QTR-8 Reflectance Sensor Array User's Guide

Table Of Contents

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 0.1" header strip is included with the module; you can break this strip into smaller strips and solder them as

desired, or you can solder wires directly to the unit for a more compact installation. The two connection methods are

pictured below:

QTR-8x reflectance sensor array with 11×1 connection pins labeled.

QTR-8x reflectance sensor array with 8×2 connection pins labeled.

Several pins appear in multiple locations, but you can leave duplicate connection points disconnected. For example,

you do not need to connect ground to all six ground pins along the lower edge of the board. Duplicate pins exist so

that you can choose the most convenient points to make your connections.

Vcc, GND, and 3.3V BYPASS

The Vcc and GND pins are where the sensor array receives its power. Your Vcc connection must be between 3.3

and 5 V and must be able to supply at least 100 mA. The sensor’s outputs will be relative to GND.

The module is calibrated so that its IR LEDs will achieve optimal brightness when Vcc is 5 V; using a lower Vcc

will decrease the LED brightness or cause them to turn off completely. You can compensate for this by shorting the

two 3.3V BYPASS pins together, which bypasses one stage of the LED current-limiting resistors and increases LED

brightness.

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. When this pin is driven high or left disconnected (it is internally pulled high), the LEDs are all

on; when this pin is driven low, the LEDs are off. You can use this pin to save power by turning the LEDs off while

5. Module Connections Page 6 of 9