Stepper motor interfacing
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A stepper motor is controlled by sending electrical pulses to its windings to cause incremental rotational movement. There are different types of stepper motors that have varying numbers of windings and step angles. An AVR microcontroller can be used to control a stepper motor by outputting stepping sequences to a motor driver chip, like a ULN2003, that amplifies the current to drive the motor windings. The document provides examples of stepping sequences, step angles, and code for rotating a stepper motor connected to an AVR.
Stepper motor interfacing
- 2. Title and Content Layout with List • Introduction • Add your second bullet point here • Video
- 3. Introduction A stepper motor is a widely used device that translates electrical pulses into mechanical movement. In application such as disk drives, dot matrix printers, and robotics, the stepper motor is used for position control. Stepper motor commonly have a permanent magnet rotor (Shaft) surrounded by a stator. There are also steppers called variable reluctance stepper motors that do not have a permanent magnet rotor.
- 5. STEP Winding A Winding B Winding C Winding D 1 1 0 0 1 2 1 1 0 0 3 0 1 1 0 4 0 0 1 1 Clockwise Anti-Clockwise
- 6. Step Angle Steps per Revolution 0.72 500 1.8 200 2.0 180 2.5 144 5.0 72 7.5 48 15 24
- 7. The step angle is the minimum degree of rotation associated with a single step. Various motors have different step angles. Table 14-4 shows some step angles for various motors. In Table 14-4, notice the term steps per revolution. This is the total number of steps needed to rotate one complete rotation or 360 degrees (e.g., 180 steps x 2 degrees = 360). It must be noted that perhaps contrary to one's initial impression, a stepper motor does not need more terminal leads for the stator to achieve sma11er steps.
- 8. Step Angle The step angle is the minimum degree of rotation associated with a single step. Various motors have different step angles. Above Table shows some step angles for various motors. In Above Table, notice the term steps per revolution. This is the total number of steps needed to rotate one complete rotation or 360 degrees (e.g., 180 steps x 2 degrees = 360). It must be noted that perhaps contrary to one's initial impression, a stepper motor does not need more terminal leads for the stator to achieve sma11er steps.
- 9. Steps per second and RPM relation The relation between RPM (revolutions per minute), steps per revolution, and steps per second is as follows. Steps per second = RPM x Steps per revolution 60 The 4-step sequence and number of teeth on rotor The switching sequence shown earlier in Table 14-3 is called the 4-step switching sequence because after four steps the same two windings will be "ON". How much movement is associated with these four steps? After completing every four steps, the rotor moves only one tooth pitch. Therefore, in a stepper motor with 200 steps per revolution, the rotor has 50 teeth because 4x 50 = 200 steps are needed to complete one revolution. This leads to the conclusion that the minimum step angle is always a function of the number of teeth on the rotor. In other words, the smaller the step angle, the more teeth the rotor has.
- 10. Types of Stepper Motor 1. Universal: 2. Unipolar: 3. Bipolar:
- 11. That types of stepper motor are identified by the number of connections to the motor in winding. The universal stepper motor can be configured for all three modes, while the unipolar can be either unipolar or bipolar. Obviously the bipolar cannot be configured for universal nor unipolar mode.
- 12. Programme INCLUDE "M32DEF.INC“ LDI R20, HIGH (RAMEND) ; initialize stack pointer OUT SPH, R20 LDI R20, LOW(RAMEND) OUT SPL, R20 LDI R20, OxFF ; Port B as output OUT DDRB, R20 LDI R20, 0x06 ; Load step sequence L1:OUT PORTB, R20 ; PortB = R20 LSR R20 ; Shift Right BRCC L2 ; If not carry skip next ORI R20,0x8 L2:RCALL DELAY ; wait RJMP L1 DELAY:LDI R16, 0x50 D_L1:NOP NOP DEC R16 BRNE D_L1 RET Change the value of delay to set this speed of rotation.
- 13. step Winding A Winding B Winding C Winding D 1 1 0 0 1 2 1 0 0 0 3 1 1 0 0 4 0 1 0 0 5 0 1 1 0 6 0 0 1 0 7 0 0 1 1 8 0 0 0 1
- 14. AVR lacks sufficient current to drive the stepper motor windings, we must use a driver such as the ULN2003 (or ULN2803) to energize the stator. Instead of the ULN2003, we could have used transistors as drivers. One reason that using the ULN2003 is preferable to the use of transistors as drivers is that the ULN2003 has an internal diode to take care of back EMF.