QTR-8RC Reflectance Sensor Array

295.00EGP

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Description

qtr dim

Functional Description

The QTR-8RC reflectance sensor array is intended as a line sensor, but it can be used as a general-purpose proximity or reflectance sensor. The module is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at intervals of 0.375″ (9.525 mm). To use a sensor, you must first charge the output node by applying a voltage to its OUT pin. You can then read the reflectance by withdrawing the externally supplied voltage and timing how long it takes the output voltage to decay due to the integrated phototransistor. Shorter decay time is an indication of greater reflection. This measurement approach has several advantages, especially when coupled with the ability of the QTR-8RC module to turn off LED power:

  • No analog-to-digital converter (ADC) is required
  • Improved sensitivity over voltage-divider analog output
  • Parallel reading of multiple sensors is possible with most microcontrollers
  • Parallel reading allows optimized use of LED power enable option

The outputs are all independent, but the LEDs are arranged in pairs to halve current consumption. The LEDs are controlled by a MOSFET with a gate normally pulled high, allowing the LEDs to be turned off by setting the MOSFET gate to a low voltage. Turning the LEDs off might be advantageous for limiting power consumption when the sensors are not in use or for varying the effective brightness of the LEDs through PWM control.

This sensor was designed to be used with the board parallel to the surface being sensed

 

Specifications

  • Dimensions: 2.95″ x 0.5″ x 0.125″ (without header pins installed)
  • Operating voltage: 3.3-5.0 V
  • Supply current: 100 mA
  • Output format: 8 digital I/O-compatible signals that can be read as a timed high pulse
  • Optimal sensing distance: 0.125″ (3 mm)
  • Maximum recommended sensing distance: 0.375″ (9.5 mm)
  • Weight without header pins: 0.11 oz (3.09 g)

 

Arduino Library for the Pololu QTR Reflectance Sensors

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