How I spent a weekend reinventing a 50-cent chip

Sat, 25 Apr 2026 14:21:17 +0000

An optocoupler is a part I’d seen in schematics for a while and quietly skipped over. There’s an LED pointed at a photo-sensitive transistor with a dashed line between them. The dashed line is the entire point: the two halves of the part are not electrically connected.

The signal crosses as light, over a few hundred microns of darkness – and I wanted to see it work! So I built one on a breadboard before reaching for an actual 4N35 chip.

DIY Bluetooth Kobo page-turner remote with ESP32 and Lilka

Fri, 23 Jan 2026 17:20:24 +0000

Page-turn clickers are a real category: Kobo even sells an official remote so you can turn pages without poking the screen all the time. The official remote was out of stock when I thought of getting one, and the price was a bit on the higher end. So I thought of an interesting alternative: emulate the same thing with an ESP32 module, but with no hacks on the reader itself.

Electronics on {IT}

How I spent a weekend reinventing a 50-cent chip

DIY Bluetooth Kobo page-turner remote with ESP32 and Lilka