5K ohm 10 turn Potentiometer trouble

[rwodonnell]

We have the AndyMark Bourns 5K 10 turn pot: 3590S-2-502L (datasheet: http://files.andymark.com/am-2619.pdf). When plugged into the roboRIO, we can't see any noticeable changes in the SmartDashboard when we turn the potentiometer, even manually. We've replaced it with a 270 degree 100K ohm potentiometer (and changed the settings appropriately with RobotBuilder) and see the results we would expect in SmartDashboard. We need more than a single turn potentiometer to execute our plan.

Is it possible to use a 5K pot, or do we need to get a higher resistance model?

We've confirmed the wiring and AI port, and don't believe it has anything to do with those types of errors.

[GeeTwo]

Just to verify - do you have the red and black wires connected to the ends of the resistor, and the white to the "sweep"? (I'm assuming the usual 3-wire arrangement, black=0V, red=5V, white=signal.)

You can check this by unplugging the pot from the 'RIO and measuring the resistance between red and black with a meter - it should stay constant at about 5K no matter what position the knob is in.

Then, measure the resistance between white and either of the others - it should sweep from 0 ohms at one end to 5K at the other.

5K should work just fine. We're using a 10K 10-turn pot from Jameco, and 5V should work oh-so-slightly better for measurement purposes, at the trivial cost of drawing a full mA of current as opposed to a half mA.

[GeeTwo]

This looks just like the Jameco pot we have. It is a bit unusual for a potentiometer in that the "sweep" on ours is at the back end - the farthest from the knob; usually the sweep is in the middle.

Confirmed from the data sheet - look at the diagram at the lower left of the second page. The back connector is the sweep.

[rwodonnell]

Thank you GeeTwo! We are fixed! Our electrical guys feel a little sheepish, and I am hiding behind my "programming mentor" shield...

Thanks again!

[GeeTwo]

Originally Posted by rwodonnell

Thank you GeeTwo! We are fixed! Our electrical guys feel a little sheepish, and I am hiding behind my "programming mentor" shield...

Thanks again!

My pleasure - and we probably would have gone through the same drill if I hadn't had a strange feeling as I looked at the arrangement of lugs and decided to put a meter on the pot rather than assume that the sweep was in the middle.