Hey friends this is my 3rd year BE project ” Speed control of DC motor“which i could like to share with you .In this you will learn how to interface LCD,hex keypad and motor .The code is written in assembly
to simplify I have first explained separately LCD interfacing hex keypad interfacing ,motor interfacing with L293D
so Lets get Started !!!
Step 1: Materials Required
*89S52
*LCD
*Hex keypad
*DC motor
I assume u have basic knowledge of 8051 programming in assembly
Step 2: Interfacing DC Motor -L293D
L293D is a dual H-Bridge motor driver, So with one IC we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction we can control speed of each dc motor by giving PWM to enable pin .L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF ouput diodes are included within the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a best choice for DC motor driver.
As you can see in the circuit, three pins are needed for interfacing a DC motor (A, B, Enable). If you want to control speed enable pin is connetcted to the PWM pin of microcontroller . I have connected only one motor and used the enable pin to contol the speed of dc motor.
Step 3: Interfacing LCD
LCD consist of 16 pin
Vss-GND
Vdd-positive voltage
Vee-contrast setting
data pin D0 to D7
backlight pin LED and LED-
The LCD requires 3 control lines (RS, R/W & EN) & 8 (or 4) data lines.When RS is low (0), the data is to be treated as a command. When RS is high (1), the data being sent is considered as text data which should be displayed on the screen.
When R/W is low (0), the information on the data bus is being written to the LCD. When RW is high (1), the program is effectively reading from the LCD. Most of the times there is no need to read from the LCD so this line can directly be connected to Gnd thus saving one controller line.The ENABLE pin is used to latch the data present on the data pins. A HIGH – LOW signal is required to latch the data. The LCD interprets and executes our command at the instant the EN line is brought low. If you never bring EN low, your instruction will never be executed.
Read more: gsm based dc motor speed control using pic microcontroller