How to Make a Digital Clock at Home Using Arduino | Full Step-by-Step Tutorial

ERGREAT

Introduction

Making a digital clock at home using Arduino is an excellent hands-on electronics project that helps you understand LED multiplexing, microcontroller programming, and practical circuit design. Instead of using ready-made display modules, this project focuses on building a 4-Digit 7-Segment display using 5mm LEDs, which greatly improves soldering skills and circuit understanding.

In this tutorial, you will learn every step in detail, starting from designing the LED frame, assembling individual segments, wiring the display, programming the Arduino, and finally setting the time using switches.
This clock works in 12-hour format and is mainly designed for learning and experimental purposes.

Step 1: Designing and Making the 4-Digit 7-Segment Frame

The first step is to prepare a strong and accurate display frame.

  • Use a 6mm MDF board, acrylic sheet, or any similar rigid material.
  • Design a 4-digit 7-segment layout carefully, as shown in the reference image.
  • Each digit consists of 7 segments (A to G).
  • Each segment will contain 4 LEDs, so proper spacing is very important.

Cut the board neatly and mark the LED positions accurately to ensure uniform brightness and alignment.

Step 2: Drilling Holes and Surface Finishing

  • Drill 5mm holes at the marked LED positions.
  • Ensure all holes are straight and evenly spaced.
  • After drilling, smooth the surface using sandpaper.
  • This step improves the overall appearance and helps LEDs fit firmly.

Good finishing makes the project look professional and long-lasting.

Step 3: Inserting LEDs into the Frame

  • Insert 5mm LEDs into the drilled holes.
  • Make sure the positive leg (Anode) of each LED faces the outer side of the segment.
  • Each segment should have 4 LEDs placed uniformly.

Maintaining correct polarity at this stage to avoids major issues later.

Step 4: Wiring One Digit (Common Anode Configuration)

Now we start soldering one digit.

Segment Connection (Example: Segment A)

  • Bend the anode legs of all 4 LEDs in Segment A.
  • Solder all anodes together — this forms a Common Anode.
  • Now solder all cathode legs together separately.

Repeat the same process for:

  • Segment A
  • Segment B
  • Segment C
  • Segment D
  • Segment E
  • Segment F
  • Segment G

Key Concept:

  • All segment anodes of one digit are connected together
  • Cathodes are kept separate for each segment

This configuration allows easy multiplexing using Arduino.

Step 5: Testing the Segments

Before moving further:

  1. Test each segment using a power source (Use 3V coin cell)

  2. If any LED does not glow:

  • Check solder joints
  • Fix dry solder
  • Replace faulty LEDs if needed

Testing at this stage saves a lot of troubleshooting later.

Step 6: Repeating the Process for All 4 Digits

  • Repeat the same LED insertion and soldering steps for all four digits.
  • Ensure uniform wiring and correct polarity across all digits.
  • Keep wires organized for easy identification.

Step 7: Connecting the Dot LEDs

  1. Place Dot LEDs between the 2nd and 3rd digits.
  2. Use 4 LEDs connected in parallel for better visibility.

  3. Connect:

  • One wire to Dot Anodes
  • One wire to Dot Cathodes

Step 8: Segment and Digit Wiring (Multiplexing Method)

Segment Wiring

Connect Segment A cathodes of all 4 digits together
Repeat the same for:

  • Segment B
  • Segment C
  • Segment D
  • Segment E
  • Segment F
  • Segment G

Digit Wiring

  • Digit-1 → Common Anode
  • Digit-2 → Common Anode
  • Digit-3 → Common Anode
  • Digit-4 → Common Anode

Each digit anode must have a separate wire.

Step 9: Fixing the LEDs Using Glue

  • Use hot glue or glue stick to fix LEDs firmly in the MDF board.
  • This ensures mechanical stability and prevents wire breakage.

At this point, your 4-Digit Common Anode Display is fully prepared.

Step 10: Connecting the Display to Arduino Uno

Segment Pin Connections

  • Segment A → D8
  • Segment B → D7
  • Segment C → D6
  • Segment D → D5
  • Segment E → D4
  • Segment F → D3
  • Segment G → D2

Dot LED

  • Dot Anode → D9
  • Dot Cathode → GND

Digit Control Pins

  • Digit-1 (Hour-1) → D10
  • Digit-2 (Hour-2) → D11
  • Digit-3 (Minute-1) → D12
  • Digit-4 (Minute-2) → D13

⚠️ Carefully verify all connections before powering the circuit.

Step 11: Installing the Required TIME Library

  1. Connect Arduino Uno to your computer
  2. Open Arduino IDE
  3. Go to Sketch → Include Library → Manage Libraries
  4. Search for TIME
  5. Install the latest version
  6. Ensure your system is connected to the internet

Once installed, the library will appear in the Include menu.

Step 12: Uploading the Arduino Code

  1. Download the provided 12-Hour Digital Clock code
  2. Open it using File → Open
  3. Click Verify to compile the code

  4. Select:

  • Board: Arduino Uno
  • Port: Correct COM port
  • Click Upload

Step 13: Initial Output Observation

After uploading:

  • All segments glow
  • First digit may remain off initially
  • After 2 minutes, the clock starts updating automatically

This behavior confirms proper multiplexing.

Step 14: Controlling Dot LED Brightness

Dot LEDs may appear brighter than segments.

Solution:

  • Add a 220Ω resistor in series with the Dot LED anode
  • This balances brightness and improves appearance

Step 15: Adding Time Adjustment Switches

Switch Wiring

  • One side of all switches → GND
  • Toggle Switch → A0
  • Minute Button → A1
  • Hour Button → A2

These switches allow easy manual time setting.

Step 16: Using ATmega8A Instead of Arduino (Optional)

  • Program an ATmega8A IC
  • Use it instead of Arduino Uno
  • Wiring diagram is provided in the reference image
  • This reduces project cost and size

Step 17: Battery Power and Charging Circuit

  • Use a 3.7V Li-ion battery
  • Add a TP4056 charging module
  • Use an SPST switch for power control
  • Assemble all components neatly inside a box

Step 18: Setting and Running the Clock

  1. Turn ON the power switch
  2. Press Toggle Switch once to enter time-set mode
  3. Use Hour and Minute buttons to adjust time
  4. Press toggle switch again to start the clock

🔁 This is a 12-Hour Digital Clock
After 12:59, it automatically rolls over to 01:00

Blinking dot LEDs indicate normal operation.

Conclusion

Your Arduino-based Digital Clock is now fully functional.
This project is extremely useful for:

  • Learning LED multiplexing
  • Improving soldering skills
  • Understanding microcontroller timing logic

Limitation:

  • Manual time setting
  • Time resets on power loss

➡️ In the next upgrade, we will solve this using an RTC module, making the clock fully automatic and accurate.

Great job! Your hard work has paid off.
If you have any questions or suggestions, feel free to comment.

ERGREAT

Posted by ERGREAT

Hi, I’m Kishor Kumar — an electronics enthusiast, maker, and traveler from India. I love building DIY electronic projects, experimenting with circuits, creating tutorials, and sharing step-by-step guides that help others learn easily. When I’m not working on electronics, I travel across India with my cameras, capturing stories, places, and experiences that inspire my creativity. Through ERGREAT, my aim is to share practical projects, detailed explanations, and real-life adventures that motivate others to explore technology and the world around them.

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