SEMINAR ON STEPPERMOTOR A splendid innovation in the techsavi society….
P P E N D IX STEPPER MOTOR-INTRODUCTION OPERATION TYPES ADVANTAGE REAL LIFE APPLICATIONS CONCLUSION 2 110907
INTRODUCTION TO STEPPER MOTOR Electromechanical device which converts electrical pulses into discrete mechanical movements Shaft of a stepper motor rotates in discrete step increments when electrical pulses are applied Sequence of the applied pulses is directly related to the direction of motor shaft’s rotation. Speed of rotation is directly related to the frequency of input pulses applied 
PM type stepper motor permanent magnet is rotor and coils are put on stator. The rotor will move precisely 90 degrees for each pulse of electricity that the motor receives 
CLOCKWISE & COUNTERCLOCKWISE CONTROL Clockwise Rotation Counter Clockwise Rotation Control Control Sequence Sequence Steppers dont simply respond to a clock signalThey have several windings which need to be energized in the correct sequence before the  motors shaft will rotate. Reversing the order of the sequence will cause the motor to rotate the other way.
THEORY When current flows holding torque is produced Without power, rotor will detent or align to magnetic poles ,here 4 Such positions are present. changing the current flow to the next stator winding, the magnetic field will be changed 90°& rotor will move 90° before its magnetic fields will again align with the change in the stator field. The turn of the motor is controlled by the electric current which pours into different stator terminals
A circuit which is responsible for converting step and direction signals into winding energization patterns is called a translator. Most stepper motor control systems include a driver in addition to the translator, to handle the current drawn by the motors windings.
Basing On Internal Wiring Condition Stepper Motors are of two types : UNIPOLAR STEPPER MOTOR BIPOLAR STEPPER MOTOR Unipolar stepper motors are generally six leads in Bipolar Stepper motors are generally four leads and two triplets - each triplet powering one coil with a two pairs each powering one coil centre tap . Sometimes there are 5 leads due to Example : floppy disc drive read or write internal connection of centre taps . By using an ohm Supply two coils with phase shifted pulse train in meter and by checking equal resistances between order to rotate the motor pair of leads it can be easily found out which The leads can be identified corresponding leads corresponding to each unit . Just by ignoring To the windings of the motor with an ohm meter centre taps unipolar motors can be operated as bipolar fashion .
STEPPER MOTOR TYPES There are three basic stepper motor types. 
VARIABLE-RELUCTANCE TYPE Consists of a soft iron multi- toothed rotor and a wound stator. When the stator windings are energized with DC current &the poles become magnetized Rotation occurs when the rotor teeth are attracted to the energized stator poles. Crossectional view
PERMANENT MAGNET (PM) TYPE Crossectional view Rotor of PM type 
HYBRID TYPE :• Step Angles For Hb Stepper Motor Range From 3.6to 0.9 Degree With100 – 400 Steps Per Revolution• Detent, holding and dynamic torque characteristics of the motor are better compared to both the VR and PM types. Crossectional View 
C o mp ute r B u s in e s s M a c h in e s P e r ip h e r a lsAPPLICATION USE APLICATION USE ROBOTICS Floppy Disc position magnetic pickup Card Reader position cards INSTRUMENTATION APPLICATION Copy Machine paper feed Printer carriage drive NUMERICAL CONTROL Banking Systems credit card positioning Printer rotate character wheel OF MACHINE TOOLS Banking Systems paper feed Printer paper feed ELECTROMEDICAL Typewriters head positioning Printer ribbon wind/rewind (automatic) NUCLEAR REACTOR Printer position matrix print head Typewriters paper feed Tape Reader index tape (automatic) AEROSPACE AND INDUSTRIAL Plotter X-Y-Z positioning Copy Machine lens positioning APPLICATIONS Plotter paper feed Card Sorter route card flow CONSUMER ELECTRONICS P ro c e s s C o ntro l Machine Tools APPLICATION USEAPPLICATION USE Carburetor Adjusting air-fuel mixture adjust Milling Machines X-Y-Z table positioning Valve Control fluid gas metering Drilling Machines X-Y table positioning Conveyor main drive Grinding Machines down feed grinding wheel In-Process Gaging parts positioning Assembly Lines parts positioning Grinding Machines automatic wheel dressing Silicon Processing I. C. wafer slicingElectron Beam Welder X-Y-Z positioning I. C. Bonding chip positioning Laser Cutting X-Y-Z positioning Laser Trimming X-Y positioning Lathes X-Y positioning Liquid Gasket Dispensing valve cover positioning Sewing X-Y table positioning Mail Handling Systems feeding and positioning letters 
Used in Dot Matrix Printer Used in CD-ROM Drive 
Full Step Drive ----200 full steps per revolution and 1.8º full step angle Half Step----- 400 full steps per revolution and 0.9º full step angle Micro stepping (Continuously varying motor currents )----more than 50000 full steps per revolution and (1/256) ºfull step angle 
STEPPING MODES Frame 1: The top electromagnet (1) is turned on, attracting the nearest tooth cOnTd : of a gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from electromagnet 2. Frame 2: The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the nearest teeth slightly to the right. This results in a rotation of 3.6° in this example. Frame 3: The bottom electromagnet (3) is energized; another 3.6° rotation occurs. Frame 4: The left electromagnet (4) is enabled, rotating again by 3.6°. When the top electromagnet (1) is again enabled, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example. 
F u ll S t e p S t e p p e r H a lf S t e p M o to r S te p p e r M o to r The main difference is that the second Just as the rotor aligns with phase is turned on before the first one of the stator poles, the phase is turned off. Thus, sometimes second phase is energized. both phases are energized at the same The two phases alternate on time. During the half-steps the rotor is and off and also reverse held in between the two full-step polarity. There are four positions.  steps
A stepper motor (or step motor) is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. Control sequences : Two control sequences for single steppinga unipolar or bipolar stepper motor are shownbelow (here positive voltages are denoted by red bars, and negative / ground by blue): powers two windings at a time and produces a torque about 40% greater than for the previous sequence while using twice as much power 
TORQUE VS ROTOR ANGLE & SPEEDCHARACTERISTICS Torque vs. Rotor angle Graph between Torque graph and speed 
The curve shows behavior of rotor with one step pulse step time dependent on the ratio of torque to inertia & the type of driver used Acceleration causes overshoots & ringing as shown This behavior is reduced by micro stepping Positional Accuracy Of A Stepper Motor 
STEP ANGLE ACCURACY  Stepper motor is popular due to it’s accuracy and repeatability Step angle accuracy is 3-5% of one step Positional Error Step Position Error Positional accuracy of a stepper motor
Overall Graphics of Working : Halls Sensors sense the position of the coils The Decoder Circuit turns appropriate switches on and off The voltage through the specific coils turns the motor No Commutators Position of Coils with respect to the magnetic field is sensed electronically. Current is commutated through electronic switches to appropriate phases.
ADVANTAGES OF STEPPER MOTORS The rotation angle of the motor is proportional to the input pulse Excellent response to starting, stopping/reversing The motors response to digital input pulses provides open-loop control It is possible to achieve very low speed synchronous rotation A wide range of rotational speeds can be realized Very reliable since there are no contact brushes in the motor Accuracy of 3 – 5% of a step and this error is non cumulative from one step to the next
166 OzIn 6-Wires 260 OzIn 4-Wires80 OzIn 8-Wire Stepper Motor Stepper MotorStepper Motor NASA rover history - August 09, 2006 Micro stepping RAMS (Robot-Assisted Chopper Driver Micro-Surgery) 25
Application Examples : Stepping your wayFilm Advance Indexing Circuit Board Engine Test Scanning Stand TableEngraving Telescope Capsule Filling Surface Grinding Machine Drive Machine Machine [26 ]
CONCLUSION All types and characteristics of a stepper motor are studied throughout this paper. These are very popular in our day to day life due to a lot of advantages and also in digital control circuits, such as robotics because they are ideally suited for receiving digital pulses for step control