The QTR-8A 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). Each 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 resistors for 5 V operation are arranged in two stages; this allows a simple bypass of one stage to enable operation at 3.3 V. The LED current is approximately 20-25 mA, making the total board consumption just under 100 mA.

Technicial Specifications:

• Operating Voltage: 3.3 - 5V
  
• Operating Current: 100mA
  
• Output format: 8 analog signal voltage
  
• Output voltage range: 0 V-Supply Voltage Value
  
• Ideal sensing distance: 3 mm
  
• Maximum sensing distance: 6 mm
  
• Dimensions: 67mm x 17mm x 4mm

Documents:

• Arduino library and example application