Speed limitations of pot & arduino for angle measurement?

[CraigH]

If I am using a continuous rotation potentiometer on a pulley, and I want to use an Arduino to convert this reading into an angle as part of an angle control system, then what are the limitations for how fast the pulley can turn?

Specifically, if the pulley is turning at 450RPM, will a potentiometer be sufficient or will I have to use an encoder?

I am just worried that the faster it is turning, the more noise there will be. I'm also worried about stray capacitance's preventing the voltage from changing to rapidly. On top of this I will have to use a low pass filter to filter out the noise, which may start to filter out the actual signal at high speeds.

So what is the maximum speed (RPM) that I can still read angle data from with a continuous rotation potentiometer and arduino.

 

[rbelli1]

Besides the maximum speed you also have to consider the number of rotations before the pot fails from wear.

Can you describe your application in more detail? Do you need continuous angle readings or are discrete readings acceptable?

BoB

 

[CraigH]

Besides the maximum speed you also have to consider the number of rotations before the pot fails from wear.

Can you describe your application in more detail? Do you need continuous angle readings or are discrete readings acceptable?

BoB

Discrete readings are acceptable, if I can achieve a precision of 1 degree. The pot will be attached to a pulley, driven by a high torque DC drill motor running at 450 RPM. It is part of the control system for a (fairly heavy) robot arm.

Wear is certainly a issue, but the main concern for our project group is time. We're running out of time, and need something quick and easy to implement, otherwise we're going to end up with no robot at all. Next years group can worry about the wear on the pots ;)

We're torn between the options of pot or a rotary encoder. Unless I can find a simple encoder that is super easy to interface with an Arduino, we'll probably choose the pot. Unless you can convince me that the pot won't work very well?

Edit:

We've now decided if we use a pot it will be a 5 or 10 turn, as there is no dead zone.

 

[donpacino]

they have encoder shields for the ardunio, as well as libraries and many tutorials/pre written code

 

[CraigH]

they have encoder shields for the ardunio, as well as libraries and many tutorials/pre written code

Can you please link me to where I can buy these encoder shields? Also, where can I find a library written for it?

Thanks.

 

[meBigGuy]

just google "rotary encoder shield" and see what you find.

http://www.robogaia.com/3-axis-encoder-conter-arduino-shield.html is one example

 

[donpacino]

I just went to google and did a few searches
aduino encoder shield
ardunio encoder library

and so on

here is one good example i found
http://playground.arduino.cc/Main/RotaryEncoders