QTRX-HD-07A Reflectance Sensor Array: 7-Channel, 4mm Pitch, Analog Output, Low Current - Pololu 4207

Index: PLL-12656 EAN: 5904422319809

Compact strap with seven reflective sensors with the size of 29 x 20 mm. It has digital outputs, is powered with the voltage from 2.9 V to 5.5 V and allows for the adjustment of brightness regardless of the supply voltage. It detects the objects at a distance of about. 40 mm. The QTR sensor has no lenses.

QTRX-HD-07A Reflectance Sensor Array: 7-Channel, 4mm Pitch, Analog Output, Low Current - Pololu 4207
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Waiting time: 4-6 weeks
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Manufacturer: Pololu
Compatibility: Arduino


The strap is used in robots like line follower as sensors detecting the track as a black line on a white background. The module consists of seven reflective sensors that contain the transmitting IR LED and receiver in the form of phototransistor. Output are the analog signals that can be read using any microcontroller with A/C converter, including Arduino. QTR sensor has no lenses and features with a higher consumption of current than QTRX.



There are several solutions that allows to read data from sensors QTR-HD-03A:

  • Connecting the outputs to microcontroller with analog to digital converter, for example, analog Arduino pins
  • Connecting to the digital inputs through theanalog comparator, determining the threshold between white and black
  • Connecting directly to the digital pins, using built-in into microcontroller, internal comparator

The product is compatible with Arduino

For users of Arduino modules, manufacturer has prepared a library that simplifies the maintenance of the sensors

The optimal distance of the sensors from the surface, is 5 mm, the maximum, at which the sensor operates, is 40 mm. To picture the situation, we present the oscilograms showing the detection of black line on a white background at different distances from the surface.

The analog signal, after the detection of black lines on white surface, in the close distance - on the left side and further on the right side.



Each of phototransistors has pulling-up external resistor, allowing for the direct connection of the output to the microcontroller and the read of the voltage from 0 to VCC, appropriate for the color and distance from the surface.


Current of each transmitting LED was set to 30 mA, the maximum current consumption of the whole module is about 125 mA.

Diagram of the one channel of the module the QTR-HD-07A.


  • Number of sensors: 7
  • Supply voltage: from 2.9 V to 5.5 V
  • Current consumption: 125 mA
  • Current consumption of one LED: 30 mA
  • Outputs: analog
  • The optimal measurement's distance: 5 mm
  • The maximum distance of measurements: 40 mm
  • Light wavelength: 940 nm
  • Sensor's type: QTR
  • Distance between sensors: 4 mm
  • Dimensions 29 x 20 x 3 mm
  • Weight: 1.7 g


Package width 7 cm
Package height 0.3 cm
Package depth 5 cm
Package weight 0.001 kg

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