We are pleased to introduce our new line of QTR reflectance sensors! These modules are convenient, compact carrier boards for IR emitter (LED) and receiver (phototransistor) pairs, and are great for line following or proximity/edge detection. The QTRs come in two sizes: QTR-1x is a tiny, single-sensor unit measuring just 0.5"x0.3"x0.1" that can be mounted almost anywhere, and QTR-8x is an 8-sensor array intended for (but not limited to) use as a line sensor. If you don’t need or can't fit all eight sensors of the QTR-8x, you can break the module into two fully functionally sub-modules: a 2-sensor array and a 6-sensor array.
The QTR sensors also come in two different output formats: QTR-xA uses voltage dividers to provide x independent analog voltage outputs from each phototransistor, and QTR-xRC uses capacitor discharge circuits to provide x independent outputs that can each be read directly by a digital I/O line on a microcontroller. This latter output format relies upon the microcontroller to briefly (~10 us) drive the sensor output line high and then time how long it takes for the line to read low; this is the same interface as Parallax's QTI sensor.
Please see the following product pages for more information, including a user's guide and an application note: