View Full Version : Potentiometers ?

07-30-2007, 03:07 AM
I know these things have been discussed many times but I just have a couple of questions.

I have recently obtained some sliding pots(52mm) to use on a Piper Aerostar quadrant I got from Ebay a while back.
They are 100k ohm linear pots.

The question is,,, I don't think they are linear "TAPERED" like the other rotary pots I've used before.
Will the non tapered make a difference? What does tapered mean?

Are 100k best for throttles, yoke , etc ? They have seemed to work OK in the past for me,, as long as they are geared. I'm trying to get away from the gears with the sliding pots. They just seem ,ergonomicaly, easier to hook up.


07-30-2007, 04:01 AM
If you had (theoretically) 2 sliding pots side by side , one linear & one log taper, the linear at 50% along it's travel would be half the resistance but the log taper at the same 50% travel would not be 50% of the resistance.

It comes from back when audio circuits were using pots for volume control & it was found that a log taper is much more like human hearing works i.e. half the volume does not equate to half the travel on a pot.
Log taper is primarily used for volume controls & for nearly all other applications linear would be more suitable.

Michael Carter
07-30-2007, 10:13 AM
They are easier to hook up, that's for sure. If you mount them on a moveable or adjustable base, you can fine tune the travel for each throttle too. Mine are friction fitted into the base of the quadrant and are adjustable from the outside. There is about 1/2" of adjustment in the fore and aft directions to fine tune all three throttles.

Unless you step up to a linear transducer which are very expensive, there will be some slight variation between each of the pots. That is called pot tolerance. Typically 10-20% of the pot travel for most pots. The longer the pot, the less noticable the tolerance.

You want the mechanical arrangement to take advantage of as much of the full pot travel as possible. That will depend upon the throttle lever throw and how far away you mount the pot from the lever. Variances or not enough throw can be worked out in FSUIPC, but it's easier to just use as much as is mechanically possible during the build.

I chose the linear pots because there just isn't a whole lot of room in a 727 quadrant for an elaborate gear arrangement using rotary pots for three engines.

07-30-2007, 01:30 PM
It sounds like I got the right pots then.

They are 52 mm and the bottom of the throttle lever travel is about 47mm. I may try to extend (if room in the housing permits) the bottom of the levers to get closer to 52mm for full slider travel.

You are right about the rotary pots. I tried to build a 727 quadrant and it turned out much wider than the real thing and looks kind of goofy.
The good thing about it is,, that I learned a lot from the experience. Hopefully,, my next quadrant will look closer to the real thing.

May I ask where you get your sliding pots ?

Michael Carter
07-31-2007, 01:17 AM
I happened upon an e-Bay auction for a lot of Panasonic 100mm cross-fader pots used in large studio consoles. When he told me what they were used for I didn't think they were linear taper, but they were OK.

These things are built like a tank and use two stainless steel rods for the wiper to slide on.