OI potentiometer for controlling turret

[team 888]

we are using a window motor. I went over the final design robot this morning and the drive train is in the way for placing the potentiometer. Eliminating this problem would call for some major design changes that we don't want to start at this point. Does anyone one have a simple code that will measure the rotation of the potentiometer on the oi?

[Alan Anderson]

Reading the OI potentiometer is easy -- just connect it between +5 and one of the OI analog inputs (x, y, wheel, or aux) on a joystick connector.

But without a position sensor on your turret, you won't be able to do much with the value coming back from the OI. How will you know which way to drive the turret motor if you don't know where it's pointing at any given moment?

If you don't have room for a pot on the window motor, how about putting a gear on the shaft it's turning and putting the pot on a matching gear connected to it?

[kaszeta]

Originally Posted by team 888

I went over the final design robot this morning and the drive train is in the way for placing the potentiometer.

If I had a dollar for every time this has happened... Too many times the sensors get added in as an afterthought.

You won't get anything useful from the OI, you need feedback from the actual rotating turret to have a real control loop. Anything else is just open-loop control and prayer.

Methods for retrofitting some sort of feedback sensor include:

1. The abovementioned technique of adding a gear to the turning shaft, and hook a pot or encoder to that shaft.

2. Similarly, Team 95 has used friction wheels against the turning shaft. I don't recommend this, since it almost always will have a bit of slip.

3. Depending on the shaft size, you might be able to put a gear or nubs on it and use the Gear Tooth Sensor (note that with just one sensor, you won't be able to tell direction of rotation).

4. You can get shaft encoders that slip over an existing shaft, but you might have trouble procuring these in time.

5. I've seen string potentiometers (both professional and jury-rigged) used in all sorts of interesting setups where nothing else fit, if you can find or make one in time.

[Astronouth7303]

Originally Posted by team 888

we are using a window motor. I went over the final design robot this morning and the drive train is in the way for placing the potentiometer. Eliminating this problem would call for some major design changes that we don't want to start at this point. Does anyone one have a simple code that will measure the rotation of the potentiometer on the oi?

I want to see the picture of this turret with absolutely no space in its entire 360° for a ¼" by ¼" potentiometer. (You couldn't point it the other way and have it over the drivetrain?)

Bottom line: You MUST put in a pot if you expect any decent control. (How can I emphasize it further?)

Give me sensors or give me death!

A sensor is worth a thousand words.

A sensor in hand is worth two in the bush.

Early to wire and early to read makes a robot healthy, wealthy, and wise.

When the pot's away, the arms will play.

A sensor a day keeps the mentor away.

A pot is a bot’s best friend.

The sensor is always nicer on the other side.

Hell hath no fury like a sensor ignored.

Knowledge is power.

Sensors are made, not born.

It’s not whether you win or lose, it’s how you read your pots.

A bot is known by the sensors it keeps.