Mote shutting off when RPF power supply plugged in


#1

I’ve come across a weird situation when using my mote:

I wanted to do some testing with it today to see if it could light a whole room (answer: very nearly), and to get the motes to go to full retina-searing mode I plugged in an external microUSB power supply, which in this case was the Raspberry Pi Official one I have on my desk.

If I plug the power in when the mote sticks are turned on, they go from full white (255/255/255) to a more orangey shade, and flash a couple of times really quickly before the mote restarts and I get the whole rainbow flash thing again.

If I plug the PSU in before running my code, I get a python error SerialTimeoutException: Write timeout.

Mote works just fine if I plug it in to another PSU, and AFAIK the pi power supply works fine too (with a pi).

What gives?


#2

That’s odd. What’s the other PSU?

If I recall correctly we put some brightness limiting in the software since 4x16 APA102 pixels can draw an alarming amount of power on full beans.If something were to introduce line noise and flip them to 255,255,255 then that may brownout the ATMega32a4u chip!

I’m not sure why your Pi PSU would do that, though! Perhaps it’s a voltage differential problem, or there’s something not quite right with the PSU. Do you have another Pi PSU to test it with?

Oh and is it the 2A or the 2.5A Pi PSU?


#3

I did think it was a bit weird.

Maybe it is a line noise thing, though why the power supply would do that I’m not sure…

The other PSUs I’ve tried are my desktop’s USB port and an Anker PowerPort type thing - a bit like this one but an older version. I think my anker will supply either 2 or 2.5A.

I’ve only got the one pi PSU and I’ve been really impressed with it (amazing how relaxing it is to not have the rainbow square there all the time!) - I believe it’s the 2A version (it’s the one which came with the Pi 3 essentials kit).

I’m using the Anker PSU for my project so it’s not really a problem but I thought it’s a bit weird.