Microcontroller based four step linear stroke positioning system
PROCESSOR UNIT Microprocessor is widely used processer unit forprocessing the large set of data and instruction given byuser.It has only the CPU unit and require externalRAM, ROM, I/O and other peripheral. To perform the small set of specificfunction, Microprocessor is a expensive and bulkiercercuit. To overcome the problem, we use a low cost andsimpler circuit chip, called Microcontroller. Microcontroller is a mini computer on a singleintegrated circuit chip containing a processor
Microcontroller 8051 has 4K ROM(code memory) and128 byte RAM, two timer/counter, 4 general purposeinput/out port and interrupt control logic with 5 sourse.
PROJECT INTRODUCTION In the project a microcontroller based unipolar steppermotor used to creat a four stroke linear positioningsystem, this system can move up and down, along withthe floor. The opening and closing of this linear strokepositioning doors are displayed on the green and redLED’s respectively.The positioning is controlled by four micro- switches. The control program is developed in “C” language andconverted into executable or in HEX language by AVR-GCCcompiler.
LIST OF COMPONENTS REQUIRED FULL WAVE BRIDGE RECTIFIER WITH 4 IN4001DIODES, 220/12V TRANSFORMER(SINGLE PHASE)AND 1000UF CAPACITOR. LM7805 VOLTAGE RAGULATOR. 89C51 MICROCONTROLLER. UNIPOLAR STEPPER MOTOR. ULN2003 STEPPER MOTOR DRIVER. LCD(16*2) TWO ORDINARY LED’S (GREEN AND RED)
STEPPER MOTER Stepper moter is a microcontroler controlled DC moterthat can rotate in both direction and having a holdingtorque at zero speed. Stepper motors are rated with a varying degree ofinductance.A high inductance motor will provide a greater amount oftorque at low speeds and lower torque at high speeds. Stepper motor is designed to run hot between the rangesof 50-90 degree.
On the bases of wire arrangement stepper motor arecategorized into two types- 1. Unipolar stepper motor 2. Bipolar steppermotor.Center taps are present Center taps are not present so have two winding/phase so Have single winding/phase Less efficient because of More efficient(50% more 50% utilization of wire. then unipolar)Provide Low torque High torque & great power
Why we Prefer Unipolar Stepper Motor instead of Bipolar Stepper Motor- In Bipolar Stepper Motor we require a H-bridgecomplicated driver circuit to reverse the current direction inwinding, which is costely and motor efficiency decreases.But Unipolar Stepper Motor has two windings perphase, one for each direction of magnetic field, so in thisarrangement a magnetic pole can be reversed withoutreverse the direction of current. Unipolar Stepper Motor can be control using bipolarmethod by removing the connection of the common wiresbut reverse is not possibal.
STEPPER MOTER WITH MICROCONTROLLER Stepper motors with microcontrollers are used innumerous applications when there is need of controllingthe motion. The microcontroller is used to controls the speed as wellas position of stepper motor. The speed of stepper motor isdirectly proportional to the frequency of drive input pluseswhich is controllable with the help of microcontrollers andthe rotation is proportional to the number of output pulses. The speed of stepper motor is controlled by changing thedelay time of pulses and control over position is done bythe number of pulses.
STEPPER MOTOR DRIVER Microcontroller output pulse is not sufficient to drive thestepper motor, stepper motor’s coil need arround 10mA toenergize but the microcontroller’s pin can provide amaximum of 1-2mA current, so we use a driver cercuit tooperate the stepper motor. Driver cercuit is basically a current amplifier, that receivelow level signals from the controller and convert them intoelectrical pulses to run the motor. TYPES OF STEPPER MOTOR DRIVER- R/L DRIVER BIPOLAR DRIVER UNIPOLAR DRIVER
RESISTANCE LIMITED DRIVER The drives are too old as compared to the driver’stechnology. They only exist in some application becausethey are simple and inexpensive. BIPOLAR DRIVERThese driver used in bipolar stepper motor for industrialpurpose applications. These drives are more expensive butthey offer high performance and efficiency.
UNIPOLAR DRIVER CERCUIT ( ULN2003A ) It is used to drive unipolar stepper motor. Phase winding of motor have large inductance, thereforein series in each phase winding a resistance is inserted toreduce the circuit time constant. A resistance is alsoplaced in series with the diode in order to dissipate theenergy stored in the phase winding inductance.
FULL WAVE BRIDGE RECTIFIERFull wave bridge rectifier is used to convert the ac supplyinto dc supply.For this purpose four IN 4001 general purpose diodes isused in bridge configuration. An electrolytic capacitor of 1000 microfarad isconnected parallel with these diodes to filter-out theharmonics present in the DC output supply.
LM7805 VOLTAGE REGULATORLM7805 voltage regulator is used to generating outputcurrent of 1A and for changing 12V DC to 5DC.It provides thermal overload protection and short circuitprotection to the connected device.LM7805 have lower power consumption and providesbetter voltage regulation to the connected system.
LIQUID CRYSTAL DISPLAY (LCD)A LCD(liquid crystal display) is specifically menufacturedto be used with microcontroller, it cannot be activated bystandard IC cercuit.It is used for displaying different massages on a liquidcrystal display.It display all the letters of alphabet, mathematicsymbols, Greek letters etc. In addition, it is possible todisplay symbols made up by the user.Other usel features are automatic massage sift(left toright) and cursor appearance.
PROJECT DISCRIPTIONThe design project is divided into four step of equaldistance step.The stepper motor is connected to the 4 stroke linearlifting pulley with belt.The stepper motor pulley will took 40full rotations to liftthe 4stroke linear positioning to cover the distance fromone step to another.The LCD display the real time information about the 4stroke linear positioning.At desired location green LED glow which represent theopening of 4 stroke linear positioning door and after fivesec delay green LED off and red LED glow whichrepresents the closing of 4 stroke linear positioning door.
Stepper motor covers 7.5 degree rotation in one step sowe fix 40 such full rotation that moves this motor to onedesired floor .No. of steps are given by microcontroller to the steppermotor driver.For each floor position we have fixed a micro-switch.When we press switch for first floor 40 rotations areselected by controller and we reach to desired floor and ifwe want to go to second floor we select second switchwhich provide 80 full rotation of stepper motor and so on.