Turning on a circuit breaker to power hundreds of desktop computers in interactive museum exhibits is hardly ideal. Computers tend to get cranky when shut down improperly, and there’s a non-zero risk of data loss. However, financial concerns precluded commercial computer management solutions and it is impractical to manually close every exhibit at the end of the day. In charge of finding a solution, [Jeff Glass] mixed turnkey UPS (Uninterruptible Power Supply) hardware, a Featherwing, and some Python to give the museum’s computer-controlled exhibits a shot.
Without drastically changing the one-touch end-of-day procedure, the only way to properly shut down the hundreds of computers built into the museum exhibits is by using several UPS units, leaving the PCs on briefly. after the mains power failure. This in itself doesn’t solve anything – while the UPS can trigger a safe shutdown via USB, this signal could only be received by a single PC. These are consumer-grade turnkey devices and were never intended to securely shut down more than one computer at a time. However, any 300 watt UPS unit is very capable of powering multiple computers, the only limitation being the shutdown signal and the single USB connection.
To work around this, the Windows job scheduling service was set up to be triggered by the UPS shutdown signal, which itself then triggered a custom Python script. This script then forwards the UPS shutdown signal to every other computer in the museum before shutting itself down for the evening.
While many computers can be turned on to boot in the event of a power outage, the UPS and secure shutdown scripts made this not an option. To get around this, an ESP32 Featherwing and a bit like CircuitPython code automatically sends wake-on-LAN (WOL) signals over Ethernet on boot. This unit is powered by a non-UPS supported outlet meaning it will only send the WOL signal in the morning when mains power is restored through the circuit breaker.
There are undoubtedly several alternative solutions that seem “better” on paper, but these can obscure the potential cost and disruption of a multi-acre museum. Working within the confines of reality means that the less obvious solution is often the right one. How would you have tackled this problem? Sound off in the comments below. And while you’re there, be sure to check out our coverage of other UPS solutions, like this supercap UPS.
This post Power Cycling Museum computers cheap
was original published at “https://hackaday.com/2022/03/18/power-cycling-museum-computers-on-the-cheap/”