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STEPPER MOTOR .pptx

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STEPPER MOTOR .pptx

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* Introduction to Stepper Motor
* Types of stepper Motor
* Stepper Motor Construction
* How Stepper motor
* Stepper Motor Interface with Microcontroller
* Stepper Motor wiring using color code chart
* Unipolar and Bipolar configurations
* Parameters of stepper Motor
* Advantages and Disadvantages
* Application

* Introduction to Stepper Motor
* Types of stepper Motor
* Stepper Motor Construction
* How Stepper motor
* Stepper Motor Interface with Microcontroller
* Stepper Motor wiring using color code chart
* Unipolar and Bipolar configurations
* Parameters of stepper Motor
* Advantages and Disadvantages
* Application

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STEPPER MOTOR .pptx

  1. 1. STEPPER MOTOR EC8691 Microprocessors and Microcontrollers
  2. 2. AGENDA: * Introduction to Stepper Motor * Types of stepper Motor * Stepper Motor Construction * How Stepper motor works? * Stepper Motor Interface with Microcontroller * Stepper Motor wiring using color code chart (not required to study) * Unipolar and Bipolar configurations * Parameters of stepper Motor * Advantages and Disadvantages * Application
  3. 3. What is a Stepper Motor ?
  4. 4. Stepper Motor 1. A stepper motor is an electromechanical device which converts electrical power into mechanical power. 2. This motor does not rotate continuously ,instead it rotates in the form of pulses or in discrete steps. 3. Generally , it performs stepwise operation either in clockwise or anticlockwise direction.
  5. 5. 1. Stator –represents the electromagnet coils which remains stationary. 2. Rotor –represents the permanent magnet which rotates .
  6. 6. 1. There are steppers called variable reluctance stepper motor that do not have a permanent magnet rotor. 2. The most common stepper motors have four stator windings that are paired with a center tapped common. This type of stepper motor is known as 4 phase or unipolar stepper motor. 3. The center tap allows a change of current direction in each of the two coils when a winding is grounded thereby changing the polarity of the stator.
  7. 7. stator rotor
  8. 8. HOW DOES THE STEPPER MOTOR WORKS ?
  9. 9. How Stepper motor works? The stepper motor working principle is Electro-Magnetism. It includes a rotor which is made with a permanent magnet whereas a stator is with electromagnets. Once the supply is provided to the winding of the stator then the magnetic field will be developed within the stator. Now rotor in the motor will start to move with the rotating magnetic field of the stator. So this is the fundamental working principle of this motor. In this motor, there is a soft iron that is enclosed through the electromagnetic stators. The poles of the stator as well as the rotor don’t depend on the kind of stepper. Once the stators of this motor are energized then the rotor will rotate to line up itself with the stator otherwise turns to have the least gap through the stator. In this way, the stators are activated in a series to revolve the stepper motor. Driving Techniques Stepper motor driving techniques can be possible with some special circuits due to their complex design. There are several methods to drive this motor, some of them are discussed below by taking an example of a four-phase stepper motor.
  10. 10. 1.Wave-drive /Single excitation / Full step one phase 2.Full step drive 3.Half step drive Stepper motor driving techniques :
  11. 11. Single Excitation Mode The basic method of driving a stepper motor is a single excitation mode. It is an old method and not used much at present but one has to know about this technique. In this technique every phase otherwise stator next to each other will be triggered one by one alternatively with a special circuit. This will magnetize & demagnetize the stator to move the rotor forward. Full Step Drive In this technique, two stators are activated at a time instead of one in a very less time period. This technique results in high torque & allows the motor to drive the high load. Half Step Drive This technique is fairly related to the Full step drive because the two stators will be arranged next to each other so that it will be activated first whereas the third one will be activated after that. This kind of cycle for switching two stators first &after that third stator will drive the motor. This technique will result in improved resolution of the stepper motor while decreasing the torque.
  12. 12. Parameters of Stepper Motor Step angle Steps for each resolution Steps for each second Resolution per minute(RPM)
  13. 13. Parameter of stepper Motor Step Angle It is the minimum degree of rotation associated with a single step. The step angle of the stepper motor can be defined as the angle at which the motor’s rotor turns once a single pulse is given to the stator’s input. The resolution of the motor can be defined as the number of steps of the motor and the number of revolutions of the rotor. Resolution = Number of Steps/Number of Revolution of the Rotor
  14. 14. Steps for Each Revolution The steps for each resolution can be defined as the number of step angles necessary for a total revolution. The formula for this is 360°/Step Angle. Steps for Each Second This kind of parameter is mainly used for measuring the number of steps covered within each second. Revolution per Minute The RPM is the revolution per minute. It is used to measure the frequency of revolution. So by using this parameter, we can calculate the number of revolutions in a single minute. The main relation between the parameters of the stepper motor is like the following. Steps for Each Second = Revolution per Minute x Steps per Revolution / 60
  15. 15. Rotor teeth 1. Minimum step angle is always the function of number of teeth on the rotor. 2. The smaller the step angle, the more teeth the rotor possess.
  16. 16. Applications of stepper motor : 1. The stepper motor is used for position control in disk drives, dot matrix printer and robotics..
  17. 17. TYPES OF STEPPER MOTOR
  18. 18. Variable Reluctance Stepper Motor Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. The stepper motor like variable reluctance is the basic type of motor and it is used for the past many years. As the name suggests, the rotor’s angular position mainly depends on the magnetic circuit’s reluctance that can be formed among the teeth of the stator as well as a rotor.
  19. 19. STEPPER MOTOR INTERFACING WITH 8051
  20. 20. Stepper Motor Interface with Microcontroller Stepper motor interfacing with 8051 is very simple by using three modes like wave drive, full step drive & half step drive by giving the 0 & 1 to the motor’s four wires based on which drive mode we have to choose for running this motor. The remaining two wires must be coupled to a voltage supply. Here the unipolar stepper motor is used where the four ends of the coils are connected to the primary four pins of port-2 in the microcontroller using the ULN2003A. This microcontroller doesn’t supply sufficient current to drive the coils so the current driver IC likes ULN2003A. ULN2003A must be used and it is the collection of 7- pairs of NPN Darlington transistors. The designing of the Darlington pair can be done through two bipolar transistors which are connected for achieving maximum current amplification.
  21. 21. In ULN2003A driver IC, input pins are 7, output pins are 7, where two pins are for power supply & Ground terminals. Here 4-input & 4-output pins are used. As an alternative to ULN2003A, L293D IC is also used for amplification of current.
  22. 22. Stepper Motor wiring using color code chart
  23. 23. Unipolar and Bipolar configurations The main difference between “unipolar” and “bipolar” stepper motors is the availability of the center-tap wire, which splits the full coils of the winding in half. This splitting can be done with one connection wire for the pair or two wires (one for the adjacent ends of each coil). By deleting the center tap, the unipolar connection becomes a bipolar-series connection. The unipolar stepper motor has one winding with a center tap per phase. Each section of the winding is switched via the commutation circuit to control the orientation of the magnetic field. In this way, the direction can be reversed without the need to switch the direction of the current, so reversal is possible despite the single-polarity supply. The wiring usually has three leads per phase and six leads for a regular two-phase stepper motor.
  24. 24. In contrast, the bipolar stepper motor has only a single winding per phase. Therefore, the driving circuit is more complicated to reverse the direction of current flow to the coil and reverse the magnetic field. The unipolar motor requires four transistors (MOSFETS) for full control in a half-bridge configuration, while the bipolar motor needs eight transistors arranged into two H-bridges for control. However, with modern ICs and power-control devices, the difference – especially for lower power motors – is small and may be negligible.
  25. 25. UNIPOLAR BIPOLAR
  26. 26. Advantages and Disadvantages The advantages of stepper motor include the following. •Ruggedness •Simple construction •Can work in an open-loop control system •Maintenance is low •It works in any situation •Reliability is high •The rotation angle of the motor is proportional to the input pulse. •The motor has full torque at standstill. •Excellent response to starting, stopping, and reversing. •Very reliable since there are no contact brushes in the motor. Therefore the life of the motor is simply dependant on the life of the bearing. •The motor’s response to digital input pulses provides open-loop control, making the motor simpler and less costly to control.
  27. 27. The disadvantages of stepper motor include the following. •Efficiency is low •The Torque of a motor will declines fast with speed •Accuracy is low •Feedback is not used for specifying potential missed steps •Small Torque toward Inertia Ratio •Extremely Noisy •If the motor is not controlled properly then resonances can occur •Operation of this motor is not easy at very high speeds. •The dedicated control circuit is necessary •As compared with DC motors, it uses more current
  28. 28. Applications The applications of stepper motor include the following. 1.Industrial Machines – Stepper motors are used in automotive gauges and machine tooling automated production equipment. 2.Security – new surveillance products for the security industry. 3.Medical – Stepper motors are used inside medical scanners, samplers, and also found inside digital dental photography, fluid pumps, respirators, and blood analysis machinery. 4.Consumer Electronics – Stepper motors in cameras for automatic digital camera focus and zoom functions.
  29. 29. PROGRAM FOR FULL DRIVE MODE
  30. 30. MOV R0, #COUNT (initialize rotation count (count = 50d = 32H)) L2: MOV DPTR, #ETC (Initialize pointer to excitation code table sequence) MOV R1,#04H (Initialize counter to excitation code table sequence ie., 4steps) L1: MOVX A,@DPTR (get the excitation code) MOV P1,A (send the excitation code) LCALL DELAY (wait for some time) INC DPTR (increment pointer) DJNZ R1,L1 (decrement R1, if not zero go to L1) DJNZ R0,L2 (decrement R0 , if not zero go to L2) RET ORG 3000H ETC DB 03H, 06H, 0CH, 09H (excitation code seq for clkwise rotation)
  31. 31. EXCITATION CODE SEQUENCE By 8421 rule 8+1=09 8+4=12=0C 4+2=06 2+1=03
  32. 32. THANK YOU

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