22 November 2012

How to Build a Simple LED Cube 4x4x4 - Part 2

Building the Cube Structure

In part one we prepared all LEDs for the assembly of the cube. Now, we start in earnest...


Step2: Build the groups
Each group consists of eight LEDs. Here they are:



You need a template to assemble the LED groups. My LEDs are 5mm, so I drilled a set of 8 5mm-holes in two rows with 4 holes each into a piece of wood.




Insert 4 LEDs in the upper row of the template. Make sure all anodes point towards North-West.


Bend the cathode leads as shown. To give you a better understanding, the LEDs are slightly rotated in this photo:




Solder the LEDs to their neighbours.Insert the remaining 4 LEDs, again with anodes oriented towards North-West.





Again, bend the cathodes so you can use them to connect the LED. This is now the opposite way (basically all wires are bent clockwise).



Solder them to their neighbours so that the cathodes form a ring-like structure. A
lign anodes and make sure they are vertical. And then test!




Yes, it works...



Repeat this process another 7 times. You will now have set of eight groups of LEDs. Here they are, hinting at their later organisation.




Step3: Assemble the cube
Finally, all groups are connected. This step needs to be executed carefully. Make sure everything is level and aligned.

Insert the first group into the perfboard.



 
Then, add a second group. Put it on the perfboard in exactly the same orientation. Later, the columns of these two LED groups will be connected in parallel.



Now, you should do something that I only did after I had the cube finished: Connect the common cathodes to the perfboard. I wanted that connection to be invisible, so I put each vertical wire in the middle of its group. Better add them while adding LED groups, because access is easy now.

Here is a top view of the finished cube, with those vertical wires marked.


Now test those first two groups!

If everything works, start with the second level. Connect the two groups of the second level through their anodes to the corresponding anodes of the first level. Take your time! To make sure everything looks even, just start with two connections on opposite corners. If everything looks good, connect the rest.



This should be the moment for you to understand why half-cubes (i.e. groups of 8 LEDs) are easier to assemble. All solder locations are accessible from the outside. Of course it is a bit more difficult when you connect the second group of a level, because the first group gets in the way. But it is still easier that connecting a whole level at once.


Here is a side view of the next two groups.





Again, add the cathode wires and test. Add Half way there!


Keep going with the next level.



Test!

Finally, add the top level.



As mentioned before, the corresponding columns of the two half cubes have to be connected. Like so:


  
And this is the end result. The perfboard is cut so that the cube just fits on it. The rest of the board is used for the electronics.


Make sure everything works. Try all combinations of columns and levels. If you didn't know what multiplexing means: You are doing just that. Manually, of course. But that is what we have a controller for. And of course we can make the 8 LEDs of each group light up at the same time.

Congratulations! This is the hardest part done. What remains to be build is the electronics to control the cube. It is very simple. See part 3 .

23 comments:

  1. Replies
    1. I've hit a snag. The wires attached to the common Cathodes.. Solder one wire to each layer and .. where does the other end connect to? I have looked at the picture of the underside with the 8 white wires but I cant see where the wires attached to the cathodes are soldered.

      Delete
    2. Tony, have a look at part three. You are probably referring to the yellow wires of the schematic/photo there?

      Delete
    3. I'm reffering to pic 12 on this page where the vertical wires are marked with yellow rings. I understand that each wire is attached to Isits layer. The other end goes through the hole in the perf board.. but in pic 18 where you show the underside with the white wires connecting, I cant see where these vertical wires connect to :)

      Delete
    4. I have tried to intently study this. If I have it sussed, and I think I understand now, in step 3 the vertical wires are connected to the yellow wires. Under final assembly 'so far the vertical wires just end on the board...' These yellow wires connect to the vertical wires soldered to the cube?

      Delete
  2. Hi

    I wanted to make a 4x4x4 LED cube with 10mm LEDs for a 10 week project and wanted to ask you a few things which I am unsure of:

    Firstly:
    Will these plans still work or will they need to b
    e changed alot due to the more current being drawn?
    (apart from the obvious change in resistor values)

    Also I aren't sure whether to charlieplex the cube or multiplex it yet , Which is easier?

    In addition, Is the construction of the actual cube grid the same no matter which technique used ?
    {as i wanted to build the actual grid first to get it out the way then concentrate on the other parts}


    Any Help and tips appreciated


    Thanks

    Ben
    alaimob@yahoo.co.uk

    ReplyDelete
    Replies
    1. Hi Ben,

      1.) Whether the plan still works or not depends on your LEDs. Larger LEDs do not necessarily draw larger currents.

      The LEDs I was using are rated at 20mA. The controller pins of an ATMega8 can supply about 40mA (but with a significant voltage drop!).

      In the end, it is a matter of what level of brightness you expect from your cube.

      There are _no_ resistors in my simple cube design, btw.

      2.) Charlieplexing is far more complex. If this is your first cube, don't use it.

      The cube structure actually is different and far more difficult to build for a charlieplexed cube. That is why I advice you not to use charlieplexing.

      3.) Additional advice: if you are using 10mm LEDs, make sure there is enough space between them. Otherwise you will not be able to see the 3D effects, because the LEDs themselves will block the view on the lower/backside layers. I'd suggest a distance of at least 50mm between the LEDs.

      Have fun,

      Tom

      Delete
  3. Hi, how many common cathodes are there, could you please make that part more clear.
    Thank you

    ReplyDelete
    Replies
    1. Hi,

      there are 8 common cathodes. Please have another look at part1, "How it works".

      I am using the 64 LEDs in an 8x8 matrix.

      Delete
  4. I want to make a 5x10 led matrix using this single chip method. Is that possible? I could really use some advice as it is my first project. Feel free to email me:

    Munderbob@gmail.com
    Or a comment is fine.

    ReplyDelete
    Replies
    1. Hi Bob, that is possible. Actually, the cube is really a 8x8 LED matrix, shaped into a 3D form.

      You would have to modify te software somewhat, though.

      Delete
  5. Very cool project. And very nice blog doc. I'm seriously thinking of building one of these and your instructions here will be helpful.

    I'm wondering where you got the protoboard you show in the photos. I think I had some of this 3-holes-per-row stuff years ago but can't seem to find it anywhere now. Any idea of it's brand name, product#, ect.? Thx.

    ReplyDelete
    Replies
    1. Hey Ron, thanks for the feedback. Go for it! There isn't much to lose.

      Yes, this PCB material is my favourite. I used to use the normal strip board, but interrupting those strips always is a pain. Connecting those pads is much easier and can be done simply with a solder iron, lots of solder and some practising.

      I get them from a mail order company in Germany, but I don't know where you live. But you can try to search for

      3-hole pad / 3-hole island prototype boards

      Also, one of the variants I use have an order code H25PS050. Perhaps that helps.

      And finally, I looked up "stripboard" in wikipedia
      https://en.wikipedia.org/wiki/Strip_board

      And it has a list of alternatives. And lo and behold there is something called TriPad.

      Hope that helps!

      Delete
    2. Thanks for the info and links Tom. I spent a few hours (!) cruising to various sites that mentioned TriPad and it looks like it's available, but at a premium. I live in southern Ontario, Canada and all the vendors I found were in Europe; shipping overseas doesn't really make it worth it. I can't believe the TriPad stuff isn't more popular! Oh well.

      I'm thinking I might just try to modify some standard stripboard. There's a Veroboard outfit here in Canada (http://www.veroboard.com/) that sells standard stripboard fairly cheap ($3.40 for a 4"X10" piece or ~ 2.50Euro). So, I'll try buying that and modifying it on a router table as an experiment. I'll post the results on your blog.

      Thanks again Tom, and keep the excellent projects coming.

      Delete
  6. This comment has been removed by a blog administrator.

    ReplyDelete
  7. Hey tom!You have connected the corresponding columns of the two half cubes,on what basis did u connect them?Mine isn't a mono colour cube.So u suggest i connect the cathodes of the same colour??

    ReplyDelete
    Replies
    1. Narra, are you saying that you are still building a cube with 64 LEDs, but with different coloured LEDs? It depends how you distribute the LEDs and what colours you are using.

      The problem is of course that different LEDs have different forward voltages. So it might be necessary to add series resistors for e.g. red LEDs in order to get equal brightness. It doesn't matter if you add these on anode or cathode side. Whatever is most convenient for your structure is OK.

      If possible, I would avoid changing the cube structure, because you would have to modify the software to reflect those changes.

      Delete
  8. I want to make LED cube for colleage project at home ..pls send me videos with power supply and controller on breadboard

    ReplyDelete
    Replies
    1. Sorry, but I don't understand. You want me to make a video about a battery?

      Delete
  9. Hi Tom

    Just wondering if A 50mm x 70mm vero board will be the right size

    ReplyDelete
    Replies
    1. That depends on how you solder the cube. I used a 10x5 centimetres PCB and divided it into a 5x5.5 piece for the cube and a 4.5x5 piece for the electronics.

      Delete