This document discusses stepper motors, including their types, resolutions, gear ratios, coils, phases, and drive methods. It provides details on a specific 28BYJ-48 5V unipolar stepper motor, including its specifications. It explains half-step sequencing and how stepper motor movement is controlled by pulse signals. Code examples are given for controlling a stepper motor with a Raspberry Pi. The document contrasts unipolar and bipolar stepper motors and their drive methods.

1. Stepper Motor
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2. Types of Steppers
Motor Size : NEMA 17, 23,..
Resolution: degrees per step
Gear ratio: 32:1 , 64:1
• A gear train will also increase the torque of the motor.
Some tiny geared steppers are capable of impressive
torque. But the tradeoff of course is speed
Coils and Phases
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gear train
6-slots stator 4-slots stator

3. 2-phase
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5. 28BYJ-48 Unipolar Stepper with ULN2003
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28BYJ-48 – 5V unipolar Stepper Motor
• Number of Phase 4
• Stride Angle 5.625° /64
• Speed Variation Ratio 1/64

6. if you will give the ULN2003 stepper driver a certain
pulse signal, it will drive step motor to a certain angle.
The control of Stepper Motor movement angle is
done by controlling the number of stepper motor
driver pulses. The speed of the stepper motor
rotation is also controllable by controlling the
frequency of the pulses.
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7. Half-step Sequence
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8. Half step
the number of steps per rotation: 4096
Half step: 512x8
Step Pulse Frequency: 1000 step/s
One rotation need 40.96 seconds
RPM=Frequency*60/4096
• RPM: 1000*60/4096=15
• Frequency=RPM/60*4096
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9. 接線方式
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GPIO 5 in1
GPIO 6 in2
GPIO 13 in3
GPIO 26 in4

10. Code Example
 cd stepper_motor/step_motor.py
 python3 step_motor.py
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12. How does a Stepper Motor work ?
https://www.youtube.com/watch?v=eyqwLiowZiU
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13. half step
The current has been applied to BOTH coils in an
equal amount. This causes the motor shaft to lock
into place halfway between the two coils. This would
be known as a “half step”
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14. Bipolar Stepper Motors
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15. Unipolar Stepper Motors
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Now to reverse the direction of a unipolar motor you don’t need to
reverse polarity. Instead, the negative voltage is applied to the
OTHER side of the coil. This causes the current to flow in the
opposite direction within the coil and this, in turn, moves the motor
shaft in the opposite direction.

17. Coils and Phases
stepper motor may have any number of coils. But
these are connected in groups called "phases".
All the coils in a phase are energized together.
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Bipolar drivers use H-bridge circuitry to
actually reverse the current flow through
the phases.
Unipolar : less torque

18. Unipolar vs. Bipolar
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19. References
https://learn.adafruit.com/all-about-stepper-
motors/types-of-steppers
https://cookierobotics.com/042/
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