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LED Notes / LED Cyr Wheel v2


I’m investigating LEDs for another LED cyr wheel (v2). Here is my first LED Cyr wheel and a video. I figure I’ll just make my notes on my blog for others to benefit.

Goals:

  • Individually addressable LEDs, so I can do cool patterns
  • At least as many LEDs as my first wheel, but possibly twice as many (a strip on each side), which was my original plan
  • Built in battery charger and batteries (Lithium ion)
  • Easy to access way of reprogramming (i.e.: USB port)

Extras:

  • Accelerometer for basing patterns on speed
  • Live touch strips, for dynamically changing the LEDs while in the wheel
  • Networked in some way so a 3rd party can control the wheel from a computer and dynamically send patterns to it.
  • A way for wheels to talk to each other for synchronized spinning

This post discusses Adhesives. I’m waiting to get those to experiment with gluing PVC together.

LEDs

How many LEDs? My original wheel has an inner diameter of about 5’8″ (I’m 5’6″) = 68″. Circumference is that times pi: 68*3.14 = ~214″, or 5.4356 meters.

I had ordered my first set of LEDs from AdaFruit: 11 x RGB LED Weatherproof flexi-strip 60 LED – (per 1 meter)[ID:346] = $247.50 (Yeah, seriously expensive for non-addressable LEDs, and I din’t use about 6m of the stuff – I originally planned for LED strips on each side, slightly off from center weight position). That’s $22.50 per meter, and for the entire wheel I have 5.4m*60LEDs=~324 LEDs at a price of about: $121 per wheel.

So I ‘ll say I need 330 LEDs, or potentially twice that if I want them on each side (slightly off center).

What LED strip to use? The WS2812B LED contains a driver built into it, and seems more durable based on this RGB 123 post (it has reverse polarity protection). Pololu has a blog post here and for sale hereAddressable RGB 60-LED Strip, 5V, 1m (WS2812B) – $22.45 per meter (ordering 10m+) . Adafruit also has a new LED strip which they are calling “NeoPixel” ($23.95 per meter, for 4-39 meters ordered – 6M would be $144) –It probably is WS2812 (not B) based on their info, and saying how careful you have to be to hook it up.

Should I even use LED strips? Single-item ones from Adafruit: http://www.adafruit.com/products/1379 (WS2812 5050 RGB LED with Integrated Driver Chip – 10 Pack). I’d need 330 (LEDs desired) / 10 (per pack) = 33 packs of these, at $4.05 per pack: $133.65 –– these alone would be more expensive than buying the LED strips, AND I’d need a resistor added somewhere in there. I think me trying to manually solder 330 of these LEDs together is out of the question. I have to use strips.

Finding strips: I bought some of the WS2812 (not the B!) strips — the B strips seem to have reverse polarity protection built in..which is nice…and actually not that much more expensive. I just had 10% off from Sparkfun so I ordered 6M from them https://www.sparkfun.com/products/12028 . Otherwise, I would have gotten them from Pololu in 2m strips 6 M total.

Edit: My friend matthew mentioned http://blinkinlabs.com/blinkytape/ – it looks cool (but expensive) and the software was something I was thinking about doing!

How to Protect the LEDs?

New idea: cut groove, and fill in with liquid silicon rubber to protect LEDs

I had thought about this before but couldn’t think of a good way to cover the LEDs that wouldn’t interfere with light emission. Then I realized the LED strips already have some type of protective plastic coating, and it might be possible for me to embed them in some more!

Options out there:

SORTA-Clear® Translucent Silicone Rubberhttps://www.smooth-on.com/index.php?cPath=1115_1134 – …Kind of what I want, but not clear enough.

This looks like it is perfect, but it is *super* expensive ($200-$260) to order for me to just try it out:

Clear Flex® Water Clear Urethane Rubberhttp://www.smooth-on.com/Life-Casting–Uret/c3_0_6_1117_1153/index.html
..I’m not sure if it will “stick” to the wheel; if it casts, and then simply falls out, it won’t hold everything together.

Epoxy resign might be my best bet, and comes in a small quantity ($33)
Clear Epoxy Resin: http://www.smooth-on.com/Castable-Epoxy-Res/c1295_1377/index.html
…and it might bond the things together nicely. I ordered some of this (about $50 with sipping – called EpoxAcast 690 – Trial Size (10017194))

This might be better for clarity, and seems great for allowing light to go through:
Crystal Clear® Series – Optically Clear Liquid Plastichttp://www.smooth-on.com/index.php?cPath=1156
…but they don’t have prices listed for it on their website, and it is probably hard to get.

I’m also still considering cutting the PVC and gluing it back together; I’ll experiment more with that approach, although I dislike it. Cutting a groove will be tough for sure!

Edit: My friend Chris Bensen told me Crystal Clear is sold in small quantities! I found it quickly on Amazon – search for: “Castin’Craft Clear Poly Casting Resin with Catalyst 16 oz”  – $20. I’m going to experiment with that too.

What chip/microprocessor to control it all?

I previously used Arduinos for projects; they are easy to program and have lots of code and samples out there on how to use them. However, I’ve heard they are slow, and I want something with enough RAM to handle complex patterns. So, I’m going to drop Arduino and try a much faster Teensy 3.1:  http://www.pjrc.com/teensy/

Edit: Mad suggested I look into a Spare Core Arduino clone; it has plenty of RAM and built in wifi…so I ordered one!

Connectors

I’ve had a heck of a time finding good connectors. My first wheel used really crappy connectors I bought from Frys that aren’t at all meant to connect wire to wire. The main trouble I had is that the big digital supplier sites like Mouser and Digikey are hard to navigate. I finally realized what I wanted was called “wire to wire connectors” in the industry. Eventually I found this great site on Molex: Wire to Wire connectors. I figure about 5 amps would be the max current, so I needed something that could handle that; that (should be) about the rating when all lights are powered full on (full white). I (think) 20awg wire will be fine to use to transfer power; the wire length from wheel to wheel will be short, and the wheel won’t ever be run at full white that long (full power). The Molex Micro-Fit connectors seem to fit the bill really well. Now, it took me hours and hours to find them and pick the ones I want; now I realize the website on Molex is setup really nice to filter down what you want. (I also learned I wanted “bag” and not “reel”). I don’t want “ears” on them as they won’t be “surface mount” connectors (another thing I learned). Once I had the part number, I could easily find it on Mouser (which is much better than Digikey).

 



5 Responses to “LED Notes / LED Cyr Wheel v2”

  1. corbin says:

    Next time, I’m going to try ordering LEDs from AliExpress; they are half as cheap (thanks Spencer for the tip!)

  2. Mad says:

    For a microprocessor, maybe the SparkCore could be interesting as it has Wifi build in.

  3. corbin says:

    Thanks Mad – I hadn’t heard of SparkCore (https://www.spark.io). Actually, the fact that it has wireless programming is awesome! I wouldn’t need a connector for my wheel to re-program it. It also could fit in the wheel… it also has awesome ram (20KB). I think it could work! I’m ordering one..

  4. corbin says:

    Just ordered a SpareCore to play with. The fact that it is an Arduino clone will make it a lot easier for me to play with.

  5. Mad says:

    Happy I could help :) I just got mine a few days ago and the user experience is pretty awesome, plugging it in and having it directly talk to an iphone out of the box … Its one of the only devices where connecting Wifi was absolutely simple, much better then Linux or those stupid wifi printers :)


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