Motors

General

Motors transform electrical energy into motion ( typically rotary, but there are also linear motors ). There are a large number of types of motors, but most rely on magnetic forces to produce the motion. Motors are often separated into classes based on the type of electric voltage required ( AC or DC ) or the amount of power they produce, or the internal construction. Many motors require, or can benifit from some for of motor controller or driver, these can be a simple as a current limiting resistance, or can be complex microcontroller devices. A motor controller may take a DC voltage and convert it to AC so that an AC motor may appear to be a DC one.

Stepper Motors

A stepper motor is an electric motor that turns a well define amount ( say 6 degrees ), a step, when connected to the right power source. Repeated activation will cause the motor to move any number of steps in either direction desired. Used for carefully controlled motion. Microcontrollers are often used as part of the drive system for a stepper motor.

Uses

• Printers
• Machine tools
• Robots

Links:

• Wikipedia: "stepper motor"
• Arduino: "Unipolar Stepper Motor"
• A complete project on this wiki PIC based Stepper Motor Dancing Analog Clock
• A PIC controlled tester for stepper motors on this wiki Stepper Motor Tester
• Stepper Motors Lots of info. mostly through links.
• Stepper Motors
• www.RomanBlack.com Measuring Stepper Motors Basics of stepper motor torque and how to measure it.

Micro controller driving

Main Article: motor driver

• Arduino: "Stepper Motor Control"
• The ULN2803 is a Popular Parts for putting between a small motor and a microcontroller.

Servo Motors

A nice simple way to control the position of an object is to use a servo motor. A servo motor can be any kind of motor that is equipped with a position sensor and a feedback network to control the position.. The information from that sensor is then used to control the motor. In common "RC" servos the sensor is a potentiometer and all the drive electronics are packaged inside the case with the motor. The typical RC servo is powered on 5 volts and takes a PWM signal to control its rotation. Rotation is usually limited to about 90 degrees, and the force at the end of the servo arm ( or horn ) is a few oz. or pounds ( really you should rate it by torque ). Rotation position can be quite accurately controlled, and typically the motor will move in sub second times Sometimes these motors are modified to allow continuous rotation, but then the "servo" is gone from the motor and they do not have their nice ability to set a position. RC Servo motor pricing begins at about $10.

We could use a lot more links here:

See the motor driver page for more information on the Open Servo project.

Universial Motors

Run on AC or DC.

AC Motors

Induction Motors

Current is induced from one part of the motor to another to eliminate brushes, slip rings and the like. A problem with them is getting them started. Run at a near synchronous speed ( but some slip is required to induce currents ).

Capicator Start Motors

AC motors often need a phase difference between various windings to start. In some motors this is supplied using a capacitor.

Synchronous Motors

These motors are used when the speed of the motor needs to be synchronized with the power line in an exact way, the typical motor in an AC clock.

Multi Phase Motors

Multiphase motors have several advantages including more power for a given peak current.

Gear Head Motors

Any type of motor with reduction gears integrated into the motor. Used for high torque, low speed applications.

Other Info

• Some Microchip dsPIC controllers are designed for motor control; our DsPIC30F 5011 Development Board and ARMUS Embedded Linux Board projects include such a dsPIC.
• Salvage Challange - Make Me Spin
• "DIY Motors" discusses how to re-wind commonly available parts (floppy drives, etc.) to make motors more suitable for electric model airplanes.