Make Pt0399
Latest Gadget Freak from Design News, a special Vday one! –

Looking for cool way of wowing that special someone on Valentines Day/birthday/whatever? Build her a flashing heart made from LEDs driven by a programmable microcontroller. Les’ gadget is simple to build and made from easily-obtainable parts. The unique thing about this design is the LEDs are in an X-Y matrix so each LED is addressable. This allows an unlimited combination of displayed patterns for the heart — not like some other designs out there! Source code and schematics are all available here and if you’re not into hand wiring, even the PCB can be had for a small fee. Diamonds may be a girl’s best friend but gadgets are forever.

HOW TO – Build a flashing heart – Link & how-to.