Over two years ago, I bought this awesome display panel:

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It’s a 7.5″ square, 32×32 resolution, 6mm LED spacing, panel that would normally be used for digital signage. Though it is a “dumb” display that requires CPU intensive multiplexing (it’s supposed to be driven by an FPGA or ASIC), with the right tools it can be way easier to use than building, ahem, other types of displays 😉 I have covered this exact panel a few other times, but after a couple years of sitting in my LED storage it was time to finally make it something awesome.

To jump straight to the good stuff, check out the build video below, or continue on after the break for the full details.

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First, we want to thank everyone who showed support for the LongPixel by pledging to our Kickstarter campaign. It’s always wonderful to see that our crazy ideas aren’t actually crazy and that other people like what they see and want to give it a shot.

However, we’re sorry to say that we didn’t make it this time with the LongPixel. For those of you that were hoping to get one, we’re sorry that it won’t be happening right now.

But we’ve still got plenty of future plans and are not going anywhere. So be sure to keep an eye on what we’re up to via Facebook, Twitter, or ManiacalLabs.com

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Many thanks to all our awesome backers for helping us get this far! We’re not even half way through the campaign and already over 50% funding 🙂 We can make it, but it certainly doesn’t hurt to have a little help. We are doing our best to get the word out there, but we ask that you give us a hand: share on social media, tell your friends, tell your favorite electronics DIY blog. With a little bit of help, we can make this happen and bring the LongPixel to the world 🙂

Thanks for being awesome!

The LongPixel was designed to make using analog LED strips super easy and, typically, that means RGB LEDs as they are the most common. But the beauty of the way in which the LongPixel drives these LED strips is that it really doesn’t matter what color the LEDs are. Sure, the 4 wire, 3 color RGB strips are the most convenient in most cases. But you could, for example, connect 3 single color, 2 wire, strips, of whatever color you desired. Hook up all of the strips’ power input to the V+ on the LongPixel and then each strips’ ground to a separate channel on the LongPixel and you are ready to go.

But another great use-case for choosing something other than RGB strips is if what you really need is white light above all else. Sure, you can get white light out of an RGB strip, but it’s not real white light. It’s got peaks at each of the primary wavelengths of each sub-color which looks fine to our easily tricked eyes, but is not ideal for photography or video as a lighting source. This is where the simpler white LED strips come in. But then there’s a conundrum… what color temperature do you want? Why choose?

In this demo, I’ve taken two different white LED strips, 3000K (warm white) and 6000K (cool white), and used a little math to blend the two together to maintain roughly the same total light output while fading between 3000K and 6000K. The brightness and color temperature values are stored internally as unsigned bytes (0-255) and then the following calculation is used to determine the output to send to the LongPixel:

red = ((255 - _temp) * _brightness) >> 8
blue = (_temp * _brightness) >> 8
color = (red, 0, blue)

In this case, the 3000K strip is connected to the red output and 6000K is connected to blue. The above allows fading between the two temperatures while generally maintaining the same overall brightness. For those confused by the “>> 8” code, this is just a fancy way of scaling two 8-bit values by each other. Multiply together and then right bit shift 8 places. This is much faster on a microcontroller than using larger values.

Regarding the controller, it was re-purposed from a previous project, the Fancy Pants MkII for which I built the controller as a wrist mounted device. Because of the memory demands of the controller and the pants, between having 500 pixels and a 128×64 pixel OLED display, it uses a super beefy ATMega1284p chip which is complete overkill for this project. But it certainly beat building a new board from scratch and it already came with a nice case 🙂

Enough babble… check out the demo for all the juicy details and a time-lapse build.

You can find the code, PCB, and case design on GitHub