Our friends at Evil Mad Scientist Laboratories contributed several projects to the wonderful The Hungry Scientist Handbook: Electric Birthday Cakes, Edible Origami, and Other DIY Projects for Techies, Tinkerers, and Foodies. Here's their Smart Coaster project.
Smart Coasters are cast-plastic coasters for your drink that light up red when you put a hot drink on top and light up blue with a cold drink. The design is fully analog-- no microcontrollers and no programming-- and they incorporate a solar cell so that the whole thing is hermetically sealed: waterproof and washable. Complete step-by-step DIY instructions are included for both the electronics and the resin casting.Smart coasters detect hot or cold beverages, created by Evil Mad Scientist Laboratories
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects