Rotation sensors?
 

This year we need some sort of sensor to tell us the angle of rotation of a axel or something of the sort, similar to how a servo can do it. I would use a servo but I'm afraid of forcing them to rotate. Last time I checked your not supposed to do that..

Any ideas?

Re: Rotation sensors?
 

A potentiometer would perform the task nicely. It is used to measure the angle of the input shaft, and outputs a variable resistance (which, when hooked up correctly, translates into an analog voltage which is read by the analog board).

Re: Rotation sensors?
 

An encoder or potentiometer can tell you how far something has rotated.

Edit: Aww, beat to it.

Re: Rotation sensors?
 

With some intense calculations made in the code, you could use the accelerometer, but this only gives you position of your robot and will not account for slippage. I don't think there will be any sensor that would work best for that. I would lean towards calculations in code but that might be because I'm a little biased.

Didn't even think about potentiometers. I like that. And code calculations

Re: Rotation sensors?
 

Use a potentiometer if you want to know an exact position of something (ie, a winch)

Use a Rotary Encoder if you want to know the speed of something (ie, the speed of a motor)

Re: Rotation sensors?
 

Is this axle on your drivetrain? If so, you want to use an encoder because it can rotate more than 360 degrees.

A pot can't rotate past a certain degree.

Re: Rotation sensors?
 

You have an axle you want to measure. It is probably for an arm (the OP did not specify). Assuming its for an arm (which has a rotational limit), a potentiometer would measure the exact position at all times and output an analog signal to the cRio. No math necessary (Except to scale the 0-5v into a different range if you want, but you could use the voltage raw without issue). Whenever we have a rotational joint which software has control to adjust, it is standard practice for us to put a potentiometer on it and automate control of it. We always use potentiometers, because they are absolute (you know where you are even if you just booted up, something a quadrature encoder does not give you) and reliable.

Re: Rotation sensors?
 

The potentiometer that we have "stops" after a certain degrees of rotation (<360). Is there a potentiometer that has "unlimited" amount of rotation? Or how else/what sensor could I use?

Edit: It took me a while to actually reply so by the time I replied, the answer was already given... So my new question is how do I attach an encoder to a window motor and what encoder should I use? Also, what is the difference between magnetic encoders and digital encoders? We have used encoders on the AM gen 1 shifter before but don't know how to use it in any other application.

Re: Rotation sensors?
 

You could use a multi-turn pot (one that has a range covering more than one turn)

Or you could use a magnetic encoder. When you attach the circular magnet to a shaft, it measures the angle of the magnet and outputs a value which is analog which you can read with the cRio's ADC. Two of them come in the kit. Note that every time the angle hits 0 degrees, it wraps around to 360 degrees (same with 360 degrees to 0 degrees).

Re: Rotation sensors?
 

Great thanks!

Re: Rotation sensors?
 

Where can we get an frc legal potentiometer?

Re: Rotation sensors?
 

Wherever fine potentiometers are sold. There are no particular restrictions on what kind you can use (as long as you don't violate any other robot rules).

Re: Rotation sensors?
 

Ok, and then you wire them to where?

Re: Rotation sensors?
 

A potentiometer has three connections. They all go to an input on the Analog Breakout. Using a standard PWM extension cable, the black wire (ground) goes to one end of the pot, the red wire (+5 volts) goes to the other end, and the white wire (signal) goes to the pot's wiper.

Re: Rotation sensors?
 

In general, single turn pots have ~270 degrees of rotation. Don't depend on all of them having this specification. Check the data to be sure and then expect something less. Never use the entire 270 degrees.