QTR-8RC Line Following Reflectance IR Sensor Array

QTR-8RC Reflectance Sensor Array is an essential tool for robotics enthusiasts and engineers designing line-following robots or proximity sensing systems. This compact module features an array of eight infrared (IR) sensor pairs, each comprising an IR LED and a phototransistor. It measures the reflected IR light from the surface below, providing a clean digital pulse-width modulation (PWM) output that microcontrollers, like Arduino or Raspberry Pi, can easily read. Its key advantage lies in its digital nature, offering significantly faster readings compared to analog arrays and simplifying the programming required to interpret surface reflectivity, making it the industry standard for competitive line-following robotics.

Key Features:

• 8 Individual Sensor Pairs: A dense array of eight IR emitter/phototransistor pairs allows for precise line detection and detailed surface mapping.
• Digital/RC Output: The module provides an RC (Resistor-Capacitor) timing output; a faster reading indicates greater reflectance. This digital nature significantly reduces noise and processing time.
• Integrated LED Current Limiting Resistors: These resistors protect the IR emitters, allowing you to power the board directly from a 5V supply without external components.
• Brightness Control: You can enable and disable the IR emitters via a control pin, which helps reduce power consumption or allows for multiple sensor arrays to operate without interference.
• Fast Sensing Time: Offers high-speed detection, crucial for rapid movements in competitive robotics, with typical reading times of just a few hundred microseconds.
• Compact and Lightweight: Its small footprint makes it easy to integrate into even the smallest robot chassis.

Technical Specifications:

• Operating Voltage: 3.3V to 5V
• Sensor Type: Reflectance (Infrared)
• Number of Sensors: 8
• Output Type: Digital (RC Timing)
• Optimal Sensing Distance: 0.125″ to 0.375″ (3mm to 10mm)
• Current Consumption: <100 mA (when all emitters are on at 5V)
• Compatibility: Compatible with 3.3V and 5V microcontrollers.

Mechanical Specifications:

• Sensor Pitch: 0.375″ (9.525 mm) between sensor centers.
• Mounting Holes: Two mounting holes for secure attachment to a robot chassis.
• Connector: Standard 10-pin male header for I/O connections.
• Material: High-quality PCB with a protective solder mask.

Dimensions:

• Length: 2.95″ (75 mm)
• Width: 0.5″ (12.7 mm)
• Board Thickness: ~1.6 mm

Pinout and Wiring:

• GND: Ground connection.
• VCC: Power supply input (3.3V to 5V).
• LEDON: Control pin for the IR emitters. Pull this pin HIGH to turn the LEDs ON (or leave disconnected for default ON).
• 1 to 8: Individual sensor output pins (connect to digital I/O pins on your microcontroller).
• Wiring Note: Connect VCC to the 5V rail and GND to the ground. Connect each of the eight output pins (1-8) to a separate digital input pin on your Arduino. Use the QTRSensors library for easy reading of the RC timing values.

Datasheet Reference:

• Download Datasheet

Commonly Used in:

• Line Following Competitions: The sensor of choice for MicroMouse, Sumo, and other high-speed line following robots.
• Maze Solving Robots: Detect walls and boundaries by sensing floor contrast changes.
• Educational Robotics Kits: A fundamental sensor for teaching students about feedback control systems and sensor reading.

Applications:

• Line Detection: Accurately track black lines on a white surface or vice versa.
• Edge Detection: Prevent robots from falling off tables or platforms.
• Proximity Sensing: Use the individual sensors to detect objects very close to the floor.
• Surface Contrast Measurement: Determine the reflectivity of different materials.

Equivalent Models:

• QTR-8A: The analog version of the same array, which provides a voltage output instead of an RC timing output.
• TCRT5000: A single, basic IR reflectance sensor, often used when only one point of detection is needed.

Package Includes:

• 1 x QTR-8RC Line Following Reflectance IR Sensor Array