Arduino Nano Project

DIY Time Tracking Monitor

In this ElektroBox project, I build a simple Time Tracking Monitor for gaming breaks, work sessions, or any situation where you want a clear visual timer.

The monitor uses an Arduino Nano, 12 LEDs, resistors, and one setup button. The LEDs work like a progress bar with green, yellow, and red sections, so the remaining time is easy to see at a glance.

DIY Time Tracking Monitor with Arduino Nano and LED status bar

1. Project Idea

In between ElektroBox projects, I like to play games. But sometimes, a short break gets much longer than planned. To solve this, I built a small desktop Time Tracking Monitor.

The idea is simple: before the break starts, the time is set with one button. During operation, the LED bar shows the passed time. When the time is over, a wave animation starts as a visual reminder.

Main controllerArduino Nano.

Status display12 LEDs arranged as a green, yellow, and red progress bar.

Time setupOne button. Each press adds 15 minutes, up to 3 hours.

2. How the System Works

The project has four program modes: idle, setup, tracking, and finished. The button is checked continuously, and the Arduino switches between these modes depending on the current state.

Idle mode → hold the button for 3 seconds to start setup

Setup mode → each button press adds 15 minutes

Tracking mode → the selected time is divided across all 12 LEDs

Finished mode → a wave animation runs continuously

Example: If you select 1 hour, the Arduino divides this time across the 12 LEDs. One LED then represents 5 minutes of passed time.

3. Required Parts

Arduino Nano
12 LEDs
1 push button
12 × 1 kΩ resistors for the LEDs
1 × 10 kΩ resistor for the button circuit
Prototype PCB or perfboard
Dupont wires
USB cable for power
3D-printed housing

4. LED Status Bar

The LED status bar is built with green, yellow, and red LEDs. I used four LEDs per color to create a simple progress-bar style display.

Each LED is connected from an Arduino digital pin through a 1 kΩ resistor to GND. This limits the LED current to roughly 5 mA, depending on the LED forward voltage.

Important: Check the LED orientation before soldering. The longer leg is the anode and goes to the Arduino side through the resistor. The shorter leg goes to GND.

5. Button Circuit

The setup button is connected to pin A1. In this version, the code expects an external pulldown resistor, so the input is normally LOW. When the button is pressed, A1 is connected to 5 V and reads HIGH.

Note: If your wiring uses a pullup resistor instead, the button logic in the code must be inverted.

6. Wiring Overview

LED 1 to LED 12 are connected to pins D2 to D13.
The setup button is connected to pin A1.
The Arduino Nano is powered through USB.
All LED cathodes are connected to GND.
Each LED has its own 1 kΩ current-limiting resistor.

Pin overview

Arduino Nano wiring overview

LEDs:
D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13

Button:
A1

Button wiring used by this code:
A1 — button — 5 V
A1 — 10 kΩ resistor — GND

Button not pressed = LOW
Button pressed = HIGH

7. Program Modes

IdleThe monitor waits until the button is held for 3 seconds.

SetupEach button press adds 15 minutes to the selected time.

TrackingThe LEDs show the elapsed time across the selected interval.

FinishedA wave animation reminds you that the time block is over.

8. Basic Arduino Code Structure

Timer logic structure

Arduino state machine outline

/*Arduino Nano Time Tracking Monitor

  LEDs:
  D2 – D13

  Button:
  A1 with external pulldown resistor
  Button pressed = HIGH

  Setup:
  Hold button for 3 seconds -> enter setup mode
  All LEDs blink 1 time

  In setup mode:
  Each button press = +15 minutes
  1 LED = 15 minutes
  12 LEDs = 3 hours max
  No button press for 5 seconds -> setup ends
  All LEDs blink 2 times

  Tracking:
  Selected time is divided by 12
  LEDs light up one after another to show passed time

  Finished:
  LEDs blink in a wave from D2 to D13
*/

const byte buttonPin = A1;

const byte ledPins[12] = {
  2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
};

const byte ledCount = 12;

// Time settings
const unsigned long holdTime = 3000;       // 3 seconds
const unsigned long setupTimeout = 5000;   // 5 seconds without button press
const unsigned long timePerLed = 15UL * 60UL * 1000UL; // 15 minutes

// Button debounce
const unsigned long debounceDelay = 40;

bool lastRawButtonState = LOW;
bool stableButtonState = LOW;
bool lastStableButtonState = LOW;

unsigned long lastDebounceTime = 0;
bool buttonPressEvent = false;

// Long press detection
unsigned long buttonHoldStart = 0;
bool longPressTriggered = false;

// Program modes
enum Mode {
  IDLE,
  SETUP_MODE,
  TRACKING_MODE,
  FINISHED_MODE
};

Mode mode = IDLE;

// Setup variables
byte selectedSteps = 0;
unsigned long lastSetupActivity = 0;

// Tracking variables
unsigned long trackingStartTime = 0;
unsigned long totalTrackingTime = 0;
unsigned long segmentTime = 0;
byte currentLedStep = 255;

void setup() {
  pinMode(buttonPin, INPUT); // external pulldown resistor required

  for (byte i = 0; i < ledCount; i++) {
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW);
  }
}

void loop() {
  updateButton();

  switch (mode) {
    case IDLE:
      handleIdleMode();
      break;

    case SETUP_MODE:
      handleSetupMode();
      break;

    case TRACKING_MODE:
      handleTrackingMode();
      break;

    case FINISHED_MODE:
      finishAnimation();
      break;
  }
}

void updateButton() {
  buttonPressEvent = false;

  bool rawState = digitalRead(buttonPin);

  if (rawState != lastRawButtonState) {
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    stableButtonState = rawState;

    if (stableButtonState != lastStableButtonState) {
      if (stableButtonState == HIGH) {
        buttonPressEvent = true;
      }

      lastStableButtonState = stableButtonState;
    }
  }

  lastRawButtonState = rawState;
}

void handleIdleMode() {
  if (stableButtonState == HIGH) {
    if (buttonHoldStart == 0) {
      buttonHoldStart = millis();
    }

    if (!longPressTriggered && millis() – buttonHoldStart >= holdTime) {
      longPressTriggered = true;
      enterSetupMode();
    }
  } else {
    buttonHoldStart = 0;
    longPressTriggered = false;
  }
}

void enterSetupMode() {
  mode = SETUP_MODE;

  selectedSteps = 0;
  lastSetupActivity = millis();

  allLedsOff();
  blinkAllLeds(1);
  showSelectedSetupTime();
}

void handleSetupMode() {
  if (buttonPressEvent) {
    if (selectedSteps < ledCount) {
      selectedSteps++;
    }

    lastSetupActivity = millis();
    showSelectedSetupTime();
  }

  if (millis() - lastSetupActivity >= setupTimeout) {
    exitSetupMode();
  }
}

void exitSetupMode() {
  blinkAllLeds(2);

  if (selectedSteps == 0) {
    allLedsOff();
    mode = IDLE;
    return;
  }

  totalTrackingTime = selectedSteps * timePerLed;
  segmentTime = totalTrackingTime / ledCount;

  trackingStartTime = millis();
  currentLedStep = 255;

  allLedsOff();
  mode = TRACKING_MODE;
}

void handleTrackingMode() {
  unsigned long elapsedTime = millis() – trackingStartTime;

  if (elapsedTime >= totalTrackingTime) {
    showPassedTime(ledCount);
    delay(500);
    mode = FINISHED_MODE;
    return;
  }

  byte ledsToShow = elapsedTime / segmentTime;

  if (ledsToShow != currentLedStep) {
    currentLedStep = ledsToShow;
    showPassedTime(ledsToShow);
  }
}

void showSelectedSetupTime() {
  for (byte i = 0; i < ledCount; i++) {
    if (i < selectedSteps) {
      digitalWrite(ledPins[i], HIGH);
    } else {
      digitalWrite(ledPins[i], LOW);
    }
  }
}

void showPassedTime(byte ledsToShow) {
  for (byte i = 0; i < ledCount; i++) {
    if (i < ledsToShow) {
      digitalWrite(ledPins[i], HIGH);
    } else {
      digitalWrite(ledPins[i], LOW);
    }
  }
}

void blinkAllLeds(byte times) {
  for (byte i = 0; i < times; i++) {
    allLedsOn();
    delay(250);
    allLedsOff();
    delay(250);
  }
}

void finishAnimation() {
  while (true) {
    for (byte i = 0; i < ledCount; i++) {
      allLedsOff();
      digitalWrite(ledPins[i], HIGH);
      delay(100);
    }

    for (int i = ledCount - 2; i > 0; i–) {
      allLedsOff();
      digitalWrite(ledPins[i], HIGH);
      delay(100);
    }
  }
}

void allLedsOn() {
  for (byte i = 0; i < ledCount; i++) {
    digitalWrite(ledPins[i], HIGH);
  }
}

void allLedsOff() {
  for (byte i = 0; i < ledCount; i++) {
    digitalWrite(ledPins[i], LOW);
  }
}

}

9. Common Problems

One LED does not light up

Check the LED polarity, resistor, solder joint, and assigned Arduino pin.

The button input behaves randomly

Check the pulldown resistor and add debounce handling in the firmware.

The timing is not correct

Use millis-based timing and verify the selected time interval calculation.

10. Final Result

The final result is a compact visual timer with a 12 LED progress bar. It is simple, readable, and useful as a small desktop electronics project.

The project can be expanded with different time presets, a pause function, brightness control, startup animations, or a more advanced button menu.