This year I gave my sweetheart a LED Valentine.
16 LED’s surface mounted onto flexible circuit-board material and driven by a small microcontroller. The LED’s animate a pattern which pulses (approximately) to the beat of my own heart.
The circuit incorporates 2 STP08DP05TTR constant-current shift registers (so I didn’t
have to try and place 16 resistors for the LEDs) driven by an ATTiny45V microcontroller.
The circuit itself was toner-transfer etched onto DuPont Pyralux flexible circuit-board material. The Pyralux is pretty cool stuff; it feels like a tough plastic tissue-paper that crinkles when you flex it yet stands up to a reasonable amount of ham-handing (lucky for me and my particularly ham-like hands). The circuit traces were only 11mil wide and yet they stood up to my hand-soldering on this material without breaking or lifting off. The stuff is quite handy when you need a printed circuit but don’t want the bulk of a standard PCB.
The software pattern consists of two sets of chasing LEDs sliding past each other at different speeds. This results in a visual pulse harmonic which I tuned to the approximate speed of my own heartbeat at the time of coding.
The card was presented alongside a tasty breakfast-in-bed and was well received.