STEPER MOTOR CONTROL
STEPER MOTOR CONTROL USING AT89S52
Stepper motor is found with finds lot applications in computer peripherals, business machines, process control, machine tools and robotics. Especially in robotics and process control like silicon processing, I.C.Bonding and Laser trimming applications, it is necessary to control the stepper motor from remote places. This project is to control the stepper motor using switches. This deals with the design and development of hardware and software for Stepper motor control system.
Three switches are used to control the direction of the stepper motor. When the corresponding switches are pressed the stepper motor turns in clockwise, anticlockwise and stops respectively.
16 X 2 Liquid Crystal display (LCD) is provided to display the status of the stepper motor. ULN driver is used to drive the stepper motor.
This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac out put of secondary of 230/12V step down transformer.
POWER SUPPLY:
The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any a.c components present even after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.
Transformer:
Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a required level.
Rectifier:
The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification.
The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles of the input ac voltage. The Bridge rectifier circuit is shown in the figure. The circuit has four diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge. The load resistance is connected between the other two ends of the bridge.
For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct, whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in series with the load resistance RL and hence the load current flows through RL.For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series with the load resistance RL and hence the current flows through RL in the same direction as in the previous half cycle. Thus a bi-directional wave is converted into a unidirectional wave.
Filter:
Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage.
CAPACITOR FILTER : figure 2 shows a typical capacitor filter
circuit.
It consists of a capacitor C placed across the rectifier output in parallel with load RL. The pulsating direct voltage of the rectifier is applied across the capacitor. As the rectifier voltage increases, it charges the capacitor and also supplies current to the load. At the end of quarter cycle [point A in figure(iii)], the capacitor is charged to the peak value Vm of the rectifier voltage. Now, the rectifier voltage starts to decrease. As this occurs, the capacitor discharges through the load and voltage across it (i.e. across parallel combination of R-C) decrease as shown by the line AB in figure(iii). The voltage across load will decrease only slightly because immediately the next voltage peak comes and recharges the capacitor. This process is repeated again and again and the output voltage wave form becomes ABCDEFG. It may be seen that very little ripple is left in the output . Moreover, output voltage is higher as it remains substantially near the peak value of rectifier output voltage.
The capacitor filter circuit is extremely popular because of its low cost, small size , little weight and good characteristics. For small load currents (say upto 50mA), this type of filter is preferred. It is commonly used in transistor radio battery eliminators
Voltage regulator:
As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. In this project, power supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812 voltage regulators are to be used. The first number 78 represents positive supply and the numbers 05, 12 represent the required output voltage levels. The L78xx series of three-terminal positive regulators is available in TO-220, TO-220FP, TO-3, D2PAK and DPAK packages and several fixed output voltages, making it useful in a wide range of applications. These regulators can provide local on-card regulation, eliminating the distribution problems associated with single point regulation. Each type employs internal current limiting, thermal shut-down and safe area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1 A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltage and currents.
VOLTAGE STABILISATION :
A rectifier with an appropriate filter serves as a good source of d.c. output. However , the major disadvantage of such a power supply is that the output voltage changes with the variations in the input voltage or load. Thus if the input voltage increases, the output voltage of the rectifier also increases. Similarly, if the load current increases, the output voltage falls due to the voltage drop in the rectifying element filter chokes , transformer winding etc. In many electronic applications, it is desired that the output voltage should remain constant regardless of the variations in the input voltage or load. In order to ensure this, a voltage stabilizing device, called voltage stabilizer is used. Several stabilizing circuits have been designed but only Zener diode as a voltage stabilizer will be discussed.
CHARACTERISTICS :
 +5 V output , o/p current capability of 100 mA
 Built – in over heating rating protection shuts down o/p when regulator IC gets too hot.
 Very stable 5V o/p voltage , reliable operation .
 Easy to get , uses only very basic components .
APPLICATIONS :
Part of the electronic devices , small laboratory power supply.
GENRALE DISCRIPTION
Micro controller based stepper motor control kit is used for many industrial electronics & mechanical application. There are 4 types of function in this kit (1) left (2) right (3) stop (4) speed (For RPM). There are many kinds of stepper motor but in this kit you can control 2 phase UNI-POLAR PM (permanent magnet) type motor. The main advantage of this kit is, fully microcontrolled based so easy to understand, very few components are required, and circuit become compact. It is to control a turn position correctly like the drive motor of the printer & so on. The circuit this time controlled the number of rotation of the motor by the charging of the capacitor but can control a turn angel in the drive motor of times (The step) if remodeling program.
TECHNICAL SPECIFICATION
 WORKING VOLTAGE - 6 TO 12V AC/DC
 OPRATING CURRENT - 100MA (WITHOUT MOTOR)
 KIND OF MOTOR - 2 PHASE UNI POLAR PM TYPE
 DRIVE VOLTAGE - 12VDC
 COIL CURRENT - 1 AMP (2 COILS)
 STEP ANGEL - 7.5 DEGREES (360D/48)
 (DEPENDS ON STEPPER MOTOR)
 THE MOST LOW SPEED - 27 RPM
 THE FULL SPEED - 128 RPM
BASIC DISCRIPTION OF STEPPER MOTORS
Stepper motors are a special type of motor. Instead of rotating smoothly, they move incrementally - in steps. Each step is a fixed angular displacement of the motor’s shaft. For example, if the step increment is 3.6, then 100 steps are required for a complete 360 rotation of the shaft. There are two types of stepper motors: