6 position flight mode switch

For one of my projects where I need to build a ground station and install computer, controller, camera control etc. in a case I thought it would be much easier to access the 6 different possible flight modes from a single rotary switch. For that reason I sat down, designed a small circuit which would nicely go on the back of a rotary switch barely extending the dimensions of that. In order to provide the necessary PPM pulses I employed a Microchip PIC processor. This will output a composite PPM signal on one pin.

The fifth channel is programmed to read the position of the rotary switch and based on that to modify the pulse length for channel 5. All other channels output a constant 1.52ms signal.

The composite PPM signal then can be fed into the trainer port of any Futaba, TGY 9X or 9XR,  The radio has to be programmed to accept the signal coming on the trainer port - in case of the Futaba the trainer switch has to be on as well, but in case of the Turnigy one can simply select for channel five a PPM5 signal, plug the switch to the back to the radio and just use it.

The switch has a small voltage regulator so can be powered even from a 3 cell LiPo connected to your radio - but also through the Futaba trainer port.

The switch positions are programmed to the following pulse widths:

1: 1115us

2: 1295us

3: 1425us

4: 1556us

5: 1685us

6: 1875us

These are the middle of the bands shown in the mission planner software for each flight mode position.

I verified with the scope, the pulses are good and measure where they should be. Testing with the trainer cable will follow in a few days - hopefully over the weekend I will have some time.

I just wanted to share this project with the collective and see what do you think about this. See some pictures below.

Pic 1 - controller board top and rotary switch

Pic 2 - controller board bottom and rotary switch

Pic 3 - all assembled




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  • Why did you not go down having six modes without mod?
  • Developer
    Congrats on the design. You should consider posting this as a blog entry. It would be cool if it did 9 positions as 6 for some is a limiting factor.
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