How to attach a potentiometer to a servo motor shaft

I searched google but it was all about controlling a servo with a potentiometer. Thats not what i want to do. I want to have the servo motor turn the potentiometer so i can read the position of the servo motor. I know they often come with POs built in, but i will be turning the motor off and setting the position by hand. I looked at pics of them but i dont see how i would attach it to a shaft.

Thanks

I want to have the servo motor turn the potentiometer so i can read the position of the servo motor.

I know they often come with POs built in, but i will be turning the motor off and setting the position by hand.

I looked at pics of them but i dont see how i would attach them to a shaft.

"they" ?
"them" ?

Get a shaft coupler. Done. If you have heard of motors, (which, BTW, have SHAFTS)
then you must have heard of shaft couplers, since that's what everyone uses with their motors.

What exactly is your electronics background ?

Nice save on the edit of the rude, condescending post there raschemmel; I was responding but it's a pity I didn't grab a quote in time.

I may need to pick out a Servo motor first. I found a couple of hours, they look simple enough to build. But all of the servo Motors on Amazon seem to be for little plastic robots. I need something big

birddseedd:
But all of the servo Motors on Amazon seem to be for little plastic robots. I need something big

So just to clarify, you are talking of the ones that look more like steppers in those big nema style casings, not the normal Arduino world rc servo?

(fwiw, adafruit do have the latter with 4 wires, the extra one being a take-off from the internal pot to bring the position out.)

So what's wrong with these ?

I may need to pick out a Servo motor first. I found a couple of hours, they look simple enough to build. But all of the servo Motors on Amazon seem to be for little plastic robots. I need something big

I worked with the kind of servo motors you are talking about with wafer lifters and they are hella
expensive.

Servo motors

What are the specs for the motor in question ?

raschemmel:
I'll repeat it for your benefit ...
(how rude is that ? Am I not allowed to say that ?)

Well obviously even you had second thoughts about having said it, else you wouldn't have removed it.

I may need to pick out a Servo motor first. I found a couple of hours, they look simple enough to build. But all of the servo Motors on Amazon seem to be for little plastic robots. I need something big

Have you considered posting a description of you project with enough details for someone to pick out a servo motor or do want to do that yourself ?

I know they often come with POs built in

POs ?

What is that ?

birddseedd:
I want to have the servo motor turn the potentiometer so i can read the position of the servo motor.

That just doesn't make much sense as you always know where a servo is: at the position you tell it to go.

If it's not there, then there's a malfunction of the motor, or it's not strong enough. Either way that's a design error, and should never happen. Therefore having a pot to read back the position of a servo is unnecessary.

That, or your description of the problem is flawed.

wvmarle:
.... you always know where a servo is: at the position you tell it to go.

If it's not there, then there's a malfunction of the motor, or it's not strong enough. Either way that's a design error, and should never happen. Therefore having a pot to read back the position of a servo is unnecessary.

That's very simplistic, and neglects the fact that it takes time for a commanded movement to happen, even when things are all nominal. The next step in a process might rely on this process completing, and only closed loop control (which is what this is) will tell you that.

And then, when things do go wrong, which is not necessarily a design or manufacturing flaw, but perhaps unusual untoward and unforeseen circumstances preventing completion of a commanded movement, it's imperative that the system as a whole, knows that. It would need to prevent that next step happening, or perhaps reverse the incomplete movement back to a checkpoint.

If what you say is correct, there would be no need for closed loop control and everything would work on open loop, dead-reckoning.

wvmarle:
That just doesn't make much sense as you always know where a servo is: at the position you tell it to go.

If it's not there, then there's a malfunction of the motor, or it's not strong enough. Either way that's a design error, and should never happen. Therefore having a pot to read back the position of a servo is unnecessary.

That, or your description of the problem is flawed.

I will be turning the servo off to move it by hand

The OPhas not specified Radio Control servo.
He simply stated "serbo motor".
If he means RC servo , it should be explicitly stated as such .

raschemmel:
The OPhas not specified Radio Control servo.
He simply stated "serbo motor".
If he means RC servo , it should be explicitly stated as such .

Not radio controlled

Then the previous comment about knowing the position because the Servo command takes a position argument does not apply.

Why does it matter to a servo whether the command is relayed over a remote control system?

Unfortunately OP hasn't provided info on the actual servo in use, nor on the actual application, and only little information on why he would want to do this.

wvmarle:
Why does it matter to a servo whether the command is relayed over a remote control system?

Unfortunately OP hasn't provided info on the actual servo in use, nor on the actual application, and only little information on why he would want to do this.

Automating the control valve of a hydraulic driven lawn mower.

Have not picked out a serval yet, trying to find out what I need to look for in a servo. Which I believe is going to be a Servo where the motor is powered on a different wire then the power for the internal potentiometer. That way when power is lost in the motor the potentiometer still works

Why does it matter to a servo whether the command is relayed over a remote control system?

Reread the previous post. Nobody said anything about remote control.
The wording used was "Radio Control"
If you have never used radio control then perhaps you should Google "Radio control servo"

If you are an experienced radio control hobbyist then you already know that the arduino uses
the Servo Library to talk to RC servos and also that RC servos are a specific form factor
that uses RC servo "Arms" that plug onto the servo shaft. If, however the servo is NOT
RADIO CONTROLLED (at this point it is irrelevant that radio control is in fact a form of remote control since the discussion is about form factor and programming) then the term "servo
motor" means something completely different, which I might add, your typical RC hobbyist
would have no experience with , since a typical industrial servo motor costs hundreds if
not thousands of dollars, especially if equipped with absolute encoders. Even the ones
with incremental encoders are expensive.

RC SERVO

AC BRUSHLESS (NON-RC) SERVO

So, in conclusion, the difference between "RC" (which stands for RADIO Controlled, NOT REMOTE controlled) and "NON-RC" is the difference between $16 USD and $622 USD.

So yeah, it does make a difference. It's not about whether it is REMOTE controlled or
NOT REMOTE controlled, it is about WHAT KIND of SERVO we are talking about.
If we were talking about RC servos, (which we are not) then we would ALSO be talking about the SERVO library which , (as already pointed out) takes a position argument in the command so you know WHERE (what position) you are commanding it to .
If , on the other hand we are talking about industrial servos, then knowing WHERE the shaft is requires a whole other approach, hence the OP's request for a way to couple the motor shaft with the pot shaft

So if you have this:

INDUSTRIAL AC SERVO MOTOR

you can couple it to this:

POTENTIOMETER

using this:
SHAFT COUPLER

There is of course the caveat that you must write you software to NOT allow the motor
to attempt to drive the pot PAST the END-STOP.

And just for the record, we have not yet discussed AC vs DC regarding servo motor type.

It is unknown at this time whether an adaptor will be necessary since the pot shaft diameter and the motor shaft diameter remain unknown.

hat just doesn't make much sense as you always know where a servo is: at the position you tell it to go

Clearly this is a reference to an RC servo since nothing has been said about absolute encoders or incremental encoders and the OP's first post is clearly a statement of intent to build a closed loop system which he obviously wouldn't need to do if he had an absolute or incremental encoder, so no
he doesn't yet know where the servo is because he doesn't even know what kind of servo he is going to use, let alone how he is going to get feedback. (although he has a theory about that)

raschemmel:
Reread the previous post. Nobody said anything about remote control.
The wording used was "Radio Control"
If you have never used radio control then perhaps you should Google "Radio control servo"

If you are an experienced radio control hobbyist then you already know that the arduino uses
the Servo Library to talk to RC servos and also that RC servos are a specific form factor
that uses RC servo "Arms" that plug onto the servo shaft. If, however the servo is NOT
RADIO CONTROLLED (at this point it is irrelevant that radio control is in fact a form of remote control since the discussion is about form factor and programming) then the term "servo
motor" means something completely different, which I might add, your typical RC hobbyist
would have no experience with , since a typical industrial servo motor costs hundreds if
not thousands of dollars, especially if equipped with absolute encoders. Even the ones
with incremental encoders are expensive.

RC SERVO

AC BRUSHLESS (NON-RC) SERVO

So, in conclusion, the difference between "RC" (which stands for RADIO Controlled, NOT REMOTE controlled) and "NON-RC" is the difference between $16 USD and $622 USD.

So yeah, it does make a difference. It's not about whether it is REMOTE controlled or
NOT REMOTE controlled, it is about WHAT KIND of SERVO we are talking about.
If we were talking about RC servos, (which we are not) then we would ALSO be talking about the SERVO library which , (as already pointed out) takes a position argument in the command so you know WHERE (what position) you are commanding it to .
If , on the other hand we are talking about industrial servos, then knowing WHERE the shaft is requires a whole other approach, hence the OP's request for a way to couple the motor shaft with the pot shaft

So if you have this:

INDUSTRIAL AC SERVO MOTOR

you can couple it to this:

POTENTIOMETER

using this:
SHAFT COUPLER

There is of course the caveat that you must write you software to NOT allow the motor
to attempt to drive the pot PAST the END-STOP.

And just for the record, we have not yet discussed AC vs DC regarding servo motor type.

It is unknown at this time whether an adaptor will be necessary since the pot shaft diameter and the motor shaft diameter remain unknown.

Must be dc. 12v

In this project I can probably get away with less than one revolution in order to open and close the valve. But for the sake of knoledge i am hoping to find one with an internal encoder that is independantly powered so i can turn off the motor but still get a position reading.

Must be dc. 12v

That covers everything from 1 cm to who knows how large.
Can you narrow it down by adding the current rating ? (or motor size in mm ?)

What about this ? (you also haven't mentioned speed criteria (degrees per second etc)

raschemmel:
That covers everything from 1 cm to who knows how large.
Can you narrow it down by adding the current rating ? (or motor size in mm ?)

What about this ? (you also haven't mentioned speed criteria (degrees per second etc)

Fogive me for being a noob. Im not fully sure exactly how to figure that out.

Here is the application.

Im automating a lawn mower. There are handle bars that pivot at the bottom. Partway uo their attached to a rod. This gives lonear motion. The end of the rod attaches to the hydro controls. I havent measured the throw distance, but somewhere around an inch at the connecting rod. The valve itself takes virtually no effort but there is a shock absorber. It may take a bit of strength to overcome the shock absorber. Im not sure how to measure it. For testing i can use my old mower without shock absorbers on.

I will need to convert the motion from the servo to linear. Putting an arm on it would work. But threat still take quite a bit of strength from the motor. The longer the lever the more torque is needed. Im just not sure how to measure it.

Rotations per minute probably depends. The higher up on the handle bars the longer the throw. The less Needed toque and slightly needed rpms per minute. But in general. Slower rotation higher torque iss needed.

I can take some pics and measurmnts when i get home. Just let me know what you need to see

Thanks