Background
After the issues of my V1 prototype, I redesigned the PCB from the ground up trying to fix all the problems from my last version and add features I thought would be useful. These LEDEarrings V2 ended up being quite successful, and I’ve used them dozens of times!
Design
The biggest change from V1 to V2 was the addition of USB C port on the earring itself. I decided that it was a better idea to remove the need for an external charging dock by having the USB C port and a charging IC. Additionally, I added programming over USB to it, removing the need to solder connections to the board just to program it. On the power side of things, I switched from the MAX16054 power management IC to the ST6601. The ST ic had more features and was a better fit for my project. I kept the same buck-boost converter. For the RF, I redid the impedance matching pi network calculations and added a 2.4GHz ceramic chip antenna.
Assembly
After receiving and assembling my board, the only thing I had to change to get it immediately working was the addition of a pullup resistor on the PS_HOLD pin of the ST6601. Originally, when programming the MCU, the PS_HOLD pin would go into a high-z state, and since when plugged into USB the MCU is still powered by the boost converter, the ST6601 would disable the regulator IC. After programming it with some simple animations from the FastLED library, it worked incredibly well.
Results
Whenever I brought out my V2 LEDEarrings, they were a hit. I constantly had people asking me where I bought them and were interested in buying them themselves. I implemented in the code brightness control by short pressing the button to cycle through brightness options. Often times the lowest brightness was perfect for most parties or shows I went to, and the highest brightness was blindingly bright. I also added a feature where by double tapping the button the earring would go full brightness white to be used as a mini flashlight- a feature I actually ended up using multiple times to look for something I dropped on the floor or in my purse.
