LEDs Make An “Analog” Wristwatch

If you just came down in the last shower, you’re probably used to living in a world where LEDs are cheap, awesome, and practically everywhere. Spare a thought for those of us who lived before the invention of high brightness LEDs – these things still amaze us! A great example of how far we’ve come is this “analog” watch build by [Kevin], featuring no less than 73 of the critters.

The microcontroller running the watch is an STM32, chosen for its easy programmability. It’s running the LEDs in an emulation of the dial of an analog clock, hence the high part count. Naturally, it’s no simple task to cram 73 LEDs and all the necessary connections into the confines of a watch-sized PCB. [Kevin] goes into great detail about the challenges involved, from routing the traces to a tricky power draw problem caused by some odd blue LEDs.

Watch builds are always fun, and they make great conversation pieces for when you want to amaze strangers with your tales of battles fought in the PCB design suite. Now check out this similar build with an entirely different style. 


6 thoughts on “LEDs Make An “Analog” Wristwatch

  1. Had one of those forty years ago, except it used an LCD instead of LEDs. Went a bit more than a year on a CR3032 battery. Google on “Texas Instruments Starburst”.

  2. The first time I ever saw blue LEDs, they were $3 each, which is probably closer to double that today after inflation. The store had an LED chaser with about 20 of them, it was just amazing. I still have a bunch of red LEDs that must date to the early 70’s, they’re so dim it’s hard to tell if they’re lit during the day. I remember buying some waterclear red LEDs in the late 80’s or early 90’s that actually had good brightness for the amazing price of 25 cents each.

    1. I paid $10 for my first blue LED. Drove it with an ir receiver taken from a top loading vcr to make a simple remote control tester. Was mostly a demo for a class I taught

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