Via Hack N Mod comes this cool LED project:

The Glowies use a small microcontroller, but they are really quite simple in both parts and function. The core of the unit is a silicon diode used as a temperature sensor (actually, two of them). These Glowies sense when temperature drops, and it turns blue. If the temperature rises, it turns red. Plus, it’s completely solar powered, so you never have to change the battery. And I used very inexpensive parts, so you can’t get much cheaper!

Color-Changing Hot & Cold LED Glowies

Gareth Branwyn

Gareth Branwyn

Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy person’s memoir,” called Borg Like Me.