The transmitter

I decided to buy a Graupner MX16S. This transmitter is already fully rigged in series and has the mixing functions needed to meet my requirements. I wanted to control the two driving motors with one joystick, namely, forward, backwards, right, left and turn on the spot. In order to be able to control all of these movements with only one joystick, I used a wing mixer for Delta/Wings.

The receiver

A R16SCAN receiver was already contained in the set. The size and weight of this receiver makes it suitable for airplanes, but for our useage this is completely insignificant. In order to protect the receiver against vibrations and impacts, I wound foam material around it. I moved the antenna as far as possible away from the remaining electronics and electrical connection, so that there are no interferences with the reception even at longer distances.

The pictures show the "interior life" of my R2D2, viewed through the opened Rear Access Door.

The speed controllers

Speed controllers are needed to convert the receiver signals into the high performance signals that are needed to control the motors. 

There are many factors to consider:

- the kind of the motor – with brushes or brushless
- the voltage of the rechargeable battery and the operating voltage of the motor
- the power input (Ampere) of the motor
- a reverse function
- a selectable brake function

The "Navy V40R" that I chose provides all of these requirements. These speed controllers also provide the operating voltage for the receiver and the servos (built in voltage regulator), so that an external receiver battery is not needed.

The dome motor

For the rotatable dome I used the same type of gear motor as in the feet. This is totally overpowered for this function, but it was cheap and I had already the necessary connecting parts needed to fix the plastic wheel to it. The motor was mounted so that it could swivel and pushed against the bearing by a spiral spring. In this way the plastic wheel is always tensioned onto the bearing of the dome and thus the plastic wheel will not slip as a result of wear or unevenness.

Programming

The transmitter and the speed controllers must be programmed. For the RC-layman this is already a challenge. Reading the operating instructions makes one ponder over the various possibilities and is confusing at the same time. My tip is to read the instructions and then carry on with "learning by doing". A great help here is the LCD display of this remote control. You can read off the movements of each channel directly and recognize immediately the success or failure of your programming. This also prevents your R2D2 from running amok due to bad programming.

You need also some patience, in order to program the speed controllers, because for this procedure you have only the On/Off switch and a transparent silicone cast push-button available. The push-button can only be operated with a thin, rounded piece of wood such as a brush handle. Here my settings:

Program 1   BRKMIN = 0%
Program 2   BRKMAX = 0%
Program 3   AUTOBRK = 0%
Program 4   BACKWARDS = 100%
Program 5   Time to REAR WALL = 0
Program 6   Speed controller behaviour = 0

With these settings you get the same speed for forward and backwards, no speed controller-lateral Expo as well as undelayed switching from forward on backwards. This is particularly important for soft and smooth cornering at slow speed. Undelayed switching, however also covers up dangers: It is possible to switch the 50 kg R2D2 from full speed forwards to full reverse using driving motors which have only plastic gear wheels !!!

Servos

Servos are small electromechanical parts, usually with a mounted "arm". These are attached to the receiver and make it possible to move parts, in our case the utility arm and the holoprojector and they also operate the micro switches needed for lighting the holoprojectors and controlling the sound circuit.

To move an utility arm you need a larger and stronger servo. A time-delayed control, namely, the times which is needed, to move a servo arm from one side to the opposite side would be fantastic. Unfortunately the MX 16 doesn't offer this feature. The servo I use is fortunately not too fast, so I can use it directly without a time-delay. Use a fast servo isn´t recommended because either the gears of the servo or the connecting parts say good-bye due to the inertia caused by the weight of the utility arm.

Current supply

My R2D2 uses a 12 V lead-gel rechargeable battery (7 Ah). I wasn't completely sure, whether the power would be sufficient and therefore installed a mounting plate for a second battery. My R2D2 doesn´t need to drive long-distance and so the second battery was never needed. The receiver and the servos operate on approx. 5 - 6 V. Now the advantage of the mentioned speed controllers becomes clear. The speed controllers are connected directly to the 12 V supply. The three pole cable, which connects the speed controller to the receiver, not only transmits the data from the receiver to the speed controller, but also supplies, in reverse direction the 5 - 6 V operating voltage from the speed controller to the receiver.