A while ago we did a hack where we attached a NeoPixel ring to a Crazyflie. It was just a quick hack to show the concept, but we really liked the results. So we added some more firmware to easily be able to create new effects for the ring and also made it controllable using the Leap Motion. When we started talking about what expansion boards to do for the Crazyflie 2.0, we instantly thought about this hack. It’s fun to play around with the patterns, but it’s also great for lighting up the ground below that Crazyflie. To be able to light up in front of the Crazyflie we also added two strong white LEDs facing forward. Imagine a Sci-Fi movie where an abandoned alien ship is found. To explore it they first send in a small autonomous flying vehicle for exploration that lights up the walls and floor while blinking with some patterns, that’s the look we were going for 
To accomplish this we have designed an expansion board with a ring of 12 W2812B RGB modules as well as two strong front facing LEDs (the kind that’s used for LCD backlight). The board is 3cm in diameter and weighs about 3,5g. To make sure the LEDs are lit correctly as the battery voltage changes (especially when it get’s low) we added a DC/DC step-up/down to the board.
Like always, we are looking forward to seeing what fun things our users will do with this board