My friend got all excited this morning about LED cubes; a good thing. Having searched and searched I cannot find another supplier for breakout boards for the 40 IO i2c expander that GHI used to sell (which was awesome)
Does anyone know where I can get it?
Also, using the upcoming fez hydra, would it be possible to bit bang the 40 IO so that they produce PWM control of LEDs? Since white multicolor diffused leds in bags of 100 can be had on ebay for 30 bucks I was hoping to be able to do it with 1000 leds (10x10x10 cube) x3 colours (i.e. 3000 PWM IOs)
Before I even consider going forward, can someone tell me if this is even technically possible? I know that the arm9 200mhz 32 bit hydra can handle it but what about i2c.
I built a 3x3x3 cube last week and have what I believe to be a fairly robust software framework that I’ll be adding to Codeplex probably tonight (http://netmfx.codeplex.com). It might be a good place for you to get started and I’d love to see a CubeLed10 class added You’ll really have to work on optimizing your effects code at that size. If all goes according to plan, I’ll have alot more detail added to my blog tonight. I’ll keep you posted.
Personally, I can’t imagine having enough time to solder up a 10x cube. I’ve recovered enough from the 3x cube enough that I am considering a 5x cube.
@ ianlee74 Yes I expect soldering and wiring 4000 led pins (3 color) would take me a few weeks but apparently I like challenges. My recent attempts with CNC makes that clear to me
So it seems that the refresh rate of the CharliePlexing might be an issue, but I’ll come up with something. Also, it would be cost effective to use the fez hydra to do the math and 3 or 4 usbzi’s to do the work.
@ kurnelle Soldering 4000 LED pins isn’t a challenge, it’s a practice in boredom. By the end of the 3x cube my brain so badly wanted to move on to something more challenging. The software is the fun part of the project for me. Your CNC project on the other hand is an interesting challenge!
@ nicolas3 Post a link to what you’re talking about. I don’t see any solderless solutions on their site.
@ kurtnelle, I wish you a lot of success ! I have seen several 10x10x10 cube video on youtube, and I find it definitly mesmerising
If anyone interested, I will release on the code site a rainbowduino driver next week, using the RainBowDashBoard serial firmware. It is limited to a 8x8 RGB display or a 4x4x4 RGB cube (for which I think they are selling the kit somewhere…).
Problem with shift register, is that you need either several wires and a lot of time to address them (especialy in netmf, but not a problem in RLP). However, an efficient way to address them is to use very fast SPI bus. Look at my driver for the DFROBOT SPI LED display: http://code.tinyclr.com/project/361/dfrobot-8x-spi-led-display/
It is basicaly many 595 shift registers in serie working in SPI. My driver allows both software and harware SPI. If you use hardware SPI, it is very fast (megabits !) and you can daisy chain dozens of 595 addressed on a single bus. However, farther you go down into the chain, slower it is to address.
I suggest you test the SPI bus with thoses IC’s
However, shift registers provides only 0 and 1’s output : hard to make theluminosity vary as if using PWM chips.
Another problem about the shift registers might be “power” if you address many of them.
Each led is drawing some amount of current. If does not count if you are having dozens, but not hundreds. That is usualy taken care by making some “visual” multiplexing : like TV or cinema, you light each led at least 50 times a second, and the human eye sees it always on. That spares a lot of power at the end !
You light a first row / panel
Then the second one, etc etc
then go back to the first row
All very fast. At the end, you save a lot of power. Look a the rainowduino schematics to have a clue how it’s done for an example.
You’ll really have to work on optimizing your effects code at that size. If all goes according to plan, I’ll have alot more detail added to my blog tonight. I’ll keep you posted.
