My obsession of this year is full-color LED. I have made Aurora 9x18 as a result. As much as I love the scale of Aurora 9x18, I also wanted to have something smaller, perhaps something that can go on a costume.
Here's Aurora mini 18. It has 18 full-color/RGB LEDs on a smallest possible circle. With a single PIC microcontroller, changing 18 RGB LEDs smoothly is reaching the technical limit. With the new PIC with wider supply voltage, the circuit is simplified compared to Aurora 9 bar, and use of two AA or AAA batteries (3V operation) or one Lithium battery is now possible.
Step 1: Concept & Circuit
Like Aurora 9 bar, Aurora mini 18 borrows its circuit from Aurora 9x18. Operating principle is exactly the same. Just extended the hardware and software to control more LEDs.
One of the new 24F line of PIC microcontrollers is PIC24FV16KA302. Unlike the similar PIC24F series controllers which are 3.3V limited, this controller can operate fully up to 5V. This eliminated the need for the 3.3V voltage regulator, and simplified the LED driving circuits. The resulted circuit with fewer parts count made this Aurora to be very compact.