My first attempt at heat remediation was: put some rubber feet on the bottom; drill two holes in the wooden plug; add a 5v fan that I had lying around, PWM controlled from the Moteino (so the Pro Mini can continue driving the LEDs full bore).

I had a 2n2222 at hand, and grabbed a 3055 NPN power transistor. The 3055 is totally overkill here: I'm talking about a 5v couple hundred mA fan, at best. The 3055 is rated for something like 20A at 75v. But I'm not using it for anything else, and this combination makes a fine fan driver (with a couple 200-ish ohm resistors, one on the base and one on the supply of the 2n2222; and the 3055 dumping current rampantly through the fan - yes, probably with some ringing that I don't really care about yet - and whatever diode I can find lying around to deal with the motor's current backrush).

As usual, I've totally bodged this together. I didn't sit down and plan it, so I didn't draw out a schematic. I didn't put it on a proto board. I just soldered it all up dead-bug style and jammed it in the cylinder to see if it worked. And voilà, the fan sprung to life!

With no demonstrable improvement in heat load. The fan was just some 20mm DC fan I had lying around and really didn't move enough air. Off to Mouser, then, and a suitable high-CFM 5v 35mm fan was bought.

Now, I'm trying desperately to keep the wood plug on the bottom. I like how it looks with the glass exposed on top. But I realize this is a terrible idea for reasons of physics (convection). I really want to let the heat out the top. And to make it worse, where I had planned to mount things to the wooden plug, I now had to make a substantially larger hole for this fan.

Okay, okay, it's finally time to give up on the plug-on-the-bottom. I flipped the whole thing over, and this is where I actually start taking pictures. The components all get a circuit board as a home; I routed a nice hole in the plug, and filled it with some perforated black aluminum. The fan screws on to the aluminum, and now I'm thinking that there's a good amount of air flow (6 CFM max, which my back-of-the-envelope heat load calculations say ... well, that I have two unknown variables and I can't possibly solve the equation, so I give up and figure I'll see how it goes).

With the fan running well, I figured I'd spend some time repairing the pixels. Of course, at this point I've used up my spare 144-LEDs-per-meter WS2812b strips, so I have to actually spend money on some. So I find a cheap supplier and get them somewhat slowly.

Friends, there is a problem here. There are two price brackets for the same product: you can spend $30/meter for these from suppliers, or $60/meter from resellers. That kind of markup always makes me go the cheap-but-slow route. Well, let me tell you: order them from Adafruit at $60/meter.

The first problem is counterfeits. In this case, that means LEDs that have excessive heat load (or 2812s that are being sold as 2812bs). Which maybe you can tolerate, or maybe you can't. And maybe you find the good suppliers that are using the good WS2812b, so it's not a problem.

The second problem is the real kicker: about 2% of these LEDs are DoA. About 3 per meter. A little research shows that this is typical for these buggers. If that's truly the failure rate, then companies like Adafruit must be putting a ton of staff time in to testing, replacing, and returning the defective runs. No wonder they're marked up so much. All of the LEDs I'd started with were from Adafruit, because reasons: they're in New York, I'm in Philly; Lady Ada is awesome, and I want to support her business; Adafruit makes great materials available to novices, which I think is really important for budding electronics nerds. So I had absolutely no problems with the 2m that I had lying around from early Christmas tree light tests.

But these replacements *suck*. I wound up spending hours replacing individual LEDs, splicing together larger runs, removing the old dead runs from the cylinder and putting in place new runs - just to find out that the new runs worked well under light load, but had substantial problems when they ran full-out. Heat failure was very common, even with more massive airflow (outside the candle holder). Some pixels appear to have mechanical problems, not having been soldered on the strip very well, and slight heat variations cause them to fail. This is, in short, not a working solution.

Time to think about a better solution.