QTR-8RC Digital Infrared Line Follower Sensor
It has 8 IR LED / phototransistor pairs mounted 1cm apart and is a perfect detector for line follower robots. It can also be used as a general-purpose proximity or reflection sensor.
The outputs are all independent, but the LEDs are arranged in pairs to halve current consumption. The LEDs are controlled by a MOSFET with a gate normally pulled high, which allows the LEDs to be turned off by setting the MOSFET gate to a low voltage. Turning off the LEDs can be advantageous to limit power consumption when the sensors are not in use or to change the effective brightness of the LEDs with PWM control.
Schematic Diagram of the Module
Technical Specifications
- Operating voltage: 3.3-5.0V
- Supply current: 100mA
- Output format: 8 digital I/O compatible signals
- Output voltage range: 0V to delivered voltage
- Optimal detection distance: 3mm
- Recommended maximum sensing distance: 6mm
The QTR-8RC module, like the Parallax QTI, has a digital I/O line that can drive the output line high and then measure the decay time of the output voltage. It has eight identical sensor outputs that need Typical sequence to read a sensor:
- Turn on IR LEDs
- Set the I/O line to an output and drive it up
- Sensor output rises Allow at least 10μs for
- Turn the I/O line into an input
- Measure the voltage drop time by waiting for the I/O line to drop
- Turn off the IR LEDs
These steps can typically be performed in parallel across multiple I/O lines.
With a strong reflection, decay time can be as low as a few dozen microseconds; without reflection, decay time can be up to several milliseconds. The exact time of degradation depends on your microcontroller's I/O line capabilities. In typical cases, meaningful results can be obtained within 1 ms.
Pololu AVR library offers functions that make it easy to use these sensors with robot controllers. For more information QTR library command You can check the section. For the QTR-8RC Arduino library,
click
Splitting the Module in Two
If you do not need all eight sensors, you can break two sensors and use all 8 sensors as two separate modules as shown below . Each of the two resulting parts functions as an independent line sensor.
Pololu QTR Sensors Application Notes
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