TruSens HC-SR505 Mini PIR Motion Sensor

For the most part, these work exactly as intended. They output just over 3v on the output pin when movement is detected. After about 10 seconds, it returns to 0v. Unfortunately, when testing these, I noticed that one was causing my power supply to current limit at around 500ma. After doing a bit of touch-testing with my finger on the board, I noticed one of the two large capacitors was very hot. Believing that the component was already faulty, I saw no harm in turning up the PSU to the full three amps, which the board drew. Eventually, the faulty capacitor was recognizable by smoke, and I was able to push it from the board. Fortunately, this self-de-soldering capacitor was able to resolve the issue completely, and it's working again now, albeit with a 10uf cap on the input pins to compensate. I'm sure this was a once off defect, and it was internal to a component, so not easy to find during manufacture. I still recommend using these components where motion detection is required, but be wary of this possible fault, and design your circuitry with some kind of basic current limitation. Even a 470R resistor will prevent a full current short, while allowing enough current to pass for this device to function correctly.

For the price this is an excellent device. Output sits at 0v and responds rapidly to something coming in range. The output then switches to 3.32v (5v supply) and stays there for 7-8 seconds before returning low. Ideal for school projects.