LED Cube Vertical Animation Failure

Thread Starter

enbde

Joined Jun 14, 2021
5
Hi everyone,

I successfully completed my 8x8x8 LED cube (by CHR) (https://www.instructables.com/Led-Cube-8x8x8/) 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.

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 https://www.instructables.com/CHRs-8X8X8-LED-Cube-Revisited-with-improvements/) 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.

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.

These tests 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.

Thanks
 

Thread Starter

enbde

Joined Jun 14, 2021
5
Sorry I forgot to mention that I have also tested this with my power supply outputting ~5V with well enough current and the issues persist.
 

click_here

Joined Sep 22, 2020
267
Do you have an Oscilloscope?

You'll have to check how quickly the clocking of the latches are. My guess is that there is something wrong with the program speed, but I'd need to work see with a oscilloscope
 

Thread Starter

enbde

Joined Jun 14, 2021
5
@click_here thanks for the response. Unfortunately I don't have an oscilloscope. That is an interesting thought though, I hadn't given that much thought. Would the fact that my cube worked for a few days when I first finished it (then I put it away for a month or so) align with that issue?
 

click_here

Joined Sep 22, 2020
267
You'll have to test it another way

Write a program that turns every led on at once, 5 sec delay, and then off, 5 sec delay, and then loop. Have a stopwatch or something with seconds in the video as you record to compare it with what is actually happening.

It might be worth it to take some measurement when all of the leds are on, such as voltages and current (as a sanity check).
 

Almir

Joined Jun 21, 2021
1
Sorry I forgot to mention that I have also tested this with my power supply outputting ~5V with well enough current and the issues persist.
I had a similar problem after I finished my 8x8x8 cube. After hours checking if there was anything wrong with the cube, I changed the arduino nano to a old version I had around and it worked just fine. So I figured there is something about the microprocessor on some arduino.
 

Thread Starter

enbde

Joined Jun 14, 2021
5
I had a similar problem after I finished my 8x8x8 cube. After hours checking if there was anything wrong with the cube, I changed the arduino nano to a old version I had around and it worked just fine. So I figured there is something about the microprocessor on some arduino.
Thanks @Almir I'll try that. Fingers crossed.
 

click_here

Joined Sep 22, 2020
267
Another way I've seen people do these is using shift registers and daisy chaining them together.

All of the info is sent out serially (bit banging), and then all of the latch registers are set at the same time

This syncs every LED :)
 
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