4x4x4 cube help

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4x4x4 cube help

Post by Ian.G » Sat Aug 07, 2021 6:02 pm

I have recently completed a blue 4x4x4 cube kit. On first powering up it ran OK for several tens of minutes before freezing. Since then the cube has not run for very long before freezing, Sometimes it freezes with a no LEDs on and sometimes with a fixed pattern. I assume that this freezing is due to the processor clock stopping. I saw a reference in a forum note to raising the crystal a little clear of the PCB. I tried that with no effect.
I had a hunch that the problem lay with the power supply and tried the supplied serial interface cable in a number of different USB sources with out any change.
I have added a 22uF capacitor across the supply pins of the header on the cube PCB and the cube has now been running without a problem for a couple of hours.
May my supply capacitor have masked a different problem? Have you any thoughts?

A couple of hints that may help others -
When I had assembled each of the 4x4 LED slices, I tested the LEDs with a 5V supply and series resistor. It is much easier to correct any errors at this stage than when the cube is assembled.
When I assembled the 4x4 arrays into the cube I used 2 pieces of card with four slots cut into them to hold the 4x4 arrays at the correct spacing while making the last soldered joints.
I hope this is helpful.
Best regards Ian

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Re: 4x4x4 cube help

Post by andrew » Mon Aug 09, 2021 9:17 am

If the cube randomly crashes then it's likely to be one of two things, an issue with the crystal, which is unlikely in your case, or a power supply issue.

My guess is you may have a bad USB cable. If it's impedance is too high it could be causing the power to the cube to dip resulting in a brownout and the microcontroller crashing. I'd suggest trying a different cable (if you had that option) to confirm it is the cable. But then to do that you'd have to remove the capacitor.

Thanks for the feedback though. Maybe adding a small power supply capacitor to a future update may be the way to go.
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