I reached out to Disney support to get the overall size of the sphere, but I heard no reply. That’s pretty understandable for a weird question like mine.
Fortunately, my brother had a friend that worked near one of the readers and they were able to get me the dimensions I needed!
They told me that the circumference is 17.3 inches, which means the diameter is 5.5 inches. I knew that I wanted the sphere to be full-sized, but I wasn’t thrilled about having a tall pole and base for it. I took the same approach as the existing designs would use a wide base and stem to hold the sphere up. I also thought that If this item works with a Magic Band, then it should hold it too while the user isn’t needing it. The base will have a place for the band to sit in, below the sphere.
It needs to light up in a circular perimeter and interior, and it needs to play a sound once the lights are done.
It needs to support Magic Band V2 and V3 (current gen). I only have V2, but I found this blog post which had a side-by-side photo from which I could get the larger V3’s size.
https://www.disneyfoodblog.com/2022/05/01/photos-why-wearing-disneys-new-magicband-will-feel-different/
Both V2 and V3 are confirmed to use 13.56 MHz NFC RFID, 915 MHZ UHF RFID, and 2.4 GHz like wi-fi. https://news.ycombinator.com/item?id=9177375. It’s reasonable that the readers, needing very close contact to work, are using the 13.56 MHz RFID standards to communicate the band’s ID and encrypted information. This chip is specifically a NXP Semiconductors MIFARE DESFire EV1 https://www.disboards.com/threads/magicbands-can-be-read-by-nfc-enabled-phones.3171483/. Any reader(s) that I use for this project will need to read any of the 4 levels of the communication standard ISO/IEC 14443A. https://www.nxp.com/products/rfid-nfc/mifare-hf/mifare-desfire/mifare-desfire-ev1:MIFARE_DESFIRE_EV1_2K_8K.