Servo motor position feedback

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AmmarAkhlaq

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Hello,
I want to know is there is any method through which I can have the position feedback from servo motor? without modifying the servo.
I want to find the error between required angle and actual angel servo had moved.
I am working on hexapod using 18 servo motors and feedback for accurate movement.
Looking for any help.
 

Use an analog feedback servo, which is just a servo motor with a 4th extra wire to read the position.

Or if you want a cheaper, dirty solution, stick an ordinary potentiometer on the shaft of the servo motor. As the servo rotates, the potentiometer rotates as well and you can read the analog voltage to determine the actual position.
 

I have HS485 so feedback servo is not of equation. can you tell me little bi more about the potentiometer thing.
I got what you saying and how to use but want to clear my idea.
I have to take back feedback from 18 servos
 

18 servos? thats a lot..

I imagine my potentiometer suggestion wont be practical.

If you have time, you might want to modify the servo motor yourself, and add an extra wire, like the one **broken link removed**. It also includes an Arduino example program.
 

what are the risks involves in modifying the servos?
and more over I am not using Arduino as we are not allow to use any already built kits or controllers. In simples words I have to build my own servo controller system. From last 2weak I am not making any progress due to feedback thing.
 

If you have the hardware skills (soldering, etc), then modifying the servo should be easy, minimal risk. Have you look at the tutorial link? Do you think you can do it yourself? I am sure you can.

The Arduino is just an example, the code should give you an idea how the modified servo is to be used.

Controlling 18 servos using a single microcontroller would be very difficult. You need to generate 18 PWM signals to control each servo. And you will also need another 18 analog input to read the feedback position.

This means you might need several 2-3 MCU to drive the 18 servo, plus another 'master' MCU to control the other 2-3 MCUs
 

Yes I had visited the link. what I understood is "just to open the servo and solder an extra wire at back side of the wire for input signal the yellow one and use ADC to put that in my controller".
I have good hardware skills.
your are right about the complexity. My robot have six lag so I divided the servos in group of three for one leg.one controller for one lag to control 3 servos.
so 6 legs 6 controllers and 1 master controller to implement the inverse kinematics, controlling and user interference.
 
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I had looked at the link what its explain is just to open the servo sold any extra wire at the back side of yellow(input signal wire).I have good hardware skills and I can do it. I am just warring about the damage it will cause.
You are right about the complexity. I have six legs to control so here what I am doing each leg has one MCU to control 3 servos so I have six legs 6 MCU and master MCU to control the other 6 MCU
 

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