The calculator will have a working keyboard, with a layout familiar to anyone who’s ever used a real calculator. When you press a key the display will update in real time. I also wanted to have a selection of common mathematical functions on the calculator keyboard. And most of all I wanted it to be colourful – no drab grey keys here!

Here are some prototypes of the key faces I’ve designed. They use 2×2 yellow tiles for on a black tile background.

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I came up with some very simple key face designs using 2×2 colour tiles. These are mounted on a small assembly holding a touch sensor. Each key is made from 2 6×12 plates mounted side by side, with coloured tiles on top. The keyboard layout is 5×5; 5 rows of keys with 5 columns. This picture from my notebook shows roughly what I’m thinking, though the finished product will no doubt be quite different!

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For the key mechanisms I played around with various approaches to mounting a touch sensor before settling on this vertical setup. My goal is to build each key as a separate unit that can be slotted into the calculator frame. This makes it easier to remove and repair each key without disassembling the entire calculator.

Each key plate is mounted to the top of the mechanism. This gives me some flexibility to move keys around on the calculator body.

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