Backstory
These “MoniCard” keychains have been trending all over social media here in Japan (unsure if anywhere else?) and I fucking want one. But I refuse to pay the costs I have seen them at, and they seem pretty locked down and like weirdly secretive about selling them? IDK it’s weird and I hate when I can’t have things so I’m making an open source version.
The Plan
So all that being said I’m making my own and I figured as per usual I’d bring y’all along for the ride!
MVP Objectives
- Easy to load new things onto it via a web interface
- Ability to charge via a magnetic connector
- Have at least 12 hours of battery life
- Magnetic key chain system for easy swapping / oshikatsu stuff
Extra Objectives
- Add the ability to have a sleep mode when not moved for a while to save battery
- Build a proper full charging stand for it
- Add NFC to it
- Add a “streetpass” system to it
Their so called “high definition screen” (240 by 320 is high def nowadays? wild) is most likely the same or similar to the one found in T-HMI dev board by LILYGO. So I’m using that as my base for the entire project. It’s a fairly bare bones dev board but it features a esp32 / 2.8 touch display / battery charging circuit all for less then 20 bucks a unit. This gets me basically halfway to the MVP objectives without anything else (besides just a literal lipo battery to plug in).
Current WIP Build Part List
- LILYGO T-HMI
- 2000mah LiPo Battery
- 2pin Magnetic Pogo-Pin Connector
- Rectangular Strong Magnets
Total Cost : ~4500円
Mockup Design
As usual I’m horrible at coming up with names so let me know if y’all have any ideas?