allpixel

3 Articles

Doubling Down On A Big LED Display

October 4, 2015 by 16 Comments

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.

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The Epoch Christmas Tree

December 10, 2014 by 8 Comments

It’s that time of the year again, and the halls are being decked with trees, the trees covered in lights, and everyone working in retail is slowly going insane from Christmas songs piped over the PA. [Dan] has a tree and a bunch of programmable LEDs, but merely pumping jollity down that strip of LEDs wouldn’t be enough. The Nerd Quotient must be raised even higher with a tree that displays a Unix timestamp.

This build was inspired by an earlier, non-tree-based build that displays Unix time on a 32 LED array. That build used an ATMega328p for toggling LEDs on and off. This time around, [Dan] is using a dedicated LED controller – the AllPixel – that just wrapped up a very successful Kickstarter campaign. The AllPixel is, in turn, controlled by a Raspberry Pi running the BiblioPixel library,

The tree displays the current time stamp in binary across 32 spaces, with green representing a ‘one’ and a red representing ‘zero’. The top of the tree is the least significant bit, but in case [Dan] gets tired of the bottom of the tree staying completely still for the rest of this holiday season, he can switch the order making the base of the tree the LSB.

Video below.

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A USB-Controlled POV Light Stick

November 20, 2014 by 10 Comments

Wanting to showcase their USB LED strip controller, the folks at Maniacal Labs built a POV LED stick this weekend. Yes, it’s pretty much the same as any other POV LED display you’ve seen; set a camera for a long exposure, wave the POV light stick around, and get a cool pixely image in mid-air. This build is a little different, though: it’s controlled over WiFi with a Raspberry Pi connected to a WiFi network.

The USB LED strip controller in question is the AllPixel, a small board that controls NeoPixels, WS2801, LDP8806, and a bunch of other LED strip controllers over USB. The Stick used for this project consisted of two meters of LPD8806 LEDs, giving 96 pixels of horizontal resolution. A big battery and Raspberry Pi rounds out the rest of the electronics.

Building a LED POV display isn’t that much different from building a LED matrix display; all you have to do is break up the image into individual columns and display them sequentially. To do this, the Maniacal Labs folks whipped up a LEDPOV class that does just that. To get the images, just open the shutter on a camera, wave the stick around, and if you get it right, you’ll have a great pixely image of nyan cat or the rainbow wrencher.