# Introduction

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 or Step Motor for 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

Stepper Motor can be easily interfaced with PIC Microcontroller by using readymade ICs such as L293D or ULN2003. As I said in the article Stepper Motor or Step Motor, we have three different types of stepping modes for unipolar stepper motor.

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.

Wave Drive Stepping Sequence

Step A B C D
1 1 0 0 0
2 0 1 0 0
3 0 0 1 0
4 0 0 0 1

## Full Drive

In this mode two stator electromagnets are energised 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.

Full Drive Stepping Sequence

Step A B C D
1 1 1 0 0
2 0 1 1 0
3 0 0 1 1
4 1 0 0 1

## Half Drive

In this stepping mode, alternatively one and two phases are energised. 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.

Half Drive Stepping Sequence

Step A B C D
1 1 0 0 0
2 1 1 0 0
3 0 1 0 0
4 0 1 1 0
5 0 0 1 0
6 0 0 1 1
7 0 0 0 1
8 1 0 0 1

Bipolar Stepper Motor Windings

## Driving Bipolar Motor

Bipolar motors are simpler in construction as it contains two coil and no centre tap. Being simple, driving is little complex compared to unipolar motors. To reverse the magnetic polarity of stator windings, current through it must be reversed. For this we should use H-Bridge. Here I using L293d, H-Bridge Motor Driver for that. We can distinguish bipolar motors from unipolar motors by measuring the coil resistance. In bipolar motors we can find two wires with equal  resistance.

Bipolar Motor Stepping Sequence

Step A B C D
1 1 0 0 0
2 0 0 1 0
3 0 1 0 0
4 0 0 0 1

# Interfacing Unipolar Stepper Motor with PIC Microcontroller

PIN Diagram of L293D

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.

ULN2003 is a monolithic high current and high voltage Darlington transistor arrays. ULN2003 consists of seven NPN Darlington Transistor pairs that have high-voltage outputs with common-cathode clamp diode for switching inductive loads. The collector-current rating of a single darlington pair can be up to 500mA. We can connect Darlington Transistor pairs in parallel if higher current capability is needed..

## Interfacing using L293D

Interfacing Unipolar Stepper Motor with PIC Microcontroller using L293D Circuit Diagram

Note: VDD and VSS of the pic microcontroller is not shown in the circuit diagram. VDD should be connected to +5V and VSS to GND.

PORTB of PIC Microcontroller is used for controlling the stepper motor.

## Interfacing using ULN2003

Interfacing Unipolar Stepper Motor with PIC Microcontroller using ULN2003

Note: VDD and VSS of the pic microcontroller is not shown in the circuit diagram. VDD should be connected to +5V and VSS to GND.

# 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

```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);
}```

## MikroC Code for Full Drive

```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);
}```

## MikroC Code for Half Drive

```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);
}```

# Interfacing Bipolar Stepper Motor with PIC Microcontroller

Bipolar Stepper Motor can be easily interfaced with PIC Microcontroller using L293D.

## Circuit Diagram

Interfacing Bipolar Stepper Motor with PIC Microcontroller Circuit Diagram

Note: VDD and VSS of the pic microcontroller is not shown in the circuit diagram. VDD should be connected to +5V and VSS to GND.

## MikroC Code

```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);
}```

• -31%

### PIC 16F877A Microcontroller

0 out of 5

This powerful (200 nanosecond instruction execution) yet easy-to-program (only 35 single word instructions) CMOS FLASH-based 8-bit microcontroller packs Microchip's powerful PIC architecture into an 40- or 44-pin package and is upwards compatible with the PIC16C5X, PIC12CXXX and PIC16C7X devices. The PIC16F877A features 256 bytes of EEPROM data memory, self programming, an ICD, 2 Comparators, 8 channels of 10-bit Analog-to-Digital (A/D) converter, 2 capture/compare/PWM functions, the synchronous serial port can be configured as either 3-wire Serial Peripheral Interface (SPI™) or the 2-wire Inter-Integrated Circuit (I²C™) bus and a Universal Asynchronous Receiver Transmitter (USART). All of these features make it ideal for more advanced level A/D applications in automotive, industrial, appliances and consumer applications.

200.00 139.00
• -11%

### ULN2803A Driver IC

0 out of 5

ULN2803A is a one of the most commonly used High Current, High Voltage Darlington Transistor Array IC. It contains 8 NPN darlington  pairs with common cathode clamp diodes for each outputs for switching inductive loads. The current rating of each darlington pair is 500mA and you may connect two or more darlington pairs in parallel to increase current capability. This IC is commonly used in applications such as Relay Driving, Hammer Driving, Lamp Driving, LED and Gas Discharge Display Driving etc.

18.00 16.00
• ### ULN2803A Relay Stepper Motor Driver

0 out of 5

This is a high voltage, high current driver board made using the IC ULN2803, which consists of 8 NPN Darlington Transistor Array with Common Cathode clamp diodes for switching Inductive Loads. Each darlington pairs can drive currents up to 500mA and they may be connected in parallel for higher current capability.

109.00 95.00

• Janelle Serrano Polinga

can you please give me a sample program for five degree freedom robotic arm using servo motor? we are using mikroc in 16f84a as our pic and we are having a hard time solving it. thanks! 😀

• Esala

What does 0x0f mean?I am newbie to mikro c.

• 0x indicates hex code…
0b indicates binary…
0 = 0000 in binary
F = 1111 in binary..
there for .. 0x0f in hex equal to 00001111 in binary..
0x0f = 0b00001111

• jatindecoded

I want four steppers to be controlled from a single PIC16 or ATMega16. I want o have speed control (i.e the steps and the direction to be controlled by the user via a serial hyper -terminal). In that case do I need to use PWMs ?
How many PWMs are there on PIC16F877a ? Would I be able to run four motrs witha single MCU chip and L293D ?

• You needn’t use PWMs as you are using Stepper Motor….
You can adjust speed by changing the delays between steps

• Hafiz

hello, my question… i follow this circuit….. my project i use 2 ldr as input at portA… but motor cannot move. why?? please reply or send to me the program. email :[email protected]… Urgent!!!

• mechaliomar

Hi .1st thx.I need to construct a mobol robot ,so wich kind of motor should i use to control it for forward ;backward;right and left?
Could u give me the code plz?

• You can use Geared DC Motor..
Sorry I haven’t any codes for that…. Read our DC Motor interfacing tutorial..

• mechaliomar

Ligo ,what do you think about stepper motor is it suitable for mobil robot?

• Sorry, I haven’t any experiences with Mobil Robot.

• mechaliomar

Thx Ligo

• RAMYA

how to interface two stepper motor with the pic 16F877

• Same as above.

• George

Hello Ligo,is Micro C code going to work with MPLAB ?

• NO.

MPLAB is an IDE only. MikroC is a compiler + ide.

For MPLAB you have to use Hi-Tech C, XC8 or XC18 etc..

• Don Xavier

Hello Ligo, please upload the program to stop the motor after rotating 50 steps (using 1.8 degree step. 1.8 x 50 = 90 degree )
and need to rotate back to 0 degree position after a few minute delay

• asmaa

hello

I want to vary the speed using a potentiometer and I want to display this speed on an LCD , how to calculate this rate !!

• Kshitij Labhasetwar

Ligo i want to make 5 steps in one revolution…
Pls provide me code for mplab x…
Its urgent..

• Mark Moinjeh

I am Mark, I need a code in MikroC to control the speed of my steeper motor using a potentiometer when the switch is on/ high. Thank you

• Mark Moinjeh

sorry it is stepper motor

• You can use for loop for that.

• You can calculate depending on the number of steps on that stepper motor.

• You can control the speed by adjusting the delay in each step and reading the potentiometer using adc.

• Rakesh

HI…Ligo geroge
. I want to rotate unipolar stepper motor with atmega16a
and i configure it with following code

#include

#include

int main()

{

DDRA = 0xFF; //All pins of PORTB as output

PORTA = 0x00; //Initially all pins as output high

while(1)

{

PORTA = 0x01; //0001

_delay_ms(10);

PORTA = 0x04; //0100

_delay_ms(10);

PORTA = 0x02; //0010

_delay_ms(10);

PORTA = 0x08; //1000

_delay_ms(10);

}

return 0;

}
and common terminal connected to vcc

its not rotating properly

will you suggest me any solution

• Sorry, the above article is not about Atmega. Please use our forums ( https://electrosome.com/forums ) for asking doubts outside the scope of above article.

Hi.. Ligo George
I want to rotate my stepper motor for 1.8 degree. For that what process i should follow. If i run this above program its working well and good but the rotation is about 45 degree for every cycle.

• It depends on the minimum stepping angle of your motor. What is minium step ?