A 100k ohm potentiometer is a very useful but very simple sensor that I would like to see. It would enale fairly precise positioning of arms and other appendages. With standard 3 wire output, it would plug into an analog port.
You can buy 100K Ohm Pots from Radio Shack, Digikey and Jameco. Be sure to place a 100-Ohm resistor in series with the Analog input pin on the Vex controller and the wiper pin on the Pot in order to prevent damage to the ADC.
I thought the controller already had like 1K in the input circuit already. I am not sure 100 ohms would do any good.
I would also like to see a vex potentiometer, it would help greatly in arm control.
Yeah. A pot would be an extremely usefull sensor in applications where torque gearing is required but servo like movement.
couldnt you do that wit’ an optical shaft encoder? just rewire it for the application that you want
The optical shaft incoder isn’t very acurate and it wokrs by “interrupting” the processor, where as a potentiometer actually will count rotations.
I think this is all correct…
The current Vex encoder creates an interrupt every 4 degrees. Using gears you can change this to 4 degrees divided by the gear ratio.
A pot won’t count rotations. A computer connected to a pot can detect the changing resistance as the pot turns, just like it can detect the interrupts the encoder produces. Where their usefulness differs the most from that of the current Vex encoder is in situations where direction of rotation is important or situations where you want to keep something pointed in a single direction.
Wiggle the encoder back and forth and you get lots of counts. Without attaching a second modified Vex encoder you can’t tell if these represent continuous turning or wiggling. Wiggle a pot back and forth and it’s resistance wiggles, but stays near where it began. You can tell that it is only wiggling (or is turning very fast).
Turn a pot, and sample its resistance often enough while it is turned and you know how both how far it turned, and what direction it turned. Sample it too infrequently and you only know where the shaft of the pot ends up, but not how it got there.
Using gearing to increase the angular resoultion you can get from a pot tends to create the same pproblems that you have with an encoder, if you don’t sample the pot often enough.
Blake