Output Up To 768 PWM Signals From One Arduino

July 20, 2011 by Mike Szczys 46 Comments

Here’s an Arduino library that will let you drive a very large number of LEDs. [Elco Jacobs], an electrical engineering student, is the author of the library. He has a work-study job that has him helping out others with their electrical projects and he was constantly being solicited for methods to control droves of light emitting diodes. This was the motivation that led him to produce the dazzling 16 RGB LED example seen in the video after the break.

His setup doesn’t use expensive LED drivers, but instead utilizes 595 shift registers which are both common and cheap. He calculates that it is possible to control up to 96 of these shift registers, each driving 8 LEDs, with reasonably satisfying results. This is thanks to his well-optimized code that manages to drive the clock pin of the registers at 1.33 MHz. This optimization is done by writing each command in assembly, which allows him to precisely count the cycles. Each individual pin takes 12-13 cycles to address, totally 9984 cycles at worst when addressing the maximum number of outputs.

[Elco] thinks this is as fast as he can make the routine run, but he is asking for help with testing. If you think you know how to squeeze out a few more cycles, make sure you join in on his forum thread.

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LED Headgear Is Marvel Of Free-formed Circuitry

July 17, 2011 by Mike Szczys 6 Comments

Hackaday contributor [Nick Schulze] popped out an impressive set of LED headgear for a hat-themed party.

[Nick] is no stranger to working with LEDs. Previously he built a blue 8x8x8 cube something like this other 512 node full color version. He had a bunch of LEDs left over from that project and decided to put them to ~~good~~ use.

The first part of the build is the frame itself, made from thick fencing wire. He just started bending it around his head and got an uncomfortable head-shaped hoop to which he could solder. From there, enameled copper wire wraps its way through the system, supplying logic levels to all of the LEDs. Everything is done without a circuit board of any kind. The LED drivers themselves are attached by first using a zip tie to affix a resistor to the frame, then by soldering the TLC5916 chip to that resistor. Even the ATmega8 is included dead-bug style by soldering it to the frame which we think servers as ground. Program it with the free-floating female pin header and you’ll get the fantastic animations seen in the video after the break.

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Race Car POV LED Displays

July 15, 2011 by Mike Nathan 26 Comments

race_car_pov

Last year, when [Alex] was asked by his friend [Martin] to help him out with building some LED POV modules for a race car, his response was a enthusiastic “YES!”

[Martin’s] goal was to involve fans more deeply in the race, so he decided that the POV modules would carry messages from fans on-board, printing them in the night as the race cars screamed around the track. The pair started prototyping and testing a design, wrapping things up shortly before this year’s 24 hours of Nürburgring.

The modules consist of an Arduino-compatible AVR, a GPS module, a 16-LED light bar, and the circuitry for driving the LEDs. While most of the components are pretty standard fare, the we don’t often see a GPS sensor built into a POV display. [Alex] says that the sensor is used to calculate the speed of the cars, ensuring a uniform font size.

They took their LED displays to the 24 hours of Nürburgring, where they were invited by Audi to install the modules on a pair of R8 Le Mans race cars. As you can see by the pictures on his blog and Flickr set, the POV units worked out nicely without having to stretch the camera exposure times too far.

If you’ re interested to hear a bit more about how the displays were built, check out this entry in[Alex’s] blog, where he goes through some additional details.

Update:[Alex] pointed us to the videos!

Faux LED Scroller Using Phosphorescence

July 13, 2011 by Mike Nathan 38 Comments

poor_mans_phosphorescent_led_scroller

Hackaday reader [BGR] wrote in to share a video he put together showing off a cool “poor man’s LED scroller” that he built. Rather than build a huge array of LEDs, spending tons of time time wiring and programming, he decided to use only a handful of LEDs on a moving display instead.

The scroller is built upon a PIC16F887 microcontroller which resides on an EasyPIC6 dev board he borrowed for the project. The PIC controls a strip of eight bright white LEDs, which are used to write text on a long strip of phosphorescent paper that can be found at many printing supply outfits. The paper’s dispensing mechanism was cobbled together with parts from several sources, including a laser printer and VCR.

When he wants to display a message, he inputs text into a flash application he wrote. The app sends the LED byte values to his scroller via a separate serial proxy that talks to the pic over his computer’s COM port.

The effect is pretty slick, looking similar to a slow-moving diffused LED scroller. The messages disappear after about 5 minutes in a pitch black room, which is perfect, since he originally intended to use the device for displaying Twitter updates. He is already considering a second revision of the project, which he wants to mount on the wall – sounds great to us!

Be sure to swing by YouTube to see the video, or continue reading to watch it here.

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Wearable Video Coat

July 12, 2011 by Brian Benchoff 13 Comments

[David Forbes] is no stranger to the weird and esoteric, so he created a color LED TV built into a lab coat. He plans on bringing it to Burning Man next month.

The RGB LEDs are mounted narrow flex boards, providing a 160×120 pixel NTSC display. Video processing is taken care of by an Xilinx FPGA that takes the YCrCb video feed from a video iPod and converts it into four separate RGB streams for the front, back, and the two sides. The requisite controls for brightness and color are on the shoulders.

Of course, the build wouldn’t be over-the-top without the ability to plug a Nintendo into a lab coat, so there’s an NTSC input on an RCA jack. Everything is powered by two 11.1 V, 5Ah radio-control LiPo battery packs that should power this for a while.

Check out a video of the LED lab coat below.

[youtube=http://www.youtube.com/watch?v=jtSm8Oom2n4&w=470]

DIY Clock Replica Is Better Than The Real Thing

July 11, 2011 by Mike Nathan 14 Comments

After seeing the TIX clock for the first time, [Gweedo Steevens] really wanted one, but wasn’t interested in paying the seemingly high asking price over at ThinkGeek. He figured it wouldn’t be too incredibly hard to build his own, so he decided to give it a shot.

The clock relies on 27 LEDs to display the time, which were multiplexed to make the most of his ATMega16 microcontroller’s available IO pins. Once he was happy with how things functioned on breadboard, he migrated the LEDs to a piece of perf board, and etched his own PCB for the controller circuit.

He used an office overhead lighting grate to separate the LEDs, providing nice uniform light segments. He put a piece of clear perspex on the front to cover the LEDs, but later switched it out for a much darker piece, for better daylight viewing.

The finished product is fantastic, and in our opinion looks even better than the retail version – awesome job!

[via HackedGadgets]

LED Wand For Light Painting Photography

July 11, 2011 by Brian Benchoff 8 Comments

[Michael Ross] is a photographer who has been getting into light painting recently. He’s come up with his own RGB light wand to create some amazing images, and also written a very, very thorough tutorial (PDF warning) on how to build your own light wand.

The light wand is based on an Arduino Mega board and uses an RGB LED strip based on the HL1606 controller chip. We’ve covered these LED strips before, and they’re very easy to use with the requisite library. So far, [Michael] has built a 48-LED light wand and a 16-LED wand with a 6-position program selector, making it easy to do awesome single-exposure photos like this.

[Michael] creates his images in an Excel spreadsheet – rows are which LED to address and columns are units of time. The picture data is then copied and pasted straight from the Excel worksheet to the Arduino source code. This in itself is a pretty clever use of Excel.

Check out the how [Michael] creates one of his light paintings here.