Description and concept behind digital clock
This digital alarm clock project uses 4026 IC which is a decade counter as well as the seven-segment driver. Seven segment display is used for displaying numbers from 0 to 9 and it will display numbers when the enable pin of 4026 is high on the rising edge of the clock ie the circuit starts counting and displaying results when the enable pin is made high. Each seven-segment display needs very little current to glow the LED inside it so we have to use a 500-ohm resistor on each segment so that we would not be blown off the LED.
7806 is a voltage regulator IC this part of the circuit is used to maintain the power supply to the circuit but if you are using a simulation tool like Proteus you will not need this circuit.
Another important thing to be noted is counting less than 9 can be achieved by connecting that pin to the reset. For example, to count from 0 to 5 6 should be connected to the reset pin so that if the counter reaches to threshold ie 5 then it goes to reset in the next counting step.
And the last thing to remember is this circuit uses an external clock source of 1 Hz frequency. If you want to make your own clock please refer to this diagram of 555 timer ic. This will produce an exact 1 Hz clock. if this is not a 1 Hz frequency please maintain it by changing the variable resistor or capacitor.