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The Hack Factory has many glass block windows, on all sides. The universal reaction we all have to those windows is - “hey! We could put LEDs behind them! And then play Tetris!”. This project is our effort to make the Tetris wall.
At the current time, the pieces of this project are scattered. The plan is to locate 6 strings on to fully cover the window behind the class room (that window faces east, and brings no light into the space).
Darco generated a lot of excitement when he reverse engineered the GE Color Effects lights. The GE lights are individually addressable and are easy to get in the fall, if a bit pricy (about $1.30 / pixel at Costco). Pete proved the concept by obtaining a 36 light strand and making a simple 5×7 sign board in a box. Jeremy did exhaustive research into alternate LED pixel lights, and while there are a number of cheaper options available, using ICs with data sheets, the spacing of the GE lights (~ 9”) so perfectly matches our glass block (~ 8”), that the GE lights became the clear choice for us. Jeremy developed a further version, and refined the understanding of the protocol required.
The basic design is GE lights on 4×8 sheets of plywood, all connected to our controller using 4 flat trailer hitch wiring. Our controller is primarily an arduino microprocessor that can do basic control + sign boarding. To program the arduino, and for more sophisticated apps (e.g. web server and so on), we have another PC connected to the arduino.
You need a set of 50 leds of the GE Color Effects brand. About $65 at Costco. You also need a 4×8 sheet of plywood (thin is fine) and a 4 flat trailer hitch wire (we've been using 5' lengths). With that, follow these steps:
- Test the lights to make sure they work, remote control and all.
- Cut the green light wiring between the first bulb and the plug/controller.
- Cut the trailer hitch wiring connector so you have a male end and a female end; we've been using 5' cables, and cutting them so we have 4' on the male connector end.
- Wire the male end of the trailer hitch wiring to the light cable just before the first led. Our convention is that white is neutral (which is the ridged wire on the GE lights), brown is +5V (which is the smooth sided wire), and that green is signal (the center wire). You can use the scotch clips that come with a hitch, or perform a better splice at your discretion.
- Wire the female end of the wiring to the power/control unit that came with the lights. Same color pattern; ridge is neutral/white; brown is +5V, and green is signal/center. Here's what one such wiring job looks like: string_with_hitch.jpg
- Test that the lights still work when you connect the trailer hitches.
- Remove the light covers. You can set them and the original power pack + remote control aside in case we ever want to restore these lights to their original function.
- Drill 50 holes in a 5×10 grid, 8” on center, into your plywood. A 15/16” spade seems to make a nice hole that lets the lights pressure fit cleanly.
- Mount the 50 lights into the plywood. You might want to check with Jude on size of plywood and positioning of bulbs; he's been doing all the hanging, and will likely be the expert.
- Your strings are ready. Plug them into one of the female hitches on our controller, edit the led.cfg file in the ~/geled directory, and you should be good to go.
The controller can be structured many different ways. Because we had an Arduino at hand, that's what we've chosen as the primary controller. Nicely, the Arduino has 6 free TTL control pins on Port B, and the largest window would require 6 strings of 50 bulbs to cover it; like it was meant to be. To save space, we use a PC power supply to provide a 5V supply to all the strings; this saves the bulk and space the six individual power supplies would require. We have a bus for the +5 side, a bus for the neutral side, and then a terminal strip where we break out each of the 6 signal lines. Female ends of trailer hitches are wired in with brown to +5, white to neutral, and green to the signal terminal. We use a 12” length of wire attached to the female 4 flat ends. The Arduino itself is powered by the +5V line as well. This means the PC power supply on/off switch works very nicely to turn the whole rig on and off.
We also have an out bound USB cable, which provides a way to program the Arduino. This is connected to a Raspberry Pi running Debian. This computer also has a web server, and has a set of web pages that allow basic control of the lights.
The current software is all tracked in a git hub repository.
The software task list is tracked in a text file in git. The computer hardware is now mostly complete; a Raspberry Pi provides a web server, and programs the Arduino.
Everything is ready to go into production, with a planned installation in the window behind the classroom.
Remaining tasks include:
- Prepare the 3 spare strands of 50 (remove the bulb covers, rig the trailer wiring)
- Hang the control box
- Run Cat5 to the control box
- Run power to the control box
- Pull together 5 sheets of plywood, properly drilled, mount the lights
- Hang the 5 sheets of plywood, connect the lights in
- Beg/borrow/steal 1 more 50 string sets (target: 6, current: 5; they cost $65 each at Costco)
- Provide an operations guide for it so others feel free to hack/use it
|shot_of_signboard_mode.jpg||Shot of the led's in sign board mode. (MAKER is scrolling past).|
|Shot of the interior behind the glass block, showing the build and control.|
|Shot of the simple space war game, showing that the blue dude has just fired three bullets while the red dude lurks below.|
|Space war 1|
|Space war 2|