Remote Control Aircraft: Control Repeater Upgrades

Now that I have two models being flown with Dragon Link (the Sabre and the Mojo), I realized that there is a complication with the control system. The reason for the complication is that the repeater receiver must be bound to selected model in the DX20, and it must have failsafe programmed correctly.

For the Sabre, this means that the repeater receiver must be programmed to engage return to home, which means the equivalent of the top two right switches on the DX20 are "down."

For the Vortex, since it does not have a return to home, the desired failsafe is to simply cut the throttle. In this case, that means the top two right switches must be "up" (opposite the failsafe position for the Sabre).

The switch positions that cut the throttle in the Mojo and that engage return to home in the Sabre are arbitrary, but that's how I have them set up and how I am used to them.

I had three options to remedy the failsafe issue for two models:

1) Rebind, reprogram failsafe, and re-test failsafe (turn off DX20 and see what happens) every time I switch models.

2) Reprogram the switch positions on one of the two model programs in the DX20, to ensure that the desired failsafe behavior results are trigger the same for each model (Would require overriding Model Match in the DX20).

3) Use two repeater receivers, one for each model, and switch receivers when switching models.

I didn't choose number one because it's hugely inconvenient and prone to messing up the failsafe programming, resulting in potentially unsafe conditions during the necessary failsafe test. I didn't want to do two either because it is also hugely inconvenient, but I also am very used to the way the two switches are used in each model. Changing the switch positions would slow down my reaction in the event of an emergency and could cause problems.

I chose number 3. It may seem more clumsy than necessary, but I think I made it pretty convenient with my setup. I also chose to "package" all the gear in the repeater ground station in a much nicer and more durable way than the previous foam board version. (I used some foam board, but more for convenience than for structure.)

I used a DPDT (double-pole, double-throw) switch and completely rewired the whole ground station. Now, when choosing a model, I simply plug the battery in to the BEC, which powers the Dragon Link transmitter, and then use the switch to pick which model I am flying. The switch directs power from the BEC to the correct receiver, and directs the SBUS control signal from the correct receiver to the input of the Dragon Link transmitter.

The case I found at Target is the perfect size for this application because I was able to get all the electronics in one side, and leave the perfect space on the other side for the battery that powers the whole ground station. On top of that, the whole thing fits perfectly in my DX20 case.

Here are some pictures from the build: