Archive for the ‘8x8x8 RGB LED Cube’ Category

Writing software for the TLC5940 LED drivers.

Friday, March 2nd, 2012

Last week I had a week off, so I decided to put some time in the LED-cube project again.

Led driver test.

TLC5940 LED driver test.

I’ve been working on the LED matrix on and off (in between  working, gaming and my other project: piko3d) but being free from work for the week seemed like a good opportunity to get some work done on the Cube.

So this week, I thought I’d work on the software part of it all.

In his blog posts, Vespine talks about a free digital book called “Demystifying the TLC5940” by Matthew T. Pandina.

If you are planning on using the Texas instruments TLC5940 LED drivers for your project, than make sure you check out this book. Especially if you are working with AVR microcontrollers like the Arduino sets. What was most interesting to me was a reference to the TLC5940 programmer flowchart by Texas Instruments. The first code-example in the book describes a reference implementation of this flowchart, which is a great starting point for your own project.

Any reference implementation can be VERY useful. As you continue to work on your program, and your own implementation, the reference program can be a great way to see if you messed up your program, or if your TLC somehow got fried whenever it stops working.

So I wrote my own version of the reference implementation for the Pic32 and it works! It was very nice to finally be able to see how this driver business works, and gives me a lot of new ideas about architecture and the next parts of the my Cube’s design. Still brainstorming about a lot of things, but we’re getting there!

If you’re developing on Pic32 btw, make sure you use MPLAB X. I only updated today, and was very pleasantly surprised. A BIG step forward from MPLAB 8.x

Aside from the software, I also managed to build another layer for the LED matrix, which brings me at 5 of 8 layers total now.

Well that’s it for now!
If you have any questions, don’t hesitate to mail me, or leave a comment below!

Thanks for reading!
Wracky.

 

 

 

The LED matrix. First 2 Planes done.

Wednesday, October 26th, 2011

So I’ve started on the LED matrix.

I have finally decided on how I am going to structure the matrix, but after creating 2 planes, I already regret one of my decisions ;-)
Although it’s probably a minor thing.

I thought about how each LED in the matrix should be mounted, and came up with three points:

  • Too many brass rods will block the light.
  • If you place the support rods close to the LEDs, they will cast a fairly large shadow.
  • Too little brass rods will cause the cube to become unstable and wobble when moved.

With this in mind, I came up with this design:

LED close up.

RGB LED close up.

I decided to use 1 brass rod for every row and column in a vertical plane. It might be a bit overkill. I believe eightcubed only  uses 3 vertical rods per plane, but you can’t really make a uniform distribution of rods if you go higher than 2, which is too weak.  I decided to go for a uniform look, and think the extra rods will provide a bit more stability, hoping they won’t block too much light :)

I could have used a different orientation on the LED to have the leads all point in the same direction. However, since these are 5mm RGB Leds, the 4 leads are really close together. Bending them like this makes for a better “distribution” of the space between the leads, and puts them a bit further apart which leaves me a bit more room for error :)

As you can see, there is quite some space between the vertical support rods and copper wire, and the LEDs. As noted above, I did this to reduce the shadows cast by the rods. The result is actually quite nice. After finishing 2 planes and putting them together however, I noticed that the 3 horizontal leads block quite a bit of light if you view the cube from the top. I’m not starting over ;-) But were I ever to make a second cube, I would place the copper wires closer to the LED. The copper is 0.2mm and doesn’t cast a big shadow, and this way the length of 2 of the 3 leads could be reduces, which makes the cube slightly more transparent :)

With 2 planes finished  I’m rather happy with the result so far. I will finish 8 planes first before I go and try to build the cube. I’m building vertical planes. I guess this way it will be easiest to de-solder an entire plane, and take it out if any repairs need to be done to a single LED. Making vertical planes means de-soldering the brass connections on the outside and bottom and lifting plane out. Making horizontal planes would mean de-soldering all the LED cathodes, which  is 3 per led :) I test every LED, row and plane before putting it in, so I don’t expect any problems, but hey, better be safe then sorry right? :D

Well, that’s it for now! Don’t know when I’ll be making my next blog post, since the next part is just a WHOLE LOT of soldering work to do. After that I’ll start on programming a single led driver, to decide on my circuitry based on what I’ve learned from that :)

Talk to you later!
Wracky.

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Building an 8x8x8 RGB LED Cube!

Tuesday, September 20th, 2011

Hi there!

It’s been a while since I posted anything here, but I have a new project I’m working on, and I figured I’d make a work log here.
I’ve always been interested in electronics,  but never really got into it. I was more into programming.  However last year I came across this video.

This is what got me interested in Led cubes. The video nicely demonstrates what these are: Low resolution 3D displays! Soon after, I found that people were also making these with RGB Leds which spiked my interest even further. I was looking into how to get one, and found a ton of information of people building these from scratch. This is when I decided I wanted to build one myself.

I started out by reading a lot. I learned about different cubes, why they were build the way they were, and drew my own conclusions on how I wanted to design mine. My current plan is roughly a mix of two RGB cubes I found online.

vespine.com is my major inspiration. There is a LOT of information on this page. Vespine started out with a lot of research of his own, and has shared a lot of his findings in his blog, together with links to where he found more information on LED cubes.

lumisence.com has a 3D LED project called eightCubed which is currently in it’s second revision. They have a lot of detailed pictures on how they build the cube itself, and a lot of cool videos.

The LED cube basically consists of 3 parts:

  • 3D LED matrix
  • driver circuit (usually with some kind of micro controller)
  •  Power supply.
Copper wire and brass rods.

Copper wire and brass rods.

For the 3D LED matrix, I was inspired by the eightCubed. Every RGB led needs 4 connections. 1 for the common anode/cathode and 1 for every color. Every connection needs a lead. As you can imagine, since this is a 3D matrix, these leads might get in the way, and block light from LEDs further in the cube. eightCubed provides a nice solution: A sturdy structure made of brass rods, with very thin copper wire for the remaining leads. I decided to follow this example. It’s a bit more work, but the result should be a sturdy but rather transparent mesh.

Pic32 starter kit

Pic32 ethernet starter kit + expansion board.

Vespine introduced me to the Pic32 starter kits. Being a programmer, it was the first thing I bought for this project, and I have to say I’m not disappointed. It’s an overly capable little processor combined with a programmer and a debugger. The board comes with a simple IDE that makes developing, and debugging on the platform easy as pie.

Downside is that the starter kits need an expansion board before they can be of any use. However the expansion board does provide you with ample connections to the IO pins Pic32, along side the option to connect an external power supply, and extend the board further with things like wireless modules. The entire combination does make this solution a lot more expensive than for instance an arduino solution.

I choose the Pic32 Ethernet starter kit because it also featured the USB host connector and the ethernet port, which could be fun for later communication with the cube. The ethernet starter kit also sports the most RAM @ 64KB and the biggest flash storrage at 512KB.

Vespine also used Texas Instruments TLC5940NT LED drivers for his project. I’ve looked into these, and they seem like a really good choice for me. These are constant current sink LED drivers, which means they NEED “common anode” RGB leds. They save you a LOT of trouble on designing your circuit, but might give me a big headache in return when I try to set up a proper data bus and program 12!! of them.

5mm straw hat RGB LEDs

600x 5mm "straw hat" RGB LEDs

I’m planning on making a smaller cube. Vespine’s cube and eightcubed are made with 10mm RGB LEDs and are about 33-ish CM. I’m going to give 5mm “straw hat” diffuse RGB LEDs a shot, which I bought for about $0.34ct/pcs on ebay. Placing them 3 centimeters appart makes my cube around 21CM wide/high. It will be “fun” to see how to get it all wired, but hey, I’m up for a challenge :)

I will use a factory made power supply for my cube once I’ve decided on the working voltage. I’ll do some tests before I decide on a power supply.

As a final note, I want to give you a little warning. If you are planning on building an 8x8x8 RGB LED cube by yourself, I found that these things are not cheap :) 8x8x8 pixels will give you 512 RGB leds that you need to buy. DO LOOK AROUND because prices vary A LOT. You could probably make the cube cheaper by using a different micro controller platform, but in materials alone, I’ve currently spent well over 400 euros on this project :) It will probably reach 500 euros easily.

That’s it for now! I’ve started on putting the mesh together, of which I will post some fotos soon.

Thanks for reading!

Wracky.