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Arduino & IR Sensor Setup

This guide walks you through wiring the IR sensor to an Arduino Nano and uploading the lap timer sketch.

What You Need

  • Arduino Nano (or compatible clone with USB-C or Mini-USB)
  • IR obstacle sensor module (FC-51 / MH-B or similar)
  • 3 jumper wires (female-to-female or female-to-male)
  • USB cable (matching your Arduino)
  • A computer with the Arduino IDE installed

1. Understanding the IR Sensor

IR sensor module diagram

The sensor module has three pins on one end:

Pin Description
VCC Power — connect to 5V on the Arduino
GND Ground — connect to GND on the Arduino
OUT Digital output — connect to D2 on the Arduino

The small blue trimpot on the module adjusts detection sensitivity/distance. Turn it clockwise to increase range, counter-clockwise to reduce it.

IR sensor with wires connected

2. Wiring

Breadboard wiring diagram

Connect the three sensor pins to the Arduino Nano as follows:

Sensor Pin Arduino Nano Pin
VCC 5V
GND GND
OUT D2

The wiring diagram above uses a breadboard for clarity, but you can connect the jumper wires directly from the sensor to the Arduino header pins.

Arduino Nano with wires

3. Install the Arduino IDE

  1. Go to https://www.arduino.cc/en/software
  2. Download the Arduino IDE 2 for your operating system (Windows, macOS, or Linux)
  3. Run the installer and follow the on-screen steps
  4. Launch the Arduino IDE

4. Add Arduino Nano Board Support

If you are using a clone Arduino Nano with the CH340 USB chip (common on budget boards):

  1. Open Arduino IDE → Preferences
  2. In "Additional boards manager URLs" add: 
    https://raw.githubusercontent.com/nanochip/arduino-boards/master/package_index.json
  3. Go to Tools → Board → Boards Manager, search for Arduino AVR Boards, and install it
  4. Go to Tools → Board and select Arduino Nano
  5. Go to Tools → Processor and select ATmega328P (Old Bootloader) if the standard option fails to upload

5. Open the Sketch

  1. In the Arduino IDE, open File → Open
  2. Navigate to the arduino/lap_sensor/ folder in this project
  3. Open lap_sensor.ino

The sketch sends a TRIGGER line over serial (9600 baud) each time the IR beam is broken, with a 500 ms debounce to avoid duplicate triggers.

6. Upload the Sketch

  1. Connect the Arduino to your computer via USB
  2. Go to Tools → Port and select the port that appeared when you plugged in the Arduino
    • On macOS/Linux it looks like /dev/tty.usbserial-XXXX or /dev/ttyUSB0
    • On Windows it looks like COM3, COM4, etc.
  3. Click the Upload button (→ arrow icon) or press Ctrl+U / Cmd+U
  4. Wait for "Done uploading" to appear in the status bar

The built-in LED on pin 13 will flash briefly each time a trigger is detected — a quick way to confirm the sensor is working without opening the serial monitor.

7. Mount the Sensor on the Track

Position the sensor across the track so the IR beam is broken by the car as it passes. Keep the emitter and receiver facing each other at the same height as the car body.

Sensor mounted on track with Mini 4WD car

Adjust the trimpot until the sensor LED lights up reliably when the car passes and turns off between passes.

8. Start the Lap Timer

Once the sketch is uploaded and the sensor is mounted, follow the User Guide to start the Go server and begin timing laps.