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  • PIC16F84A Based Alarm Clock

  • Created: May 25, 2016

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Description

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Summary

An alarm clock is a device designed to sound at a specific time it was set. It can be used to awaken people from sleeping or short naps. Sometimes it is also used for other reminders. Old types of alarm clocks have an extra hand or inset dial that is used to specify the time at which to activate the alarm. Other traditional alarm clocks are mechanical in nature. They have bells that ring by means of mainspring that powers a gear to drive a hammer back and forth between the interior sides of a single bell. Nowadays, digital alarm clocks are widely used as compared to its analog alarm clocks predecessors.


This reference design is just a simple digital alarm clock. The circuit is comprised mainly of PIC16F84A microcontroller, a 4-digit seven-segment display, and few discrete components. This alarm clock design counts seconds, minutes, hours and days of a week. The time is displayed on the LED displays, and is adjustable with three pushbuttons at the start time. These pushbuttons are up, down, and enter which adjust the time incrementally, detrimentally and set the alarm respectively. The PIC16F84A microcontroller can be programmed to set the alarm at a certain day, hour, minute, and duration of the alarms. The number of alarms are only limited on the ROM space of the microcontroller. A buzzer can be connected to the RA4 open collector output of the microcontroller.


In this design, the 4-digit seven-segment display is connected to the pins RB0-RB7 pins of the PIC16F84A microcontroller. These pins are bi-directional I/O ports that can be programmed for internal weak pull-up on all inputs. This design simply explores the capability of the PIC16F84A to be programmed to function as an alarm clock.