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EPICfan

Rewiring Joystick part 2 - potentiometers (Watts, HiFi?)

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As described in a previous posting, I am trying to convert my old rig from Parallel to USB.

 

I can solder etc., but what I cannot do is to build a controller.

 

So the plan is to cannibalize a USB-joystick and use the controller. I will have to put in my own potentiometers, as I have to use sliding pots, and the joysticks only come with turning pots.

 

I understand that pots for a USB joystick are 10 k Ohm unlike my old pots for the parallel port which were 100 k Ohm.

 

I was now thinking of using sliding pots that are used for Audio / HiFi equipment. These can be found easily, the levers have rather long ways of travel, and the quality is usually good.

 

These pots are available at 10 k Ohm, but I see they are 0,5 Watt. Now the post for a joystick seem to be 0,125 Watt.

 

If I am replacing a 0,125 Watt pot, can it be done with a 05, Watt, or does it have to be 0,125 Watt as well?

 

Best,

Holger

 

 

 

 

 

 

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<p>Wattage for a pot does not matter. You can use a .5 W instead of a .125W.</p>

<p>tc</p>

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One important thing to look for in purchasing an aftermarket potentiometer is to get one which has "linear taper". Pots intended to be used as volume controls in audio systems often use non-linear taper.

 

With a linear taper pot, the change in resistance vs. distance moved is constant over the entire range of the control's movement. Example: a "slider" type pot, with a total range of movement of 5 inches, and a maximum resistance of 5000 ohms. Moving the slider one inch (from its minimum setting) would increase resistance by 1000 ohms. Moving one more inch would increase resistance by a additional 1000 ohms (for a total of 2000 ohms) and so forth...

 

Because the operating characteristics of audio amplifiers follow a logarithmic curve, potentiometers used to control audio levels often use a non-linear taper, where there is NOT a 1:1 change in resistance vs. distance moved. Audio taper pots obviously would not be suitable for use in a home-built FS joystick.

 

The type of taper (linear or audio) will usually (but not always) be listed in the specifications for specific potentiometers in printed or online catalogs of electronic parts suppliers.

 

Just something to be aware of.

 

 

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Thank you very much, this all very useful advice. I had not been aware of the taper issue, although it sounds quite logical.

 

Best regards,

Holger

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Dear all, thanks for the help. I have read up on this topic, and I have found some good supplyers. What is actually so great about using HiFi parts is that you have a wide variety of knobs that seamlessly slip on the potis on their inside and on their outside can be worked on easily to fit into all kinds of mechanical installations.

 

Anyway - just to make sure that I use the correct potis as a replacement, I have attached a picture of the original potis.

 

"10" = 10 kOhm which I think is standard for USB

"4A" = 4 Ampere?

And what are 78 and 2N?

 

Glad about ideas.

 

Best regards,

Holger

 

 

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Yes, but my project goes a little further. The old pots need to be replaced anyway, as they are "flickering". And the pot for the ailerons will need replacement as I am installing a new yoke.

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