Line following using QTR-8RC

[laraib1]

I want to start by saying that I am really new to all this electrical stuff and any advice would be greatly appreciated. So, I am building a line following robot with the following components:

1. 4 brushless motors
2. Adafruit motor shield
3. QTR-8RC sensor
4. Arduino mega

The robot is supposed to follow a white line on a black grid. I have been trying to callibrate the sensors using the code below but the sensors are only able to detect the white line if I shine a bright light using my phone's flashlight to remove the shadow that is casted on the grid by the sensor itself. Also note that I am using analog pins instead of the digital pins on my arduino, not sure if this is causing the issue.

Code:

#include <QTRSensors.h>

// Create an instance of the QTRSensors library
QTRSensors qtr;

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

void setup()
{
  // --- CHANGE 1: Set the sensor type to RC (Resistor-Capacitor) ---
  qtr.setTypeAnalog();

  // --- CHANGE 2: Use digital pins. Make sure you connect the sensor to these pins on your Arduino Mega ---
  // A good choice on the Mega is a block of digital pins like 22-29.
  qtr.setSensorPins((const uint8_t[]){A8,A9, A10, A11, A12, A13, A14, A15}, SensorCount);
  
  // You can also set a timeout for the RC sensors, which is good practice.
  // This prevents the code from getting stuck waiting for a sensor to respond. 2500 microseconds is a good starting point.
  qtr.setTimeout(2500);

  Serial.begin(9600);
  
  delay(500);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, HIGH); // Turn on LED to indicate calibration is starting

  // Calibrate for about 10 seconds:
  // During this time, you should slide the sensor array back and forth over the black line 
  // and the white surface to expose it to the minimum and maximum reflectance values.
  Serial.println("Starting Callibration");
  for (uint16_t i = 0; i < 400; i++)
  {
    qtr.calibrate();
    delay(20);
  }

  digitalWrite(LED_BUILTIN, LOW); // Turn off LED to indicate calibration is done

  // Print the calibration data to the Serial Monitor for debugging.
  Serial.println("Calibration complete. Minimum and Maximum sensor 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();
  Serial.println();
  delay(1000);
}

void loop()
{
  // The readLineBlack() function returns a value from 0 to 7000 (since you have 8 sensors).
  // 0 means the line is on the far left (under sensor 0).
  // 3500 means the line is in the middle.
  // 7000 means the line is on the far right (under sensor 7).
  // It also fills the 'sensorValues' array with the current calibrated readings from each sensor.
  uint16_t position = qtr.readLineWhite(sensorValues);

  // Print the raw calibrated values from each sensor.
  // For an RC sensor, a value of 1000 means fully black and 0 means fully white.
  for (uint8_t i = 0; i < SensorCount; i++)
  {
    Serial.print(sensorValues[i]);
    Serial.print('\t');
  }
  
  // Print the calculated line position
  Serial.print("  Position: ");
  Serial.println(position);

  delay(250);
}

[xfpd]

Show the output you see.

Verify each line sensor works with white cloth. The shiney surface is probably creating a false "line!" indicator. The algorithm to find the line is bizarre.