PROJECT ON MICROCONTROLLER BASED STEPPER MOTOR

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MICROCONTROLLER

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PROJECT ON MICROCONTROLLER BASED STEPPER MOTOR:

PROJECT ON MICROCONTROLLER BASED STEPPER MOTOR BY : AMIT SHANDILYA

INTRODUCTION:

INTRODUCTION 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 (please refer What is 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 micro controlled 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 SPECIFICATIONS:

TECHNICAL SPECIFICATIONS 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 DESCRIPTION OF STEPPER MOTORS:

BASIC DESCRIPTION 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.

TYPES OF STEPPER MOTORS:

TYPES OF STEPPER MOTORS There are two types of stepper motors : Unipolar stepper motor Bipolar stepper motor

UNIPOLAR STEPPER MOTOR:

UNIPOLAR STEPPER MOTOR These have two center-tapped coils, which are treated as four coils. These motors can have five, six or eight wires. Five-wire motors have the two center-taps commend internally and brought out as one wire . Six-wire motors bring out each center-tap separately. The two center-taps need to be commending externally . Eight-wire motors bring out both ends of each coil. The four “center-taps” are joined externally to form one wire. In each case the center-tap(s) are connected to a positive motor power supply

5-WIRE STEPPER MOTOR:

5-WIRE STEPPER MOTOR

6-WIRE STEPPER MOTOR:

6-WIRE STEPPER MOTOR

8-WIRE STEPPER MOTOR:

8-WIRE STEPPER MOTOR

BIPOLAR STEPPER MOTOR:

BIPOLAR STEPPER MOTOR These have two coils and are controlled by changing the direction of the current flow through the coils in the proper sequence. These motors have only four wires and cannot be connected to this kit. They are declining in availability.

OPERATION PRINCIPLE OF STEPPER MOTOR:

OPERATION PRINCIPLE OF STEPPER MOTOR In the PM type stepper motor, a permanent magnet is used for rotor and coils are put on stator. The stepper motor model, which has 4-poles, is shown in the figure 1A. In case of this motor, step angle of the rotor is 90 degrees. As for four poles, the top and the bottom and either side are a pair. X1 coil, X2 coil and Y1 coil, Y2 coil correspond respectively. For example, Y1 coil and Y2 coil are put to the upper and lower pole. Y1 coil and Y2 coil are rolled up for the direction of the pole to become opposite when applying an electric current to the Y1 coil and applying an electric current to the Y2 coil. It is similar about X1 and X2, too. The turn of the motor is controlled by the electric current, which pours into X1, X2, Y1 and Y2. The rotor rotational speed and the direction of the turn can be controlled by this control.

Slide 13:

You can find by the figure, the rotor is stable in the middle of 2 poles of stator. When one side of the stator polarity is changed, the bounce by the magnetism occurs. As a result, the direction of rotor's turn is fixed. The characteristic of stepper motor is the angle can be correctly controlled and to be stable rotates (It is due to the reliability of the control signal). Moreover, because the rotor is fixed by the magnetism in the stationary condition as shown in the principle, the stationary power (Stationary torque) is large. It suits the use to make stop at some angle. The Motor, which was used this time, is 48 steps and the step angle is 7.5 degrees. The way of controlling is the same as the previous example completely. It operates when controlling the electric current of X1 coil, X2 coil, Y1 coil and Y2 coil. The case of the clockwise control is shown below.

CLOCKWISE CONTROL:

CLOCKWISE CONTROL

ANTICLOCKWISE CONTROL:

ANTICLOCKWISE CONTROL

MOTOR DRIVING CIRCUIT:

MOTOR DRIVING CIRCUIT This is the circuit, which drives the coil of stepper motor. There are circuits, which drive X1 coil, X2 coil, Y1 coil and Y2 coil respectively. Darlington connection-type transistor (Q1&Q2) is used for the drive of the coil. As for the Darlington connection, 2 stages of transistors are connected inside in series. The " hfe " of this transistor is the multiplication of the " hfe " of each transistor inside. In case of Q1 & Q2, which was used this time, the hfe is over 4000. Because the ratio of the input electric current and the output current is big, the rising edge and the falling edge of the control signal can be made sharp. The diode to be putting between the collector and the power is for the protection of the transistor. When the transistor becomes OFF from ON, the coil of the motor tries to continue to pass an electric current and generates high voltage. An electric current by this voltage is applied to the diode and the high Voltage, which applies over the transistor, is prevented. TO

SPEED CONTROL CIRCUIT:

SPEED CONTROL CIRCUIT

SPEED CONTROL CIRCUIT:

SPEED CONTROL CIRCUIT This is the circuit is controls the rotational speed of the motor. TR1 becomes ON condition when RB7 becomes H level. In this condition, the electric charge of capacitor C1 flows through the transistor and the voltage of the both edges of the capacitor become 0V almost. When RB7 becomes an L level, the transistor becomes OFF condition. In this condition, the electric current flows through VR1 and R4 into capacitor C1 and the charging to the capacitor begins. The voltage of the both edges of the capacitor becomes high gradually as charging is done. The voltage of the capacitor is detected by RB5. The software of PIC interrupts the control of the motor until it checks RB5 after making RB7 an L level and RB5 becomes H level. When making the value of VR1 small, the charging time of the capacitor is short and the control of the motor becomes quick. The control of the motor becomes slow when making VR1 big. The speed control, range can be changed by changing the value of the capacitor.

START – STOP CIRCUIT:

START – STOP CIRCUIT This is the circuit for the clockwise rotating, the counterclockwise rotating or stopping a motor. The baton switch of the Non lock is used. Pull-up resistor is used for the port to become H level when the switch is OFF. The RB port of PIC16F84A has an internal pull up feature. However, because RB5 is used for the voltage detection of the capacitor at the circuit this time, an internal pull up feature isn't used. If using RA port for the voltage detection of the capacitor, the RB internal pull up feature can be used. The circuit this time put an external pull-up resistor in the relation of the pattern

START STOP CIRCUIT:

START STOP CIRCUIT

PCB ASSEMBLY LAYOUT:

PCB ASSEMBLY LAYOUT

CIRCUIT DIAGRAM:

CIRCUIT DIAGRAM

STEPPER MOTOR (42SPM -24DCZA) :

STEPPER MOTOR (42SPM -24DCZA) This is a 2-phase Uni - polar PM type stepper motor with 48-poles. Step angle - 7.5 degrees (360 degrees/48) Drive voltage - 6V to 48V (as per motor) Coil current - 250Ma 2 coils (as per motor)

2] PIC16F84A (Microcontroller) :

2] PIC16F84A (Microcontroller) The control of the stepper motor is done by this PIC. X1 coil, X2 coil, Y1 coil and Y2 coil are controlled by the software. For more information please refer Data sheet 0f PIC16F84A

LM7805 :

LM7805 3 terminal Positive Voltage regulator. This is used to make the stable voltage of +5V for microcontroller. The LM7805 is three terminal positive regulators are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output current. Although designed primarily as fixed voltage regulators, More information please refer Data sheet 0f LM7805

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