Binary Card Reader
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- Опубликовано: 3 июл 2024
- 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 
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Great idea and implementation, as always.
Love this channel and the ideas that you come up with
Alistair, you've outdone yourself. Amazing
Excellent! As always very interesting.
You could have a version of this puzzle where there's only like, 4 cards that have loads and loads of holes on them, and they're really long, and they have to push them in a certain distance (perhaps marked on the actual cards) and if you wanted to make it really really difficult, you could have a card that is on display, but can't be picked up, like, behind some plexiglass, and they have to imagine in their mind's eye what positions were being blocked and what symbol they'd expect to see. Too hard for most groups but if you made it really clear that the holes/non-holes related to different symbols or numbers, you could make a nice difficult version of this puzzle very easily
Interesting as always; although I did think that the use of the laser diodes. rather than simple LEDs, to be a little overkill. You did mention the effects of ambient light at various intensities, so I defer to your judgement on that, given that a bleed of illumination from the diodes can also work the other way around to mess with, or otherwise skew, your detected levels.
I really like your way of multiplexing the LDRs, and have to concede that I have had a bunch of laser diodes for a couple of years, gathering dust, and have never really found an application for them (modulated link)!
I enjoyed your presentation and appreciate the amount of work that you put into each video. Thank you.
Ian_
Thankyou for your kind and considered comment! Yes, I originally had intended to do an array of simple IR beam-breaks, but what I found was that the IR LEDs I was using simply had too much spread, and also the readings varied based on environmental conditions (I like to have a lot of natural sunlight as much as I can, and that plays absolute havoc on anything that tries to detect IR!) . It would probably be possible to use them IR LEDs combined with some sort of sheath to narrow and focus the light they produced onto the corresponding sensor, but then it occurred to me that there are already narrow-beam light sources that are plenty easily-accessible - those little laser diodes!
@@PlayfulTechnology I've used simple opto slot sensors hacksawed in half outdoors with no issues, I've also used a longer rage IR break beam, the key thing with those being the IR is modulated meaning sunlight has little effect as the receiver is looking only for a modulated signal, the output is a simple open collector output.
I think i will use the esp32 and use separate analog inputs for each LDR and try different color LEDs instead of the lasers. . Nice code! Cleaver ideal.
Amazing!
Thankyou! :)
I believe those wheels are similar to how bcd rotary switches work.
can you make the portable safe puzzle from resident evil 2
I'm a bit confused on the if statement at line 103.
It stops the program from resending a value to the screen, if it's the same, but if that's the case, how could you send the 2 S's in MESSAGE?
I'm probably missing something obvious..
I would guess the space between the holes would show a zero and set it up for the next set of holes to show the second S.
I guess that makes sense, there does seem to be a space between the gaps.
Thanks.