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H-BRIDGES AND STEPPER MOTORS
E R I C T A S E S K I , Y I H E H U A N G , R O N A K M E H T A
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STANDARD DC MOTORS
Speed determined by voltage level.
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Motor
Vcc
GND
+ -- +
STOPPING
No movement, holds position.
4
Motor
Vcc
GND
STOP
FREE SPINNING
Disconnected, does whatever it wants.
5
Motor
Vcc
GND
WHAT IF YOU WANT PRECISION?
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STEPPER MOTORS!
Precision movement via stepping
Can count revolutions
Can rotate continuously unlike a standard servo
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HOW STEPPER MOTORS WORK
Divides a full rotation into a number of steps.
Move one ‘step’ at a time.
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STEPPER MOTORS
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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.
HOW STEPPER MOTORS WORK
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STEPPER MODES: WAVE MODE
11http://en.wikipedia.org/wiki/File:Drive.png
A
B
C
D
(codeproject.com)
STEPPER MODES: FULL STEP MODE
12http://en.wikipedia.org/wiki/File:Drive.png
A
B
C
D
(codeproject.com)
STEPPER MODES: HALF STEP MODE
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http://en.wikipedia.org/wiki/File:Drive.png
A
B
C
D
(codeproject.com)
STEPPER MOTORS CONTD.
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http://www.pololu.com/catalog/product/1205/specs
HOW DO WE POWER THEM?
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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
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Motor Voltage
Logic Enable
Motor
Logic Input
H-BRIDGES
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EN 1,2
EN 3,4
Input 1
Input 2
Input 3
Input 4
Output 1
Output 2
Output 3
Output 4
Vcc, Motor Supply Voltage
GND
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
20http://www.ti.com/lit/ds/symlink/l293d.pdf
FULL-BRIDGE WITH DC MOTOR
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Motor
+ -
Enable
Input A
Input B
ENABLE Input A Input B Result
1 1 0 Motor turns CW
1 0 1 Motor turns CCW
1 0 or 1 0 or 1 Fast Stop
0 0 or 1 0 or 1 Free Spin
1
0
1
0
1
1
- +
HOW TO WIRE UP A STEPPER MOTOR AND
THE L293D
Left side can be adapted to our SmartFusion kits.
22(codeproject.com)
PROTIPS #1-4
1. Heatsinks, or drive low to all pins to not drive current
2. Non-negligible voltage drop across H-Bridge
3. Varying PWM Duty Cycles can be used on ENABLE to
control voltage supplied (speed control)
4. Frequency response of motor
• Low PWM frequencies may create audible buzz or hum
• High PWM frequencies waste power
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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:
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BACKUP SLIDES
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H-BRIDGE WITH DC MOTOR
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S
1
S2 S3 S4 Result
1 0 0 1 Move CW
0 1 1 0 Move CCW
0 0 0 0 Free Spin
0 1 0 1 Brake
1 0 1 0 Brake
1 1 0 0 Shoot-
through
0 0 1 1 Shoot-
through
1 1 1 1 Shoot-
through
http://en.wikipedia.org/wiki/H_bridge
MICROSTEPPING
Half stepping with sinusoidal transitions between steps allowing
theoretically infinitesimally small step sizes.
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http://en.wikipedia.org/wiki/Stepper_motor
