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June 13, 2011 AT 2:00 pm

Working 7-Segment LED Cake

Geeks-Cooking

Cross-Section

Great project at Hack-a-day – A mostly edible cake is animated with LEDs placed underneath, here’s how to make your own. Uses our Adafruit 12mm Diffused Digital RGB LED Pixels (Strand of 25) – 12mm Diffused.


12Mmledpixel Lrg

12mm Diffused Digital RGB LED Pixels (Strand of 25) – 12mm Diffused . RGB Pixels are digitally-controllable lights you can set to any color, or animate. Each RGB LED and controller chip is molded into a ‘dot’ of silicone. The dots are waterproof and rugged. There are four flanges molded in so that you can ‘push’ them into a 12mm drill hole in any material up to 1.5mm/0.06″ thick. They’re typically used to make outdoor signs. Compared to our other 20mm LED dots, these are diffused 8mm LEDs so they are not as bright but they color mix a little nicer.

The pixels are connected by a 4-conductor cable. Red is +5V, Blue is Ground, Yellow is Data and Green is Clock. Data is shifted down from one pixel to the next so that you can easily cut the strand or attach more onto the end.

12Mmledpixelclose Lrg-1

Each dot is digitally controlled, with an internal 5-bit PWM LED driver (15-bit color for 32,768 different shades). The pixels must be clocked by a microcontroller, we have an example code linked below that works on an Arduino, it should be simple to adapt it to any other microcontroller.

The pixels use 8mm diffused RGB LEDs, with brightness of about 300 mcd per individual r/g/b LED.

  • 12mm diameter (0.45″) 75mm deep (1.5″)
  • 88mm / 3.5″ apart on the strand
  • 25 pieces per strand
  • 15 bit color
  • 5V power, 60mA maximum per pixel (LED on full white)
  • 2-pin SPI protocol
  • LPD6803 Datasheet for the chip inside each pixel

Sold by the strand, each strand has 25 pixels in series! You can solder multiple strands in a row, as many as you wish, just watch for how much current they want. We have a 5V/2A supply that should be able to drive 2 or more strands.

You can drive these with an Arduino using any two digital pins, check this library which also has example code to demonstrate the strands.

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1 Comment

  1. Hey there! Thanks for the nod.

    To clarify a bit: this ended up using a different company’s RGB pixels (our Adafruit pixels were busy illuminating a different project already, and we had these others on hand). Outwardly, they look identical, but the software protocol works a little differently (using an internal PWM clock). Since you provide a nice Arduino library, I’m pretty sure most anyone could easily adapt the demo sketch there to work with the Adafruit pixels, and the net effect would be the same.

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