The strap is used in robots like line follower as sensors detecting the track as a black line on a white background. The module consists of seven reflective sensors that contain the transmitting IR LED and receiver in the form of phototransistor. Output are the analog signals that can be read using any microcontroller with A/C converter, including Arduino.
There are several solutions that allows to read data from sensors QTR-HD-03A:
- Connecting the outputs to microcontroller with analog to digital converter, for example, analog Arduino pins
- Connecting to the digital inputs through theanalog comparator, determining the threshold between white and black
- Connecting directly to the digital pins, using built-in into microcontroller, internal comparator
The product is compatible with Arduino
The optimal distance of the sensors from the surface, is 10 mm, the maximum, at which the sensor operates, is 40 mm. To picture the situation, we present the oscilograms showing the detection of black line on a white background at different distances from the surface.
The analog signal, after the detection of black lines on white surface, in the close distance - on the left side and further on the right side.
Each of phototransistors has pulling-up external resistor, allowing for the direct connection of the output to the microcontroller and the read of the voltage from 0 to VCC, appropriate for the color and distance from the surface.
Current of each transmitting LED was set to 30 mA, the maximum current consumption of the whole module is about 125 mA.
Diagram of one channel of the module QTRX-HD-07A.
- Number of sensors: 7
- Supply voltage: from 2.9 V to 5.5 V
- Current consumption: 17 mA
- Current consumption of one LED: 3.5 mA
- Outputs: analog
- The optimal measurement distance: 10 mm
- The maximum distance of measurements: 40 mm
- Light wavelength: 940 nm
- Sensor's type: QTRX
- Distance between sensors: 4 mm
- Dimensions 29 x 20 x 3 mm
- Weight: 1.7 g