The final product is more proof-of-concept than practical, but with each version it has gotten more usable.
I was inspired to make this one day in Earth Science a couple of years ago when i took a piece of cardboard and drew a calculator on it and thought, cool.
Sometime in May I decided that I would go right to my room (then sans computer) and get to work on something productive. Instead, I made v1.
Step 1: Materials
2. Thin pieces of cardboard. I used the material from the back cover of an old spiral notebook and some other bits of thin cardboard I found lying around my basement.
3. One "faceplate". I followed a 3x5 theme so I used a piece of lined 3x5 notecard with numbers written write on it. You can use whatever you like.
4. Foil for the contacts. I'm thinking about getting some aluminum tape, but is fine.
2. Hobby knife
3. Clean, non-smudgy hands
Step 2: Strip Down Your Calculator
Step 3: Cut out your cardboard
The last picture shows the ideal thickness of the cardboard. You'll see why that matters more in a later step.