QTR-1RC Digital Infrared Sensor Pair (Qty 2)
The QTR-1RC reflectance sensor is a single in an inexpensive, small 0.5"x 0.3" module that can be mounted almost anywhere It carries an infrared LED and phototransistor pair. The reflectance measurement is given as digital voltage. 2 qtr1rc sensors are shipped.
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 vary the effective brightness of the LEDs with PWM control. LED current limiting resistors for 5V operation are arranged in two stages; This allows a simple tap bypass to enable operation at 3.3V. LED current is approximately 20-25mA, reducing the total board consumption to less than 100mA.
Schematic Diagram of the Module
Specifications
- Dimensions: 0.3"x0.5"x 0.1"(without optional header pins installed)
- Operating voltage:5V
- Supply current: 17 mA
- Output format: digital voltage
- Optimal detection distance: 3mm
- Recommended maximum detection distance: 9.5mm
- Weight without header pins: 0.2g
Interfacing QTR-1RC Outputs to Digital Input/Output Lines
The QTR-1RC module has eight identical sensor outputs, like the Parallax QTI, requiring a digital I/O line that can drive the output line high and then measure the decay time of the output voltage:
- Turn on IR LEDs
- Set the I/O line to an output and drive it up
- Allow at least 10μs for the sensor output to rise
- Make the I/O line 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 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 the I/O line capabilities of your microcontroller. 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-1RC Arduino library,
click
Set Contents
This module has a single mounting hole designed for #2 screws (screws not included); In case this mounting hole is not needed, this part of the PCB can be grounded to make the unit even smaller. Each package of two infrared sensors includes a straight male header and a right angle male header, allowing you to mount them in the orientation you choose.
Pololu QTR Sensors Application Notes
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