Advertisement
QTI stands for Charge Transfer Infrared, an acronym describing how the sensor uses the
charge/discharge time of a capacitor to provide a scaled output, without requiring any additional
analog-to-digital circuitry.
In a working circuit, your microcontroller measures the time it takes for the QTI's capacitor to
decay. This decay time is a measurement of the rate of charge transfer through the infrared
phototransistor, and indicates how much infrared light is reflecting off a nearby surface.
Parts List
QTI Sensor
•
BASIC Stamp HomeWork Board, Propeller BOE, Propeller QuickStart, or Arduino Uno
•
microcontroller (solderless breadboard as needed)
22 gauge solid conductor hookup wire
•
Basic Wiring
Power requirements: 3.3 to 5 VDC
•
Communication: Analog output of capacitor decay time depending on level of infrared
•
reflectivity
Dimensions: 1.25 x 0.37 in (31.7 x 9.4 mm)
•
Important! The labeling on the QTI Sensor refers to the colors of a 3-wire servo extension wire:
Black, Red, and White. The QTI does not follow the typical arrangement of 3-wire connections
where the center (red) wire is power. Be sure not to reverse the +V and Gnd wires!
Copyright © Parallax Inc.
Page 2 of 6
Advertisement
