Doubling Down on a Big LED Display

Last year at the 2014 NC Maker Faire, Manical Labs brought a large LED display. Blinking LEDs and pixel animations are always welcome, but at 24 inches square this build was impressive, but it wasn’t impressive enough. This year, [Adam] at Manacal Labs wanted to go bigger. Much bigger. This build is called Colossus, and at two square meters and with 1250 individual LEDs, this LED display is a colossal build.

When building a big LED display, an enormous amount of planning pays off in dividends. The backbone of this project is a sheet of 3/8″ plywood, ripped down to 1 meter by 2 meters. 1250 half-inch holes are drilled in this sheet over four or five very long and very tedious evenings. The LEDs are installed in the thousand or so holes, and a grid of foam core board encases each individual LED.

One of the biggest problems with large arrays of LEDs is the sheer scale of it all. If one LED pixel draws 60mA, 1250 pixels means a draw of 75 Amps. This current will melt most wires, so the power is delivered over custom made copper bus bars. Driving this display with a reasonable refresh rate is another important consideration; WS2812 lights, with an 800kHz signal over one wire, is far too slow for a huge display. Instead of the 2812s, [Adam] went with LPD8806 LEDs that can be clocked at 30MHz. This is controlled with two AllPixels, effectively making this two displays acting as one. It all comes together in a very big LED display. You can check out a video of it below.


16 thoughts on “Doubling Down on a Big LED Display

  1. Thanks for posting! Slight correction: The Colossus is, in fact, using WS2812 LEDs. The LPD8806 were just too expensive and don’t come in the string form factor. But through the magic of the AllPixel and the creative output threading of our library, BiblioPixel, we were still able to maintain 30+ fps on the display, which was more than enough for our use case. I’ve updated our build log to make that more clear :)

  2. “WS2812 lights, with an 800kHz signal over one wire, is far too slow for a huge display. Instead of the 2812s, [Adam] went with LPD8806 LEDs that can be clocked at 30MHz.”

    Hmm.. from the linked article:

    “Using the LPD8806 would have been great, but that’s just to expensive. We had to stick with the WS2811/WS2812.”

    1. They should have used APA102 – almost same price as WS2812, no timing issues, higher PWM frequency and some sources claim, that you can comunicate with it at 50 Mhz (I haven’t tried it yet)

      1. We love the APA102, great chipset! It was considered but a) we got a REALLY good deal from the manufacturer on the WS2812 and b) we couldn’t find the APA102 in a low enough pixel density. The who thing was a balancing act between physical size, resolution, and cost. We could make it the same size, but the resolution would be higher and therefore the cost. Or we could’ve made it smaller. But the main goal besides a lot of pixels was to make it as big as reasonably possible (it has to fit in my home office). To fix the density problem, we went with the string lights and they sadly don’t make those in the string format… our manufacturer offered to do a custom run of APA102 strips with a lower density, but that still added a lot of extra cost. The being said… not planning on ever making anything this big with WS2812 again… they are such a pain.

  3. It wouldn’t hurt to have an output diode on each of the switching power supplies driving the LEDs, some of these supplies become unhappy being in parallel and one or both will stress and flake out over time.

  4. What will be nice is when the price of RGB LEDs, and their power needs, drop to the point where the nearly 50,000 required for a 256×192 display becomes affordable and practical. Then a MSX-1, TI-99/4A, Colecovision or other game or computer using that resolution could be connected to it.

    1. Of course :) We went high tech… it’s a white bed sheet :P Actually it’s two. The original plan was to use semi-transparent white acrylic, but it was just too expensive to buy in the size needed. However, I am going to buy a 1/8″ sheet of clear acrylic and attach it over the sheet to protect them… fortunately, that’s much cheaper.

      1. Awesome, thanks for that. I have a similar project on the go here and the acrylic sheet has proven far too expensive at nearly £600 per sheet…and we need 2 :-(.

        Great build though, well done…, Oh and the buzz bars you used have certainly helped out on the power distribution issue we were having.

        D

        1. 600 per sheet! Wow… how big is this thing? I just bought some clear acrylic to cover the fabric diffuser for the final installation in my house and it was only $80 for a 4’x8′ sheet. I recommend finding a local industrial plastics supply company instead of trying to buy online.

          Glad our power setup helped :) It was overkill, but it was probably the easiest thing in the end.

          1. We are attempting to custom build a curved DJ booth and it currently measures 2.5 meters x 1.2meters. Steel framed for the benefit of remaining robust against the toils of life on the road. The acrylic sheeting was to be formed around the curvature of the frame hence the price, plus it was also going to be 10mm thick.

            Will pop up some photos when I get a chance.

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