It is a Really Big Keyboard for public typing.
I designed and built this Really Big Keyboard for an interactive public installation that explored the meaning and structure of words. The Thing about Words was conceived for Northern Spark 2015 in Minneapolis, in partnership with the University of Minnesota Institute for Advanced Studies, and the Instructable is specific to both the project and the site. However, the Really Big Keyboard can be adapted to any project that could benefit from a little public typing.
Step 1: Collect Materials for the Really Big Keyboard
The Really Big Keyboard uses DIY switches built from laser-cut 1/4" MDF, a QWERTY kit available from lucidtronix.com, and other supplies commonly available from your typical big-box retailers and Radio Shack. For this project, I chose a 20/2 twisted bell wire, but any low-voltage 2-wire cable will work.
Step 2: Cut Big Button Parts
The switches are built from three pieces of MDF: a face, a spacer, and a backer.
The raster layer, shown in black on the backer cutfile, is designed to create space for 1" wide velcro tape to allow the actuators to be attached flush to a pane of glass. Adjust the files to your mounting needs.
Since material dimensions and laser cutting kerfs can vary, be sure to cut a test button. Verify that when the spacer is glued to the button face, the backer easily fits inside of the small void. When assembled, this allows for the face to move freely, and close the circuit when it's pressed. The wood screws should fit through the holes on the backer pieces.
Step 3: Glue and Paint
Using wood glue and clamps, attach the spacer to the face with the gap aligned downward, at the bottom edge of the letter. Prime and spray paint in the color palette of your choice: I went with a deep red for the backer, and matte white for the rest of the button.
If you choose, you can adhere a 1/2" veneer to the edge of the front piece to hide the spacer, but I found that the matte white did a sufficient job of concealing the construction.
Using a template, cut thicker packing foam fit inside the button face.
Cut one piece of copper wire to about 11", with both ends stripped to about 3/8". Wrap each stripped end around a 3/8" washer and crimp with needlenose pliers. Secure to either side of the button with a piece of copper tape, and use a glue gun to adhere the wire.
Glue a piece of the foam to the top and bottom edges of the button, covering the jumper wire.
Step 5: Finish the Button
Attach the backer to the face with the 3/4" screws through the eye of the washer below. The screws should not be tightened, and should allow for enough movement for the two halves of the button to be pushed together and bounce back out, using the foam as a spring.
Use a multi-meter to check the continuity between the two screws fastened through the copper wire.
Place longer lengths of bell wire (I estimated 3 feet per actuator), with each end stripped to about 1/2 inch across the screw head and attach with staples on either side. Verify that when the button is pushed, the screw head makes contact with the exposed wire.
Place Velcro tape, and test your button's continuity at the end of the longer leads to verify that pushing the button closes the circuit.
Step 6: Assemble the Keyboard
You can follow the first part of the tutorial at Lucidtronix to solder in the shift registers and resistors. Instead of the button switches, connect individual wires or header pins along one edge of the button contact pads. (Though the PCB ships with 4-pin button switches, only two pins are needed to activate them.)
For my installation, I used female/female jumper cables to attach the Big Button lead wires to the circuit board, but you can attach connector ends to your leads to clean things up a bit.
Step 7: Install the Really Big Keyboard
Attach each button's leads to the corresponding pins on the PCB, and mount to the wall using velcro or another adhesive. I used a projector to line the buttons up perfectly.
For this installation, I created a game that would set up three parts of a simile using a randomized library of words, and a player would enter a fourth word to create a nonsensical relationship. Each new word was entered into the library, and got cycled in at random. The arduino keyboard was used as an input for a Raspberry Pi, which created an animation that was rear-projected onto the window. You can find more at BitBucket. (programming by Kurt Froehlich.)
As an added bonus, any public typing project needs a well-crafted blacklist, and I've included ours here.