Pololu QTR-8RC User Manual
QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation
QTR-8A and QTR-8RC Reflectance
Sensor Array User's Guide
1. Overview and General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Distinguishing the QTR-8A from the QTR-8RC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Module Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Breaking into Two Submodules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Additional Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
http://www.pololu.com/docs/0J12/all Page 1 of 12
QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation
1. Overview and General Specifications
The Pololu QTR-8A [http://www.pololu.com/product/960] and QTR-8RC [http://www.pololu.com/product/961] reflectance
sensor arrays are intended as line sensors, but they can be used as a general-purpose proximity or reflectance
sensors. Each module is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at
intervals of 0.375" (9.525 mm). 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.
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. The schematic diagram of the module is shown below:
Specifications for the QTR-8x Reflectance Sensor Array
• Dimensions: 2.95" x 0.5"
• Operating voltage: 3.3-5.0 V
• Supply current: 100 mA
• Output format for the QTR-8A: 8 analog voltages ranging from 0 V to supplied voltage
• Output format for the QTR-8RC: 8 digital I/O-compatible signals that can be read as a timed high pulse
• Optimal sensing distance: 0.125" (3 mm)
1. Overview and General Specifications Page 2 of 12
QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation
• Maximum recommended sensing distance for the QTR-8A: 0.25" (6 mm)
• Maximum recommended sensing distance for the QTR-8RC: 0.375" (9.5 mm)
• Weight without header pins: 0.11 oz (3.1 g)
1. Overview and General Specifications Page 3 of 12
QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation
2. Contacting Pololu
You can check the QTR-8A page [http://www.pololu.com/product/960] or QTR-8RC page [http://www.pololu.com/product/
961] for additional information. We would be delighted to hear from you about any of your projects and about your
experience with the QTR-8A reflectance sensor array. You can contact us [http://www.pololu.com/contact] directly or post
on our forum [http://forum.pololu.com/]. Tell us what we did well, what we could improve, what you would like to see
in the future, or anything else you would like to say!
2. Contacting Pololu Page 4 of 12
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