Revision as of 23:44, 3 February 2011

Led Floor

How to turn the 11 windows of the hacklab into a big led display ?

• what have we got to do it ?
  • Windows that are H189xW95.5 centimeters
  • 1000 red leds
  • loads of RJ45 and old IDE/SCSI/floppy buses

• what we need ?
  • a system to control each diode (or group of diodes) independantly
  • that is not too expensive

Question: do we need on/off for each led, or more advanced modes (eg PWM for various intensities).

• on/off:
  • is simpler as regard to schematics
  • is simpler as regard to driving code (led bits per image, obviously)
  • isn't as cool
  • can still, to some extend, allow some variable intensities

PWM "natural" ability is prefered, but choice will be made depending on total cost of solution.

Solution #1

use a TLC5940NT that can control about 16 LED each

• datasheet: http://datasheet.octopart.com/TLC5940NT-Texas-Instruments-datasheet-153017.pdf
• schematic: http://webhome.csc.uvic.ca/~mcheng/samples/led_wheel/images/hack_schematic.jpg
• O(price) = $180 for the 64*TLC5940NT, so we'll need also several protoboard to be cut to bind them on.

Naturally leads to a PWM version

Solution #2

use the snootlab's i2c led driver solution that can control 16 LED each

• 64*i2c led driver = 9.95*64 = 636.80
• 1*i2c shield = 17.95
• 1 ardunio = 20
• O(price) = 674.75 euros

Solution #3

• use shift registers... ?

Solution #4

use two Peggy 2 board :

• 2* http://evilmadscience.com/tinykitlist/157
• O(price) = 95*2 = $180 --or far less as you won't need the giant PCB. They have a "parts kit" that includes the 328 and the IC's for $15. you'd still need LED's and transistors and other support components. --cw

looking at the peggyLE schematics, they are not using several of the outputs, it looks like a 32x30 grid is possible with the IC's included, and by adding another IC in place of the buttons 32x45 is possible. --cw => they use two 4 to 16 demux for highside driving. They therefore *have* to keep one output not connected, to allow an "off" state for each of these chips. One solution would be to use two such chips, plus two generic I/O, leading to a (quite ugly) 10 to 32 demux functionality. -- cq

Solution #5

• Check with Electrolab, where another similar project is ongoing :-)

=> actually, the (current) project there is about a 8x8x8 led cube. Which is a bit different.

Solution #6

• 42 ?