For obvious reasons, many people today have been focused on disinfecting surfaces, and especially things like mobile devices or keys that are prone to exposure. This is all well and good, but with disposable items such as hand sanitizer and disinfectant wipes in short supply, Botfactory applications engineer “Md” decided to instead make a UV-C (ultraviolet C) disinfection chamber that uses only light to kill germs.
The concept is actually pretty simple, in that a roughly phone-sized things is placed on a piece of glass inside a chamber with UV-C lights arranged on the top and bottom. This chamber is closed — like a miniature tanning bed — and the lights are fired up for five minutes under control of an ATtiny85 microcontroller and two transistors. A 7-segment display then “counts down the five minute death sentence of any germs caught by the UV LED's light.” With this disinfection process finished, the timer shuts down and you can open it up to find your newly germ-free (or at least less-so) belonging inside.
Three separate PCBs are used for the build, two for lights and one for the controls. Each was designed in KiCAD and printed out on a very cool looking PCB fabrication machine.BotFactory's blog post gives the story of the machine’s conception and quick iteration, and this separate write-up takes a more how-to approach if you're interested in creating your own.