Thermometer ball

Winter is upon us again, so I made a thermometer, with, you might have guessed it, leds! Since I only need 4 pins for this project, (3 leds pins and 1 sensor pin), I used a small Attiny13 microcontroller. It was a bit tricky fitting all the code in there though, since there is only 1kbyte memory on those things, but I managed to get it working.

When it’s 20°C, the led is green. This slowly changes over to red at 25°C, and blue at 15°C.