Kitchen Timer Built Around PIC16F84 Microcontroller

The device makes use of a PIC16F84 microcontroller in order to create a kitchen timer that may be used to time spaghetti or an egg.

Two PICs are being used by the timer where one is used to drive the display and supports the functions of the timer and the other functions as a keyboard encoder. The keyboard encoding was done by one PIC and the display driving by another since the PIC16F84 does not have enough I/O lines to drive the display and keyboard. The accuracy of the device is 1/100th of a second. The desired time is keyed in and followed by pressing ‘#’.

A single serial line is used to transfer the keyboard data to the display. A 4 to 16 line decoder is used since there were no enough lines for the display driver PIC to drive the LED segments and select the display digit directly. To select one of 16 outputs, a 4-bit binary encoded input is used. This enables the PIC to select each of six digits using only 4 output lines.

The display is flashing when the buzzer is sounding since they cannot operate concurrently.

Rest of the project