Aurora mini 18 using PIC24FV16KA302 microcontroller




Aurora mini 18

My obsession of this year is full-color LED. I have made Aurora 9×18 as a result. As much as I love the scale of Aurora 9×18, I also wanted to have something smaller, perhaps something that can go on a costume?

Aurora mini 18 RGB
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

 

schematics of  Aurora mini 18

Like Aurora 9 bar, Aurora mini 18 borrows its circuit from Aurora 9×18. 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.

Step 2

PCB & Parts

Aurora mini 18 uses surface-mount technology (SMT). If you’ve never built anything with SMT, this might be a good opportunity to try out. You will most likely realize that there’s nothing to fear about SMT. (If you are not familiar with soldering, you might get your feet wet with something simpler than this though.)
The high-quality, custom made PCBs as well as the full kits are available at a reasonable price. Please view the details at “For Sale” section of the forums.
Parts
Here is the list of parts. All except LEDs are available at Digi-Key (digikey.com).
  • 1x 10k Ohm (0603)
  • 3x 220 Ohm (0603)
  • 3x 2.2k Ohm (0603)
  • 18x 150 Ohm (0603)
  • 2x 0.1uF (0603)
  • 2x 10uF (1206)
  • 3x Q1x: MMBT2907A
  • 1x PIC24FV16KA302 (SS)
  • 18x Tricolor LED (common-cathode) (SparkFun COM-09264 should be identical) http://www.sparkfun.com/products/9264
  • 1x Tactile Switch
  • 1x 3 – 5V power supply: regulated AC adaptor, 4 NiMH, 2 AA/AAA batteries & case, single cell Lithium battery, or USB cable
  • 1x 2 pin Molex header (right-angle recommended) (optional)
  • 1x 2 pin Molex connector with corresponding terminals (optional)
There are many places to purchase LEDs. I source LEDs directly from China via AliExpress. Takes a few weeks for delivery, but the prices are great. (If you are purchasing a lot of LEDs.)

You can substitute transistors if you have something compatible.




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