Journal

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2026-05-06 -- Research

Time spent: ~3hrs

So far I have mostly done research on some of the parts that I will be using and made a general plan of what the project will be.

Plan:

• A sand simulation keychain
• Either 16x16 or 12x12 LED matrix. Not sure of which LEDs but either standard RGB or single color. Probably in 0606 or 0603 size.
• Gyro for interaction

• Magnetic charging base. Using either sheet metal spring contacts (like this) or pogo pins.

Parts:

• STM32U031K8U
• LIR2450
• 0606 (maybe larger) for RGB or 0603 single color leds

2026-05-11 -- Start charger base & general design

Time spent: ~3hrs

I started on the actual design mostly with the basic placement/shape. For the keychain part I will probably be using a pcb with all of the leds on it and maybe some of the components and then a secondary pcb with contacts for the charger and the power management. There will be a small mound in the middle for space for the battery and as a locating feature for the base and the battery will be close enough that it should be able to be attracted by a magnet to hold it on the charger base.

I also made the schematic. I have not yet decided on the exact parts but it should only require a USB C port, a few passives and the contacts.

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