Sliding potentiometers for cabin vent, carb heat and primer

The next step in my “Arduino career” was to play around with potentiometers.

I needed (for now):

  1. Cabin vent
  2. Carb heater
  3. Primer
  4. (Future) Defroster
  5. (Maybe) Cabin heat

1. Cabin vent

It’s just a matter of a few months until summer arrives and I’m going to need a fan to keep my from sweating my a** off in my home cockpit. One solution is to put up a desk fan or floor fan. But an even better solution would be to set up some fans, in the rough area where air vents would usually be, inside a cockpit, and control them using the “cabin vent”. Potentially even connect it to the in-game cabin vent feature as well, if this has a use (not sure if it may help against internal window fogging or something).

2. Carb heater

This is kinda self explanatory. The carb heater in both C152 (my “proof of concept”) cockpit and my future Piper Comanche PA24 cockpit uses a pull-push lever thingy as the carb heater. I don’t want a switch for on/off toggle for this.

3. Primer

Same as the carb heater. I’d rather have something I can pull out, push in, pull out, push in, to prime the engine. Instead of a toggle switch that I had before.

4. (Future) Defroster

In the future I need a defroster. Right now I don’t fly in icing conditions anyway, so it has low priority and so I just stick with a simple toggle switch on my Honeycomb Bravo for this. Mainly because the temporary area where I’m putting my 3 sliding potentiometers, only had cutout for 3 sliders, not 4. Otherwise I would have made the 4th one as well. But they need to be re-arranged for my next cockpit anyway, so I decided not to build a Defroster for now.

5. (Maybe) Cabin heat

This one I haven’t included in my design yet.  So far I haven’t found any actual use for it in the planes that I fly. But it would be easy to add it later on.

How to build all this

This is my original self-thought design. And it’s properly over-engined and over-complicated and lacks a lot of things. But it works.

It took several attempts to get where I needed. One of them can be seen at the top photo.

Here’s the tinkercad design:

Basically I needed some kind of frame for the sliding potentiometer to fit into, and have it’s “tap” slide through and into my push-pull lever so I could control it, you can see the “tap” is the red one, in the middle here:

And here’s one of them being printed, with “supports” (as it’s called in the 3D Printing world) for the belly of the sliding pot frame:

After several revisions, these were the 3 that I ended up with, somewhat stackable:

Starting to wire them up:

And here’s the mess, looking from behind. They are installed in the upper left corner, with voltage wires going up, and 3 signal wires going down to the analog pins on an Arduino:

One more, from the top:

And from the front, this is how it looks in my “proof of concept” cockpit, first one is all of them being pushed in, and the 2nd one the top one is pulled all the way out:

The text on the bottom one, PRIMER, was made with a “filament change” on the 3D printer, read more about that here. The two top ones are just a Dymo label, white text on transparent background and a drop of glue (my Dymo doesn’t stick well to 3D printed PLA).


Making the cabin vent work with Air Manager

As mentioned, the cabin vent will need to control some fans. I connected a few 12V computer fans using a “IRF520 MOSFET Driver Module”, configured as a PWM in Air Manager.

In Air Manager, I configured a simple lua script that if the analog read from the pot was between certain values, it should send a certain duty cycle to the PWM of, say, “0.5” if I wanted 50% speed or “1.0” if I wanted 100%. The PWM frequency I had to play around with and settled on 25000 hz (25 khz). At this setting, my fans didn’t have a “whining” sound like they did at other Hz settings.



Overall, this implementation with a 3D printed sliding potentiometer holder works fine, and acceptable. The “feel” is not as realistic as it would have been with metallic rods and refined friction compared to just 3D printed PLA rubbing against another piece of PLA, with the resistance of the sliding pot. But I think this works well enough for a home sim.


For more Flight Simulator / Home Cockpit building related articles, click here.


%d bloggers like this: