I built a trio of LED helmets for Roikoi's use at SXSW over the

I built a trio of LED helmets for Roikoi’s use at SXSW over the past couple weeks. (FastLED 2.1-dev running on a Teensy 3.1 driving 300 WS2801 pixels.) They were a huge hit. A big thanks to all of FastLED’s contributors!

Nice! Got any video of it running?

very very nice thats what i want to do in the future haha awesome

wow, those look awesome!

Dopesauce - Definitely need to see some video of these in action!

@Daniel_Garcia @Matt_Starbuck I’m waiting for Roikoi’s official video footage to be edited, but here’s someone’s Vine of the three goofing off in a pedicab: https://vine.co/v/MqqrLJptdXU

Wow! Great job, the fit and finish on those helmets really shows!

Yeah, very clean job. I also notice the bum-bags—couple of 12Ah SLAs in there? :slight_smile:

Thanks for the compliments!
@Robert_Atkins The batteries are all LiPo “USB external batteries” – one per 25-LED strand. Expensive, but they hit all the requirements in a very clean package.

You mean like external iPad chargers, so a maximum of 2.1A per USB port? I was thinking of going this way for my next wearable project. Any particular brand? I was looking at Anker, they had a 2-port model they claimed you could pull 3A from in total.

Yep, that’s the idea, hence one battery per strand. Some models such as the big Anker put out enough current (across multiple ports) that it would be possible to run two strands per battery, but the recharge time goes up because the recharge current is only 1A or so. I needed a fast turnaround to get near-continuous use of the helmets via two sets of batteries, so that wasn’t a good option.

After testing a few models I settled on one from Lumsing. None of the batteries I tested had actual capacities/efficiencies anywhere near what was advertised. Anker makes very nice products – I did buy several of their 5-port, 8A chargers – but their batteries were too expensive considering I was shopping for 78 of them.

If you want to venture into building your own charger, the MAX8903 can be configured for an up-to 2A current output over a DC input. That’s the configuration I’m using for my design. It is a single cell charger, so if you’re using multiple batteries in series, you’ll need a different one and deal with proper balancing.

Now that’s interesting, there has been something funny going on with the supply of those Anker 5 port/40W chargers. Reading between the lines, I’d say they had reliability problems with the first production run and they pulled the existing stock and had to do a bit of a redesign. But Amazon US now says they’ll be back in stock by the end of March. Good catch that the batteries themselves will only charge at a 1A rate, there’s less utility in the 2A-capable 5 port charger if that’s the case.