Introduction to Computer Engineering Design
Stepper Motor
Unipolar
Bipolar
1
Unipolar Stepper Motor
The stepper motor converts a train of input pulses into a precisely defined increment in the
shaft position. Each pulse moves the shaft through a fixed angle.
S N
A
D
Unipolar Stepper motor
Common +V
C
B
Coil D
•
Four-coil unipolar windings
•
A rotor of permanent magnet
Common +V
Rotor
Coil C
Coil A
Coil B
Interrupts
2
Unipolar Stepper Motor
S N
A
D
Unipolar Stepper motor
Common +V
•
C
B
Full-stepping
Coil D
Common +V
Coil C
Coil A
Coil B
Interrupts
A
B
C
D
1
0
0
0
3
Unipolar Stepper Motor
S N
A
D
Unipolar Stepper motor
Common +V
• Full-stepping
C
B
Coil D
Common +V
Coil C
Coil A
Coil B
Interrupts
A
B
C
D
0
1
0
0
4
Unipolar Stepper Motor
S N
A
D
Unipolar Stepper motor
Common +V
• Full-stepping
C
C
Coil D
Common +V
Coil C
Coil A
Coil B
Interrupts
A
B
C
D
0
0
1
0
5
Unipolar Stepper Motor
S N
A
D
Unipolar Stepper motor
Common +V
• Full-stepping
C
B
Coil D
Common +V
Coil C
Coil A
Coil B
Interrupts
A
B
C
D
0
0
0
1
6
Bipolar Stepper Motor
The stepper motor convert a train of input pulses into a precisely defined increment in the
shaft position. Each pulse moves the shaft through a fixed angle.
S N
Bipolar Stepper motor
A1
B1
A2
B2
•
2 wirings (Coil A and Coil B) with a
core of ferromagnetic material
•
A rotor of permanent magnet
Coil A
Rotor
Coil B
Coil B
Coil A
Interrupts
7
Bipolar Stepper Motor
The current in the coil polarizes the ferromagnetic material which attracts the rotor. By
changing the current direction the polarity can be reversed attracting the rotor in different
position.
S N
The Bipolar Stepper motor can be drive
using three different modality:
A1
B2
A2
B1
Interrupts
•
One-phase
•
Two-phase
•
Half-step
8
One-Phase Stepper motor
Consumes the least power. Only one phase is energized at a time. Assures positional accuracy
regardless of any winding imbalance in the motor.
A1
B2
A2
B1
A1
B2
A2
B1
A1
B1
A2
B2
1
0
0
0
A1
B2
A2
B1
A1
B1
A2
B2
0
1
0
0
A1
B2
A2
B1
A1
B1
A2
B2
A1
B1
A2
B2
0
0
1
0
0
0
0
1
Interrupts
9
One-Phase Stepper motor
The stepper motor convert a train of input pulses into a precisely defined increment in the
shaft position. Each pulse moves the shaft through a fixed angle.
Interrupts
A1
B1
A2
B2
1
0
0
0
0
1
0
0
0
0
1
0
0
0
0
1
10
Two-Phase Stepper motor
Hi Torque - This sequence energizes two adjacent phases, which offers an improved torquespeed product and greater holding torque.
A1
B2
A2
B1
A1
B2
A2
B1
A1
B1
A2
B2
A1
B1
A2
B2
1
0
0
1
1
1
0
0
A1
B1
A2
B2
0
0
1
1
A1
B2
A2
B1
A1
B2
A2
B1
A1
B1
A2
B2
0
1
1
0
Interrupts
11
Two-Phase Stepper motor
A1
B1
A2
B2
1
0
0
1
1
1
0
0
0
1
1
0
0
0
1
1
A1
A2
B1
B2
Interrupts
12
Half-step Unipolar Stepper Motor
The stepper motor convert a train of input pulses into a precisely defined increment in the
shaft position. Each pulse moves the shaft through a fixed angle.
S N
A
D
Common +V
C
B
Coil D
Coil C
Coil A
Common +V
Coil B
A
B
C
D
1
0
0
0
Interrupts
A
B
C
D
1
0
0
0
1
1
0
0
0
1
0
0
0
1
1
0
0
0
1
0
0
0
1
1
0
0
0
1
1
0
0
1
13
Half-Step Bipolar Stepper motor
Half Step - Effectively doubles the stepping resolution of the motor, but the torque is not
uniform for each step. This sequence reduces motor resonance which can sometimes cause a
motor to stall at a particular resonant frequency. Note that this sequence is 8 steps.
Interrupts
A1
B1
A2
B2
1
0
0
0
1
1
0
0
0
1
0
0
0
1
1
0
0
0
1
0
0
0
1
1
0
0
0
1
1
0
0
1
14
Microcontroller-unipolar motor interface
Interrupts
15
Microcontroller-bipolar motor interface
The Driver amplifies the controller’s command signals into power necessary to energize the motor
windings. A bipolar motor requires some external device such as an H-Bridge (SN754410) to reverse the
polarity of the winding and thus, powering one end of the coil pair reverses the flux. The current can be
reversed through the coil by closing the appropriate switches - AD to flow one direction then BC to flow
the opposite.
Enable line (5V)
PIC port (A1)
PIC port (B1)
PIC port (A2)
PIC port (B2)
Interrupts
16