LED Cube Verticle Animation Failure

Hi everyone,

I successfully completed my 8x8x8 LED cube (by CHR) (LED Cube 8x8x8 : 72 Steps (with Pictures) - Instructables) some months ago. The vague idea is that an ATMEGA32 sends data to shift registers which then store it and choose which LEDs to give the most percentage on time in the PWM signal sent to the column (apologies for absolutely botching this).

Recently decided I wanted to make it more portable by simply adding a 3xAA battery pack to power it. However, in the process of completing that (taking the boards out of the casing and adding in the battery pack to the power lines), my cube has now started running into issues. The issues may have occurred before this changeover but not that I was aware of. I have attached schematics of the boards below. I have also tested this with my power supply outputting ~5V with well enough current and the issues persist.

In particular, the cube appears to struggle to draw patterns upwards or downwards when lighting up more than a few columns. Roughly 90% of the animations from CHR (original instructable poster) and SuperTech-IT (a second 8x8x8 LED cube instructable poster) work flawlessly.

The first video shows a diagnostic test. It shows that each column can be lit up without issue. The diagnostic is then meant to light up each and every LED one by one from the bottom. However, mine instead appears to light up each layer (via each LED) one by one, but the last verticle plane always fails to do so. In the end the whole cube is meant to be lit.

(I unfortunately can't link this here as I am a new user to the forums but I will try post in a reply below)
In the second video, it shows more clearly the issue my cube has with lighting up each of the horizontal layers one by one. This is shown when it looks like a single column lights up dimly. It also shows how other (potentially less power consuming) animations work flawlessly.

The changes I have tried to make so far are.I have replaced electrolytic capacitors in case they were damaged through reverse polarity potentially (I do not specifically remember doing this but it may have occurred). I have also done continuity tests on all ICs + ATMega32 + to the cube and everything appears fine.

The tests above make me vaguely think it could be something to do with the transistor layer select array however I am not sure (the instructable used PN2222 transistors as it was what they had laying around, I followed this as I too had them lying around). Any advice would be beyond appreciated.


Link for second video referenced in above post:

Hi, @enbde
Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".

The problem will probably be that the batteries cannot supply the current required by all those LEDS.
Where did you connect the battery pack to?
8 x 8 x8 = 512 LEDs

Even though its multiplexed, the current requirement would be more than those batteries were designed for.
Have you measured the current consumption?

Tom... :smiley: :+1: :coffee: :australia:

Hi @TomGeorge, thanks for your response.

Unfortunately that is not the problem, as I have tested with my 5V ATX power supply which can output ~12A of current.

In terms of measuring the current draw, I have done so with a multimeter and it appears to be around 0.12A when 64 of the LEDs are illuminated. However I suspect the instantaneous current to be larger than that as it is probably measuring the average? Regardless, my power supply should be able to deal with it, so I'm not sure what the go is there.