Specification:
- Number of sensors: 3
- Supply voltage: 5 V
- Current consumption: 50 mA
- Outputs: digital - frequency signal
- The optimum distance for measurement: 3 mm
- The maximum distance for measurement: 6 mm
- Dimensions 32 x 8 x 3 mm
- Weight: 0.6 g
The kit includes one module with sensors and two goldpin straps: straight and corner for self-soldering.
Description
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 three reflective sensors that contain the IR transmitting LED and receiver in the form of phototransistor. The output are the digital signals which can be read using any microcontroller with an A/C converter, including Arduino.
Between the sensors left is 9.5 mm space so that a strap was reliable on the tracks applied with the standard insulating tape with the width of 19 mm.
Service
Strap QTR-3RC, similarly to the QTR-8RC module, has digital outputs. Reading the measurement data, is carried out by charging the capacitor (the indication of high status), and measuring the time of discharge of it through phototransistor. This option has the following advantages:
- It does not require an analog-to-digital converter
- Gives the possibility of parallel read of the values of three sensors
A typical sequence of the reading of sensor's values:
- Setting the I/O pins of the microcontroller as outputs and the creation of the high status
- Waiting a few micro seconds - charging the capacitor of 2.2 NF
- The setting of the I/O pins as input (high impedance status)
- Measuring the discharge time of the capacitor by waiting till the I/O lines come to low status
With a high intensity of the reflected signal, the measured time will be oscilating within a few microseconds. A small amount of reflected light will be discharging the capacitor for a few milliseconds. The exact time depends on characteristics of the pins of the microcontroller.
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The product is compatible with Arduino For users of AVR microcontrollers and modules of Arduino, the manufacturer has prepared special libraries facilitating the convenient operation of sensors: the AVR library, the Arduino library. |
Scheme
Each of phototransistors uses a capacitor and an auxiliary circuit that can read data from the sensors by measuring the time of discharge.
Current to each transmitting LED was set to 17 mA, what at powering with the voltage of 5 V makes that the average current consumption of the whole module is about 50 mA.
Diagram of the module QTR-3RC.
Useful links |
