Break Your Wrist? Twitter-Enable That Plaster Cast

Plaster casts are blank canvases for friends and family to post their get well messages. But if it’s holiday season, adding blinky LED lights to them is called for. When [Dr Lucy Rogers] hurt her hand, she put a twitter enabled LED Christmas tree on her cast.

The hardware is plain simple – some RGB LEDs, an Arduino, a blue tooth module and a battery. The LEDs and wires formed the tree, and all the parts were attached to the plaster cast using Velcro. This allowed the electronics to be removed during future X-ray scans. The fun part was in connecting the LEDs to the #CheerLights project. CheerLights is an “Internet of Things” project that allows people’s lights all across the world to synchronize to one color set by a Tweet. To program the Arduino, she used code written by [James Macfarlane] which allowed the LED color to be set to any Cheerlights color seen in blue tooth UART data.

Connectivity is coordinated using MQTT — lightweight standard popular with connected devices. By connecting the MQTT feed to the cheerlights topic from [Andy Stanford-Clark’s] MQTT feed (mqtt://iot.eclipse.org with the topic cheerlights) the lights respond to tweets (Tweet #cheerlights and a color). The LED colors can also be selected via the phone from the color picker tool in the controller, or directly via the UART. If the Bluetooth connection is lost, the LEDs change colors randomly. Obviously, delegates had great fun when she brought her Twitter enabled LED blinky lights plaster cast arm to a conference. It’s not as fun unless you share your accomplishments with others!

RGB LED Ceiling Display

yP8PoVDisco Floor’s are passé. [dennis1a4] turned them upside down and built an awesome RGB LED ceiling display using some simple hardware and a lot of elbow grease. His main room ceiling was exactly 32 ft x 20 ft and using 2 sq. ft tiles, he figured he could make a nice grid using 160 WS2812B RGB LEDs. A Teensy mounted in the ceiling does all the heavy lifting, with two serial Bluetooth modules connected to it. These get connected to two Bluetooth enabled NES game controllers. Each of the NES controller is stuffed with an Arduino Pro Mini, a Bluetooth module, Li-Ion battery and a USB charge controller.

Bluetooth is in non-secure mode, allowing him to connect to the Teensy, and control the LEDs, from other devices besides the NES controllers. The Teensy is mounted at the centre of the ceiling to ensure a good Bluetooth link. Programming required a lot of thought and time but he did manage to include animations as well as popular games such as Snake and Tetris.

LED_Ceiling_deadbugThe hard part was wiring up all of the 160 LED pixels. Instead of mounting the 5050 SMD LED’s on PCBs, [dennis1a4] wired them all up “dead bug” style. Each pixel has one LED, a 100nF decoupling capacitor, and 91 ohm resistors in series with the Data In and Data Out pins – these apparently help prevent ‘ringing’ on the data bus. Check the video for his radical soldering method. Each SMD LED was clamped in a machine shop vice, and the other three parts with their leads preformed were soldered directly to the LED pins.

The other tedious task was planning and laying out the wiring harness. Sets of 10 LEDs were first wired up on the shop bench. He then tacked them up to the ceiling and soldered them to the 14 gauge main harness. The final part was to put up the suspended ceiling and close the 2 sq. ft. grids with opaque plastic.

[dennis1a4]  did some trials to figure out the right distance between each LED and the panel to make sure they were illuminated fully without a lot of light bleeding in to adjacent panels. This allowed him to get away without using baffles between the tiles.

Check out the video to see a cool time-lapse of the whole build.

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Because Burning Man Needed More LEDs

There are a lot of blinky glowy things at Burning Man every year, and [Mark] decided he would literally throw his hat into the ring. He built a high visibility top hat studded with more RGB LEDs than common sense would dictate. It’s a flashy hat, and a very good example of the fashion statement a few hundred LEDs can make.

[Mark]’s top hat has 481 WS2812b addressable LEDs studded around the perimeter, a common LED choice for bright and blinky wearables. These LEDs are driven by a Teensy 3.1, with a Bluetooth transceiver, a GPS module, a compass, and gyro/accelerometer attached to the microcontroller. That’s a lot of hardware, but it gives [Mark] the capability of having the hat react to its own orientation, point itself North, and allow for control via a modified Nintendo NES controller.

The WS2812 LEDs draw a lot of power, and for any wearable project having portable power is a chief concern. [Mark]’s original plan was to use an 8x battery holder for the electronics enclosure, and use five AA batteries to power the hat. The total idle draw of the LEDs was 4.5 Watts, and with even a few LEDs blinking colors there was a significant voltage drop. The idea of powering the hat with AA batteries was discarded and the power source was changed to a 195 Watt-hour lithium ion battery bank that was topped off each day with a solar panel.

The hat is awesome, exceedingly bright, and something that gets a lot of attention everywhere  it goes. For indoor use, it might be too bright, but this could be fixed with the addition of a bit of black stretchy fabric, like what our own [Mike Szczys] did for his DEF CON hat. [Mark]’s hat is just version 1, and he plans on making a second LED hat for next year.

An Introduction To Individually Addressable LED Matrices

The most fascinating project you can build is something with a bunch of blinky hypnotic LEDs, and the easiest way to build this is with a bunch of individually addressable RGB LEDs. [Ole] has a great introduction to driving RGB LED matrices using only five data pins on a microcontroller.

The one thing that is most often forgotten in a project involving gigantic matrices of RGB LEDs is how to mount them. The enclosure for these LEDs should probably be light and non-conductive. If you’re really clever, each individual LED should be in a light-proof box with a translucent cover on it. [Ole] isn’t doing that here; this matrix is just a bit of wood with some WS2812s glued down to it.

To drive the LEDs, [Ole] is using an Arduino. Even though the WS2812s are individually addressable and only one data pin is needed, [Ole] is using five individual data lines for this matrix. It works okay, and the entire setup can be changed at some point in the future. It’s still a great introduction to individually addressable LED matrices.

If you’d like to see what can be done with a whole bunch of individually addressable LEDs, here’s the FLED that will probably be at our LA meetup in two weeks. There are some crazy engineering challenges and several pounds of solder in the FLED. For the writeup on that, here you go.

The Possibility Of Driving 16,000 RGB LEDs

Like just about everyone we know, [Luis] decided a gigantic RGB LED matrix would be a cool thing to build. Gigantic LED matrices are very hard to build, though: not only do you have to deal with large power requirements and the inevitable problems of overheating, you also need to drive a boat load of LEDs. This is not easy.

[Luis] found a solution to the problem of driving these LEDs with a new, fancy ARM Cortex M4 microcontroller. All Cortex M4 ARMs have DMA, making automatic memory transfers to peripherals and LED strips a breeze.

The microcontroler [Luis] is using only supports 1024 transfers per transfer set, equating to a maximum of 14 LEDs per transfer. This problem can be fixed by using the ping-pong mode in the DMA controller by switching between data structures for every DMA request. Basically, he’s extending the number of LEDs is just switching between two regions of memory and setting up the DMA transfer.

The result is much better than [Luis]’ original circuit that was just a bunch of SPI lines. It also looks really good, judging by the video below. It’s not quite a gigantic LED matrix yet, but if you want to see what that would look like, check out the huge 6 by 4 foot matrix hanging in the Hackaday overlord office.

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A Hacker-Friendly Blinky USB Stick

The availability of Smart RGB LED’s, either as individual units, as strips or even as panels, have made blinky light projects with all kinds of color control and transition effects easy to implement using even the simplest of controllers. Libraries that allow control of these smart LEDs (or Smart Pixels as they are sometimes called)  make software development relatively easy.

[overflo] at the Metalab hackerspace in Vienna, Austria recently completed development of usblinky – a hacker friendly blinky USB stick. It can control up to 150 WS2812B smart LED’s when powered via an external power supply, or up to 20 LED’s when powered via a computer USB port. The micro-controller is an ATTiny85 running the Micronucleus bootloader which implements software USB using vUSB. The hardware is based on the DigiSpark platform. The usblinky software sources are available on their Github repo. The section on pitfalls and lessons learned makes for interesting reading.

Metalab plans to run workshops around this little device to get kids into programming, as it is easy enough and gives quick visual feedback to get you started. To round off the whole project, [overflo] used OpenSCAD to design a customizable, 3D printable “parametric orb” which can house the LED strip and make a nice enclosure or psychedelic night light. Check out the mesmerizing video of the usblinky Orb after the break.

Thanks to [papst] for sending in this tip.

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LED Matrix Infinity Mirror

[Evan] wrote in to let us know about the LED matrix infinity mirror he’s been working on. [Evan] built a sizable LED matrix out of WS2812B LEDs and mounted them to a semi-reflective acrylic sheet, which makes a pretty awesome infinity mirror effect.

Instead of buying pre-wired strands of serial LEDs like we’ve seen in some other projects, [Evan] purchased individual WS2812 LEDs in bulk. Since the LEDs just had bare leads, [Evan] had to solder wires between each of his 169 LEDs (with some help from a few friends). After soldering up hundreds of wires, [Evan] drilled out holes for each LED in a piece of semi-reflective acrylic and inserted an LED into each hole.

To create the infinity mirror effect, [Evan] mounted the LED matrix behind a window. [Evan] put some one-way mirror film on the outside of the window, which works with the semi-reflective acrylic to create the infinity mirror effect. The LEDs are driven by an Arduino, which is controlled by a couple of free programs to show a live EQ of [Evan]’s music along with patterns and other effects.