Makers certainly aren’t above pranks, and annoying noise generators and throwable LED blinkies have been popular projects for years. Most of those noise generators are battery-powered and produce a small chirping sound every minute or two. The idea is that your victim won’t be able to locate it and will be slowly driven mad by the sound. It will just keep chirping along until the battery eventually dies. But what if you could ensure that it continued making noise forever? That’s what Redditor okuboheavyindustries has done with this solar-powered ATtiny85 random tone generator.
This itty bitty device is powered by eight small photodiodes. Each one of those is capable of producing up to half a volt at 2mA. The eight of them together are just barely sufficient to provide enough power to run the Microchip ATtiny85 microcontroller when it is set to the 1MHz clock speed. The only other components are a capacitor to clean up the voltage from the photodiodes, and a passive piezo speaker.
okuboheavyindustries has programmed the ATtiny85 to produce random square wave tones. Theoretically, it will keep running as long as it is exposed to light (or until the capacitor fails). When hidden in a nice, well-lit location, it will continue to annoy coworkers or spouses until the end of time. The parts cost a mere $5, which is a bargain for a good ol’ fashioned prank device.