Review on DIYmall Pack of 10 HC-SR501 PIR Infrared IR Sensor Body Motion Modules - Arduino Raspberry Pi Compatible by Jim Bethea

HC-SR501 is a fairly standard part, instructions and examples of this are easy to find online. They can be used without a Pi or Arduino, for example to turn on a light when someone is nearby - just connect pin 2 to the MOSFET gate. I tested two of these with 5 volts on the power rail and a multimeter on the output. Works as it should. Easy AF. Sensitivity and timing twitch pots. You could use pots with more revolutions - or you can modify them. The build quality is mass-produced consumer electronics quality (think Furby, not the iPhone), not aerospace quality.