Comment by oniony
9 months ago
The weirdest decision, for me, was putting the music on the cartridges, so that each cartridge needs an SD card holder and SD card.
I would imagine putting all the music on the device and just giving each cartridge an address would have been considerably cheaper and easier. This could have been electrically, connecting different pins of the existing battery holder solution; mechanically, such that each cartridge has a key shape that depresses different microswitches in the device; magnetically, using magnets on the cartridges; or optically, using different pattern holes on the cartridges and leds with optical sensors on the device.
I think, personally, I would have gone the mechanical route and just have an array of switches in the device. Then the cartridges can be simple plastic keys and the device can draw no power when there's no cartridge.
I think the Fischer Price record player worked this way: https://www.amazon.co.uk/Fisher-Price-Interactive-Packaging-.... The tracks on the record form a binary number and the record player head has mechanical switches.
I actually went with a design like you proposed in the first iteration. It turned out to be more time consuming than the SD card solution, specifically for my non technical SO. Now, she just stuffs an SD card into her laptop, transfers files, puts the card into a prepared cartridge, and sticks a label on it. The cartridges can be ordered fully assembled, so she doesn't have to solder anything.
With a fully mechanical solution, she would still have to extract the SD card from the player (or I spend considerable more effort on the software side, so the device can somehow also act as a mass storage device when connected via USB, givng access to the internal SD card), print or construct the "key", stuff the key into a cartridge and label the cartridge.
There's no great practical difference. The only difference is a higher per cartridge cost. Since that's around €2.50 and could be further reduced by bulk orders, I was fine with this design decision.
The ESP 32 has Wi-Fi. You can just connect to it and upload the next track.
So your easier solution is adding an entire network stack, getting it to connect to your wifi, adding a server and client component?
Duuuuude. What?
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A couple of years ago, inspired bu the Tonie box, I built a similar yet much simpler device for a toddler in my family but without such a lofty goal of the learning experience.
I wanted to retain the same "always offline" and "physical" aspects of the experience. I used NFC labels hidden under the cover art label on old (edit: not SD) CF cards because I had a bunch of old ones around and they were all standard size and not easy to swallow. An internal microSD that held all the files needed. Plugging the cartridge in the fake socket which was actually just a hidden power on switch would trigger the playing of a specific file. It's a tad more maintenance heavy but much quicker to pull of.
That’s essentially what Tonie boxes do. They have internal storage and NFC stickers on the figurines. The box is then caching on the SD card and playing from their based on the ID on the NFC chip. If you take the box offline, it can still play the stuff on the box because of that.
With the very big difference that in my case it never needs to (or can, really) be connected to a network and someone else's service [0]. Only to the "parents' service", which was a more convoluted experience for them. They had to manually transfer the file to the internal memory, link it to the NFC label, and print an appropriate cover art label.
It was also interesting to see that when all the kids were gathering around with their toys they were all gravitating towards the one none of them had. But that was an unintended side effect.
[0] When I first heard of Tonies my mind jumped at the idea that the content is stored on the figurine and somehow wirelessly transmitted to the box. The child, parent, and engineer inside me were all thoroughly disappointed this is not the case, and even more so at the perspective of the service being stopped one day or who knows, monetized more aggressively.
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Why not just put an RFID reader in the box and an RFID tag on each cart? The reader modules are sub $10, and the tags are a few cents.