Line Follower 8-channel Infrared Tracking Detection Sensor QTR-8RC Red

Functional Description:

• Each sensor uses a capacitor discharge circuit for reading reflectance values.
• Shorter discharge time indicates higher reflectivity (white surface).
• LEDs can be turned off using a MOSFET gate pin to save power or adjust brightness.
• Pairs of emitters are grouped to reduce current draw.
• Can also operate at 3.3V by bypassing one of the two current-limiting stages.

Specifications:

Pin Functions:

• Sensor Outputs: Each channel has an individual signal output to a digital input on your MCU.
• CTRL / LEDON: Connect to a digital output to enable or disable emitters (optional).

Typical Applications:

• Line Following Robots
• Edge Detection
• Surface Reflectance Sensing

Arduino Wiring Example:

The following code uses digital pins 3 to 10 for the 8 sensor inputs, and pin 2 to control the LED emitters. The QTRSensors library is used to manage the reflectance readings and line position estimation.

Sample Code:

#include 

QTRSensors qtr;
const uint8_t SensorCount = 8;
uint16_t sensorValues[SensorCount];

void setup() {
  qtr.setTypeRC();
  qtr.setSensorPins((const uint8_t[]){3, 4, 5, 6, 7, 8, 9, 10}, SensorCount);
  qtr.setEmitterPin(2);

  delay(500);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, HIGH); // LED ON: Calibration mode

  // Calibrate over 10 seconds
  for (uint16_t i = 0; i < 400; i++) {
    qtr.calibrate();
  }
  digitalWrite(LED_BUILTIN, LOW); // LED OFF: Calibration complete

  Serial.begin(9600);

  // Print min and max calibration values
  for (uint8_t i = 0; i < SensorCount; i++) {
    Serial.print(qtr.calibrationOn.minimum[i]);
    Serial.print(' ');
  }
  Serial.println();
  for (uint8_t i = 0; i < SensorCount; i++) {
    Serial.print(qtr.calibrationOn.maximum[i]);
    Serial.print(' ');
  }
  Serial.println();
  delay(1000);
}

void loop() {
  // Read reflectance sensor values and calculate line position
  uint16_t position = qtr.readLineBlack(sensorValues);

  for (uint8_t i = 0; i < SensorCount; i++) {
    Serial.print(sensorValues[i]);
    Serial.print('\t');
  }
  Serial.println(position);
  delay(250);
}

How It Works:

• Each sensor pair emits IR light and measures the reflected light intensity from the surface.
• White surfaces reflect more IR and result in a faster capacitor discharge (lower time = higher reading).
• Black surfaces absorb IR, producing slower discharge times (lower readings).

Resources:

• QTRSensors Arduino Library (Click Here)
• Line Follower Arduino Example Code (Click Here)