the spendy side with zero functional difference from what I could tell to the other (5v) clones. However, keep in mind this is NOT a 5v/3.3v module. I did a quick test with an Uno and an ESP32 (w/a voltage divider to drop the output signal, pay attention to currents) and it worked as expected.

The physical design is really nice and lends itself well to a custom enclosure. All of the components are mounted opposite the sensor and there are no parts or traces waiting to be damaged on the sensor side. It's a simple 3-wire connection (VCC, GND, OUT) and it has an on-board regulator to allow it to run off anything from 5-20V. The output is 3.3V, which may be problematic for some devices expecting 5V, but it was fine on my Arduinos. It also has a jumper for 1-shot or repeatable trigger and pot adjustments for sensitivity and hold delay.The only "nice to have" that I could really ask for would have been software control over the sensitivity and hold delays, but at this price point, that's an unrealistic expectation.In operation, it works reliably and without any issues. No special drivers or software required. It's a simple 3.3V on/off signal that's all configured in the hardware itself. If you've got a logic pin to connect it to, it's going to do the trick.