DJI Mini 2 Payload Dropper

While drones are great for photography and exploration, Everett Bradford decided to enhance his DJI Mini 2 further with a payload dropping apparatus. Instead of using an external radio – like other options available for purchase – Bradford hijacked the drone’s lighting signals for control.

As seen in the project video, the first step was to open up the drone and examine its control setup. New wiring was attached, with a connector mounted behind gimbal, and he identified the three lines as +5V, ground, and serial data. This is similar to what you would expect from a WS2812B LED, though with a faster transmission rate of 780kHz is used instead. With nine different lighting options, decoding this signal meant that open/close control would be more than possible, using orange and yellow to as proxies for each operation.

The new add-on hardware employs a PIC18F26K40 for control, which is just fast enough to decode the signal when running at 64Mhz. This microcontroller was chosen for its low power usage, which is further economized by staying asleep for seconds at a time between control cycles. A small planetary gearbox physically controls the 3D-printed dropping mechanism, with closed-loop feedback added via a magnet and linear hall effect sensor. A tiny LiPo with a charging circuit provides direct power for the operation, allowing it to constantly recharge from the drone at 5mA so as not to overload any internal circuitry.

With this system, all Bradford has to do to drop something off is select the correct lighting color, no extra transmitter required! 3D print and code files are found on GitHub if you'd like to make your own!