Arduino Carrera Lap Timer With LCD (Real-Time Racing Timer)

Ever wanted to track lap times on your Carrera racing track in real time?

In this project, I built a simple Arduino-based lap timer that connects directly to the Carrera Control Unit. It measures lap times for two cars and displays them live on a 16x2 LCD screen.

The system automatically detects when a car crosses the sensor, calculates the lap time, and highlights the fastest lap with a crown symbol 👑.

This project is perfect for beginners and can be extended with more features like lap counting or race modes.

You will need:

1. Arduino Uno / Nano (or compatible)
2. 16x2 LCD display (HD44780 compatible)
3. Carrera Control Unit
4. Jumper wires
5. Breadboard (optional)

The Arduino reads data directly from the serial output of the Carrera Control Unit.

This project uses the official PC UNIT interface, so no modification of the Control Unit is required

When a car crosses the sensor:

1. The Control Unit sends a data packet
2. The Arduino reads the data until a delimiter ($)
3. The system detects which car triggered the sensor
4. The lap time is calculated using millis()

Each lap is displayed instantly, and the fastest lap is tracked.

The Carrera Control Unit has a connector called “PC UNIT”.

This port provides a serial output, which includes lap trigger data.

Why this is useful

1. No modification of the Control Unit required
2. No soldering needed
3. Plug & play connection
4. Designed for external devices

Connect like this:

1. GND (6) (Control Unit) → GND (Arduino)
2. 5V (3) (Control Unit) → 5V (Arduino)
3. PC UNIT TX (2) → Arduino RX (Pin 0)
4. PC UNIT RX (1) → Arduino TX (Pin 1)

Important: TX and RX

1. TX = Transmit (send data)
2. RX = Receive (receive data)

Always connect:

1. TX → RX
2. RX → TX

The wiring diagram above shows how to connect the LCD to the Arduino.

+---------+-------------+

| LCD Pin | Arduino Pin |

+---------+-------------+

| RS | 11 |

| EN | 12 |

| D4 | 2 |

| D5 | 3 |

| D6 | 4 |

| D7 | 5 |

+---------+-------------+

1. Open the Arduino IDE
2. Copy the code
3. Select your board (Arduino Uno/Nano)
4. Select the correct COM port
5. Click Upload

The project assumes a fixed data format from the Carrera Control Unit

Baud rate: 19200

Make sure TX/RX are connected correctly

If it doesn’t work, try swapping TX/RX

Modifying or connecting additional hardware to your Carrera Control Unit may void your manufacturer's warranty.

This project is provided for educational and experimental purposes only. Use it at your own risk.