Electric Motors

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ELECTRIC MOTORS
An Introduction to DC and Stepper Motors
Electric Motors
Electric motors are everywhere!
In your house, almost every mechanical movement that you see around you is caused by an AC or DC electric motor.
Direct Current Motors
overall plan of a simple 2-pole DC electric motor
A simple motor has 6 parts, as shown in the diagram
Direct Current Motors
Direct Current Motors
Brushed DC Motor
The brushed DC motor is one of the earliest electric motor designs
Easy to understand design
Easy to control speed
DC STEPPER MOTORS
Stepping motors are electric motors without commutators
Commutation is handled externally by the motor controller
Controller charges opposite coils attracting the center rotor magnets
DC STEPPER MOTORS
DC STEPPER MOTORS
Voltage Rating
provides desired torque
Resistance-per-winding determines
the current draw of the motor
Maximum operating speed
Degrees per Step
Sets the number of degrees the shaft will rotate for each full step
UNIPOLAR STEPPER MOTOR
Relatively easy to control
simple 1-of-'n' counter circuit can generate the proper stepping sequence
1 transistor per winding
UNIPOLAR STEPPER MOTOR
two center-tapped coils
represents the connection of a 4 -phase unipolar stepper motor
UNIPOLAR STEPPER MOTOR
6 wires with a center tap on each of two coils
IDENTIFYING WIRES
Check make and model to see if wire colour code is available
Observe the wires to see if you can identify groups of 3 wires
Measure resistance between wires
Wire with lowest resistance is power wire
IDENTIFYING WIRES
6 wire motors
Groups of 3 wires
1 power & 2 signal
5 wire motors
1 power & 4 signal wires
CONTROL PROGRAM
Once wires identified and connected to the circuit: a program is needed to run the motor
Example Turing Program:
loop
parallelput (1)
delay (500)
parallelput (2)
delay (500)
parallelput (4)
delay (500)
parallelput (8)
delay (500)
end loop
STEPPER MOTOR CONTROL
4 signal wires fired in the correct sequence will turn the motor