Progress on my RGB cube

I made two of these wire tensioning rigs to speed up the process of making the RGB columns:

I can wire up 10 of them at a time.

This is what the RGB columns end up looking like with the resistor added:

This is a close up of the shrink tube insulators on which the leads of the RGBs are wound. I had to use a small amount of epoxy glue because the shrink tube does not quite shrink enough for these wires.

One slice almost completed:

The horizontal wires are soldered to all the anodes on each level.
They will be soldered to vertical wires that extend inside the base for access.
There is a smear of araldite on the wrapped ends of the RGB leads that are adjacent to each other to make sure there are no electrical contact between the columns.

That's pretty clever assembly, keeps things aligned well. Not sure I understand the resistor/LED leg. Typical multiplexing would have common Anode per layer (or level), then 1 resistor per column. Resistor limits current flow to the layer/level that has power on the anode. Are you implementing something different?

CrossRoads: That's pretty clever assembly, keeps things aligned well. Not sure I understand the resistor/LED leg. Typical multiplexing would have common Anode per layer (or level), then 1 resistor per column. Resistor limits current flow to the layer/level that has power on the anode. Are you implementing something different?

Ahhhh I think I know why you are saying this - because normal LEDs are often multiplexed by stringing up to 8 in series on one TLC5940 channel.

But it is pretty much impossible to series up RGB LEDs anyway. The cathode leads are connected in parallel on those vertical support wires, so each one needs it own resistor.

Originally I was constructing it without the resistors but then someone pointed out to me that LEDs do not share current evenly and that one of the LEDs in the RGB was likely to hog all the current and stuff things up nicely. May have been you in fact. I actually tested it and seemed that the red LED hogged all the current.

All the cathodes are electrically connected through the resistors to 3 of those vertical support wires and each one will be controlled by a BC327 and a TLC5940 channel. So it means that all the RGBs in a column must have the same colour and intensity - a necessary limitation but it wont cause to many limits on the possible animations.

All the anodes on a particular level are electrically connected via those horizontal wires. Each will have a BC337 on it distributing current to up to 8 RGBs / 24 LEDs in each of 64 rows.

These 64 x BC337s will in turn be multiplexed by 8 x TIP125s supplying their collectors and 8 x BC327s supplying their bases. These 16 transistors will be controlled by 16 channels of one TLC5940.

The 192 cathode transistors will be controlled by 12 x TLC5940s.

A total of 13 x TLC5940s.....not to bad.

The complete schematic is too much of a head fuck to reproduce in Multisim 12.

And if I drew it by hand then the sheet of paper would probably be too big to fit in my flat bed scanner.

I am assuming you know enough about electronics to picture the schematic - it is no doubt pretty basic stuff for experts.

If I multiplex it any further so as to use less transistors and TLC5940s then I will surrender to much flexibility and place more limits on the possible animations.

E.G. I had considered connecting all the vertical support wires with the red cathode leads together in a slice, controlled by one transistor and TLC5940 channel. But then that would mean that all the RGBs in a slice would have to have the same colour and intensity. And that would place a big restriction on the animations.

Damn this was tedious!

192 transistors and 384 resistors.

The wires you see there are soldered to the bases.

I need to solder the free ends of those to 5 cut out strips of circuit board and then I will solder another ste of wires coming from the TLC5940 channels to each of these base wires via the circuit board strips.

I still need to solder wires on to the transistor emitters, the free ends of which will eventually soldered to 3 of the support wires of my RGB columns.

How is this going? No updates recently :roll_eyes:

rlogiacco: How is this going? No updates recently :roll_eyes:

A bit of a pause in construction at present.

I am currently building a website and SQL database for my employer whohas finally decided that it is time to bring his business into the 21st century.

Thats a hell of work.... :grin: Thanks for sharing :D

I was just reading about some new RGB LEDs with a WS2811 inside them.

https://www.tindie.com/products/SolderingSunday/pixelbits-8mm-rgb-leds-with-ws2811chip-through-board/

They will make RGB cube building almost trivial.

(The price has to come down a bit, but that's just a question of time...)

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