Topics: Flip-flop, Switch, Logic gate Pages: 2 (541 words) Published: December 17, 2012
We were assigned with the task of designing and building a digital clock that displays the time in Binary. First a power supply that outputs a 60Hz square wave is fed into the circuit. We used 74160 decade counters in the project. A 74160 divided the clock down to 6Hz, and then a truncated 74160 divided it down to a 1Hz wave that would be the input for the clock. This clock will display in military time. The 1HZ is equal to one second and is fed into the first 74160. There are six 74160 counters and one J/K Flip-Flop to count and display the time in 4 bit blocks. One nibble for the ones column of seconds, One nibble for the tens column for seconds and so on, except the hours which has only 2 bits. The outputs are hooked to LEDs. It the LED is on it represents a 1 and if it is off it represents a 0.

The first counter displaying time shows the seconds and is not truncated. The next counter is truncated at 6 so that it once it reaches 59 seconds it will clear and output to the next chip’s clock and show one minute. The seconds minutes and hours are all arranged this way. We used 7420 NAND chips for truncating purposes, and 7404 inverters when needed as the 74160s are active low. All unused inputs are tied to high, and loads tied to ground. Once the time reaches the tens column for hours it is fed into a J/K Flip-flop because it is only needed to count to 2. Once the time reaches 23:59:59 the next pulse is decoded and causes the circuit to clear back to 0.

This clock is also equipped with an alarm. With a super bright LED to display the alarm. 7485 comparators were used to detect when the alarm time is reached. The alarm is set with DIP switches corresponding to each bit. A SPDT switch is in place to set the alarm to on. An LED indicates when the time set on the alarm is reached regardless if the alarm is set to on. When the alarm time is reached the outputs of counters and the outputs of the DIP switches are equal and the A=B outputs all go...
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