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Infrared

Infrared Sensors
 
 

   

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  1. Pololu IR beacon transceiver

    Pololu IR beacon transceiver

    $32.24

    The Pololu IR beacon is a compact board that is used in pairs to allow robots to locate each other. Each board has infrared emitters that shine in all directions and four IR receivers for detecting the other beacon. The IR beacons have a range of about fifteen feet indoors. This item is for a single unit.

    Pololu’s new IR beacon (infrared beacon) is an updated version of our original IR beacon. Like the original unit, the devices are transceivers meant to be used in pairs to give robots a simple means for detecting each other. You can use the beacons to build pairs of robots that interact or chase one another, or to make a robot that can identify and return to a home base. For example, you could build a “cat robot” and “mouse robot” that each have an IR beacon, where the cat chases the mouse and the mouse runs away from the cat. The beacons are ideal for autonomous robot contests in which robots compete in pairs, such as MIT’s annual 6.270 autonomous robot design competition, where our original beacons were used for several years.

    The new IR beacons feature round PCBs with six wide-angle emitters to provide uniform broadcasting in all directions. The operating voltage range has increased to 6 – 16 V, and on-board voltage monitoring enables a more consistent output brightness over the voltage range. Most components are pre-assembled, so all you need to solder is the capacitor, connectors, and sensors (make sure you solder them in from the bottom of the PCB!).

    Note: The Pololu IR beacon is a kit; before using it, you need to assemble the beacon by soldering its components onto its circuit board. To use the kit in robotics projects, you need to connect it to your own robot controller. Please note that the IR beacons only work in pairs and that certain kinds of artificial lighting (e.g. some fluorescent lights) can interfere with the sensors.

    Device Specifications

    • PCB size: 1.35" circle
    • IR modulation frequency: 56 kHz
    • Output refresh rate 20 Hz
    • Detection range: 6 inches to 20 feet
    • Supply voltage: 6-16 V
    • Data voltage: 5 V
    • Number of IR detectors: 4

    How the IR Beacons Work

    The beacons work by transmitting and detecting infrared light, much like a television remote control. Each beacon has four IR emitters and four IR detectors. The beacons alternate between transmitting and receiving so that they never get confused by reflections of their own transmissions.

    The transmit and detect cycle is carried out more than one thousand times per second, and a small microcontroller monitors all four detectors to decide the direction to the other beacon. The beacons have four red LEDs that indicate the direction to the other beacon; if you take two beacons and rotate them, the LEDs will always keep lighting up in the direction of the other beacon.

    Interfacing to the beacon is simple — it has four digital outputs that indicate which of its four sides detects the other beacon the strongest. You can establish the direction to another beacon to within a few degrees by rotating the beacon back and forth and noting the point where the output switches from one side to another. An enable input lets you select between active mode and a low-power mode.

    IR Beacon Development Kit (Transmit-Only Beacon)

    In response to customer requests, the IR beacon is available as just an assembled PCB with no IR sensors or firmware. This item is intended for advanced users who want to customize their IR beacon functionality by writing their own firmware. The main processor is a Microchip PIC16F630, and the PCB includes a footprint for a 5-pin header compatible with the PIC kit 2 programmer. The IR Receiver Modules are available separately. The schematic is shown below and is the only documentation shipped with this IR Beacon Devlopment kit:

    It is important to note that the IR beacon achieves its brighness by pulsing the IR LEDs with very high currents; turning on the IR LEDs continuously will burn them out. When testing the IR beacon, a digital camera can be useful in determining whether the IR LEDs are on. However, some cameras (usually more expensive ones) have better filters that block IR. In the picture below, a point-and-shoot camera shows the IR LEDs shining (in purple) but the DSLR with which the picture is taken does not show the LEDs.

    Learn More
  2. QTR-1RC Reflectance Sensor

    QTR-1RC Reflectance Sensor

    $4.75

    The QTR-1RC reflectance sensor carries a single infrared LED and phototransistor pair in an inexpensive, tiny 0.5" x 0.3" module that can be mounted almost anywhere and is great for edge detection and line following applications. The output is designed to be measured by a digital I/O line.

    Note: The QTR-1RC reflectance sensor requires a digital I/O line to take readings. The similar QTR-1A reflectance sensor is available with an analog output.

    Functional Description

    The Pololu QTR-1RC reflectance sensor carries a single infrared LED and phototransistor pair. The phototransistor uses a capacitor discharge circuit that allows a digital I/O line on a microcontroller to take an analog reading of reflected IR by measuring the discharge time of the capacitor. Shorter capacitor discharge time is an indication of greater reflection.

    The LED current-limiting resistor is set to deliver approximately 20-25 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power.

    Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity/edge detection.

    Specifications

    • Dimensions: 0.3" x 0.5" x 0.1" (without header pins installed)
    • Operating voltage: 5.0 V
    • Supply current: 25 mA
    • Output format: digital I/O compatible
    • Optimal sensing distance: 0.125" (3 mm)
    • Maximum recommended sensing distance: 0.375" (9.5 mm)
    • Weight without header pins: 0.008 oz (0.23 g)
    Interfacing the QTR-1RC Output to a Digital I/O Line

    Like the Parallax QTI, the QTR-1RC module has sensor outputs that require a digital I/O line capable of first charging the output capacitor (by driving the line high) and then measuring the time for the capacitor to discharge through the phototransistor. This measurement approach has several advantages, especially when multiple units are used:

    • No analog-to-digital converter (ADC) is required
    • Improved sensitivity over voltage-divider analog output
    • Parallel reading of multiple sensors is possible with most microcontrollers

    The typical sequence for reading a sensor is:

    1. Set the I/O line to an output and drive it high
    2. Allow at least 10 us for the 10 nF capacitor to charge
    3. Make the I/O line an input (high impedance)
    4. Measure the time for the capacitor to discharge by waiting for the I/O line to go low
    These steps can typically be executed in parallel on multiple I/O lines.

    With a strong reflectance, the discharge time can be as low as several dozen microseconds; with no reflectance, the discharge time can be up to a few milliseconds. The exact time of the discharge depends on your microcontroller’s I/O line characteristics. Meaningful results can be available within 1 ms in typical cases (i.e. when not trying to measure subtle differences in low-reflectance scenarios), allowing up to 1 kHz sampling.

    Our Pololu AVR library provides functions that make it easy to use these sensors with our Orangutan robot controllers and other AVR-based controller boards such as Arduinos. Please see section 11 of our library command reference for more information.

    Included Components

    This module has a single mounting hole intended for a #2 screw (not included); if this mounting hole is not needed, this portion of the PCB can be ground off to make the unit even smaller. The reflectance sensor ships with a 3-pin 0.1" header strip, which can be soldered in the conventional perpendicular orientation or parallel to the PCB, as shown below. You can also solder wires, such as ribbon cable, directly to the pads for the smallest installation.

     

     

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  3. QTR-8A Reflectance Sensor Array

    QTR-8A Reflectance Sensor Array

    $19.95

    This sensor module has 8 IR LED/phototransistor pairs mounted on a 0.375" pitch, making it a great detector for a line-following robot. Pairs of LEDs are arranged in series to halve current consumption, and a MOSFET allows the LEDs to be turned off for additional sensing or power-savings options. Each sensor provides a separate analog voltage output.

    Important Notice: Some units shipped prior to 5 March 2009 were shipped with pre-biased NPN transistors instead of MOSFETs for the IR LED control. The LEDs on these units can still be controlled by the LEDON pin, but they do not default to being on when nothing is connected to LEDON. The LEDON pin should be connected to Vcc for applications that do not require LED control. We apologize for any inconvenience the mistake has caused. Please contact us if you have one of these units and would like the NPN transistor replaced with the MOSFET.

    Note: The QTR-8A reflectance sensor array requires analog inputs to take readings. The similar QTR-8RC reflectance sensor array is available with digital I/O-compatible outputs.

    Functional Description

    The QTR-8A reflectance sensor array is intended as a line sensor, but it can be used as a general-purpose proximity or reflectance sensor. The module is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at intervals of 0.375" (9.525 mm). Each phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analog voltage output between 0 V and VIN (which is typically 5 V) as a function of the reflected IR. Lower output voltage is an indication of greater reflection.

    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, allowing the LEDs to be turned off by setting the MOSFET gate to a low voltage. Turning the LEDs off might be advantageous for limiting power consumption when the sensors are not in use or for varying the effective brightness of the LEDs through PWM control.

    The LED current-limiting resistors for 5 V operation are arranged in two stages; this allows a simple bypass of one stage to enable operation at 3.3 V. The LED current is approximately 20-25 mA, making the total board consumption just under 100 mA. The schematic diagram of the module is shown below:

    Specifications

    • Dimensions: 2.95" x 0.5" x 0.125" (without header pins installed)
    • Operating voltage: 3.3-5.0 V
    • Supply current: 100 mA
    • Output format: 8 analog voltages
    • Output voltage range: 0 V to supplied voltage
    • Optimal sensing distance: 0.125" (3 mm)
    • Maximum recommended sensing distance: 0.25" (6 mm)
    • Weight without header pins: 0.11 oz (3.09 g)

    Interfacing with the QTR-8A Outputs

    There are several ways you can interface with the QTR-8A outputs:

    • Use a microcontroller’s analog-to-digital converter (ADC) to measure the voltages.
    • Use a comparator with an adjustable threshold to convert each analog voltage into a digital (i.e. black/white) signal that can be read by the digital I/O line of a microcontroller.
    • Connect each output directly to a digital I/O line of a microcontroller and rely upon its internal comparator.

    This last method will work if you are able to get high reflectance from your white surface as depicted in the left image, but will probably fail if you have a lower-reflectance signal profile like the one on the right.

    Our Pololu AVR library provides functions that make it easy to use these sensors with our Orangutan robot controllers and other AVR-based controller boards such as Arduinos. Please see section 11 of our library command reference for more information.

    Breaking the Module in Two

    If you don’t need or cannot fit all eight sensors, you can break off two sensors and still use all 8 sensors as two separate modules, as shown below. The PCB can be scored from both sides along the perforation and then bent until it snaps apart. Each of the two resulting pieces will function as an independent line sensor.

    Included Components

    This module ships with a 25-pin 0.1" header strip and a 100 Ohm through-hole resistor as shown below.

    You can break the header strip into smaller pieces and solder them onto your reflectance sensor array as desired, or you can solder wires directly to the unit or use a right-angle header strip for a more compact installation. The pins on the module are arranged so that they can all be accessed using either an 11×1 strip or an 8×2 strip.

    The resistor is required to make the two-sensor array functional after the original eight-sensor array is broken into two pieces. This resistor is only needed once the board has been broken.

    Learn More
  4. QTR-8RC Reflectance Sensor Array

    QTR-8RC Reflectance Sensor Array

    $19.95

    This sensor module has 8 IR LED/phototransistor pairs mounted on a 0.375" pitch, making it a great detector for a line-following robot. Pairs of LEDs are arranged in series to halve current consumption, and a MOSFET allows the LEDs to be turned off for additional sensing or power-savings options. Each sensor provides a separate digital I/O-measurable output.

    Important Notice: Some units shipped prior to 5 March 2009 were shipped with pre-biased NPN transistors instead of MOSFETs for the IR LED control. The LEDs on these units can still be controlled by the LEDON pin, but they do not default to being on when nothing is connected to LEDON. The LEDON pin should be connected to Vcc for applications that do not require LED control. We apologize for any inconvenience the mistake has caused. Please contact us if you have one of these units and would like the NPN transistor replaced with the MOSFET.

    Note: The QTR-8RC reflectance sensor array requires digital I/O lines to take readings. The similar QTR-8A reflectance sensor array is available with analog outputs.

    Functional Description

    The QTR-8RC reflectance sensor array is intended as a line sensor, but it can be used as a general-purpose proximity or reflectance sensor. The module is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at intervals of 0.375" (9.525 mm). Each phototransistor uses a capacitor discharge circuit that allows a digital I/O line on a microcontroller to take an analog reading of reflected IR by measuring the discharge time of the capacitor. Shorter capacitor discharge time is an indication of greater reflection.

    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, allowing the LEDs to be turned off by setting the MOSFET gate to a low voltage. Turning the LEDs off might be advantageous for limiting power consumption when the sensors are not in use or for varying the effective brightness of the LEDs through PWM control.

    The LED current-limiting resistors for 5 V operation are arranged in two stages; this allows a simple bypass of one stage to enable operation at 3.3 V. The LED current is approximately 20-25 mA, making the total board consumption just under 100 mA. The schematic diagram of the module is shown below:

    Specifications

    • Dimensions: 2.95" x 0.5" x 0.125" (without header pins installed)
    • Operating voltage: 3.3-5.0 V
    • Supply current: 100 mA
    • Output format: digital I/O compatible
    • Optimal sensing distance: 0.125" (3 mm)
    • Maximum recommended sensing distance: 0.375" (9.5 mm)
    • Weight without header pins: 0.11 oz (3.09 g)

    Interfacing the QTR-8RC Outputs to Digital I/O Lines

    Like the Parallax QTI, the QTR-8RC module has eight identical sensor outputs that require a digital I/O line capable of first charging the output capacitor (by driving the line high) and then measuring the time for the capacitor to discharge through the phototransistor. This measurement approach has several advantages, especially when coupled with the ability of the QTR-8RC module to turn off LED power:

    • No analog-to-digital converter (ADC) is required
    • Improved sensitivity over voltage-divider analog output
    • Parallel reading of all eight sensors is possible with most microcontrollers
    • Parallel reading allows optimized use of LED power enable option

    The typical sequence for reading a sensor is:

    1. Turn on IR LEDs (optional)
    2. Set the I/O line to an output and drive it high
    3. Allow at least 10 us for the 10 nF capacitor to charge
    4. Make the I/O line an input (high impedance)
    5. Measure the time for the capacitor to discharge by waiting for the I/O line to go low
    6. Turn off IR LEDs (optional)

    These steps can typically be executed in parallel on multiple I/O lines.

    With a strong reflectance, the discharge time can be as low as several dozen microseconds; with no reflectance, the discharge time can be up to a few milliseconds. The exact time of the discharge depends on your microcontroller’s I/O line characteristics. Meaningful results can be available within 1 ms in typical cases (i.e. when not trying to measure subtle differences in low-reflectance scenarios), allowing up to 1 kHz sampling of all 8 sensors. If lower-frequency sampling is sufficient, substantial power savings can be realized by turning off the LEDs. For example, if a 100 Hz sampling rate is acceptable, the LEDs can be off 90% of the time, lowering average current consumption from 100 mA to 10 mA.

    Our Pololu AVR library provides functions that make it easy to use these sensors with our Orangutan robot controllers and other AVR-based controller boards such as Arduinos. Please see section 11 of our library command reference for more information.

    Breaking the Module in Two

    If you don’t need or cannot fit all eight sensors, you can break off two sensors and still use all 8 sensors as two separate modules, as shown below. The PCB can be scored from both sides along the perforation and then bent until it snaps apart. Each of the two resulting pieces will function as an independent line sensor.

     

    Learn More
  5. Sharp GP2Y0A21YK distance sensor

    Sharp GP2Y0A21YK distance sensor

    $11.54

    The Sharp distance sensor is a great way to add obstacle avoidance to your robot or motion sensing to any other project. With a detection range of 4” to 32” and an analog voltage indicating the distance, this sensor is very easy to use.

    The Sharp distance sensor is a popular choice for many projects that require accurate distance measurements. This IR sensor is more economical than sonar rangefinders, yet it provides much better performance than other IR alternatives. Interfacing to most microcontrollers is straightforward: the single analog output can be connected to an analog-to-digital converter for taking distance measurements, or the output can be connected to a comparator for threshold detection. The detection range is approximately 10 cm to 80 cm (4" to 32"); the distance-to-output voltage graph is shown below.

    The distance sensor uses a 3-pin JST connector that we do not carry; however, it is simple to solder three wires to the sensor where the connector pins are mounted. The three connections are power, ground, and the output signal.

    Feature summary

    • 4.5 V to 5.5 V operating voltage
    • 30 mA average current consumption
    • 10 cm to 80 cm range (4" to 32")
    • 1.9 V output voltage change over distance range

     

     

     

     

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  6. IR Receiver Breakout

    IR Receiver Breakout

    $10.88

    This is a very small IR receiver based on the TSOP85 receiver from Vishay. This receiver has all the filtering and 38kHz demodulation built into the unit. Simply point a IR remote at the receiver, hit a button, and you'll see a stream of 1s and 0s out of the data pin.

    Documents:
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  7. Infrared Proximity Sensor - Sharp GP2Y0A21YK

    Infrared Proximity Sensor - Sharp GP2Y0A21YK

    $12.95

    Infrared proximity sensor made by Sharp. Part # GP2Y0A21YK has an analog output that varies from 3.1V at 10cm to 0.4V at 80cm. The sensor has a Japanese Solderless Terminal (JST) Connector. We recommend soldering wires directly to the back of the module and installing the header of your preference.

    Information: GP2Y0A21YK.pdf

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  8. Pololu IR beacon development board

    Pololu IR beacon development board

    $17.25

    The IR beacon development board is just an assembled IR Beacon PCB with no IR sensors or firmware. This item is intended for advanced users who want to customize their IR beacon functionality by writing their own firmware. No documentation is shipped with this IR Beacon Devlopment kit.

    Pololu’s new IR beacon (infrared beacon) is an updated version of our original IR beacon. Like the original unit, the devices are transceivers meant to be used in pairs to give robots a simple means for detecting each other. You can use the beacons to build pairs of robots that interact or chase one another, or to make a robot that can identify and return to a home base. For example, you could build a “cat robot” and “mouse robot” that each have an IR beacon, where the cat chases the mouse and the mouse runs away from the cat. The beacons are ideal for autonomous robot contests in which robots compete in pairs, such as MIT’s annual 6.270 autonomous robot design competition, where our original beacons were used for several years.

    The new IR beacons feature round PCBs with six wide-angle emitters to provide uniform broadcasting in all directions. The operating voltage range has increased to 6 – 16 V, and on-board voltage monitoring enables a more consistent output brightness over the voltage range. Most components are pre-assembled, so all you need to solder is the capacitor, connectors, and sensors (make sure you solder them in from the bottom of the PCB!).

    Note: The Pololu IR beacon is a kit; before using it, you need to assemble the beacon by soldering its components onto its circuit board. To use the kit in robotics projects, you need to connect it to your own robot controller. Please note that the IR beacons only work in pairs and that certain kinds of artificial lighting (e.g. some fluorescent lights) can interfere with the sensors.

    Device Specifications

    • PCB size: 1.35" circle
    • IR modulation frequency: 56 kHz
    • Output refresh rate 20 Hz
    • Detection range: 6 inches to 20 feet
    • Supply voltage: 6-16 V
    • Data voltage: 5 V
    • Number of IR detectors: 4

    How the IR Beacons Work

    The beacons work by transmitting and detecting infrared light, much like a television remote control. Each beacon has four IR emitters and four IR detectors. The beacons alternate between transmitting and receiving so that they never get confused by reflections of their own transmissions.

    The transmit and detect cycle is carried out more than one thousand times per second, and a small microcontroller monitors all four detectors to decide the direction to the other beacon. The beacons have four red LEDs that indicate the direction to the other beacon; if you take two beacons and rotate them, the LEDs will always keep lighting up in the direction of the other beacon.

    Interfacing to the beacon is simple — it has four digital outputs that indicate which of its four sides detects the other beacon the strongest. You can establish the direction to another beacon to within a few degrees by rotating the beacon back and forth and noting the point where the output switches from one side to another. An enable input lets you select between active mode and a low-power mode.

    IR Beacon Development Kit (Transmit-Only Beacon)

    In response to customer requests, the IR beacon is available as just an assembled PCB with no IR sensors or firmware. This item is intended for advanced users who want to customize their IR beacon functionality by writing their own firmware. The main processor is a Microchip PIC16F630, and the PCB includes a footprint for a 5-pin header compatible with the PIC kit 2 programmer. The IR Receiver Modules are available separately. The schematic is shown below and is the only documentation shipped with this IR Beacon Devlopment kit:

    It is important to note that the IR beacon achieves its brighness by pulsing the IR LEDs with very high currents; turning on the IR LEDs continuously will burn them out. When testing the IR beacon, a digital camera can be useful in determining whether the IR LEDs are on. However, some cameras (usually more expensive ones) have better filters that block IR. In the picture below, a point-and-shoot camera shows the IR LEDs shining (in purple) but the DSLR with which the picture is taken does not show the LEDs.

    Learn More
  9. Pololu IR beacon transceiver pair

    Pololu IR beacon transceiver pair

    $57.62

    The Pololu IR beacon is a compact board that is used in pairs to allow robots to locate each other. Each board has infrared emitters that shine in all directions and four IR receivers for detecting the other beacon. The IR beacons have a range of about fifteen feet indoors. This item is for a pair of beacons in one package.

    Pololu’s new IR beacon (infrared beacon) is an updated version of our original IR beacon. Like the original unit, the devices are transceivers meant to be used in pairs to give robots a simple means for detecting each other. You can use the beacons to build pairs of robots that interact or chase one another, or to make a robot that can identify and return to a home base. For example, you could build a “cat robot” and “mouse robot” that each have an IR beacon, where the cat chases the mouse and the mouse runs away from the cat. The beacons are ideal for autonomous robot contests in which robots compete in pairs, such as MIT’s annual 6.270 autonomous robot design competition, where our original beacons were used for several years.

    The new IR beacons feature round PCBs with six wide-angle emitters to provide uniform broadcasting in all directions. The operating voltage range has increased to 6 – 16 V, and on-board voltage monitoring enables a more consistent output brightness over the voltage range. Most components are pre-assembled, so all you need to solder is the capacitor, connectors, and sensors (make sure you solder them in from the bottom of the PCB!).

    Note: The Pololu IR beacon is a kit; before using it, you need to assemble the beacon by soldering its components onto its circuit board. To use the kit in robotics projects, you need to connect it to your own robot controller. Please note that the IR beacons only work in pairs and that certain kinds of artificial lighting (e.g. some fluorescent lights) can interfere with the sensors.

    Device Specifications

    • PCB size: 1.35" circle
    • IR modulation frequency: 56 kHz
    • Output refresh rate 20 Hz
    • Detection range: 6 inches to 20 feet
    • Supply voltage: 6-16 V
    • Data voltage: 5 V
    • Number of IR detectors: 4

    How the IR Beacons Work

    The beacons work by transmitting and detecting infrared light, much like a television remote control. Each beacon has four IR emitters and four IR detectors. The beacons alternate between transmitting and receiving so that they never get confused by reflections of their own transmissions.

    The transmit and detect cycle is carried out more than one thousand times per second, and a small microcontroller monitors all four detectors to decide the direction to the other beacon. The beacons have four red LEDs that indicate the direction to the other beacon; if you take two beacons and rotate them, the LEDs will always keep lighting up in the direction of the other beacon.

    Interfacing to the beacon is simple — it has four digital outputs that indicate which of its four sides detects the other beacon the strongest. You can establish the direction to another beacon to within a few degrees by rotating the beacon back and forth and noting the point where the output switches from one side to another. An enable input lets you select between active mode and a low-power mode.

    IR Beacon Development Kit (Transmit-Only Beacon)

    In response to customer requests, the IR beacon is available as just an assembled PCB with no IR sensors or firmware. This item is intended for advanced users who want to customize their IR beacon functionality by writing their own firmware. The main processor is a Microchip PIC16F630, and the PCB includes a footprint for a 5-pin header compatible with the PIC kit 2 programmer. The IR Receiver Modules are available separately. The schematic is shown below and is the only documentation shipped with this IR Beacon Devlopment kit:

    It is important to note that the IR beacon achieves its brighness by pulsing the IR LEDs with very high currents; turning on the IR LEDs continuously will burn them out. When testing the IR beacon, a digital camera can be useful in determining whether the IR LEDs are on. However, some cameras (usually more expensive ones) have better filters that block IR. In the picture below, a point-and-shoot camera shows the IR LEDs shining (in purple) but the DSLR with which the picture is taken does not show the LEDs.

    Learn More
  10. QTR-1A Reflectance Sensor

    QTR-1A Reflectance Sensor

    $4.75

    The QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair in an inexpensive, tiny 0.5" x 0.3" module that can be mounted almost anywhere and is great for edge detection and line following applications. The reflectance measurement is output as an analog voltage.

    Note: The QTR-1A reflectance sensor requires an analog input to take readings. The similar QTR-1RC reflectance sensor is available with a digital I/O-compatible output.

    Functional Description

    The Pololu QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair. The phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analog voltage output between 0 V and VIN (which is typically 5 V) as a function of the reflected IR. Lower output voltage is an indication of greater reflection.

    The LED current-limiting resistor is set to deliver approximately 20-25 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power.

    Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity/edge detection.

    Specifications

    • Dimensions: 0.3" x 0.5" x 0.1" (without header pins installed)
    • Operating voltage: 5.0 V
    • Supply current: 25 mA
    • Output format: analog voltage
    • Output voltage range: 0  to supplied voltage
    • Optimal sensing distance: 0.125" (3 mm)
    • Maximum recommended sensing distance: 0.25" (6 mm)
    • Weight without header pins: 0.008 oz (0.23 g)

    Interfacing with the QTR-1A Output

    There are several ways you can interface with the QTR-1A output:

    • Use a microcontroller’s analog-to-digital converter (ADC) to measure the voltage.
    • Use a comparator with an adjustable threshold to convert the analog voltage into a digital (i.e. black/white) signal that can be read by the digital I/O line of a microcontroller.
    • Connect the output directly to the digital I/O line of a microcontroller and rely upon its internal comparator.

    This last method will work if you are able to get high reflectance from your white surface as depicted in the left image, but will probably fail if you have a lower-reflectance signal profile like the one on the right.

     

    Learn More
 
 

   

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