Stepper Motor

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Stepper Motor

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

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