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# Step motor

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stepper motor

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### Step motor

1. 1. Stepper Motor 77
2. 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 78 gear train 6-slots stator 4-slots stator
3. 3. 2-phase 79
4. 4. 80
5. 5. 28BYJ-48 Unipolar Stepper with ULN2003 81 28BYJ-48 – 5V unipolar Stepper Motor • Number of Phase 4 • Stride Angle 5.625° /64 • Speed Variation Ratio 1/64
6. 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. 82
7. 7. Half-step Sequence 83
8. 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 84
9. 9. 接線方式 85 GPIO 5 in1 GPIO 6 in2 GPIO 13 in3 GPIO 26 in4
10. 10. Code Example  cd stepper_motor/step_motor.py  python3 step_motor.py 86
11. 11. 87
12. 12. How does a Stepper Motor work ? https://www.youtube.com/watch?v=eyqwLiowZiU 88
13. 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” 89
14. 14. Bipolar Stepper Motors 90
15. 15. Unipolar Stepper Motors 91
16. 16. 92 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. 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. 93 Bipolar drivers use H-bridge circuitry to actually reverse the current flow through the phases. Unipolar : less torque
18. 18. Unipolar vs. Bipolar 94