One of the problems with using a Raspberry Pi or most other systems in a production environment is dealing with sudden shutdowns due to power loss. Modern operating systems often keep data in memory that should be on disk, and a sudden power cycle can create problems. One answer is an uninterruptible power supply, but maintaining batteries is no fun. [Scott] wanted to do better, so he built a UPS using supercapacitors.

A supercapacitor UPS is nearly ideal. The caps charge quickly and don’t wear out as a battery does. The capacitors also don’t care if they stay in storage for a long time. The only real downside is they don’t have the capacity that batteries can have, but for a small computer like a Pi Zero it is pretty easy to gang up enough capacitors to do the job.

In particular, [Scott’s] design uses five 10F capacitors, each charged to 2.5V. The downside is that this requires a 12V supply, so he did a second design that uses only two capacitors each taking half of a 5V supply.

There are several options for converting the capacitor voltage to the desired output voltage. There’s also software to run the onboard microcontroller and force a shutdown in the Pi if the main power drops.

Naturally, this isn’t an original idea, but it is well done. You can also buy cheap ready-made UPS boards in the Pi form factor, but you might want to check out some aftermarket software for them if you use one.


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