A customizable, low-power digital alarm clock built using an Arduino Nano. Supports multiple alarms with per-day scheduling, a minimalist two-button interface, and a compact 3D-printed enclosure. Designed for reliability, power efficiency, and an intuitive user experience.
- Set up to 8 independent alarms with weekday scheduling
- 16x4 I2C LCD with large, block-style custom digits
- Two-button interface with context-aware short/long presses
- Ambient light detection to auto-dim or disable display
- Deep sleep mode with RTC interrupt wake every minute
- AC-powered with voltage sensing for brownout warnings
- Compact 3D-printed case for clean and durable packaging
- Date Started: September 2018
- Date Completed: October 2018
alarmclock_demo.mp4
| Component | Description |
|---|---|
| Arduino Nano | Microcontroller (ATmega328P) |
| 16x4 LCD (I2C) | Display with custom character support |
| DS3231 RTC | Real-time clock with 1-minute interrupt |
| Photoresistor | Ambient light sensing |
| Piezo buzzer | Audible alarm output |
| Push buttons (x2) | User input interface |
| EEPROM (internal) | Non-volatile alarm data |
| AC adapter (5V) | Power supply |
| Voltage divider | Power voltage monitoring |
| 3D-printed enclosure | Custom case for electronics |
Public Circuit Designer link: Alarm Clock Circuit
| Function | Pin | Setting (pinMode) |
|---|---|---|
| RTC minute‑tick interrupt | 2 | INPUT_PULLUP |
| External wake interrupt | 3 | INPUT_PULLUP |
| Buzzer output | 5 | OUTPUT |
| UI Button A | 11 | INPUT_PULLUP |
| UI Button B | 10 | INPUT_PULLUP |
| Photo‑resistor ADC | A0 | Analog input |
- Developed in Arduino C++ using the Arduino IDE
- LCD and RTC communicate via I2C using
Wire.h - Alarm system uses a weekday bitmask for flexible scheduling
- Finite State Machine (FSM) handles display and user interaction
- Custom glyphs used to render large-format digits across LCD
LowPower.henables deep sleep to conserve energy
- Open
AlarmClock.inoin the Arduino IDE. - Select Arduino Nano (ATmega328P, 5 V) under Tools → Board.
- Choose the correct COM port.
- Click Upload.
- Ensure you have connected the required components to the Arduino correctly
- Folow the guide above
- Supply the Circuit with 4.5V DC, recommended to get AC -> DC stepdown converter with barrel plug
| Gesture | Result |
|---|---|
| Short press A | Navigate / toggle field |
| Long press A | Confirm / enter sub‑mode |
| Short press B | Increment / select value |
| Long press B | Cancel / back / exit |
| During alarm – tap | Snooze 5 min |
| During alarm – hold B ≈2 s | Stop alarm until next schedule |
| Hold B 3s | Disable/Enable alarm function |
- Idle: Large time display + next‑alarm icon
- Set Time: Adjust hour/minute
- Edit Alarm: Choose index, set time, select weekdays
- DS3231 INT triggers every minute → MCU wakes.
- Current weekday + time compared to enabled alarm list.
- Match: Buzzer sounds continuously.
- User tap ➜ snooze 5 min; user hold B ➜ stop.
- MCU returns to deep sleep until next INT.
MIT License. See LICENSE for details.