LED Valentines Day Card

LED Valentines Day Card

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.

Valentines Day Card 2009 Circuit

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.

6 responses to “LED Valentines Day Card”

  1. J. Peterson says:

    Could you identify the “constant current shift registers”? Thanks.

  2. xander says:

    I edited the post to include the part no. for the constant-current shift registers. Note there are quite a few parts in existance made by other manufacturers which are pin-compatible with this part. The Toshiba TB62705 or TB62725 are two examples. Look for “8-bit constant current LED drivers”

  3. jhaase says:

    Neat. Overall a very good looking card/project. Congrats.

  4. Phil R says:

    That is anerable!

  5. Oscar Valdez says:

    Where did you get the DuPont material from? I have several circuits that would greatly benefit from a flexible PCB. What toner-transfer method did you use? (regular clothes iron?)


  6. clamoring says:

    Hi Oscar,

    You can sometimes find Pyralux on ebay.

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