Unicorn pHAT in Mood Light Kit not working


I purchased a Mood Light kit and it was such a big hit with one kid, that I finally gave in and purchased another for a different child. It arrived today and I assembled it and installed Raspian and the Unicorn modules on it. But I can’t seem to get the Unicorn hat to light. Tried quite a few of the samples but no lights anywhere. If I grab the first Unicorn hat off the first Mood Light kit and put it on the new one, it works fine while the new Unicorn does not work on the older Mood Light. So it seems to be narrowed down to the new Unicorn.

I checked the soldering on the Unicorn header and it looks fine, but I went ahead and touched up anything that looked like it could have been the least bit suspect but still no pretty lights.

Anything else potentially to try before I order a new Unicorn pHAT?


The pinout is here https://pinout.xyz/pinout/unicorn_phat# showing what pins are actually used.
BCM 18 is the big one, thats the one that does all the trickery as they say. Thats physical pin no 12 on the GPIO header. Have one more look at that I guess. I don’t know what else to check.
It’s just a big array of addressable LEDs.
If you go to the Shop page there is a contact us link at the bottom that will let you e-mail Pimoroni tech support directly.


Indeed! Don’t put yourself out of pocket for a new one. It sounds like you’ve been pretty thorough with your tests. If it’s not working, let us know via the tech support email and we should get a replacement sent out.

I will say, however, be careful when soldering these. Those LEDs can be pretty sensitive to extreme heat, specially after being unpackaged and exposed to any humidity. I’ve broken a couple of Neopixel sticks (same type of LEDs) just by soldering headers to them.


What I like to do, when soldering something with as many pins as a GPIO header is as follows:
I solder every second pin on one row. 1, 5, 9, etc
Then solder every second pin on the second row. 2, 6, 10, etc
Then do the ones I skipped on the first row. 3, 7, 11, etc
Then do the ones I skipped on the second row. 4, 8, 12, etc.
It spreads the heat out and by the time you go back to solder the ones you skipped the ones you already soldered are cooled off. It was something I was taught when soldering multi pin IC’s. You know the old through hole stuff, showing my age much lol. ;)


I’ll have to give it a try. I usually to 1-21-2-22 etc. when doing headers. Your way seems more efficient in solder iron movement and leaving the time gaps between pins though. And while I’m pretty good at spotting pin 21 in the middle there, I am off sometimes :)


Its pretty well just a learned routine for me now. Its habit to do it that way. I usually just do one at each end, check to see that the header is level / straight, then carry on. The single row ones are pretty easy to get slanted and not straight up. Like the ones on Arduino shields etc.