Cheerson CX-10 Quadcopter Controller Mode Modification
Here is a modification I did to change the controller from Mode 2 to Mode 1.
In the RC (remote control) hobby when talking about air (quads, helis, planes, gliders etc) controllers, the layout of the controls is referred to as Modes. A picture tells a thousand words so here is a picture showing the difference between Mode 1 and Mode 2. Notice only the Throttle and Elevator are reversed.
|Mode 1||Mode 2|
Why The Mod?
I fly helicopters. I fly Mode 1. When I wanted one of the CX-10's, I could only find CX-10's that came with a Mode 2 controller. So I decided just to buy it with the intention of mod-ing it to change it to Mode 1.
How The Mod?
Of the 4 controls, the Throttle and Elevator (in both Mode 1 & 2) are the north-south (for want of better terminology) axis of the two controller sticks. To change from Mode 2 to Mode 1 it is just a matter of swapping the wiring of the Throttle and Elevator potentiometers.
Another thing to note is that the Elevator is spring loaded while the Throttle is not and Throttle should rest anywhere it is left and not spring back to centre. After opening up the controller I found that the potentiometers and spring mechanisms, as well as a tactile switch were coupled together and encased in a metal housing which was also soldered to the PCB. There are two of these arrangements, one for each of the control sticks. Refer the pic below:
And a photo of the back just because.
To achieve my main objective of swapping the Throttle and Elevator inputs, I can just cut the PCB trace and physically install 2 jumper wires to swap the input pins of the IC to which the two potentiometers feed. This effectivly swaps the Throttle and Elevator controls.
After finding that I was not simply able to relocate a spring to achieve my other objective of maintaining a spring loaded Elevator and a sloppy Throttle now that they had switched, I had an idea. This involved de-soldering both control stick mechanisms from the PCB and swapping them as one was spring loaded and the other was not. This was not easy as there were 6 pins from 2 potentiometers, 4 pins from the tactile switch, and 4 more pins from the metal housing that were all coupled together and soldered to the PCB. Without a proper de-soldering iron, I used a thick piece of copper wire, to bend and wrap around all 10 pins that needed de-soldering. Using the thick piece of wire helped keep the solder of all 10 pads molten while I heated it up and gradually worked the components off the PCB. This left a mess, but it is only flux from the solder so will not impact functionality, it just looks messy. (Oh and ignore those wires for now, I forgot to get a photo before I installed them.)
Now that I had removed the control stick mechanisms I went about tracing the centre pins of the Throttle and Elevator pots and using a hobby knife to cut and break the circuit of the 2 PCB coppers tracks. I have sat the mechanisms back on the PCB in the next photos but you can see the cut tracks. The first photo of the front on the PCB the cut track is above the R503 resistor which is above the 16 pin SOIC chip. The second photo of the back of the PCB is a little more obvious.
Next I reinstalled the control mechanisms and tac soldered them in. I also installed the two jumper wires from the pots to the IC.
I put the controller back together and proceeded to test it out. I powered up the quad and controller. After calibration the quad flew straight up and hit the roof! I had to hold the Throttle high to stop the rotors. I found that both the Throttle and Elevator inputs were reversed, in that no throttle was full throttle and full throttle was no throttle and forward was back and back was forward. This is caused by a reversing of polarity on pins 1 and 3 of the pots. However, I did check for this with a multimeter when I had the components off the PCB and the two potentiometer pin arrangements matched up. But the logic in the controllers IC must be reversed when comparing the Throttle and Elevator inputs. Fortunately the fix for this is as easy as reversing the polarity of the outer pins of the potentiometers. The hard part is having to remove the whole mechanism again to do this. Instead of altering tracks to the pots what I did was bend the pot pins out so they were not connected to the PCB, and wire straight to the pot from the original pads, crossing them in the process.
I tested it and it works! I can now fly forward without hitting the roof, or back without falling out the sky.
Here is an original Mode 2 type controller in orange and my modified Mode 1 type controller in blue.
Original Rudder Potentiometer
Original Throttle Potentiometer
Original Aileron Potentiometer
Original Elevator Potentiometer
Ready for reassembly.