PiGlow causes crash - power supply trouble?


#1

Hi, I recently bought a PiGlow and have been playing with it, trying to generate various colour-changing effects. It is connected to a Raspberry Pi 1 model B.

I soon noticed that if more than about half the LEDs are on at full brightness, the ethernet port became flakey (the yellow link light flickered and went out); and with all the LEDs on, the RPi crashed. Which is a bit disappointing.

I’m guessing it’s drawing too much current… is that a known problem? Is the bottleneck likely to be somewhere in the RPi itself, or my external PSU (which is rated 5V 1.2A)?

Thanks, Nick


#2

the problem is almost certainly the PSU. I seem to recall figures around the 500 mA mark as a minimum for the Rpi B with typical 700-800 mA. Piglow all guns blazing I would have to guess around 400 mA.

… those figures might be off, but not surprised at all you’d be able to starve the poor thing on a 1.2A PSU.


#3

Ah. Thanks! I will have to try with a better PSU, if I can find one with the right USB connector. (Edit: my PSU was originally from an RS kit; I see Pimoroni do a 2A one.)

In the meantime if I restrict it to less than 12 LEDs on I can still get good range of colours and brightness.


#4

I did a bit more investigation and some reading. It turns out my PSU is fine, the problem is the “polyfuse” on the Pi. It’s supposed to blow at 1.1A but apparently there’s a big slop region between 750mA and 1.1A in which it can misbehave.

Either I’ve upset mine with the PiGlow, or it’s always been flakey and I never noticed before, because it’s dropping 0.5V with the lights off, and more with them on. Looks like I need to find a replacement, or bypass it with another fuse!