Digital clocks are a fundamental part of everyday life, from the clocks on our phones to the ones we see in our homes or workplaces. They are also one of the best projects to learn about digital logic, time division, and electronics in general. In this DIY project, we’ll be building a Simple Digital Clock using ACT14 logic gates.
This clock will be able to display the current time in hours and minutes on a 7-segment display. We’ll use the ACT14 series of logic chips to create the timing and counting circuit needed for the clock, and we’ll also use a few additional components like a 7-segment display to show the time.
● ACT14 Logic Gates (AND, OR, NOT gates)
● 7-Segment Displays (2 for hours, 2 for minutes)
● Clock Oscillator (for time base, can use a 32.768 kHz crystal)
● Resistors (for current limiting)
● Capacitors (for debouncing, if necessary)
● Transistors (to drive the 7-segment displays)
● Breadboard and jumper wires
● Power supply (5V or 9V depending on the circuit)
● Switches (to set time)
The ACT14 series refers to a family of CMOS (Complementary Metal-Oxide-Semiconductor) digital logic gates. These gates, such as AND, OR, and NOT, are the building blocks of digital circuits. They are used to perform logical operations and are fundamental in constructing counters, timers, and clocks.
Each ACT14 chip will provide a specific type of logic gate, and by combining them, we can create the clock's counting mechanism and time division. For this project, the main components from the ACT14 series will be used to build a binary counter, which will count from 0 to 59 for the minutes and 0 to 23 for the hours.
To keep track of the time, we need a consistent time base, which will serve as the heartbeat for the clock. A common approach is to use a 32.768 kHz crystal oscillator, which is widely used in clock circuits because of its low cost and accuracy. This oscillator generates a high-frequency signal, which we’ll divide down to create seconds, minutes, and hours.
1. Frequency Division:
The crystal oscillator's frequency is too high to directly display the time in seconds or minutes. We need to divide this frequency down to a more usable form. For example, a divide-by-60 circuit will give us a signal once every minute, while a divide-by-60 again for seconds will allow us to track the seconds.
2. ACT14 Logic Gates for Division:
Using the ACT14 series logic gates, we can design counters that divide the frequency of the oscillator. These counters will increment every time the oscillator completes a cycle, and the output will be used to drive the clock's display.
Now that we have our time base (the 32.768 kHz oscillator), we need to build a counter that will track seconds, minutes, and hours. A binary counter can increment the time in base-2, and we can convert the binary output to a 7-segment display later.
1. Counting the Seconds:
First, we will create a divide-by-60 counter to count the seconds. The output of this counter will pulse once every second.
To build the counter, we can use flip-flops from the ACT14 series. A flip-flop is a simple logic circuit that has two states and can store one bit of information. By chaining flip-flops together, we can create multi-bit counters. A divide-by-60 counter will require a chain of flip-flops, each dividing the frequency by a factor of 2.
2. Counting the Minutes:
Once we have a second counter, we will need a similar mechanism for counting minutes. After every 60 seconds, the minute counter will increment by one. The output of the second counter will drive the minute counter.
3. Counting the Hours:
After counting 60 minutes, the hour counter will increment by one. The hour counter will reset after reaching 24, completing one cycle of a full day.
4. ACT14 Components for Counting:
The ACT14 gates will be used to create logic circuits that control how the counters interact. For example:
● An AND gate can be used to trigger the minute counter once the second counter reaches 60.
● An OR gate can be used to reset the counter after it reaches 24 hours.
By combining AND, OR, and NOT gates, we can build a simple binary counter that tracks the time in a 24-hour format.
Once we have the counters in place, we need to display the time. A 7-segment display is perfect for this job, as it can display decimal digits from 0 to 9. We will use two 7-segment displays for the hours (two digits) and two 7-segment displays for the minutes.
1. Driving the 7-Segment Display:
To control the 7-segment display, we need to send specific signals to each segment (A through G) of the display. Each segment is either ON or OFF, depending on the binary value of the number to be displayed. We will use transistors to drive the current to each segment of the display.
2. ACT14 Logic Gates for Displaying Digits:
We can use ACT14 logic gates to create decoding circuits that convert the binary output of the counters into signals that will turn on the appropriate segments of the 7-segment display. For example, if the counter outputs a binary value corresponding to the digit "3", the decoding circuit will turn on the segments corresponding to the number "3".
The logic gates will perform the necessary binary-to-decimal conversion, ensuring that the correct segments light up to form the desired digits.
3. Multiplexing the Displays:
To avoid driving each 7-segment display continuously, we will use a technique called multiplexing. With multiplexing, we can rapidly switch between the displays, lighting up one display at a time for a short period. The human eye perceives this as if all displays are lit at once, but in reality, they are switched on and off fast enough that it appears as continuous.
To make this clock useful, we need to be able to set the time. This is typically done with two buttons:
1. One button to increase the hours.
2. One button to increase the minutes.
When either button is pressed, the corresponding counter will increment by one. If the hour counter reaches 24, it will reset to 0, and if the minute counter reaches 60, it will reset to 0 as well.
To ensure the buttons work correctly, you might need to add debouncing circuits using capacitors or extra logic gates to prevent multiple presses from being registered with a single button push.
Once the circuit is complete, you can assemble everything onto a breadboard for testing. Once the system is working correctly, you can mount the circuit into an enclosure, leaving the buttons accessible for adjusting the time.
1. Connecting the Power Supply:
Make sure your circuit is powered by a suitable 5V supply, as most of the ACT14 chips operate within this range.
2. Testing the Clock:
With everything connected, the clock should now be operational. The 7-segment displays will show the hours and minutes, and the time will update every second. The buttons will allow you to adjust the time as needed.
This DIY Digital Clock project using ACT14 logic gates is a fantastic introduction to building digital circuits, especially for those who are interested in time-based systems and logic design. By using simple components like logic gates, flip-flops, and 7-segment displays, you can create a fully functional clock that demonstrates fundamental principles of electronics.
The beauty of this project lies in its simplicity, yet it also provides ample opportunities for expansion. For example, you could integrate an alarm feature, use a larger 7-segment display for better visibility, or even add a buzzer for a sound alert when a specific time is reached.
By mastering these concepts, you'll have a better understanding of how digital systems work, and you’ll be well on your way to more complex projects.
