Microcontroller based Digital Alarm Clock Circuit with Working

A clock built with an alarm is called as an alarm clock, that includes a preset time to remember something or awaken people at that time by generating an alarm. Alarm clocks work as reminders to wake up people in a preset time. These clocks are designed with buzzers, sensors and lights to alert the persons. The sound of an alarm can be stopped by pressing the button or automatically stop by producing beep sound in particular time duration. The modern alarm clocks are designed with convert spy cameras or AM/FM radios. These alarms can come in both the traditional or digital form with a variety of cartoon models. This article discusses about a digital alarm clock with digital clock circuit diagram and its working.

What is a Digital Alarm Clock

A digital clock is a one kind of clock used to display the time in the form of digital includes  symbols or numerals. These clocks are frequently connected with electronic drives, but the term digital  refers only to the LCD display, not to the drive mechanism. The digital clock circuit uses the 50-60hz oscillation of AC power.Most digital alarm clocks display the hour of the day in the form of 12 hours or 24 hours with an indication of AM or PM. Most digital alarm clocks use LCD display, seven segment display or VFD.

Digital clocks run with mains electricity and must be reset the time when the power is off. Most of the clocks don’t have a battery back up, so this will cause to fail to generate an alarm sound at the fixed time. To overcome this problem, many digital alarm clocks are available to operate with a battery during the power outage. Commercial digital clocks are generally more consistent than consumer clocks. Because, these clocks give backup to maintain the time using multi decade battery during power off.

8051 Microcontroller based Digital Alarm Clock with LCD Display

The required components of this 8051 microcontroller based digital clock circuit with LCD display mainly include LCD display, AT89C51 Microcontroller, Preset, piezo buzzer and speaker. The function of each and every component of this project is discussed below.

LCD Display

A 16×2 LCD display is an electronic display and it is used in a wide range of applications.These kind of displays is used in a multi segment LEDs an 7-segment displays. In this LCD display, each character is shown in 5×7 pixel matrix. This LCD display consists of two registers, they are data register and command register. A command register is an order for  LCD display to do a task like clearing of its screen, initializing, controlling of display and cursor position setting. The data (ASCII value of the character) register is used to display the stored data on LCD display.

Microcontroller AT89C51

AT89C51 microcontroller belongs to 8051 microcontroller. It has 128 bytes of RAM and 4kb of PEROM. It can be deleted and reprogram to a max of 1000 times. It consist of 40-pins and that are separated into four ports, namely P1, P2, P3 and P4. These four ports are 8-bit bidirectional ports. Except Port P0, remaining ports are used as both i/p and o/p ports

Ports P0 & P2 are used to offer high and low byte addresses when these ports are connected to an external memory. Port 3 consist of multiplexed pins for distinctive functions such as hardware interrupts, serial communication, timer i/ps and read or write operation from external memory. This microcontroller has an integral UART for serial communication. The operation of the UART can be done based on the program at different baud rates.

Preset

Preset is a three terminal electronic component, used to vary resistance in a circuit by adjusting the rotary control on it.The controlling can be done by using a similar tool and a screw driver. The resistance does not fluctuate linearly, but slightly varies in logarithmic or exponential manner. Such variable resistors are used to adjust sensitivity with a sensor. The variable resistance is acquired across the front terminal and remaining two other back terminals. The backside two terminals offer stable resistance which is separated from the front leg. So whenever the back two terminals are used, it acts as a stable resistor. Presets are stated by their static value resistance.

Piezo Buzzer

The piezo buzzer is used to produce sound based on the opposite of the piezoelectric effect. This buzzer can be used to give an alert to a user of an event equivalent to a switching action, sensor input or counter signal. Piezo buzzer is used in alarm circuits.

Buzzer

A buzzer is a transducer that alters electrical energy into sound. When an electric signal is applied to the i/p pin of the speaker then it produces sound waves. The remaining pin is connected to GND terminal. A speaker is normally used to generate sound in response to a o/p of the sensor. For instance, in an intruder alarm, whenever an interruption takes place the speaker goes on

Digital Clock Circuit Diagram

This is an enhanced version of digital clock circuit with an LCD display. It has an extra feature to set the alarm in the first. To reset, the display stimulates the user to set an alarm. By pressing the corresponding switches continuously components can be set. These switches are active low switches and they can provide ground to the equivalent i/p pins of the microcontroller. The AM and PM mode is fixed by the moving the switch between VCC and GND terminal. GND would fix the CLK in AM mode while Vcc would set in PM mode

After the alarm is fixed, the pin of an alarm is connected to VCC through the switch. The process of setting  the time reminds the same as with a simple digital clock. When the time of the digital clock becomes equivalent to the alarm time, a message Alarm is shown on the LCD and the alarm pin of AT89C51 microcontroller goes high for some duration. This alarm pin can be associated to a buzzer or speaker to generate the alarm at the pre-set time.

This is all about digital clock circuit, which is designed by using a Microcontroller AT89C51, Preset, Piezo Buzzer, Buzzer and an LCD display. We hope that you have got a better understanding of this digital alarm clock project. Furthermore, any queries regarding this concept or electronics projects please give your feedback by commenting in the comment section below. Here is a question for you, what are the applications of the digital alarm clock?

Photo Credits:

• Digital Alarm Clock tuvie
• LCD Display wikimedia
• Microcontroller AT89C51 electrosome
• Preset engineersgallery
• Piezo Buzzer hiwtc
• Buzzer spacekraft