We’re going to go out on a limb here and declare this minuscule incandescent light flasher the smallest such circuit in the world. After all, when you need a microscope to see it work, you’ve probably succeeded in making the world’s smallest something.

Even if it’s not record breaking, [Ben Krasnow]’s diminutive entry in the 2017 Flashing Light Contest, which we recently covered, is still pretty keen. For those not familiar with the contest, it’s an informal challenge to build something that electrically switches an incandescent light on and off in the most interesting way possible for the chance to win £200. [Ben] says he’ll donate the prize money to a STEM charity if he wins, and we’d say he has a good chance with this flea-sized entry.

The incandescent lamp he chose is a specialty item for model makers and scale railroad enthusiasts; we’d heard of “grain of wheat” bulbs before, but this thing is ridiculous. The bulb makes the 4.6 mm diameter SR416 hearing aid battery that powers the flasher look enormous. The driver is a clever Schmitt trigger inverter with a tiny RC network to flash the bulb at about 1 Hz. The video below shows the flasher working and details the development and the build, which featured spot welding to the battery. [Ben] has even spec’d precisely how many Joules of energy will rupture the thing steel cases on these cells — we suspect involuntarily through trial and error.

[Ben]’s entry in the contest is now our favorite, and not just because he’s been a great friend to Hackaday with such classic hacks as watching a phonograph needle with an electron microscope and a homebrew CT scanner. This circuit is genuinely fascinating, and we hope it inspires you to try to top it. There’s a little less than a month left in the contest, so get to it.

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