Ladybird with Devention 2402D and Expo-Settings

The Ladybird is a nice little Quadcopter, that is great for indoor and outdoor flying, it is only 32g and very stable. In its most basic package it comes ready to fly with a Devo 2402D Transmitter. This Transmitter is okay’ish, except for one misfeature, that makes it hard to control the quadcopter: The stick-response for nick and roll is much too strong. After some practicing, I found that I would only use the 10% around neutral of the nick-roll stick for normal flying. This is not user friendly. It calls for an expo setting, so that it is less sensitive around the neutral values, but still has the full range when needed for acrobatics.

Being a computer transmitter, I spent some time in the settings menu looking for expo settings or dual range. It is disappointing, there is nothing useful there. They only left a very basic reverse switch per channel, everything else got stripped out of the software. Walkera obviously wants me to do some cursing, and then grudgingly spend good money on a better transmitter. I decided against that, with a smile.

The graph below shows (bright blue curve) that it is possible to create an expo-curve in hardware, by adding two SMD-Resistors per potentiometer!

The Potentiometers in the 2402D have 5kohms. Choosing R=4k7 creates a moderate expo curve, 3k3 or 2k7 would make stronger expo curves, but I found the response with 4k7 quite right. Please also keep in mind, that the lower you choose R, the more current is drawn from the batteries. Soldering SMD Resistors onto the potentiometers is not quite trivial, the photo below shows the placement marked with little pink circles. Normal wired resistors would do fine too. I just happend to have them around as SMD.

If you want to experiment with different resistor values yourself, find the spreadsheet attached here. Besides an expo-curve with parallel resistors, it also supports a flattened dual rate curve by adding resistors in series to the potentiometer. -> expo_poti.ods

CAUTION: The potentiometers are not used up to their full travel. Thus, the min and max values also change with this mod.
We do not intend to change min & max, and we should not, as the full range is needed for flight mode switching. When the instructions say move elevator 4 times up and down, the movement is not recognized if the travel is limited too much.
With 4k7ohm resistors, the min value is 8% instead of 0%, the max value is 94% instead of 100% and I am unable to switch flightmodes. With 6k6ohm resistors the the range is 6% to 98%, and flight mode switching works.

It’s hackweek time again!

For converting your ladybird into a flying SUSE Hackweek8 Log, follow these instructions:

The final result can be seen at: