Speed limitations of pot & arduino for angle measurement?

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Discussion Overview

The discussion revolves around the feasibility of using a continuous rotation potentiometer versus a rotary encoder for angle measurement in a control system involving a pulley driven by a high torque DC drill motor. Participants explore the implications of speed, noise, wear, and precision in the context of angle readings at high RPMs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant questions the sufficiency of a potentiometer for angle measurement at 450 RPM, expressing concerns about noise and stray capacitance affecting voltage readings.
  • Another participant highlights the importance of considering the wear on the potentiometer due to repeated rotations and asks for more details about the application requirements.
  • A participant indicates that discrete angle readings are acceptable if precision of 1 degree can be achieved, noting the urgency of the project and the potential choice between a potentiometer and a rotary encoder.
  • Some participants mention the availability of encoder shields for Arduino, along with libraries and tutorials, suggesting that these may be easier to implement than initially thought.
  • There are requests for links to purchase encoder shields and find libraries, indicating a need for practical resources to support the decision-making process.

Areas of Agreement / Disagreement

Participants express differing views on the suitability of potentiometers versus encoders for the application, with no consensus reached on which option is definitively better. The discussion remains unresolved regarding the maximum speed at which a potentiometer can effectively provide angle data.

Contextual Notes

Participants mention concerns about noise, wear, and the need for precision, but do not provide specific calculations or thresholds for maximum RPM limits. The discussion reflects a range of assumptions about the performance of both potentiometers and encoders under different conditions.

Who May Find This Useful

This discussion may be useful for individuals or groups working on robotics projects, particularly those considering different sensor options for angle measurement in high-speed applications.

CraigH
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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.
 
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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
 
rbelli1 said:
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.
 
Last edited:
they have encoder shields for the ardunio, as well as libraries and many tutorials/pre written code
 
donpacino said:
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.
 

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