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I recently dug up an old joystick (Trust Predator) to see if my old flight simulator install would still work.

The joystick however didn't work at all satisfactory (erratic behaviour and drifting) so I took it apart to see if there were any bad connections. And there were... a lot. The reason is that all rotation sensors (which are just simple potentiometers) are located, I thought rather oddly: the 'base' was the part that moved, while the 'knobs' were fixed. As a consequence, the connecting cables move on every joystick movement, and without exception all of them were in a bad shape (especially the solder connections, but also broken insulation etc).

Why would the sensors be placed this way? Is it just bad design (Trust is a budget brand, after all), or is there a good reason why potentiometers used as rotation sensors are positioned this way? Is this design common in other applications?

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  • \$\begingroup\$ Perhaps if the base is fixed and knob turning (I have seen also this type of it) would suffer braking pins of potentimeter if they are soldered directly on pcb. \$\endgroup\$ – Marko Buršič Oct 10 '15 at 9:01
  • \$\begingroup\$ Interesting point, although not applicable to this device. I'm becoming more convinced it's just bad quality design. \$\endgroup\$ – Sanchises Oct 10 '15 at 9:38
  • \$\begingroup\$ If you go into a testing lab they have all kinds of jigs that do repetitive motions like move the joystick repeatedly. This design probably satisfied the reliability spec and probably simplified (thus cheaper) the mechanical design. \$\endgroup\$ – crasic Nov 8 '15 at 19:01
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There is a reason for this when the joystick has more than one axis. In that case the "inner" axis potentiometer has to be mounted on the "outer" one. Rather than that it is a purely mechanical design consideration.

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  • \$\begingroup\$ I'm sorry if that wasn't clear from the question, but these sensors could without problem be fixed by just turning them upside down. As a mechanical engineer, I couldn't find out why they would place it like this, so I reasoned there might be an electrotechnical reason. But perhaps it's just bad design after all. \$\endgroup\$ – Sanchises Oct 9 '15 at 16:02
  • \$\begingroup\$ Nope. There is really no electrical reason for that. \$\endgroup\$ – Eugene Sh. Oct 9 '15 at 16:03

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