The various flavors of Raspberry Pi single-board computers have allowed for a wide and wonderful range of experimentation, and have improved dramatically since the first came on the scene in 2012. If you need full control over the board’s power, however, there are still a couple of small annoyances. First, when you shut a Pi down via software, it draws 30–50mA of power. Second, if your Pi freezes for whatever reason, you’ll have to manually reset the board to get it working again.
If either of these are important to your application, Omzlo’s PiWatcher provides a solution for both. It can be programmed to fully cut power off after a software shutdown command has been issued, keeping your batteries charged, or simply not wasting power. Additionally, it can be configured to cycle power if it doesn’t receive a “heartbeat” signal from the host Raspberry Pi after a certain amount of time, automatically restoring functionality. Communication between the Pi and PiWatcher is via I2C, and behavior for both functions is user programmable.
The PiWatcher also features a status LED, as well as a micro pushbutton. This button is used to manually shut the Pi off after a five-second press, and powers it on with a normal press when off — similar to how many computers function. Short presses when on can function as a user interface if needed. The board is available on Tindie for purchase, and compatible with the Pi Zero, Pi 3, and most other models it would seem — you’ll just need to add the proper micro USB power supply!