PiGlow causes crash - power supply trouble?

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

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.

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.

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!