The QTR-1RC reflectance sensor carries a single infrared LED and phototransistor pair. The phototransistor uses a capacitor discharge circuit that allows a digital I/O line on a microcontroller to take an analog reading of reflected IR by measuring the discharge time of the capacitor. Shorter capacitor discharge time is an indication of greater reflection.
The LED current-limiting resistor is set to deliver approximately 20-25 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power.
Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity/edge detection.
This module has a single mounting hole intended for a #2 screw (not included); if this mounting hole is not needed, this portion of the PCB can be ground off to make the unit even smaller. The reflectance sensor ships with a 3-pin 0.1" header strip, which can be soldered in the conventional perpendicular orientation or parallel to the PCB. You can also solder wires, such as ribbon cable, directly to the pads for the smallest installation.
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Would this work outdoors or does it need to be shielded from sunlight?
It needs to be shielded from sunlight.
Can anyone tell me the chip used on this board? I would really love to use it in some projects I've been putting off because I can't find a chip I need and this would be perfect!
According to the Pololu website, it's Fairchild QRE1113GR