8x8x8 led cube transistors question

Other Hardware General Electronics
1

So i'm hoping to build the cube in this instructable http://www.instructables.com/id/Led-Cube-8x8x8/

I can understand the multiplexer circuit although on the control board, I don't understand the transistor array.
What is it for, what does it do, why do we need it? (Can you tell I've never used transistors?)

Thanks in advance!

2

They turn on and off each of the 64-LED (8x8) planes. According to the text, they needed 2 for each plane to sink enough current. They should have loaded the emitters with small ohm value resistors (1 ohm or so). The way they it, they risk the chance that one transistor will have a lower C-E voltage at saturation and carry all the bulk of the current. Separate emitter resistors would be more effective than separate base resistors, which is of no use at all.

3

okay.
I'm just trying to decipher how they made it since they provided no schematics of their controller board. Only of the multiplexer array.

4

Anybody wanna help me understand transistors? Haha.

5

funkyguy4000:
okay.
I'm just trying to decipher how they made it since they provided no schematics of their controller board. Only of the multiplexer array.

Apart from this?

And made a bit more readable:

1375×879 21.4 KB

6

Oh....haha, I didn't see that!

Thanks a lot! You've always been a big help. Everybody here has.

7

Had you taken the time that Nick did you would have discovered the same information and a lot of electronic theory as well... ALL Useful stuff too... for cubes and for control as well. IMO

Doc

8

For some reason the pictures weren't loading for me so I wasn't looking at the pictures and looking for a .sch file to download but I couldn't find it.

9

Sometimes it is better to read the whole book before you prepare a report on it... I saw a set of PCB's for this cube on Ebay, only $27.00 or $120.00 for a whole kit... He is either dumb or dumb as the idea wouldn't survive a patent examination in this country and likely the whole set will be sold by as many people who can make a copy of the boards and the parts list... in a month or so, On Ebay...
It's a really cool looking project but personally I think I would tire of it in a month or so...

Doc