# Joystick Potentiometers

#### tspcrowther

Feb 5, 2010
2
Hello. I dont know much about electronics so please excuse any lack of basic knowlege or terminology.

Im in the middle of building some precision simulator flight controlls using a usb interface from an old Saitek joystick. It requires 50K rotary potentiometers that have a specific angle of elecrical contact. Two 65 degree pots for the stick, 145 for the throttle and 45 for the rudder. Does anyone know where I might get some? or do they have a specific name? Ive been looking for a couple of days and cant find much below about 220 degrees. And Id like them to be much better quality than the originals. Im also certain they would be linear pots.

As the interface uses all 3 pins on each pot, I tried a couple of methods to try and get the same results. First I mounted two standard 220k pots so they were joined, facing each other and offset at the required amount so I could get a reading of 0 to 50k on two pins of one pot, while 2 pins of the other pot read 50k to 0 and the mechanical movement was limited to about 90 degrees. But when this was wired to the interface and I tried to calibrate it, I was only getting about 25% of the required deflection in each direction and it was very jumpy... I figured Id got this all wrong..

Desperatley now, I took apart a standard 100K pot, drilled a tiny hole through the outer track and bakerlite and fastened a tiny nut and bolt to get a good connection on the track. When I put this together It seemed to give similar readings as the original pots using my new 4th pin and it had a mechanical limit of about 120 degrees that was just about usable. But again when connected to the interface, although the results were much better, it was still quite jumpy and vague. Again, I was missing something.

Does anyone think any of these methods could work with a bit of tweeking? Or am I better off giving up and tracking down exact replacments?

Another possible option Ive stumbled apon is a Hall Effect potentiometer... They are commenly availble in a variaty of usable angles and have the added bonus of being contactless... But, can they be used as a replacment for a standard pot?

Any help would be gratefully appreciated...

Cheers,
Paul.

#### Resqueline

Jul 31, 2009
2,848
It seems you have exhausted many viable options. I don't know about any sources for such pot's.
But if you need quality you could use conductive plastic pot's. They're less noisy than carbon pot's, and/or you could add some capacitors to filter out the noise.
One other option to get the angles you need is to apply some gearing.
Hall-effect pot's seems to require 5V across them and will give 0.25-4.75V out. Some seems to be "programmable" for angle & such at the time of manufacture, and if so they might just as well be modifiable.

#### tspcrowther

Feb 5, 2010
2
Thanks for the tips Resqueline. Glad I wasnt far off in my experimenting.

Ive since discovered a cheap, simple but extreamly precise and versatile little usb joystick controller based on a BU0836A chip.. Apparantly It can handle a vast array of pot values as well as any other sensing device that requires 5v accross it, such as Hall sensors, on up to 8 axes!. And a 6x6 button matrix that can handle rotary encoders.. It comes with software to edit and configre it if required. Im going to get one as it seems it will be a lot easyer to use and could inspire me to construct a few extra controls which I could just solder straight on.

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