Comment by theamk
9 months ago
For people who are thinking about getting into electronics: that project is very complex for what it does. Nothing wrong with it as long as your goal is to learn advanced fabrication techniques, but most people don't need any of this stuff for one-off, home projects with no strict low price / small size requirements.
The main culprit is that "custom ESP32-S3 board" - in this application, it is equivalent to a combination of a random off-the-shelf ESP32 board and a separate battery charger/protector. Half of the equipment on the list (hot air, hot plate, microscope, logic analyzer, etc...) is only needed for this board.
Weirdly enough, the rest of the device is a solid design, suitable for someone with "a few months" of electronic experience: lots of pre-made modules, and designing a carrier PCB for them. This means large and easy to solder 2.54mm hole spacing, regular soldering iron, no microscope, etc.. It's a really weird contrast for me....
This surely could be recreated with off-the-shelf components, no question. It would be a bit of a challenge to stuff another breakout board into the available space, but certainly doable.
But there's a reason for doing the custom board. As my projects get smaller in size, I need to get away from breakout boards. This project was a good fit to come up with sub circuits for different tasks that I can just copy and paste onto a new design, say for a little gaming handheld, or a micro RC car with a much thinner/smaller form factor.
What might be overkill for the current project might be the enabler for the next project. And it let's me iteratively learn new skills.
That said, I might do another version of this with off the shelf parts only for easier reproducibility.
> This surely could be recreated with off-the-shelf components, no question.
I would love to know how does one go about doing this with off-the-shelf components. Can you share more, please
Replace any custom PCB with off the shelf breakout boards. Redesign the enclosure so the breakout boards can be mounted. Instead of a custom motherboard PCB, solder wires between the pins of each breakout board, sprinkling through hole resistors and capacitors around where needed.
Since I didn't go down that route, I don't jave any recommendations for breakout boards that could do the job. I'm also not sure if the assembly is any easier than the assembly of my design.
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.
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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.
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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.
I suppose this project served as a source of joy not only to the kid, but to the maker, too. It likely was a good excuse to do a lot of stuff that's not strictly necessary but is fun to do, and buy a lot of gear that's not strictly necessary but is a pleasure to use. The result is somehow better and more solid due to that, too.
Regarding the solidness of the mechanical design, I have my doubts. The volume know is too small, and too close to the navigation buttons. The speaker grill is too coarse, allowing small items to easily drop inside. The cartridge attachment is not sturdy, not self-adjusting, and relatively easy to snap off. If anything, I would rework the mechanical part. (Alas, my kids are too old now.)
Agreed, and it seems to stem from the NiMH requirement. Maybe designing a protective shell around a LiPO battery (to avoid puncture damage) would have made more sense?
Pretty impressive work though! I think you must have learned a lot. I've spent quite some time on about 5 different projects that were way less polished, but it seems we have picked up the same level of skills along the way. The post is very recognizable ;) Looking forward to the your project!
I can understand not wanting to puncture a pouch style lithium-ion cell (what most people call LiPo), but then why not go for an 18650 or 14500 battery? Same lithium ion chemistry packaged into a more traditional and durable metal can.
Although if I wasn't too confident and wanted to avoid the fires of lithium ion I'd probably gone for NiMH too.
But then the decision to put both charger types on the board when only one will ever be used? Strange, but you can't let indecision paralysis get to you I guess.
As I understood, 18650 and 14500 don't like water too much. Our 3yo will find ways to spill water onto and into it.
As for the dip: I designed the board to be multi-purpose, including new projects down the line, where I might need LiPo energy density. I think I mentioned that in the blog post.
> For people who are thinking about getting into electronics: that project is very complex for what it does.
For people who want to get into electronics, I can recommend getting started with an LED strip, an ESP32 and WLED. You can dip your toes into soldiering, and using an ESP32, for very cheap and with a large margin of error.