70 LED matrix in a Jack-o-lantern

What takes eight hours to solder and uses more shrink tubing that you thought imaginable? An LED matrix installed in a real pumpkin. When I mentioned that we’d like the LED pumpkin in last Friday’s post scaled up to a full LED matrix I had no idea it would be me doing the work. But [Caleb] and I thought it might be just the thing to present for the hacker’s favorite holiday.

Installed in the autumn vegetable is a marquee made from a 5×14 matrix of light emitting diodes. I spaced them by printing out a grid on the computer, taping it to the pumpkin, and drilling 70 holes in the front of the thing. The real trouble came when inserting all of the LEDs from the inside; each of them has four wires soldered to it, creating a net of black wiring. Above you can see it turned out great. This is a shot of it scrolling the message HAPPY HALLOWEEN.

Join us after the break for video of this prop. But we’re not just sharing the finished product. I’ll take you through the build process. Along the way you’ll learn the design considerations that go into an LED matrix and how you can use these techniques to build your own in any size and configuration you desire.

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Laser marquee projector

This laser message scroller is built with inexpensive parts. The heart of [Raul's] system is a spinning pill-box with eight mirrors on it. Each redirects the laser to a different vertical portion of the projection surface. There are eight small arms on the apparatus that each break the beam of an optical sensors as it spins, facilitating the precise synchronization needed to generate the projected image correctly. In the video after the break we can make out what looks like an Arduino controlling the system. This makes sense as it’s easy to connect the laser pointer and sensor, and the USB connection allows for the streaming of messages to the system.

Want to see a more complicated setup? Check out the POV laser projector from a few years back. [Read more...]

Web-enabled LED pegboard

[Norm Santos] whipped up an LED light board that you can draw on through their web interface. We tried it out but unfortunately the live feed is currently offline. That doesn’t diminish our appreciation for the time-lapse build video after the break. Indeed it was a mountain of hot glueing and a couple of days of soldering. Our only beef is that for every LED on the board there are three empty peg holes. To us this is just begging to be augmented with blue, green, and white LEDs for a more spectacular result. What they have now encompases 350 LEDs managed by five microcontrollers, which took about two days to solder (for five people) and to hammer out some code. [Read more...]

LED matrix with a gross of pixels

This LED matrix is arranged in a 24×6 pattern for message scrolling. There’s no etched boards here, making us wonder where [Syst3mX] found protoboard this long. He’s using an Arduino to drive the demonstration (clip after the break) but you can use any microcontroller with this setup. That’s because he’s using three shift registers for column data and a decade counter for row scanning, requiring just five control pins.

While you’re going to the trouble of ordering components, maybe you should try your hand at building a touch sensitive LED matrix too.

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Wire-wrapping an LED matrix

Regular reader [Osgeld] built a 1024 LED display matrix. This is a proof-of-concept design and he admittedly has overloaded the components. Most notably, the 595 shift registers (featured over the weekend) are sourcing too much current if all eight pins are active. That’s easy enough to fix in the next design by moving up to cascading LED drivers. Instead of soldering every connection in the display, [Osgeld] soldered the components in place and then used wire wrapping to make the point-to-point connections. This must have saved him a ton of time and frustration. We can’t wait to see what comes out of this first prototype.

What kind of LED matrix does your vodka come with?

Medea Vodka comes with a bottle that includes a blue scrolling LED Marquee. OK, great? It’s an interesting marketing ploy but kind of a waste don’t you think? Friends, it’s up to us to repurpose this  hardware. It can’t be that difficult to hack into the programmable display and make it do your bidding. Our friend Google tells us that you can get your hands on this 750 milliliter bottle for about $40. That’s around $25 more than a passable grade of Vodka sells for, a mere pittance for the challenge of cracking open the hardware for fun and profit. Don’t forget to document your work and tip us off once you’ve accomplished something. See Medea’s programming instructional video after the break. Oh yeah, remember to hack first and drink later… cheap soldering irons get hot!

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Modular systems using SPI

[Humberto] is at it again with a NerdKits video detailing the use of an SPI bus to communicate between microcontrollers. He started with a previous LED marquee project which was limited to a 5×24 LED Matrix and developed a modular solution to increase the size limitation.

The writeup and video embedded after the break do a great job of detailing the important differences between a stand-alone and a modular system. The good news is that the ATmega168 chips being used have a built-in interrupt based SPI protocol. Once wired correctly, a master control chip addresses each module separately, adding data to their buffer until a full frame has been transferred, then moves onto the next module.

Some of the caveats to this system such as digital transmission over long distances are discussed. We do wonder about power limitations if all LED’s in the marquee are illuminated at once. But that concern aside, if you’re thinking of playing around with an LED display don’t forget that there’s usually a huge price break for orders of 500 or 1000 LEDs!

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