Quiet Hobby Servos

Discussions regarding building a walking robot at home. Most of the robots participating at Robo-One competitions are custom fabricated.
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Quiet Hobby Servos

Post by wthierry » Sun Feb 21, 2010 6:25 pm

Post by wthierry
Sun Feb 21, 2010 6:25 pm

What are the most popular hobby servos for making a biped? What are the worst ones to use, and the best ones, and maybe a middle of the road idea...

Also, are there any servo's that run fairly quiet?

thanks
What are the most popular hobby servos for making a biped? What are the worst ones to use, and the best ones, and maybe a middle of the road idea...

Also, are there any servo's that run fairly quiet?

thanks
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Post by PedroR » Mon Feb 22, 2010 3:38 pm

Post by PedroR
Mon Feb 22, 2010 3:38 pm

Hi

The most popular would be by far the Robotis AX-12 servos.
They are a bit noisy sometimes, probably the DC motor when the electronics are trying to hold the position.
They are also have one major drawback which is the 1 wire data bus. This forces you to use some specific electronics in order to be able to talk to the bus (or just use a Robotis controller).

There are also Robobuilder Servos. These are not as popular as the AX-12 (not even close) but they have some very interesting features:

- They have proper RX and TX line separation, making it much easier to interface it with third party microcontrollers.
- They can operate up to 1Mbps just like the Bioloid but they come with a factory default of 115 Kbps, again making it much easier to interface it with third party micro controllers.
The AX-12s can not operate properly (without error) bellow 400kbps in practice so you need a FAST micro controller.

- The wCK 1111 have good torque, almost similar to AX-12 (especially if you use higher voltages).

- They have a nice networked protocol similar to AX-12 with extended functionalities:
. They have full PID control so they are very quiet (they don't have the noise issue that sometimes plagues worn ax-12s).
PID also lets you tune them for more or less of an elastic feel.
. They have a nice Dynamic Brake feature which is a kind of third power state: Holding Position/Torque and Free Motion (just like AX-12) and the third Dynamix Brake mode where they are in between the two: in this mode there is no power consumption but they still offer tonus/strength (although with some force you can move them).
. Load feedback seems to work better on Robobuilder servos than on AX-12 but still not great.

The main issue with Robobuilder servos are gears breaking.
The wck 1111 already come with 2 metal gears and some of the new servos come with the 4th gear (the main one) in metal too, which essentially eliminates all of these problems with gears breaking.

You can use something as basic as an Arduino to operate Robobuilder Servos, where for AX-12 you need a better Micro controller.

Having said this, Robotis is still the leader in the servo area. They have the best quality and are seen as the best products if you're into the "real deal".
Robobuilder is kind of a "cheapper" alternative but they are still quite good if you want to do it as hobby.


As for Kondo/Hitec, they are PWM servos, which means you will need some dedicated PWM pulse generator to operate them.
We have a board from Inex that can work as a bridge for this, offering a TTL interface to control PWM servos, but in my personal opinion, I would preffer networked servos (Robotis/Robobuilder) instead of PWM servos as the first tend to offer more advanced functionality and feedback of a much larger number of parameters.

Pedro
Hi

The most popular would be by far the Robotis AX-12 servos.
They are a bit noisy sometimes, probably the DC motor when the electronics are trying to hold the position.
They are also have one major drawback which is the 1 wire data bus. This forces you to use some specific electronics in order to be able to talk to the bus (or just use a Robotis controller).

There are also Robobuilder Servos. These are not as popular as the AX-12 (not even close) but they have some very interesting features:

- They have proper RX and TX line separation, making it much easier to interface it with third party microcontrollers.
- They can operate up to 1Mbps just like the Bioloid but they come with a factory default of 115 Kbps, again making it much easier to interface it with third party micro controllers.
The AX-12s can not operate properly (without error) bellow 400kbps in practice so you need a FAST micro controller.

- The wCK 1111 have good torque, almost similar to AX-12 (especially if you use higher voltages).

- They have a nice networked protocol similar to AX-12 with extended functionalities:
. They have full PID control so they are very quiet (they don't have the noise issue that sometimes plagues worn ax-12s).
PID also lets you tune them for more or less of an elastic feel.
. They have a nice Dynamic Brake feature which is a kind of third power state: Holding Position/Torque and Free Motion (just like AX-12) and the third Dynamix Brake mode where they are in between the two: in this mode there is no power consumption but they still offer tonus/strength (although with some force you can move them).
. Load feedback seems to work better on Robobuilder servos than on AX-12 but still not great.

The main issue with Robobuilder servos are gears breaking.
The wck 1111 already come with 2 metal gears and some of the new servos come with the 4th gear (the main one) in metal too, which essentially eliminates all of these problems with gears breaking.

You can use something as basic as an Arduino to operate Robobuilder Servos, where for AX-12 you need a better Micro controller.

Having said this, Robotis is still the leader in the servo area. They have the best quality and are seen as the best products if you're into the "real deal".
Robobuilder is kind of a "cheapper" alternative but they are still quite good if you want to do it as hobby.


As for Kondo/Hitec, they are PWM servos, which means you will need some dedicated PWM pulse generator to operate them.
We have a board from Inex that can work as a bridge for this, offering a TTL interface to control PWM servos, but in my personal opinion, I would preffer networked servos (Robotis/Robobuilder) instead of PWM servos as the first tend to offer more advanced functionality and feedback of a much larger number of parameters.

Pedro
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Post by mahin » Fri Mar 26, 2010 4:37 pm

Post by mahin
Fri Mar 26, 2010 4:37 pm

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I am agree to visit this site and read this post.Because this post has many important things. I am really happy for knowing this great post.
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