IoT POV Fidget Spinner

So the first step of any good project is research. There are multiple important parts to this:

What size is a regular fidget spinner?

That question was actually very easy to answer:

How many LEDs do you need? How fast do you need to control them?

Especially the speed can be challenging. So I started with that. After some perusal of google, I found an article on hackster.io which gave me numbers of about 200-1500rpm when spun by hand. Of course, they can get quite a bit faster, as shown in the Hackaday article I referenced previously. [Frank] spun his spinner up to 2200rpm. For a rough estimate, that's already sufficient data. It means, that there are essentially three ways of controlling a LED this fast. Either I use a fast shift register (most '595 chips get to about 100MHz, so plenty fast), an FPGA or an LED with a very fast PWM controller. Some more perusal of Google, the Mouser site and Aliexpress led me to believe, that there was a single "best" solution. Since I want a regular size spinner with as many RGB LEDs as possible, I more or less have to use the APA102-2020. That's the APA102 (think of it as a SPI driven WS2812 on steroids) in a tiny 2x2mm package.

Even at this size, I can still only fit 11 LEDs in a row on a normal size fidget spinner. That's a lot more realistic than having to fit 12 shift registers or an FPGA with 100+ pins and 32 RGB LEDs on a dual layer PCB that can be produced reasonably cheap.

Since we could get down to 200rpm (or about 3.3 revolutions per second), we need a way to still get a sufficient refresh rate. That's easy, though, since we have three "wings" on a regular fidget spinner. This still gives us a about 10fps at 200rpm.

How do you power this thing? Where do you store the battery?

I decided to go with a 1S LiPo and put it where you would usually have one of the outer bearings. This means, that I will probably have to find a way to add more weight to this wing. This also gives me enough space for a charger, ESP8285, accelerometer, and so on. Also, I don't want to disassemble the device to charge it. So I decided to use the remaining two outer bearings as conductors for the 5V supply the charger IC needs. Since soldering to the bearings would probably be complicated, a battery contact seems like the best solution. The batteries usually have a diameter of 20mm, the bearings come in at 19mm. That's close enough.

I never had any fidget spinner (though I tend to play with ball bearings from time to time) and also never had a POV display. Both of these captured my attention, although they never quite made it to the "can't live without it" stage.

Recently, there have been a few setbacks in my personal life that I currently want to distract myself from. So when I read the article about fidget spinners, I started to wonder if anyone had ever made one into a POV display. Apparently, no one had, but I was still not sufficiently motivated to make one. When Mike reminded us of the IuT contest, however, that was more or less the final straw. So I decided to hack together a IoT POV fidget spinner by Monday. Obviously, I won't be able to have a working device by then, but at least PCB design and the parts order should be done by then. Also, everything required for this round of the Prize should be achievable this weekend:

1. Discuss the challenge the project addresses
2. Discuss how the project will alleviate or solve the problem that the project addresses
3. Discuss how the project might be world changing
4. Publish at least one (1) image illustrating how the project might be used. This may be a sketch, schematic, flow chart, rendering, or other type of image.
5. Link to any repositories (e.g., Github)
6. Document all open-source licenses and permissions as well as any applicable third-party licenses/restrictions
7. Submit the Project to 2017 Hackaday Prize using the “Submit project to...” option found on the published Project Profile.
8. Show at least four (4) Project Log or Instructions updates on your Project Profile