ELECTRIC MOTORS

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ELECTRIC MOTORS

• An Introduction to DC and Stepper Motors

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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.

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Direct Current Motors

• overall plan of a simple 2-pole DC electric motor
• A simple motor has 6 parts, as shown in the
  diagram

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Direct Current Motors
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Direct Current Motors
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Brushed DC Motor

• The brushed DC motor is one of the earliest
  electric motor designs
• Easy to understand design
• Easy to control speed

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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

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DC STEPPER MOTORS
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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

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UNIPOLAR STEPPER MOTOR

• Relatively easy to control
• simple 1-of-'n' counter circuit can generate the
  proper stepping sequence
• 1 transistor per winding

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UNIPOLAR STEPPER MOTOR

• two center-tapped coils
• represents the connection of a 4 -phase unipolar
  stepper motor

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UNIPOLAR STEPPER MOTOR

• 6 wires with a center tap on each of two coils

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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

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IDENTIFYING WIRES

• 6 wire motors
• Groups of 3 wires
• 1 power 2 signal
• 5 wire motors
• 1 power 4 signal wires

• power wire has lowest resistance to the others

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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

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STEPPER MOTOR CONTROL

• 4 signal wires fired in the correct sequence will
  turn the motor