A Stepper Motor is a brushless, synchronous DC electric motor, which divides the full rotation into a number of equal steps. It finds great application in field of microcontrollers such as robotics. Please refer the article Stepper motor explainedfor detailed information about working of stepper motor, types and modes of operation. Unipolar Motor is the most popular stepper motor among electronics hobbyist because of its ease of operation and availability. Here I explaining the working of Unipolar and Bipolar Stepper Motor with PIC 16F877A Microcontroller.
- Unipolar Stepper Motor Windings
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Note: 1 – Represents Supply Voltage and 0 – Represents Ground
Wave Drive
In this mode only one stator electromagnet is energised at a time. It has the same number of steps as the full step drive but the torque is significantly less. It is rarely used. It can be used where power consumption is more important than torque.
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In this mode two stator electromagnets are energized at a time. It is the usual method used for driving and the motor will run at its full torque in this mode of driving.
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In this stepping mode, alternatively one and two phases are energized. This mode is commonly used to increase the angular resolution of the motor but the torque is less approximately 70% at its half step position (when only a single phase is on). We can see that the angular resolution doubles in Half Drive Mode.
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- Bipolar Stepper Motor Windings
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L293D and L293 are dual H-bridge motor drivers. The L293D can provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V while L293 can provide up to 1A at same voltages. Both ICs are designed to drive inductive loads such as dc motors, bipolar stepping motors, relays and solenoids as well as other high-current or high-voltage loads in positive-supply applications. All inputs of these ICs are TTL compatible and output clamp diodes for inductive transient suppression are also provided internally. These diodes protect our circuit from the Back EMF of DC Motor. In both ICs drivers are enabled in pairs, with drivers 1 and 2 are enabled by a high input to 1,2EN and drivers 3 and 4 are enabled by a high input to 3,4EN. When drivers are enabled, their outputs will be active and in phase with their inputs. When drivers are disabled, their outputs will be off and will be in the high-impedance state.
- PIN Diagram of L293D
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Interfacing using L293D
- Interfacing Unipolar Stepper Motor with PIC Microcontroller using L293D Circuit Diagram
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PORTB of PIC Microcontroller is used for controlling the stepper motor.
Interfacing using ULN2003
- Interfacing Unipolar Stepper Motor with PIC Microcontroller using ULN2003
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MikroC Programming
Since same pins of PIC Microcontroller is used for controlling Stepper Motor in both circuits, we can implement Wave, Full and Half Drives in the same circuit just by changing the program.
MikroC Code for Wave Drive
Code: Select all
void main()
{
CMCON = 0x07; // To turn off comparators
ADCON1 = 0x06; // To turn off analog to digital converters
TRISB = 0; // PORT B as output port
PORTB = 0x0F;
do
{
PORTB = 0b00000001;
Delay_ms(500);
PORTB = 0b00000010;
Delay_ms(500);
PORTB = 0b00000100;
Delay_ms(500);
PORTB = 0b00001000;
Delay_ms(500);
}while(1);
}
Code: Select all
void main()
{
CMCON = 0x07; // To turn off comparators
ADCON1 = 0x06; // To turn off analog to digital converters
TRISB = 0; // PORT B as output port
PORTB = 0x0F;
do
{
PORTB = 0b00000011;
Delay_ms(500);
PORTB = 0b00000110;
Delay_ms(500);
PORTB = 0b00001100;
Delay_ms(500);
PORTB = 0b00001001;
Delay_ms(500);
}while(1);
}
Code: Select all
void main()
{
CMCON = 0x07; // To turn off comparators
ADCON1 = 0x06; // To turn off analog to digital converters
TRISB = 0; // PORT B as output port
PORTB = 0x0F;
do
{
PORTB = 0b00000001;
Delay_ms(500);
PORTB = 0b00000011;
Delay_ms(500);
PORTB = 0b00000010;
Delay_ms(500);
PORTB = 0b00000110;
Delay_ms(500);
PORTB = 0b00000100;
Delay_ms(500);
PORTB = 0b00001100;
Delay_ms(500);
PORTB = 0b00001000;
Delay_ms(500);
PORTB = 0b00001001;
Delay_ms(500);
}while(1);
}
Bipolar Stepper Motor can be easily interfaced with PIC Microcontroller using L293D.
Circuit Diagram
- Interfacing Bipolar Stepper Motor with PIC Microcontroller Circuit Diagram
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MikroC Code
Code: Select all
void main()
{
CMCON = 0x07; // To turn off comparators
ADCON1 = 0x06; // To turn off analog to digital converters
TRISB = 0; // PORT B as output port
PORTB = 0x0F;
do
{
PORTB = 0b00000001;
Delay_ms(500);
PORTB = 0b00000100;
Delay_ms(500);
PORTB = 0b00000010;
Delay_ms(500);
PORTB = 0b00001000;
Delay_ms(500);
}while(1);
}
Article courtesy of electrosome.com