⚠️Warning This entire project is in C++ do not edit unless you know C++.

-Good luck, PresidentPeppermint

Secure Arduino Clock — RFID Access Panel

An RFID-locked clock display built on an Arduino Uno R4 WiFi. Scan an authorized card to unlock the display and show the live time (synced automatically over WiFi). Scan an unauthorized card and it gets rejected with a buzz.

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Parts List

Part	Qty	Notes
Arduino Uno R4 WiFi	1	Main controller — has built-in WiFi and RTC
RC522 RFID Reader Module	1	Runs on 3.3V, not 5V
16x2 I2C LCD Display	1	Shows locked/unlocked status and time
RFID Key Cards/Tags	2+	One (or more) authorized, extras to test rejection
Small Speaker or Piezo Buzzer	1	Wired directly to a digital pin
Jumper Wires (male-to-female)	~12	For direct pin connections, no breadboard required
USB Cable	1	For programming and power

No separate power supply is needed — the reader, display, and speaker all draw power from the Arduino itself.

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Wiring

RC522 → Arduino

⚠️ VCC must go to 3.3V, not 5V — connecting it to 5V can damage the module.

RC522 Pin	Arduino Pin
VCC	3.3V
GND	GND
RST	Pin 9
MISO	Pin 12
MOSI	Pin 11
SCK	Pin 13
SDA (labeled SS)	Pin 10
IRQ	Not connected

LCD → Arduino

LCD Pin	Arduino Pin
VCC	5V
GND	GND
SDA	SDA (dedicated pin near AREF, or A4)
SCL	SCL (dedicated pin near AREF, or A5)

Speaker → Arduino

Speaker Wire	Arduino Pin
Signal	Pin 8
Other	GND

Polarity doesn't matter for this type of speaker — either wire can go to either pin.

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Software Setup

1. Install the Arduino IDE

1. Go to arduino.cc/en/software and download the IDE for your operating system (Windows, macOS, or Linux).
2. Run the installer and follow the prompts, keeping the default options.
3. Open the Arduino IDE once installed.

2. Install board support for the Uno R4 WiFi

1. In the Arduino IDE, go to Tools → Board → Boards Manager (or click the boards icon in the left sidebar).
2. Search for "Uno R4".
3. Install the package called Arduino UNO R4 Boards.
4. Once installed, plug in your Arduino via USB, then go to Tools → Board and select Arduino UNO R4 WiFi.
5. Go to Tools → Port and select the COM port your Arduino shows up as.

3. Install required libraries

1. Open the Library Manager (icon on the left sidebar, looks like stacked books).
2. Search for and install each of these:
   • MFRC522 by GithubCommunity
   • LiquidCrystal I2C by Frank de Brabander
3. The RTC and WiFiS3 libraries are already included with the Uno R4 board package — no separate install needed.

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Getting the Code

This repo contains two sketches:

• find_uid.ino — a helper sketch that reads and prints any scanned card's unique ID. Use this first to find your own card's UID.
• rfid_lock.ino — the main sketch that runs the actual lock, display, and buzzer logic.

To copy the code:

1. Click on either file above in this repository.
2. Click the copy icon in the top-right corner of the code view (or select all the text and copy it manually).
3. In the Arduino IDE, go to File → New Sketch.
4. Delete the placeholder code in the editor, then paste in the copied code.
5. Save the sketch. The IDE will ask to put it in a matching folder name — click OK, this is normal.

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Step 1: Find Your Card's UID

1. Open find_uid.ino in the Arduino IDE (using the copy/paste method above).
2. Upload it (click the arrow button in the top-left).
3. Open the Serial Monitor (magnifying glass icon, top-right), and set the baud rate to 9600.
4. If nothing appears, press the small reset button on the Arduino board.
5. Hold your card against the RC522's antenna coil (the square area in the middle of the board).
6. Copy the UID that prints out (e.g. 66 7D A1 04) — you'll need it next.

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Step 2: Set Up and Upload the Main Sketch

1. Open rfid_lock.ino in the Arduino IDE.
2. Find this line near the top:

   byte authorizedUID[4] = {0x00, 0x00, 0x00, 0x00};

   Replace the four values with your card's UID from Step 1 (format each byte as 0x followed by the hex pair, e.g. 0x66, 0x7D, 0xA1, 0x04).
3. Find these lines:

   const char* ssid = "YOUR_WIFI_NAME";
   const char* password = "YOUR_WIFI_PASSWORD";

   Replace with your own WiFi network name and password. Do not commit your real credentials back to a public repo — keep them only in your local copy on the Arduino.
4. Also check the UTC offset line matches your timezone:

   const long utcOffsetSeconds = -5 * 3600;

5. Upload the sketch.

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Testing

• On boot, the LCD shows a WiFi connection screen with a loading bar and beeps, then the time syncs automatically over the internet.
• Once ready, the display shows "Locked / Scan your card."
• Scan your authorized card → display shows "Unlocked!" with the live time.
• Scan it again → goes back to Locked.
• Scan any other card → display shows "Access Denied" with a low buzz, then returns to whatever state it was in.
• Every hour on the hour, the speaker plays a short chime.

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License

See LICENSE for details.