The QTR-8A reflectance is intended as a line sensor, but it can be used as a general-purpose proximity or reflectance sensor. The array is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at intervals of 0.375″ (9.525mm). Each phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analogue voltage output between 0V and VIN (which is typically 5V) as a function of the reflected IR. The lower output voltage is an indication of greater reflection.

Features Of Reflectance Sensor Array 8 channel Line Following Line Tracking Sensor Module QTR 8A:

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

Specifications Of QTR-8A Reflectance Sensor Array:

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

Ways Of Interface With QTR-8A Outputs:

• Use a microcontroller?s analogue-to-digital converter (ADC) to measure the voltages.
• Use a comparator with an adjustable threshold to convert each analogue voltage into a digital (i.e. black/white) signal that can be read by the digital I/O line of a microcontroller.
• Connect each output directly to a digital I/O line of a microcontroller and rely on its internal comparator.

This last method will work if you are able to get high reflectance from your white surface as depicted in the left image, but will probably fail if you have a lower-reflectance signal profile like the one on the right.

Package Includes:

• 1 x Reflectance Sensor Array QTR-8A

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