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270 Neopixels in an Icosahedron
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Please be positive and constructive with your questions and comments.

270 Neopixels in an Icosahedron

by Grey_Area on Mon Feb 18, 2019 5:27 pm

So I made a thing, but it needs improvement...https://www.youtube.com/watch?v=4c3NLTvN6y8

I know what the problem is but solving it may cause me other problems!

There are 270 LEDs here running from a single Pro Trinket. THe Trinket delivers 1500mA...the LEDS could take up to 16,200 mA!

At the moment the voltage also goes into one end only...the arrangement in the icosahedron is literally one long chain. I'm amazed it works at all, but I've had it running 48 hours and it doesn't even get warm.

I "upgraded" to a 3A capable desktop supply and it helped a little, but I'm wondering how best to fix it so that the colours don't dim on the more distant LEDs (anything beyond n=81 or so in the chain is noticeably dimmed)

Ther "path" overlaps itself several times, so I could add a couple of new power sources - or would I be better just having one big one?

Secondly...I'm using home made copper contacts rather than wires. They are flat like traces and measure 1.75mm by 0.1mm - I reckon based on some calculator websites that they could take around 6A...and the recommendation based on animations is 20 per LED, so that's about right, but I don't want to risk melting the whole thing.

Advice please!

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Re: 270 Neopixels in an Icosahedron

by adafruit_support_bill on Mon Feb 18, 2019 7:53 pm

Nice project! To avoid voltage drop issues, you should feed power directly to the pixels. And you should interconnect power and ground at all the vertices of the icosahedron.

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Re: 270 Neopixels in an Icosahedron

by kcl1s on Mon Feb 18, 2019 8:30 pm

One of the best Neopixel projects I have seen. Do you have a write up on it?

Fellow hobbyist
Keith

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Re: 270 Neopixels in an Icosahedron

by Grey_Area on Tue Feb 19, 2019 4:11 am

I have inadvertently wandered into an alternative reality where people’s first comments on forums are complimentary! Sorry, I’m not used to this...can someone please post something like “OMG you noob you don’t know the first thing about electronics” so I know I’m not actually dreaming?

Thank you both for the kind words. I’ll have to look at the way I route the neopixels to see how best to connect power and ground at multiple vertices...it may make things either easier or harder, not sure currently.

As I do NOT actually have a lot of electrical knowledge, I’m assuming there’s no way of getting around that I should have closer to 6A minimum to run these, whereas I’m actually using just 1.5? I’m also assuming that the lack of amps is more of a problem rather than volts...I know voltage will drop over the length (we’re talking 30 arms of 20cm or so, which is a good 6m in a single line the way I have it laid out currently).

The only problem with more power connections is aesthetics...I don’t really want wires coming out of it all over the place...a beefier power supply would be okay as I may be able to hide that in the base (not shown as I have neither designed nor built it yet).

I don’t have a how to for this project; I’m actually hoping to sell a couple of them as I’ve been working on it for over a year and have ploughed substantial time and money into it in terms of design, printing the parts and programming the animations...that said certainly for any overseas customers I am looking at a kit form so I’m writing some assembly instructions. I’m reluctant to release things like the stl for the parts into the public domain...it would be too easy for someone to resell at a fraction of the cost, given that they invested no time in it. One starts to realise why good stl files are so eye wateringly expensive!

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Re: 270 Neopixels in an Icosahedron

by adafruit_support_bill on Tue Feb 19, 2019 7:11 am

As I do NOT actually have a lot of electrical knowledge, I’m assuming there’s no way of getting around that I should have closer to 6A minimum to run these, whereas I’m actually using just 1.5? I’m also assuming that the lack of amps is more of a problem rather than volts...I know voltage will drop over the length (we’re talking 30 arms of 20cm or so, which is a good 6m in a single line the way I have it laid out currently).

Current demand will depend on the intensity you run them at. If you keep it low enough, you can get by with much less current: https://learn.adafruit.com/sipping-powe ... s/overview
If you are overloading your power supply, the output voltage will probably droop a bit - exacerbating the voltage drop issue toward the end of the strip.

The only problem with more power connections is aesthetics...I don’t really want wires coming out of it all over the place.

You don't need wires coming out everywhere. Keep the single power feed point you have now and connect all the +5v pads together and all the GND pads together for all 5 strips at each vertex. (leave the signal connections as you have them). By connecting all the power and ground lines at each vertex, the power has multiple and shorter paths from the beginning of the strip to the end of the strip. That reduces the effective resistance of the strip, so the voltage drop will be minimized.

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Re: 270 Neopixels in an Icosahedron

by kcl1s on Tue Feb 19, 2019 7:29 am

I’m reluctant to release things like the stl for the parts into the public domain...it would be too easy for someone to resell at a fraction of the cost, given that they invested no time in it. One starts to realise why good stl files are so eye wateringly expensive!

I can respect that.


Keith

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Re: 270 Neopixels in an Icosahedron

by Grey_Area on Tue Feb 19, 2019 9:27 am

Thanks again...going to have practice my soldering in tight places skills again, unless I can get at them some other way...foolishly I set all the mirrors in place with silicone sealant already....

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Re: 270 Neopixels in an Icosahedron

by adafruit_support_bill on Tue Feb 19, 2019 9:40 am

You don't really need to do every single vertex. Anything to give the power a shorter path to the end of the strip will help. Reworking just a few well chosen vertices should go a long way to minimizing the voltage drop.

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Re: 270 Neopixels in an Icosahedron

by Grey_Area on Tue Feb 19, 2019 11:55 am

Currently (ha-ha, CURRENT-ly) I'm having great results from following the power sipping instructions.

I originally reduced brightness from 255 to 55 - and it stopped the powerfade pretty much entirely.

But since some of my animations use more pixels than others, I'm working on setting a "per animation" power limit...so far working pretty well...I will follow up the soldered bridges idea as well, then I can go back and see if I can raise my power limit figures a little.

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Re: 270 Neopixels in an Icosahedron

by adafruit_support_bill on Tue Feb 19, 2019 12:32 pm

By law (Ohm's law that is...) V = IR. The voltage drop (V) will be proportional to the current (I). So "sipping" power will definitely minimize the issue.

The voltage drop is also proportional to the resistance "R". So reducing the effective resistance on the power and ground paths to the last pixel will let you run at higher intensities

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Re: 270 Neopixels in an Icosahedron

by devoh on Wed Feb 20, 2019 3:06 pm

I would love to see a build video or some instructions or anything like that :) This is absolutely amazing!

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Re: 270 Neopixels in an Icosahedron

by Grey_Area on Thu Feb 28, 2019 11:58 am

I'm building a second one in transparent PLA instead of black - from prior experience the transparent PLA reacts really well to colour changes in the LEDs. However I'd really like to get LEDs on white tape and they seems rarer at the 60/m pitch than the black ones...but, they're on order as is the glass for the project, so watch this space.

I tried to build a smaller one with 144 pitch LEDs, but the difficulties of working in the smaller space and with those stupidly tiny soldering tabs are just too much...I find I'm constantly getting shorts and other issues that means it just takes forever, so I think I'll be giving up on the smaller ones.

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Re: 270 Neopixels in an Icosahedron

by Disciple on Fri Mar 01, 2019 3:05 am

Inspiring! I'm an animator and this inspired me to animate the infinite fly-through of the icosaverse.

IcosaFlythru001.gif
IcosaFlythru001.gif (995.44 KiB) Viewed 57 times
Keep up the good work, and showing us the pictures. (c:

Hallelujah!
Disciple

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Re: 270 Neopixels in an Icosahedron

by Grey_Area on Fri Mar 01, 2019 5:58 pm

Disciple wrote:Inspiring! I'm an animator and this inspired me to animate the infinite fly-through of the icosaverse.

IcosaFlythru001.gif
Keep up the good work, and showing us the pictures. (c:

Hallelujah!
Disciple


Now that is cool...and no need to solder tiny bits of copper the size of a gnats testicle...why didn’t I think of that?

I’d really like to cooperate with someone from Adafruit to make my icosahedron with the rigid dotstar bars...at $75 a pop no way I can afford the 30 it would take...and at 128 leds per strip it would probably need a small nuclear reactor to power it...but the higher resolution would allow for some far more subtle animations...

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Please be positive and constructive with your questions and comments.