Joystick reproduction (RC transmitter)

Assuming there are no typos there, this sounds like one of those joystick mechanisms that only uses the middle bit of the rotation of a normal potentiomete (hence the swing to +/-2V, not +/-12V). A lot of joysticks I've seen have special pots with a shortend resistive track so you get an output swing essentially the same as the supply voltage -- this is not what you want here. Howeer, assuming the input inmpedance of the ADC card is fairly high, the actual value of the potentiometer resistance is not likely to be critical. If you have _any_ analogue joystick, you can probably convert it to work. If it's a 3-terminal potentiometer type, fiddle the voltages applied to the ends of the track to get the right swing on the slider (e.g. if the slider goes from one end of the track to the other, you could supply it resistance is too high), you can buffer the output from the wiper using an op-amp wired as a unity gain buffer. If you have a 2-terminal joystick (a variable resistor), like most old PC joysticks, it's a bit more work. WHat I did wa make a current sink (op-amp + transistor + R's) and connect the variable resistor between the top of that and +5V (I kept it going to +5V, as in a PC, so that any autofire circuits in the joystick would still work). Then the voltage drop across the variable reisstance is proportional to the resistance (constant current, remember). I tapped that off, and used an op-amp or two to get the right output swing and offset. -tony