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Digiral second indicator
The second display in the digital clock main board is only the flickering of LED. Thereupon, I made the one that displays the second with digital.
The circuit uses the signal of 1Hz that is out from the digital clock main board. For the 1st the ten binary counter and for the 10th the six binary counter is used.
Six binary counter count to 0 to 5 and the circuit which returns to 0 by the reset action when counting becomes 6 is made with NAND gates.
The reset of the second display does as it is carried out at the same time as the second reset( Slow time renewal (LOW) switch is pushed, while pushing the second display (SEC) switch ) of the digital clock main board.
Digital display LED of 7 segments is using a small thing. Although the LED display color of the digital clock main board changes to AM (red) and PM (green), the second indicator is a display of only red. I was not able to find small digital display LED that changes to red and green.
As the power supply, the power supply with battery backup( +12V-B ) is used for the counting circuit and the power supply without battery backup( +12V-A ) is used for the LED display circuit.
