Here’s a video of the smallest screen I’ve made to date.
It measures 15mm squared and has a total of 64 LEDs. Initially I had designed this circuit to use a (pretty expensive) LED driver chip because in the past the intensity of light was lacking. It turns out that the tiny LEDs I used for this project are so bright that I didn’t need it.
It’s a hand soldered, hand etched circuit board and employs a technique that I’d been wanting to try for quite some time. The display uses a technique called ‘Charlieplexing’ that employs columns and rows. The thought of trying to come up with a layout to facilitate this on a hand etched board was very unappealing so what I did instead was to layout the columns on the board, solder the (surface mount) LEDs and then solder the rows on top of the LEDs.
It was fiddly work, done under the microscope, but it was definitely worth it!