8x8x8 LED cube


7 posts
by Mrkva » Tue Jul 03, 2012 1:03 pm
Hey,
I've successfully built RasPi controlled 8x8x8 LED cube. Currently, I'm doing everything - generatingeffects and LED multiplexing RasPi, which is not ideal: Linux is not a real time OS and even with highest process priority there are various glitches, flashes etc. when something interrupts the multiplexing loop. I'll eventually move multiplexing code to some AVR uC, communicating with RasPi over RS232/I2C.
The whole application is designed as a client-server, client generating effects and sending them in 64B data packets through a named pipe to server. Server periodically refreshes the whole cube from its "video memory (updated with data received from FIFO)", creating desired effect.
I'll release the source code anytime soon :)
Website with more informations, incl. circuit diagram, board design: http://dev.mrkva.eu/elektro/ledcube/
Demo of first 16 implemented effects https://www.youtube.com/watch?v=S6P3jcxKh-k
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by jacksonliam » Tue Jul 03, 2012 6:27 pm
Cool, I did a similar 8x8x8 LED Cube project with arduino (to run the cube) and raspberry PI UART (only needed 4 pins from raspi)
Image

I was gunna make the Pi directly control the cube, but I used 74HC595 shift registers which wont run from the Pi's 3v3, I thought about swapping out the shift registers, but if its really difficult to make the Pi keep up, I might not bother, the only affordable 74HCT595's (3v3 compatibles) are surface mount (I don't have laser printer or lightbox to make PCB)
I prefer latching shift registers, in-fact most LED cubes I've seen use some form of latching!
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by Mrkva » Sat Jul 07, 2012 12:39 am
Yeah, latching registers are usually better - you can easily achieve almost 1/8 (12%) duty cycle. I have achieved with RPi without any latching ~75%/8 (9%) DTC and even had to decrease it a little bit - it was just too bright.
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by darkcity » Sat Jul 07, 2012 2:43 pm
Linux is not a real time OS and even with highest process priority there are various glitches


some version of Linux are real time, and some rt features are present in the mainstream kernel. not sure if rt linux kernel works on rpi?

more discussion-
http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=2376
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by jacksonliam » Sat Jul 07, 2012 3:43 pm
Mrkva wrote:Yeah, latching registers are usually better - you can easily achieve almost 1/8 (12%) duty cycle. I have achieved with RPi without any latching ~75%/8 (9%) DTC and even had to decrease it a little bit - it was just too bright.


I can get very fast looping with the help of SPI, by simply shift out next layer's 8 bytes, prev layer off, latch, new layer on and repeat! I think that will come in handy when I want to fade the LED's. Since id like 1024 levels of brightness, I could do with about 8192 fps.

I might use some counter ICs to do the latching/layer changing and then all I need is a simple level converter from the Pi's SPI to get it up to 5v and shove out bytes like nobodys business :D

ATM I think I get some ghosting, its very difficult to tell the difference between light bleeding into the other layers and ghosting - I might need some new layer transistors, since my Darlington array just don't seem to sink enough current!
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by zstryker » Mon Jan 14, 2013 5:50 am
Would love to try this, even thought the complex circuitry would fry my nooby brain :P Where did you get instructions for this? I found an instructables page, but not sure if it's for the pi...

Mrkva wrote:Hey,
I've successfully built RasPi controlled 8x8x8 LED cube. Currently, I'm doing everything - generatingeffects and LED multiplexing RasPi, which is not ideal: Linux is not a real time OS and even with highest process priority there are various glitches, flashes etc. when something interrupts the multiplexing loop. I'll eventually move multiplexing code to some AVR uC, communicating with RasPi over RS232/I2C.
The whole application is designed as a client-server, client generating effects and sending them in 64B data packets through a named pipe to server. Server periodically refreshes the whole cube from its "video memory (updated with data received from FIFO)", creating desired effect.
I'll release the source code anytime soon :)
Website with more informations, incl. circuit diagram, board design: http://dev.mrkva.eu/elektro/ledcube/
Demo of first 16 implemented effects https://www.youtube.com/watch?v=S6P3jcxKh-k
Warning: Absolute Newbie Approaching
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by TomC1 » Mon Jan 14, 2013 7:34 pm
This is literally incredible! I want to replicate and expand upon.

The only problem is I'm a huge noob - Nightmare! I'm working through the introductory material which is taking a bit of time.

i wonder if you could point me in the direction of any literature or more specific material for these kinds of projects. I eventually want to build my own Sound-to-light DJ lights, and this looks like a great starting project.

If you could let me know, that would be great.

Thanks,
Tom
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