QTR-MD-01A-S IR Reflectance Sensor, 1-Channel, Analog Output, JST SH Connector - Pololu 4240

Description

Pololu QTR-MD-01A-S is a compact reflectance sensor designed to measure the amount of infrared light reflected from nearby surfaces. The module uses an IR emitter LED and a phototransistor, enabling detection of changes in surface reflectivity or the presence of objects located close to the sensor.

                                                     Pinout of the QTR-MD-01x-S reflectance sensor (RC version shown in the illustration; pinout identical for the analog version)

The module produces an analog output signal ranging from 0 V to VCC, which can be read directly using the ADC of a microcontroller. High reflectivity surfaces result in a lower output voltage, while lower reflectivity produces a higher output voltage. The sensor operates with a supply voltage from 2.9 V to 5.5 V, making it compatible with common microcontroller platforms such as Arduino, STM32, ESP32, and Raspberry Pi Pico. An integrated LED driver allows IR emitter brightness adjustment across 32 dimming levels, independent of the supply voltage.

The optimal sensing distance is approximately 5 mm, while highly reflective objects can be detected at distances up to about 30 mm. The lensless QTR sensor design corresponds to the classic QTR style commonly used for line-following sensors and contrast detection on surfaces. The board includes a 4-pin JST SH side-entry connector, enabling quick connection using cables compatible with Qwiic and STEMMA QT systems. The sensor interface, however, provides an analog signal and does not use the I²C bus.

Features

• single-channel infrared reflectance sensor
• sensor type: QTR
• light source: IR LED (940 nm)
• reflection detection using a phototransistor
• supply voltage: 2.9 V – 5.5 V
• output: analog voltage 0 V – VCC
• maximum IR LED current: 30 mA
• maximum board current consumption: 32 mA
• IR emitter brightness control with 32 dimming levels
• optimal sensing distance: 5 mm
• maximum recommended sensing distance: 30 mm
• connector: 4-pin JST SH (side-entry)
• dimensions: 8.1 × 15.2 × 5.5 mm
• weight: 0.4 g

Kit includes

• 1 × Pololu QTR-MD-01A-S reflectance sensor (Pololu 4240)