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H-Bridges and Stepper Motors

H-Bridges and Stepper Motors. Eric Taseski, Yihe Huang, Ronak Mehta. Standard DC Motors. Speed determined by voltage level. Vcc. Motor. + -. - +. GND. Stopping. No movement, holds position. Vcc. Motor. STOP. GND. Free Spinning.

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H-Bridges and Stepper Motors

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  1. H-Bridges and Stepper Motors Eric Taseski, Yihe Huang, Ronak Mehta

  2. Standard DC Motors Speed determined by voltage level. Vcc Motor + - - + GND

  3. Stopping No movement, holds position. Vcc Motor STOP GND

  4. Free Spinning Disconnected, does whatever it wants. Vcc Motor GND

  5. What if you want precision?

  6. Stepper Motors! • Precision movement via stepping • Can count revolutions • Can rotate continuously unlike a standard servo

  7. How Stepper Motors Work Divides a full rotation into a number of steps. Move one ‘step’ at a time.

  8. Stepper Motors 1. The horizontal pair is driven with power in one direction. This pulls the oppositely polarized teeth to align with them. 2. The horizontal pair is de-energized, and the vertical pair is energized. 3. The vertical pair is de-energized, and the horizontal pair is energized in the opposite direction. 4. The horizontal pair is de-energized, and the vertical pair is energized in the opposite direction.

  9. How Stepper Motors Work

  10. Stepper Modes: Wave Mode A D B C (codeproject.com) http://en.wikipedia.org/wiki/File:Drive.png

  11. Stepper Modes: Full Step Mode A D B C (codeproject.com) http://en.wikipedia.org/wiki/File:Drive.png

  12. Stepper Modes: Half Step Mode A D B C (codeproject.com) http://en.wikipedia.org/wiki/File:Drive.png

  13. http://en.wikipedia.org/wiki/Stepper_motor

  14. Stepper Motors Contd. http://www.pololu.com/catalog/product/1205/specs

  15. How do we power them?

  16. H-Bridges! • Allows low voltage logic while driving external power to motors. • Easily control current in both directions, allowing motors to move forwards and backwards. • Useful for DC motors, stepper motors, servos, solenoids, etc.

  17. H-Bridges • Each half bridge is a transistor with an enable. • LOW Voltage Input Control Logic • HIGH Voltage Output Motor Voltage Logic Input Logic Enable Motor

  18. H-Bridges Vcc, Motor Supply Voltage Input 1 Output 1 EN 1,2 Input 2 Output 2 Input 3 Output 3 EN 3,4 Input 4 Output 4 GND

  19. H-Bridge Pinout • -EN pins enable output (1 EN pin per pair) • -A’s are control inputs • -Y’s are outputs • -Vcc1 is circuit logic voltage • -Vcc2 is the motor supply • -Grounds go to ground http://www.ti.com/lit/ds/symlink/l293d.pdf

  20. Full-Bridge with DC Motor Input A 1 0 Motor 1 1 Enable + - - + Input B 0 1

  21. How to wire up a stepper motor and the L293D Left side can be adapted to our SmartFusion kits. (codeproject.com)

  22. Protips #1-4 • Heatsinks, or drive low to all pins to not drive current • Non-negligible voltage drop across H-Bridge • Varying PWM Duty Cycles can be used on ENABLE to control voltage supplied (speed control) • Frequency response of motor • Low PWM frequencies may create audible buzz or hum • High PWM frequencies waste power

  23. References • L293D explanation with Stepper Motor details: • http://www.codeproject.com/Articles/151763/Motor-Primer-and-the-L293D-Quad-Half-H-Driver • Stepper motor configurations with microcontroller pins: • http://www.8051projects.net/stepper-motor-interfacing/stepper-motor-connections.php • Microstepping (not covered): • http://homepage.cs.uiowa.edu/~jones/step/micro.html • Different types of stepper motors explained: • http://www.wimb.net/index.php?s=motion&page=52 • Stepper wikipedia page: • http://en.wikipedia.org/wiki/Stepper_motor • H-Bridge wikipedia page: • http://en.wikipedia.org/wiki/H_bridge • Adafruit stepper with arduino tutorial: • http://learn.adafruit.com/adafruit-arduino-lesson-16-stepper-motors/breadboard-layout • L293D Datasheet: • http://www.ti.com/lit/ds/symlink/l293d.pdf

  24. Backup Slides

  25. H-Bridge with DC Motor http://en.wikipedia.org/wiki/H_bridge

  26. Microstepping • Half stepping with sinusoidal transitions between steps allowing theoretically infinitesimally small step sizes. • http://en.wikipedia.org/wiki/Stepper_motor

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