[Noisebridge-discuss] Massive LED Project at Noisebridge needs your help!

Henner Zeller h.zeller at acm.org
Wed Oct 22 19:14:21 UTC 2014


On 22 October 2014 11:32, Andy Isaacson <adi at hexapodia.org> wrote:
> On Wed, Oct 22, 2014 at 11:04:52AM -0700, James Sundquist wrote:
>> Dana and I have a grand idea for setting up easily programmable LED
>> displays at Noisebridge in a massive matrix. What we need are donations of
>> panels, which will be purchased and shipped by Mitch on his China trip. See
>> our nicely organized wiki page for details, source code, and more info.
>>
>> https://noisebridge.net/wiki/LED
>
> Awesome idea, awesome project!

+1.

(Though I am biased and would suggest to use the RPi version
   https://github.com/hzeller/rpi-rgb-led-matrix
 it has one realtime challenge right now that I'd like to fix using DMA,
 but it would have the advantage that it would be a thing made by a local
 Noisebridger. The DMA thing is on my list as soon as the access control
is finished)

>
> A few suggestions, note that this is totally not backseat driving and
> y'all should totally do the thing whatever way works for you. :)
>
> 1. Consider getting WS2812 pixels rather than cheaper knockoffs, and
> driving them with Fadecandy http://www.adafruit.com/products/1689 rather
> than other solutions.  Fadecandy has truly incredibly beautiful
> dithering, giving much much nicer subtle color gradients compared to
> straight PWM systems.  Micah (aka @scanlime, creator of Fadecandy) has a
> really nice installation of Fadecandy open to the public sidewalk at 80
> Turk St in the Tenderloin, and if you check it out at evening and then
> walk over to Yerba Buena Gardens and check out their currently installed
> non-Fadecandy LED art you can really tell the difference.

The WS2812 are way more expensive per pixel than the $20 32x32 RGB matrices

>
> However I see you're aiming at doing video, which I don't know if that
> is very well supported with fadecandy; would require additional
> research.

There is also PixelPusher.

>
> 2. Don't use an ATX power supply, get an appropriate 5V power supply
> that's properly sized for the application.  It'll be cheaper, overall,
> and easier, and save power.

+1. The Panels use a _lot_ of current. A 32x32 panel needs 3.4A tops, and there
are already  40A+ 5V power supplies readily made for these kind of
things (on ebay
in the $20-30 range). ATX power supplies typically only have 20-25A on
the 5V rail, and
useless 12V and -12V rails.

> 3. the LED wall panels are somewhat expensive per pixel, last I looked.
> It can be cheaper to get the flex-pcb strips and mount them to panels
> yourself, then mount diffuser panels appropriately.

Not sure about that.

-h

>
> -andy
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