Digital alarm clock with 8051(89c51) microcontroller

Digital alarm with 8051(89c51,89c52) microcontroller is a comprehensive project. Comprehensive in the form that its code is very lengthy. Programming is not an easy stuff for every one , and when it comes to program a microcontroller it becomes more complex to write a code for desired output if you are not familiar with the basics of programming. Digital alarm with 8051(89c51,89c52) microcontroller is an extension of digital clock with 8051(89c51,89c52) microcontroller project. The alarm works in the same way as your digital watches and mobile phone alarms works. Well all alarms works same 😀

8051 microcontroller digital alarm – Project requirements

8051(89c51 or 89c52) microcontroller
alarm(I used buzzer)
16×2 lcd
Potentiometer/variable resistor (For setting lcd contrast)
4×3 keypad(You can also use 4×4. 4×4 contains 4×3 in it :D)
Crystal(11.0592 MHz)
Bread board(Designing circuit. You can also design circuit on PCB(Printed circuit board))

Tutorials regarding 8051 digital alarm clock project

Its not possible to explain each and every statement of code. For example 16×2 lcd interfacing with 8051 microcontroller or 4×4 numeric keypad interface with 8051 microcontroller or how to generate proper time delay using internal timers of 89c51 microcontroller can not be explained in a single tutorial. So i made multiple tutorials on each component which is part of this project.

All the above tutorials play a vital role in 8051 digital alarm clock project. I will say the code of all the above tutorials is part of this project. I just arranged the code in sequence with some minor modifications and made a stream line code flow to achieve digital alarm clock functionality.

Digital alarm clock – Code flow

when you first run the program you have to set the clock time same like the digital clock project(Link given above). Once you set the clock time it will start running for ever unless you reset the microcontroller. Now when ever you want to set an alarm press the button located in first coulomb and at fourth row of 4×3 keypad. Pressing the button will lead to an event which displays messages on 16×2 lcd to set hours and minutes. Now set alarm time.

Note: No external RTC(real time clock) is interfaced with 8051 microcontroller for time calculation. Rather internal timers of 89c51 mirocontroller are utilized for producing clock time(Visit above digital clock with 89c51 tutorial).

89c51 microcontroller digital alarm – Circuit diagram

The circuit for the project is very simple. Connect 16×2 lcd with Port 1 of 8051 (89c51 or 89c52) microcontroller. Rd(read) Wr(write) and En(enable) signals are provided to 16×2 lcd using port 3 pins 5 , 6 & 7 of 8051 (89c51 or 89c52) microcontroller. Port 0 pin 0 is used to operate buzzer when ever alarm time reached to its matched clock time. Port 2 is dedicated for our 4×3 keypad. Rows are connected to pin 0, 1 ,2 & 3 of port 2. Coulombs are connected to pins 5 , 6 & 7 of port 2. Rest of the connections are simple apply 5v to pin 40 and pin 31. Connect crystal 11.0592 MHz to pins 18 and 19. Ground pin 20. Connect reset button to pin 9.

8051 microcontroller digital alarm clock

89c51 microcontroller digital alarm clock – Project code

Coming to the code. First i included the necessary header file reg52.h. This header file should be included when ever you are writing and compiling your 8051 microcontroller program in keil ide. It includes all the necessary linker and debuggers for 8051 microcontroller configuration.

Then keypad() function is declared. This function scans the keys pressed on the 4×3 keypad. Next comes tochar() function. It is used to deal with integer type numbers to be displayed on the 16×2 lcd. Integer numbers must be converted to 8-bit character format for displaying on 16×2 lcd.

Then single bits of ports are declared for connecting our buzzer and 4×3 keypad. Next character arrays are declared they are used as messages to be displayed on 16×2 lcd on suitable conditions. delay() function is used to generate some delay for suitable purposes. lcdcmd() function is sending commands to lcd. lcddata() function is sending and printing data on lcd screen. checkconditions() function is checking conditions like if seconds reached to 60 increment the minute, if minutes reached to 60 increment hour, check if clock reached the alarm time ring the buzzer.

clockdelay() function is producing seconds, minutes and hours for us. lcdinit() initializing the lcd. settime() function is setting time of clock on every reset of the program. User have to input the time using 4×3 keypad. start() function is printing the time on 16×2 lcd at start of the program execution.

The above tutorials are very important if you want to understand the functions used in the code. If you don’t care about code than just burn the hex code make the circuit and enjoy your creation 😀

The alarm is 12 hours alarm which means you can put-on alarm for maximum next 12 hours period. Do not enter hours greater than 12 and do not enter minutes greater than 60. If you want to make the alarm more intelligent just insert more functions in it like set alarm for am or pm time. Do some other work when ever clock time reaches the alarm time like switch on a bulb, start your water motor to fill the tank or switch off the oven. If you are really willing to do some extra stuff than go a head and give me your feedback.

Download the project code and hex file compiled in keil Uvision-2. If you have any questions regarding code or any thing just leave a comment below.Your comments are highly apreciated.

Digital alarm code