This video tutorial describes an #escaperoom project that uses an #ESP32 or #Arduino to decode a binary value encoded in holes punched on a card or disc.
An array of lasers is placed in a line, each facing a light dependent resistor (LDR). If a hole punched in the card lines up with the laser, light passes through and illuminates the correponding LDR, causing its resistance to drop. Alternatively, if the card obstructs the laser beam, the resistance of the LDR remains high. The pattern of holes is read by a voltage divider circuit that takes a reading from an analog pin connected to each LDR in turn. This pattern can be decoded to represent a single number, or letter, or an entire message!

You could use this prop in an escape room to provide a number card, or word, or simply as a method of object identification - using 5 lasers/LDRs means it it possible to differentiate between 32 unique patterns.

Timings
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00:00:00-00:03:32 Introduction and Demonstration
00:03:33-00:13:21 Wiring Diagram
00:13:22-00:13:29 Schematic
00:13:30-00:31:15 Arduino Code Listing
00:31:16-00:33:04 Wrapup

I'll describe the wiring and every line of code in detail, and you are welcome to copy them from the video and use them in your own projects. Or, if you'd like to download the code, together with the file containing the design for the cards and disc, together with the resources to accompany all the other projects on this channel, please consider subscribing at   / playfultech