____       _          ____                        
|  _ \ ___ | |__   ___/ ___| _   _ _ __ ___   ___  
| |_) / _ \| '_ \ / _ \___ \| | | | '_ ` _ \ / _ \ 
|  _ < (_) | |_) | (_) |__) | |_| | | | | | | (_) |
|_| \_\___/|_.__/ \___/____/ \__,_|_| |_| |_|\___/ 
                                                   
  ____            _    _                 _    
 / ___|___   ___ | | _| |__   ___   ___ | | __
| |   / _ \ / _ \| |/ / '_ \ / _ \ / _ \| |/ /
| |__| (_) | (_) |   <| |_) | (_) | (_) |   < 
 \____\___/ \___/|_|\_\_.__/ \___/ \___/|_|\_\

Connecting the TCRT5000 sensor to an analog input on the Arduino Nano

Useful links

• TCRT5000 datasheet
• Introducing the TCRT5000 reflective infrared sensor
• Motor control with TCRT5000 sensor input
• Assembly instructions for TCRT5000 printed circuit board

Example circuit from today's lecture

Example code from today's lecture

Version 1: Switch an LED on and off

//
// TCRT5000 example program
//
// This switches an LED on or off depending on whether the sensor
// voltage is greater than 2.5 V or not.
//
// Written by Ted Burke on 8-Feb-2023
//

void setup()
{
  // Configure pin D2 as a digital output
  pinMode(2, OUTPUT);
}

void loop()
{
  // Declare an integer variable to store a number (the sensor reading)
  int colour;

  // Read analog voltage from pin A0 as a number between 0 and 1023
  colour = analogRead(0);

  // Decide whether to switch the LED on or off based on the sensor voltage
  if (colour > 512)
  {
    digitalWrite(2, HIGH); // LED on
  }
  else
  {
    digitalWrite(2, LOW); // LED off
  }
}

Version 2: Control an LED and print readings via serial connection

//
// TCRT5000 example program
//
// This version controls an LED and prints sensor readings via
// the serial connection to the PC, so that they can be displayed
// using the Serial Monitor or Serial Plotter in the Arduino IDE.
//
// Written by Ted Burke on 8-Feb-2023
//

void setup()
{
  // Open a serial connection to the PC at 9600 bits per second
  Serial.begin(9600);

  // Configure pin D2 as a digital output
  pinMode(2, OUTPUT);
}

void loop()
{
  // Declare an integer variable to store a number (the sensor reading)
  int colour;

  // Read analog voltage from pin A0 as a number between 0 and 1023
  colour = analogRead(0);

  // Print the sensor reading to the PC via the serial connection
  Serial.println(colour);

  // Decide whether to switch the LED on or off based on the sensor voltage
  if (colour > 512)
  {
    digitalWrite(2, HIGH); // LED on
  }
  else
  {
    digitalWrite(2, LOW); // LED off
  }
}