potentiometer typo?

[windell747]

Hi, I've made some modifications to a steering wheel and pedal set by replacing the 10K pots with 100K pots. This was done according to the Operator Interface reference guide. On page 5, they show a wiring diagram for a typical 100K potentiometer. The way I've used pots in the past are as variable voltage dividers. By taking a look at the wiring diagram, the third pin is labeled to have no connection. If this is true, then the pot would act as a variable resistor instead of as a voltage divider. I was wondering if this is a typo, or if I should disconnect the ground lines of the pots in the steering wheel and pedal set.

Thanks,
Windell
#2477

[MrForbes]

Apparently the OI is designed to have the pot wired exactly as shown in the diagram...with only one end connected. This is a safety feature that will allow the OI to detect when the joystick cable is pulled out, and shut off the robot drive.

I've been advised by a couple knowledgeable people here to wire it as shown in the diagram when I asked the same question.

[windell747]

Thank you very much, squirrel! I was told that the joysticks that came with the KoPs are wired like voltage dividers? Is this a problem? Would voltage dividers work fine?

[Gdeaver]

IFI completes the voltage divider internaly to the OI. This allows them to determine if the analog port is used.

[Alan Anderson]

Voltage dividers will work, but not perfectly. You need to put a series resistance in the ground side to offset the voltage so the OI can read the full range of values from the potentiometer. I think the lower limit of usable voltage into the OI is about 600 millivolts.

I apologize for not being more specific, but I never actually did this. I'm just remembering a discussion from some time last year.