Continuous Rotation Servos

[Kevin Sevcik]

Originally Posted by Retired Starman

As a robot inspector, you are going to have to work real hard to convince me that this is a servo and not a motor.

I'd love to see what Big Al has to say about this!

Dr. Bob
Chairman's Award is not about building the robot. Every team builds a robot.

Well the HSR-1425CR is branded a continuous rotation servo by Hitec. I would assume they'd know.

To be extra pedantic, I play with 400V continuous rotation servos at work all the time. The primary difference between a servo and a motor is the feedback and closed loop controller.

[nathannfm]

Thanks! We will look into the HSR-1425CR, the other one is a bit too ridiculous and expensive for our needs.

[team222badbrad]

If a company is modifying an off the shelf servo for continuous rotation then as an inspector I'd say it's illegal. It doesn't matter who does the modifications as per R33. Modification is modification.

If a manufacture (not a reseller) of the servo is marketing a servo as a continuous rotation servo then you might be in luck, but I'd certainly ask FIRST in the Q/A to be sure and bring the answer and servo specs to competition with you.

[Michael Hill]

By "Continuous Rotation Servo", do you mean "Stepper Motor"

(actually, is there a difference? I feel like it's just semantics or something.)

[Kevin Sevcik]

Originally Posted by Michael Hill

By "Continuous Rotation Servo", do you mean "Stepper Motor"

(actually, is there a difference? I feel like it's just semantics or something.)

Huuuuuge difference. Stepper motors have a very specific construction involving two or more independent stationary magnetic coils with "teeth" and an unmagnetized rotor with matching teeth. Energizing the coil in a specific order makes the teeth in the rotor line up with the teeth of the coils in a specific order. So you energize the coils in a pattern and the rotor makes tiny little steps of rotation.

A continuous rotation servo is a more standard brushed or brushless motor with integrated feedback device and control logic.

[Mark McLeod]

Originally Posted by Kevin Sevcik

...
The primary difference between a servo and a motor is the feedback and closed loop controller.

The HSR-1425CR continuous servo does not have feedback (no potentiometer, no closed loop control), so it would seem to be a motor by your definition.