My project for Burning Man this year (and two years ago) was a 20'

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(Zeke Koch) #1

My project for Burning Man this year (and two years ago) was a 20’ art car with 14 pins worth of led strips (most with 139 lights per strip). That was a total of 1645 lights, but my LED Array was more like 3528 (my longest strip * 14 strips). All of the lights were controlled by a single teensy through a board I milled on my Othermill.

Most of the lights were IP67 (silicon sheathed) ws2812 wrapped over a series of pvc tubes. Many of the light strips broke in transit (coming back from BM2013, going to BM2015, likely coming back from BM15). The place where they solder together two strands to make a longer one is always the weak point.

Anyway I’m using the 16-way parallel stuff and I’m pretty happy with the performance, but obviously would always like stuff to be faster. I’m about to buy a bunch of IP65 (glue coated) lights to replac the silicone sheathed ones (assuming that they’ll be sturdier.

I can either upgrade to APA102 or stick with WS2812. Will the APA102 lights be significantly faster/more efficient than a 16-strip parallel ws2812?

It would obviously be cheaper and easier to stick with the ws2812’s, but I don’t want to invest in the past…

(Randal B) #2

pics in action?!

(John Burdett) #3

I think you said it best at then bottom of your post. Go with the APA102. As far as the epoxy resin strips, I’ve had nothing but issues with them. They seem to crack in cold weather and much more of a pita to cut and solder. Maybe just get a sample to test out before committing.

(Randal B) #4

i found even the silicon coated one fail at those same solder points also. But I find the coated ones are easier to attach to something solid if its not a wearable item

Overall would I found the coated strips would fail slightly less than the pcv tube protected ones.

i actually had an easier time soldering the coated ones (once i learnt an easy/quick way to remove the coating), than trying to adjust the pcv tube out of the way. heat-shrink wrap and some silicon sealant made those solder point solid.

(Juergen Bruegl) #5

Check whether you feel that the silicon coated LEDs are sturdy enough for you. They are quite soft and the coat can easily be pulled off just with fingernails. It is no mechanical protection.
I put a small piece of ABS plastic underneath the weak points and clear shrink tube it. Connection cables are tie wrapped and or hot-glued at the entry point.

APA102 are much faster!

With APA102 you need Data and Clock signals; means that you have to use 32 output pins. Teensy has 32 but 28 … 32 are inconveniently on the backside of the board.
You need Header like this: http://www.exp-tech.de/smt-gpio-header-for-raspberry-pi-hat-2x20-short-female-header
and for the other pins riser: http://www.exp-tech.de/break-away-headers-long.
… and 4 more RJ45

(Randal B) #6

oh thats a great idea: "I put a small piece of ABS plastic underneath the weak points and clear shrink tube it. "

(Zeke Koch) #7

Hi Juergen, my lights are strapped to PVC tubes and then covered in fabric so I’m not too worried about that. I’m more worried about distributing bending and flexing forces more evenly.

I’m a little confused by your suggestions to use multiple output pins. I’m assuming that if I’m using SPI that I’d want to have the APA102’s as a single long strip (electrically) attached to the hardware SPI port.

If the APA102 is 12Mhz (from a post from a post from Daniel) and the WS2812 is 800kHz then the amount of time it takes to write to one continuous line would be 1/15th of the amount of time it takes to write to the WS2812s…

Hmm, now that I’m doing that math maybe it isn’t worth switching at all… +Daniel Garcia, am I thinking about this correctly?

(Juergen Bruegl) #8

@Zeke_Koch maybe you post a few pics about the damages you experienced.
Sure you can electrically use only SPI and make a 1600 LED long strip. Depends on your animations etc. I personally split individual strips in different output pins, that’s easier to debug and exchange segments if necessary. When one strip ‘dies’ the rest is still working fine. Just from your WS2812 board layout I assumed you want to keep this. Btw, on Teensy I don’t use level shifters.
@Randal_B you are welcome - that’s what a community is for :slight_smile: