Potentiometer

[Team#2057-Vegas]

Originally Posted by wilsonmw04

before that it was "4 chan /b/ board" but agreed. The first rule of internet usage: Never feed the trolls.

were too busy feeding the watchdog and the watch puppies

[Matt Krass]

Originally Posted by Team#2057-Vegas

were too busy feeding the watchdog and the watch puppies

Can we train the watchdog to hunt trolls? Should get rid of those pesky watchdog not fed errors and clean up the forums. Win-win.

[kamocat]

If you're looking for good potentiometers, I would suggest Spectrol or Bourns.
I have a 10-turn Spectrol pot myself. Its linearity is rated within 0.25%.
(typical pots don't HAVE a rating for linearity)

Of course, feel free to try a cheap potentiometer, and see where it gets you.

[RyanN]

Originally Posted by kamocat

If you're looking for good potentiometers, I would suggest Spectrol or Bourns.
I have a 10-turn Spectrol pot myself. Its linearity is rated within 0.25%.
(typical pots don't HAVE a rating for linearity)

Of course, feel free to try a cheap potentiometer, and see where it gets you.

...But if you do buy a cheap potentiometer, or actually, most potentiometers (but cheap ones mostly). Even though they rotate at 270 degrees, don't expect to get all 270 degrees of data from it. Cheap ones get probably 200 degrees of reliable data. Decent 270 degree ones maybe a little more.

My point: don't get a potentiometer that will just have enough rotation to work. It won't.

[Matt Krass]

Originally Posted by RyanN

...But if you do buy a cheap potentiometer, or actually, most potentiometers (but cheap ones mostly). Even though they rotate at 270 degrees, don't expect to get all 270 degrees of data from it. Cheap ones get probably 200 degrees of reliable data. Decent 270 degree ones maybe a little more.

My point: don't get a potentiometer that will just have enough rotation to work. It won't.

Agreed, plus you want to be able to sense your soft limits before you're right on top of them, which requires some extra room at either end of the range.

We've used 300 degree pots for about 250 degrees maximum range, with some breathing room.

Matt

[rsisk]

We use these for counting the revolutions of our motor. We mount them to the output shaft of the gearbox with a piece of surgical tubing. One of our mentors manufactured some spiffy plastic mounts that strap onto the side of the motor to hold the potentiometer. Works pretty nice.

http://www.alliedelec.com/search/pro...px?SKU=9700063

[kamocat]

Originally Posted by rsisk

We use these for counting the revolutions of our motor. We mount them to the output shaft of the gearbox with a piece of surgical tubing. One of our mentors manufactured some spiffy plastic mounts that strap onto the side of the motor to hold the potentiometer. Works pretty nice.

http://www.alliedelec.com/search/pro...px?SKU=9700063

Do you know what the deadband on that is? (How much space is there between when it hits the bottom and when it starts again at the top?)

[dmitch]

Originally Posted by rsisk

One of our mentors manufactured some spiffy plastic mounts that strap onto the side of the motor to hold the potentiometer. Works pretty nice.

Could we get a picture of these?

[Joe Ross]

Originally Posted by kamocat

Do you know what the deadband on that is? (How much space is there between when it hits the bottom and when it starts again at the top?)

It's in the specs on that page (electrical rotation 340 degrees +/- 3)

[rsisk]

Originally Posted by dmitch

Could we get a picture of these?

[koo_04]

Hey everyone. Here is detailed shots, as well as a shot giving dimentions, of the POT holder for the 2.5" CIM motor. Sorry I can't find my CAD drawing. Might of went with my computer when I had it wiped.

http://doug.devicariis.org/images/robotics/

I am sure one of you guys could recreate it in no time. I have been busy, or else I would. Have fun!!

[Ross3098]

Quick question and I dont want to start a thread about it. Do potentiometers have to be reset at all some way? Ive been tinkering with code and simply using the AnalogChannel->GetVoltage() and printing it to the console gives a voltage reading somewhere around ~30,000,000 which I assume means it isnt hooked up. No one has touched it since competition season and the potentiometer was fine since the last competition.

It is plugged into port 2 on an analog module.

[Alan Anderson]

Originally Posted by Ross3098

...simply using the AnalogChannel->GetVoltage() and printing it to the console gives a voltage reading somewhere around ~30,000,000...

What format string are you using when you print the value? The GetVoltage() function returns a float. You might have accidentally tried to print it as an int instead.

[Ross3098]

That might be the problem... Im retrieving it to a double value.

And Im printing to int. Honestly I dont know how to print anything but int. Just getting to know this stuff. :/

[Michael Blake]

Here's the VEX potentiometer we used for our arm position:

http://www.vexrobotics.com/products/.../276-2216.html

It worked well once we had a completed gripper on the end of the arm that _worked_... ;-)