8051 – DC Motor Interfacing

Last Updated on: June 29th, 2022

In our previous tutorial, we saw how to interface the LCD with 8051 in 4-bit mode. In this tutorial, we are going to learn DC Motor Interfacing with 8051. Let’s run….

Suggestion to read

• Motor Driver Working (L293D)

Introduction

When we talk about controlling the robot, the first thing comes into the mind is controlling DC motors. Interfacing DC motor to the microcontroller is very important concept in Robotic applications. By interfacing DC motor to the microcontroller, we can do many things like controlling the direction of the motor, controlling the speed of the motor. This article describes you how to control the DC motor using AT89C51 controller.

A DC motor in simple words is a device that converts electrical energy (direct current system) into mechanical energy. It is of vital importance for the industry today.

The maximum output current of microcontroller pin is 15mA at 5V. But the power requirements of most of DC motors is out of reach of the microcontroller and even the back emf (electro motive force) which is produced by the motor may damage the microcontroller. Hence it is not good to interface the DC motor directly to the controller. So use motor driver circuit in between of DC motor and controller.

DC Motor Interfacing with 8051

Circuit Diagram

• Input 1 – Port 2.0
• Input 2 – Port 2.1
• Enable 1 – Port 2.2
• Enable 2 – Port 2.3
• Input 3 – Port 2.4
• Input 4 – Port 2.5

Working Algorithm

Forward

• EN Pin High  (En1 = 1 or En2 = 1)
• Input 1 or Input 3 Pin High (In1 = 1 or In3=1)
• Input 2 or Input 4 Pin Low (In2 = 0 or In4 = 0)

Reverse

• EN Pin High  (En1 = 1 or En2 = 1)
• Input 1 or Input 3 Pin Low (In1 = 0 or In3=0)
• Input 2 or Input 4 Pin Low (In2 = 1 or In4 = 1)

Code

In this code, the First motor will rotate forward and the second motor will rotate reverse.

#include<reg51.h>

sbit in1=P2^0;
sbit in2=P2^1;
sbit en1=P2^2;
sbit en2=P2^3;
sbit in3=P2^4;
sbit in4=P3^5;

void forward();
void reverse();

void main()
{
    en1=1;
    en2=1;
    while(1) {
        forward();
        reverse();
    }
}

void forward()
{
    in1=1;
    in2=0;
}

void reverse()
{
    in4=1;
    in3=0;
}

Output

[ Please find the output image ]

Notes:

• The maximum current capacity of L293 is 600mA/channel. So do not use a motor that consumes more than that.
• The supply voltage range of L293 is between 4.5 and 36V DC. So you can use a motor falling in that range.
• Mostly in Robotic application, we will use DC gear Motor. So the same logic is used for that Gear motor also.

Tasks

Just try these Tasks.

1. Connect Switch in any port pin. Connect one DC Motor. The motor should rotate whenever I turn on the switch.
2. If i send “F” from serial communication Motor rotate Forward direction. If I send “R”, it should rotate reverse.
3. Program to run a motor based on the external Interrupt

In our next tutorial, we will interface the relay to the 8051.

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