It is great for people with shaky movements and poor motor control, such as those with cerebral palsy.
This instructable describes how to make the mouse, but we have also made a midi keyboard from the same materials, which we will also post soon.
Step 1: Get the Ingredient Parts
Starting top right, and going clockwise, finally spiralling into the centre
1. 0.1" (2.54mm) Crimp Connector Housing: 2 Pin - we need 6 of these. Can use a different size, as long as you have enough for 12 pins total.
2. Male Crimp Pins for 0.1" Housings - again 12 total
3. Multi-core wire
4. Small washers - you guessed it, 12 total
5. USB to USB Micro cable
6. Breadboard. This size or bigger is great
7. Header pins - 3 sets of 12 pins, and 1 set of 6 pins
8. MPR121 chip on a breakout board, again by sparkfun
9. 3.3v Pro Micro - a mini Arduino board made by SparkFun
10. 5x jumper wires - different colours preferred, or single core wire can also be used.
Step 2: Get the Tools
1. Wire strippers - this type is very cheap and works well for our needs
2. Pliers - toothed nose rather than smooth is best - for crimping the crimp pins. A crimping tool here is even better
3. A "Third hand" tool for soldering (optional, but helps)
4. Paperclips to help soldering the header pins
6. Soldering Iron
7. Soldering iron tip cleaner - again somewhat optional, but helps
Step 3: Solder the Header Pins
Once you have 3-4 pins soldered in you can take off the paperclips to do the rest.
Solder headers onto both sides of the ProMicro, and both sides of the MPR121 Breakout board.
Step 4: Stick Into Breadboard and Wire Up
Simple stuff - Vcc to 3.3V with a red cable, ground to ground with a black one. The others as shown here:
IRQ (on MPR) to A2 (on ProMocro)
SCL (on MPR) to 3 (on ProMicro)
SDA (on MPR) to 2 (on ProMicro)
Leave one row of empty holes on the breadboard next to pins 0 to 11 on the MPR chip - we'll use these later to attach our touch sensitive pads.
You're may look more like the second photo shown if you are using jumper wires.
Step 5: Print the Stencil, Get a Scalpel
Then print the stencil as shown onto a sheet of A3.
This will be used to stencil (paint) the touch sensitive pads for our mouse. The pads with letters on (L R S D) will be mouse buttons - Left click, Right click, Drag and Scroll. The other 8 will be mouse movement directions.
Cut the 8 mouse directions out completely from the paper as shown.
Also cut around 90% of the Mouse buttons - both the letters themselves and the pads, so that they are just held into the paper at the corners, as shown in the last 2 photos on this step.
Step 6: Mount Onto Card With Spray Mount
Mount it onto card - we prefer white card of about 1mm thickness, but any card will work. Preferably not black, as the paint will be black!
Then use a knife to cut the final corners around the letters, and peel out the mouse buttons leaving the letters stuck down as shown in the last image on this page.
Step 7: Make Holes in the Corners of Every Touch Pad
Step 8: Cut the Wires for the Back
Leave about 1-2 inches spare at this stage for good measure, depending on how precise / confident you are!
Step 9: Fit the Washers and Wires
Push the wire through from the back of the cardboard, and then strip with the wire strippers as shown.
Twist the multicore next with fingers, then feed through the washer and twist back on itself.
Pull the wire back through from behind the cardboard so that the washer is right up against the hole in the card. Then push it flat so it sits flat on the card. This is quite important - if it isn't sitting flat try squeezing the wire flat against the washer with the pliers as shown- - also try pushing the washer down onto the card and then TOWARDS THE HOLE. I have found this helps form a corner in the wire so the washer sits flat.
Tape the wire on the back to keep it tidy, where it will end up - ie where the breadboard will be stuck on the front.
Repeat for the other 11 wires and washers.
Step 10: Paint With Conductive Paint!
Lift the washers so you get paint underneath as well as on top - then stick the washers down and be generous with the paint to make them stick down.
When it's just about dry, lift the paper stencil letter first, with a knife blade if you need, and then take off the whole stencil.
Be careful with mucky fingers - the paint can be very messy, and gets everywhere if you are not careful.
Step 11: Fit the Crimp Pins - Mouse Buttons First
Then cut a slot in the cardboard between the pins 0-11 on the MPR chip, and the touch pads. You might need to flip the board over and move the wires before you cut this slot, so you don't cut into them by accident.
Next feed through your first wires through the slot. Start with the 4 mouse buttons, at each end of the slot as shown.
Cut any excess wire, strip, and then crimp the crimp pins onto the ends of the wires as shown. Finally put the crimped pins into their housings. These will go into pin 0, 1, 10 and 11 on the MPR chip (in the order L, R, S, D)
Step 12: Finish Remaining Wires
Our code is set up to use the wires in this order:
Up-Right on pin 9
Right on pin 8
Down-Right on pin 7
Down on pin 6
Continue clockwise until
Up on pin 2
Step 13: Upload the Code
You'll need to follow the instructions on the SparkFun website for how to get the drivers etc for the Pro Micro first.
But once you've got that working, just hit upload. Remember it's a 3.3v ProMicro you need to select, not a 5V or a leonardo.