Can I use a pot for position feedback without an encoder?

Questions about using encoders with the Roboclaw product line
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lensfocus
Posts: 7
Joined: Mon Nov 02, 2015 3:04 pm
Can I use a pot for position feedback without an encoder?

Post by lensfocus »

Hi,

I'd like to use RC Mode to control a motor in position mode. I'm a little confused about whether or not I need an encoder on the motor. Looking at the question in this forum titled: "Using RC Mode with feedback for position control", the user says he is using "embedded potentiometers" as feedback. But in your answer, you mention "encoder support is enabled for RC mode". Does this mean that he is using encoders plus potentiometers as feedback?

I'd like to use only a potentiometer as positional feedback, but can add an encoder if necessary.

Thanks very much!
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Basicmicro Support
Posts: 1594
Joined: Thu Feb 26, 2015 9:45 pm
Re: Can I use a pot for position feedback without an encoder?

Post by Basicmicro Support »

For velocity or position control you need an encoder on the motor. You can use a pot as an encoder for an absolute position control without the need for a home switch or homing(which you would need if you used a quadrature encoder).

I expect the "embedded potentiometers" are on a linear actuator? If so then yes they are the "encoder" he is talking about. The value of the pot indicates the absolute position of the actuator. Similar to how RC servos work.
lensfocus
Posts: 7
Joined: Mon Nov 02, 2015 3:04 pm
Re: Can I use a pot for position feedback without an encoder?

Post by lensfocus »

That's great!

So I'm just confused as to how to hook up the feedback pot to the board. I'm only using one motor.

I assume I will set the encoder mode to absolute.

I'll use S1 for the RC input, but where does the voltage from the feedback pot connect?

Thanks again!
lensfocus
Posts: 7
Joined: Mon Nov 02, 2015 3:04 pm
Re: Can I use a pot for position feedback without an encoder?

Post by lensfocus »

Okay, I need to make sure I understand properly.

You said "For velocity or position control you need an encoder on the motor".

Does this mean that I need both an incremental encoder and a position feedback pot? Or is a pot only without an encoder an option?

Thanks.
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Basicmicro Support
Posts: 1594
Joined: Thu Feb 26, 2015 9:45 pm
Re: Can I use a pot for position feedback without an encoder?

Post by Basicmicro Support »

No. A pot driven by the motor(eg like a RC servo or like on some linear acuators IS an encoder. Its just an absolute encoder(eg limited range and produces and absolute position value).

You do not sue both types of encoders at the same time(atleast with a Roboclaw controller).

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