This is circuit for clock timer uses a PIC16F628 microcontroller to display digital time and control an external load. Timer output duration can be programmed from 1 to 59 minutes and can be manually switched on and off. This is the figure of complete circuit;
The clock has a correction feature that allows an additional second to be added every so many hours to compensate for a slightly slow running oscillator. The oscillator uses a common 32.768 KHz watch crystal and the frequency can be adjusted slightly with the 24pF capacitor on the right side of the crystal. The clock will also adjust itself for daylight savings time and add or subtract an hour on the first Sunday in April and last Sunday in October. The daylight savings feature is disabled at boot up and needs to be enabled after turn on.
Setting the time of day and other features is done with 3 momentary single pole, double throw switches and one non-momentary single pole, double throw. The switch functions are shown in the chart below with the letters A-H indicating the switch combination for each function. Some entries can be made with one momentary switch closure while others require toggling 2 switches at the same time.
