Circuit diagram of multifunctional digital clock

In this digital clock circuit, S1 is the function selection button, S2 is the function expansion button, and S3 is the value plus one button. During operation, if you press S1 for a short time (less than 1 second), you can continuously cycle through the above functions. If you press S1 for a long time (more than 2 seconds) in the middle, it will immediately return to the clock function state.

Function adjustment instructions:

1. Clock function: After power-on, it will display 10:10:00, which means perfection.

2. Time adjustment function: short press S1 once, the current time and colon will flash, press S2 to add 1 to the hour, press S3 to add 1 to the minute, and the second cannot be adjusted.

3. Alarm function: Short press S1 twice, the display status is 22:10:00, and the colon is long. Press S2 to add 1 to the hour, press S3 to add 1 to the minute, and the second is not adjustable. When the hour exceeds 23, it will display --:--:--, which means the alarm function is turned off. The alarm sound is a buzzer that beeps for 3 seconds.

4. Countdown function: Short press S1 three times, the display state is 0, and the colon is long off. Press S2 to display the high position from the low position in sequence, and press S3 to add 1 to the corresponding position. When S2 is pressed for the sixth time, the countdown will start at the set time state. Press S2 again to enter the adjustment function again and stop the countdown.

5. Stopwatch function: Short press S1 four times, the display status is 00:00:00, and the colon is long. Press S2 to start the stopwatch, press S2 again to stop the timing, and press S3 to reset the stopwatch when the timing is stopped.

6. Counter function: Short press S1 five times, the display status is 00:00:00, the colon is long off, press S2 to add 1 to the counter, press S3 to clear the counter.