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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

Summary of content (12 pages)

PAGE 1
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. Contacting Pololu . . . . . . . . . . . . . . . . . 3. Physical Characteristics . . . . . . . . . . . . . 4. Distinguishing the QTR-8A from the QTR-8RC . 5. Module Connections . . . . . . . . . . . . . . . 6. Breaking into Two Submodules . . . . . . . . . 7. Additional Considerations . . . . . . . . . . . .
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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).
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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.
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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/].
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation 3. Physical Characteristics Both the QTR-8A and QTR-8RC have the same physical characteristics. Each array measures 2.95" long by 0.50" wide and has a maximum thickness of approximately 0.125". Without header pins, the unit weighs 0.11 oz (3.1 g). The individual reflectance sensors are distributed evenly on the board at 0.375" intervals. The mounting holes are intended for #2 screws.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation 4. Distinguishing the QTR-8A from the QTR-8RC The QTR-8A sensor array has a different output format from the QTR-8RC, so it is important you know which sensor model you have. What distinguishes one model from another are the components placed on a common PCB. The pictures below show the two models: QTR-8A reflectance sensor array. QTR-8RC reflectance sensor array.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation 5. Module Connections The QTR-8x reflectance sensor arrays are designed to provide some connection flexibility. The pins are standard 0.1" spacing and are arranged to support connection using either an 11×1 header strip or an 8×2 header strip. A 25-pin 0.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation Note: Do not short the 3.3V BYPASS pins together while using a Vcc of 5 V. While this would make the LEDs even brighter, it would exceed their current rating and put them at risk of burning out. LEDON This pin is connected to a MOSFET that delivers power to the IR LEDs, so its state determines the whether the LEDs are on or off.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation depends on your microcontroller’s I/O line characteristics. Meaningful results can be available within 1 ms in typical cases (i.e. when not trying to measure subtle differences in low-reflectance scenarios), allowing up to 1 kHz sampling of all 8 sensors. If lower-frequency sampling is sufficient, substantial power savings can be realized by using the LEDON pin to turn off the LEDs.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation 6. Breaking into Two Submodules If you don’t need or cannot fit all eight sensors, the QTR-8x arrays can each be separated into two smaller sensor arrays that can function independently: a two-sensor array and a six-sensor array. To break the board, use a sharp knife (e.g. hobby knife or box cutter) to score along the perforation (row of vias) between sensors 6 and 7.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation If you are operating at a Vcc of 3.3 V, short those two pins together with a piece of wire. With a connection in place between these two pins, the two-sensor board will function. After the separation, sensor outputs 7 and 8 on the six-sensor board will no longer provide any signals. 6.
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QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide © 2001–2014 Pololu Corporation 7. Additional Considerations As the sensing distance of your sensors increases, the distinction between black and white surfaces starts to decrease. This problem can be exacerbated by infrared components of ambient lighting.