Great project from Dominic Canare on Hackaday.io:

Kids start by writing a word on a card. Below each letter, they write the corresponding number using an encoding table (a=1, b=2, etc). Below each of those numbers are 5 holes, representing 1 bit and labeled 16, 8, 4, 2, and 1. After determining which numbers add up to the letter’s code, those numbers are punched out, and the binary code is revealed.

The card is then fed through our reader. Letters are spoken out loud as they pass, and the full word is read when the card is pulled all the way through. Holes are detected using paper clips and aluminum tape. While optical sensors would be more reliable, we feel it’s important to keep the “magic” out of technology when using it as a teaching tool. The paperclips form a physical connection to the foil tape when a hole has been punched, and this can be directly observed.

Read more and check out the project on GitHub

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