[Robotgroup] Question ... servo or stepper motor ?

[Paul Atkinson]

Mike,
There are several reasons already posted.

One reason is that a basic R/C servo is generally cheaper than a gearhead motor. By modifying the R/C servo for continuous rotation, you can either use the existing pulse width control system or you can replace the control circuit with an H-bridge driver. Which method you use depends on how many control lines you have. A servo needs one control line, an H-bridge needs 2 or 4.

A stepper is generally much more accurate, measured in several degrees (or fractional degrees) per step. For this reason a stepper is often used where accurate rotation or displacement is needed. You also have to have either a step and direction control line or one line per phase to drive a stepper motor. So driving a couple of steppers takes (in the minimum case) half the number of control lines.

Depending on what you are building/contemplating, I'd be happy to provide some more input.

Paul

----- Original Message ----
From: Def Egge <robodigest at innervate.com>
To: The Robot Group <robotgroup at puremagic.com>
Sent: Saturday, February 3, 2007 11:33:06 PM
Subject: [Robotgroup] Question ... servo or stepper motor ?

Under what circumstances would one choose 1) to modify a servo for 
360-degree rotation over 2) a stepper motor?

Inquiring minds want to know.



All the best....

Mike



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