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.
Step 4: Make Room for the Circuit Board.
Trace out the parts of your calculator's circuit board, screen, and solar panel onto a piece of cardboard (first picture).
Don't worry if the screen or the panel stick up a bit, you can take care of those with the next layer, but if the circuit board is too tall, you'll have to repeat this step with another piece of card.
Step 5: Cut Out the Next Layer.
Cut out a grid in this layer on top of the spaces for the buttons. Make the holes as wide as possible.
Also cut out spaces for the screen and panel.
Use the grid as a template for the spacing on your faceplate.