[simpits-tech] stepper motors

[Marv De Beque]

Hey, I can answer that.

A stepper is a motor that moves in a specified direction one step at a time.
You can specify the number of steps to be taken by repeating the step
command.  Actually, that is a bit misleading.  There are different types of
stepper motors, but basically, a quadrature signal (two square waves at 90
degrees out of phase from each other) are applied to the motor.  Each cycle
of the waveform moves the motor one step.  If you reverse the phase
relationship at startup, the motor will run in the opposite direction.
There is usually no limit as to how far the motor can be turned.  That is,
it can rotate indefinitely in any direction.

A servo usually has a limit of 180 degrees.  It is controlled by a periodic
pulse.  The width of the pulse is proportional to the position of the motor.
If you stop the pulses and park the servo, the position is maintained.

Servos use a potentiometer to measure the shaft position of the servo.
Circuitry in the servo compares the pulse width of the input signal to the
resistance of the pot.  The circuitry will then move the motor to that
position and stop.

Servos can be modified to rotate continuously, but you loose the ability to
determine the shaft position.

I use servos for gauges where the needle moves less than 360 degrees.  I use
step up gears to double the shaft rotation to do that.

Marv


On 2/2/03 3:27 PM, "John P. Miguez" <jmiguez@bellsouth.net> wrote:

> Also, what is the difference between a servo and a stepper motor?
> 
> John
> 
> ----- Original Message -----
> From: "Ido Dekkers" <idekkers@clicksoftware.com>
> To: <simpits-tech@simpits.org>
> Sent: Sunday, February 02, 2003 7:35 AM
> Subject: [simpits-tech] stepper motors
> 
> 
>> 
>> 
>> 
>> 
>> What is the difference between bipolar and unipolar motors ?
>> Which of them does the stepper phidget support ?
>> 
>> Thanks
>> 
>> Ido
>> 
>> 
> 
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