QTR-1A Reflective Infrared Sensor (2 pcs)

Functional Description

The Pololu QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair. The phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analog voltage output between 0 V and VIN (which is typically 5 V) as a function of the reflected IR. Lower output voltage is an indication of greater reflection.

The LED current-limiting resistor is set to deliver approximately 17 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power.

This sensor was designed to be used with the board parallel to the surface being sensed. Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity/edge detection.

Each phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analog voltage output between 0 V and VCC (which is typically 5 V) as a function of the reflected IR. Lower output voltage is an indication of greater reflection.

QTR sensor size comparison. Top row: QTRX-HD-07, QTR-HD-07; middle row: QTR-3, QTR-1, QTR-L-1; bottom row: QTR-8.

Specifications

• Dimensions: 0.3" x 0.5" x 0.1" (without optional header pins installed)

• Operating voltage: 5.0 V

• Supply current: 17 mA

• Output format: analog voltage

• Output voltage range: 0 to supplied voltage

• Optimal sensing distance: 0.125" (3 mm)

• Maximum recommended sensing distance: 0.25" (6 mm)

• Weight without header pins: 0.008 oz (0.2 g)

QTR-1A output 1/8" away from a spinning white disk with a black line on it.

QTR-1A output 1/8" away from a spinning white disk with a black line on it.