pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

4 mm × 3

13.0 × 20.0

analog

30 mA

62 mA

5 mm

This array of IR LED/phototransistor pairs is great for precisely identifying changes in reflectance (like line detection). It operates from 2.9 V to 5.5 V and offers dimmable brightness control independent of the supply voltage. In general, the closer the object, the higher the contrast between light and dark readings, but high-reflectance objects are generally detectable out to around 30 mm. This version features the traditional-style QTR sensors without lenses.

QTR-HD-03A Reflectance Sensor Array dimensions.

Dimensions: 13.0 × 20.0 × 2.5 mm (see the dimension diagram (1MB pdf) for more details)

Operating voltage: 2.9 V to 5.5 V

Sensor type: QTR

Sensor count: 3

Sensor pitch: 4 mm

Full-brightness LED current: 30 mA (independent of supply voltage)

Max board current: 62 mA

Output format: analog voltages (0 V to VCC)

Optimal sensing distance: 5 mm

Maximum recommended sensing distance: 30 mm

Weight: 0.8 g

These reflectance sensors feature a linear array of infrared emitter/phototransistor pair modules in a high-density (4 mm pitch) or medium-density (8 mm pitch) arrangement, which makes them well suited for applications that require detection of changes in reflectivity. This change in reflectivity can be due to a color change at a fixed distance, such as when sensing a black line on a white background, as well as due to a change in the distance to or presence of an object in front of the sensor. A variety of sensor counts and densities is available so you can pick the ideal arrangement for your application. Since the outputs are all independent, you can connect just some of the channels to attain an irregular or non-standard sensor spacing.

Unlike our original QTR sensor modules, these units have integrated LED drivers that provide brightness control independent of the supply voltage, which can be anywhere from 2.9 V to 5.5 V, while enabling optional dimming to any of 32 possible brightness settings. For high-density (HD) modules with five or more sensors and medium-density (MD) modules with eleven or more sensors, there are separate controls for the odd-numbered and even-numbered LEDs, which gives you extra options for detecting light reflected at various angles. See the “Emitter control” section below for more information on using this feature.

Two different sensor options are available, denoted by “QTR” or “QTRX” in the product name. The “QTR” versions feature lower-cost sensor modules without lenses while the “QTRX” versions feature higher-performance sensor modules with lenses, which allow similar performance at a much lower IR LED current. You can see the two different sensor styles in the pictures below of the 4-channel modules:

QTR-HD-04A Reflectance Sensor Array.

QTRX-HD-04RC Reflectance Sensor Array.

We also have several single-channel modules with the “QTRXL” designator that offer extra-long range by using the QTRX-style sensor module with higher current through the emitter.

Each sensor option is available in two output types: an “A” version with analog voltage outputs between 0 V and VCC, and an “RC” version with outputs that can be read with a digital I/O line on a microcontroller by first setting the lines high and then releasing them and timing how long it takes them to read as low (typically anywhere from a few microseconds to a few milliseconds). The lower the output voltage or shorter the voltage decay time, the higher the reflectance. The following simplified schematic diagrams show the circuits for the individual channels:

Schematic diagrams of individual QTR sensor channels for A version (left) and RC version (right). This applies only to the newer QTRs with dimmable emitters.

Our Arduino library makes it easy to use these sensor modules with an Arduino or compatible controller by providing methods for controlling the emitters, calibrating the module, and reading the individual sensor values from either the A or RC versions. It also has a method specifically for line-following applications to compute the location of the line under the array.

Note: Unlike most of our products, these sensor arrays do not ship with any headers or connectors included, so you will need to supply your own or solder wires directly to the board to use it. See our selection of male headers, female headers, and pre-crimped wires for various connector options.

Each sensor on the A versions outputs its reflectance measurement as an analog voltage that can range from 0 V when the reflectance is very strong to VCC when the reflectance is very weak. The typical sequence for reading a sensor is:

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 logic threshold.

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.

QTR-1A output 1/8" away from a spinning white disk with a black line on it.

QTR-1A output 3/8" away from a spinning white disk with a black line on it.

Each sensor on the RC versions requires a digital I/O line capable of driving the output line high and then measuring the time for the output voltage to decay. The typical sequence for reading a sensor is:

QTR-1RC output (yellow) when 1/8" above a black line and microcontroller timing of that output (blue).

QTR-1RC output (yellow) when 1/8" above a white surface and microcontroller timing of that output (blue).

Turn on IR LEDs (optional).

Set the I/O line to an output and drive it high.

Allow at least 10 μs for the sensor output to rise.

Make the I/O line an input (high impedance).

Measure the time for the voltage to decay by waiting for the I/O line to go low.

Turn off IR LEDs (optional).

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

With a strong reflectance, the decay time can be as low as a few microseconds; with no reflectance, the decay time can be up to a few milliseconds. The exact time of the decay 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 sensors. If lower-frequency sampling is sufficient, you can achieve substantial power savings 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 125 mA to 13 mA.

These reflectance sensor arrays maintain a constant current through their IR emitters, keeping the emitters’ brightness constant, independent of the supply voltage (2.9 V to 5.5 V). The emitters can be controlled with the board’s CTRL pins, and the details of the control depends on the array size and density:

HD units with 5 or more sensors and MD units with 11 or more sensors have two emitter control pins: CTRL ODD and CTRL EVEN. By default, these are connected together with a 1 kΩ resistor and pulled up, turning on all the emitters by default and allowing them to be controlled with a signal on either pin, but the CTRL ODD and CTRL EVEN pins can be driven separately for independent control of the odd-numbered and even-numbered emitters.

MD units with 3-10 sensors also have two emitter control pins since these are made by only populating every other sensor on an HD board, but only the CTRL ODD pin will have an effect on these versions (it is not possible to independently control alternate emitters).

HD units with 4 or fewer sensors and MD units with 2 or fewer sensors have a single CTRL pin that controls all of the emitters.

Driving a CTRL pin low for at least 1 ms turns off the associated emitter LEDs, while driving it high (or allowing the board to pull it high) turns on the emitters with the board’s default (full) current, which is 30 mA for “QTR” versions and 3.5 mA for “QTRX” versions. For more advanced use, the CTRL pin can be pulsed low to cycle the associated emitters through 32 dimming levels.

Demo of IR LED dimming and independent even/odd control on the QTR-HD-07x (as seen through an old digital camera that can see IR).

Demo of IR LED dimming and independent even/odd control on the QTRX-HD-07x (as seen through an old digital camera that can see IR).

To send a pulse, you should drive the CTRL pin low for at least 0.5 μs (but no more than 300 μs), then high for at least 0.5 μs; (it should remain high after the last pulse). Each pulse causes the driver to advance to the next dimming level, wrapping around to 100% after the lowest-current level. Each dimming level corresponds to a 3.33% reduction in current, except for the last three levels, which represent a 1.67% reduction, as shown in the table below. Note that turning the LEDs off with a >1 ms pulse and then back on resets them to full current.

For example, to reduce the emitter current to 50%, you would apply 15 low pulses to the CTRL pin and then keep it high after the last pulse.

pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

4 mm × 3

13.0 × 20.0

RC (digital)

30 mA

62 mA

5 mm

This array of IR LED/phototransistor pairs is great for precisely identifying changes in reflectance (like line detection). It operates from 2.9 V to 5.5 V and offers dimmable brightness control independent of the supply voltage. In general, the closer the object, the higher the contrast between light and dark readings, but high-reflectance objects are generally detectable out to around 30 mm. This version features the traditional-style QTR sensors without lenses.

QTR-HD-03RC Reflectance Sensor Array dimensions.

Dimensions: 13.0 × 20.0 × 2.5 mm (see the dimension diagram (1MB pdf) for more details)

Operating voltage: 2.9 V to 5.5 V

Sensor type: QTR

Sensor count: 3

Sensor pitch: 4 mm

Full-brightness LED current: 30 mA (independent of supply voltage)

Max board current: 62 mA

Output format: digital I/O-compatible signals that can be read in parallel as timed high pulses

Optimal sensing distance: 5 mm

Maximum recommended sensing distance: 30 mm

Weight: 0.8 g

These reflectance sensors feature a linear array of infrared emitter/phototransistor pair modules in a high-density (4 mm pitch) or medium-density (8 mm pitch) arrangement, which makes them well suited for applications that require detection of changes in reflectivity. This change in reflectivity can be due to a color change at a fixed distance, such as when sensing a black line on a white background, as well as due to a change in the distance to or presence of an object in front of the sensor. A variety of sensor counts and densities is available so you can pick the ideal arrangement for your application. Since the outputs are all independent, you can connect just some of the channels to attain an irregular or non-standard sensor spacing.

Unlike our original QTR sensor modules, these units have integrated LED drivers that provide brightness control independent of the supply voltage, which can be anywhere from 2.9 V to 5.5 V, while enabling optional dimming to any of 32 possible brightness settings. For high-density (HD) modules with five or more sensors and medium-density (MD) modules with eleven or more sensors, there are separate controls for the odd-numbered and even-numbered LEDs, which gives you extra options for detecting light reflected at various angles. See the “Emitter control” section below for more information on using this feature.

Two different sensor options are available, denoted by “QTR” or “QTRX” in the product name. The “QTR” versions feature lower-cost sensor modules without lenses while the “QTRX” versions feature higher-performance sensor modules with lenses, which allow similar performance at a much lower IR LED current. You can see the two different sensor styles in the pictures below of the 4-channel modules:

QTR-HD-04A Reflectance Sensor Array.

QTRX-HD-04RC Reflectance Sensor Array.

We also have several single-channel modules with the “QTRXL” designator that offer extra-long range by using the QTRX-style sensor module with higher current through the emitter.

Each sensor option is available in two output types: an “A” version with analog voltage outputs between 0 V and VCC, and an “RC” version with outputs that can be read with a digital I/O line on a microcontroller by first setting the lines high and then releasing them and timing how long it takes them to read as low (typically anywhere from a few microseconds to a few milliseconds). The lower the output voltage or shorter the voltage decay time, the higher the reflectance. The following simplified schematic diagrams show the circuits for the individual channels:

Schematic diagrams of individual QTR sensor channels for A version (left) and RC version (right). This applies only to the newer QTRs with dimmable emitters.

Our Arduino library makes it easy to use these sensor modules with an Arduino or compatible controller by providing methods for controlling the emitters, calibrating the module, and reading the individual sensor values from either the A or RC versions. It also has a method specifically for line-following applications to compute the location of the line under the array.

Note: Unlike most of our products, these sensor arrays do not ship with any headers or connectors included, so you will need to supply your own or solder wires directly to the board to use it. See our selection of male headers, female headers, and pre-crimped wires for various connector options.

Each sensor on the A versions outputs its reflectance measurement as an analog voltage that can range from 0 V when the reflectance is very strong to VCC when the reflectance is very weak. The typical sequence for reading a sensor is:

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 logic threshold.

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.

QTR-1A output 1/8" away from a spinning white disk with a black line on it.

QTR-1A output 3/8" away from a spinning white disk with a black line on it.

Each sensor on the RC versions requires a digital I/O line capable of driving the output line high and then measuring the time for the output voltage to decay. The typical sequence for reading a sensor is:

QTR-1RC output (yellow) when 1/8" above a black line and microcontroller timing of that output (blue).

QTR-1RC output (yellow) when 1/8" above a white surface and microcontroller timing of that output (blue).

Turn on IR LEDs (optional).

Set the I/O line to an output and drive it high.

Allow at least 10 μs for the sensor output to rise.

Make the I/O line an input (high impedance).

Measure the time for the voltage to decay by waiting for the I/O line to go low.

Turn off IR LEDs (optional).

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

With a strong reflectance, the decay time can be as low as a few microseconds; with no reflectance, the decay time can be up to a few milliseconds. The exact time of the decay 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 sensors. If lower-frequency sampling is sufficient, you can achieve substantial power savings 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 125 mA to 13 mA.

These reflectance sensor arrays maintain a constant current through their IR emitters, keeping the emitters’ brightness constant, independent of the supply voltage (2.9 V to 5.5 V). The emitters can be controlled with the board’s CTRL pins, and the details of the control depends on the array size and density:

HD units with 5 or more sensors and MD units with 11 or more sensors have two emitter control pins: CTRL ODD and CTRL EVEN. By default, these are connected together with a 1 kΩ resistor and pulled up, turning on all the emitters by default and allowing them to be controlled with a signal on either pin, but the CTRL ODD and CTRL EVEN pins can be driven separately for independent control of the odd-numbered and even-numbered emitters.

MD units with 3-10 sensors also have two emitter control pins since these are made by only populating every other sensor on an HD board, but only the CTRL ODD pin will have an effect on these versions (it is not possible to independently control alternate emitters).

HD units with 4 or fewer sensors and MD units with 2 or fewer sensors have a single CTRL pin that controls all of the emitters.

Driving a CTRL pin low for at least 1 ms turns off the associated emitter LEDs, while driving it high (or allowing the board to pull it high) turns on the emitters with the board’s default (full) current, which is 30 mA for “QTR” versions and 3.5 mA for “QTRX” versions. For more advanced use, the CTRL pin can be pulsed low to cycle the associated emitters through 32 dimming levels.

Demo of IR LED dimming and independent even/odd control on the QTR-HD-07x (as seen through an old digital camera that can see IR).

Demo of IR LED dimming and independent even/odd control on the QTRX-HD-07x (as seen through an old digital camera that can see IR).

To send a pulse, you should drive the CTRL pin low for at least 0.5 μs (but no more than 300 μs), then high for at least 0.5 μs; (it should remain high after the last pulse). Each pulse causes the driver to advance to the next dimming level, wrapping around to 100% after the lowest-current level. Each dimming level corresponds to a 3.33% reduction in current, except for the last three levels, which represent a 1.67% reduction, as shown in the table below. Note that turning the LEDs off with a >1 ms pulse and then back on resets them to full current.

For example, to reduce the emitter current to 50%, you would apply 15 low pulses to the CTRL pin and then keep it high after the last pulse.

pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

4 mm × 3

13.0 × 20.0

analog

3.5 mA

9 mA

10 mm

This array of IR LED/phototransistor pairs is great for precisely identifying changes in reflectance (like line detection). It operates from 2.9 V to 5.5 V and offers dimmable brightness control independent of the supply voltage. In general, the closer the object, the higher the contrast between light and dark readings, but high-reflectance objects are generally detectable out to around 30 mm. This version features high-performance, low-current QTRX sensors with lenses.

QTRX-HD-03A Reflectance Sensor Array dimensions.

Dimensions: 13.0 × 20.0 × 3.0 mm (see the dimension diagram (1MB pdf) for more details)

Operating voltage: 2.9 V to 5.5 V

Sensor type: QTRX

Sensor count: 3

Sensor pitch: 4 mm

Full-brightness LED current: 3.5 mA (independent of supply voltage)

Max board current: 9 mA

Output format: analog voltages (0 V to VCC)

Optimal sensing distance: 10 mm

Maximum recommended sensing distance: 30 mm

Weight: 0.8 g

These reflectance sensors feature a linear array of infrared emitter/phototransistor pair modules in a high-density (4 mm pitch) or medium-density (8 mm pitch) arrangement, which makes them well suited for applications that require detection of changes in reflectivity. This change in reflectivity can be due to a color change at a fixed distance, such as when sensing a black line on a white background, as well as due to a change in the distance to or presence of an object in front of the sensor. A variety of sensor counts and densities is available so you can pick the ideal arrangement for your application. Since the outputs are all independent, you can connect just some of the channels to attain an irregular or non-standard sensor spacing.

Unlike our original QTR sensor modules, these units have integrated LED drivers that provide brightness control independent of the supply voltage, which can be anywhere from 2.9 V to 5.5 V, while enabling optional dimming to any of 32 possible brightness settings. For high-density (HD) modules with five or more sensors and medium-density (MD) modules with eleven or more sensors, there are separate controls for the odd-numbered and even-numbered LEDs, which gives you extra options for detecting light reflected at various angles. See the “Emitter control” section below for more information on using this feature.

Two different sensor options are available, denoted by “QTR” or “QTRX” in the product name. The “QTR” versions feature lower-cost sensor modules without lenses while the “QTRX” versions feature higher-performance sensor modules with lenses, which allow similar performance at a much lower IR LED current. You can see the two different sensor styles in the pictures below of the 4-channel modules:

QTR-HD-04A Reflectance Sensor Array.

QTRX-HD-04RC Reflectance Sensor Array.

We also have several single-channel modules with the “QTRXL” designator that offer extra-long range by using the QTRX-style sensor module with higher current through the emitter.

Each sensor option is available in two output types: an “A” version with analog voltage outputs between 0 V and VCC, and an “RC” version with outputs that can be read with a digital I/O line on a microcontroller by first setting the lines high and then releasing them and timing how long it takes them to read as low (typically anywhere from a few microseconds to a few milliseconds). The lower the output voltage or shorter the voltage decay time, the higher the reflectance. The following simplified schematic diagrams show the circuits for the individual channels:

Schematic diagrams of individual QTR sensor channels for A version (left) and RC version (right). This applies only to the newer QTRs with dimmable emitters.

Our Arduino library makes it easy to use these sensor modules with an Arduino or compatible controller by providing methods for controlling the emitters, calibrating the module, and reading the individual sensor values from either the A or RC versions. It also has a method specifically for line-following applications to compute the location of the line under the array.

Note: Unlike most of our products, these sensor arrays do not ship with any headers or connectors included, so you will need to supply your own or solder wires directly to the board to use it. See our selection of male headers, female headers, and pre-crimped wires for various connector options.

Each sensor on the A versions outputs its reflectance measurement as an analog voltage that can range from 0 V when the reflectance is very strong to VCC when the reflectance is very weak. The typical sequence for reading a sensor is:

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 logic threshold.

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.

QTR-1A output 1/8" away from a spinning white disk with a black line on it.

QTR-1A output 3/8" away from a spinning white disk with a black line on it.

Each sensor on the RC versions requires a digital I/O line capable of driving the output line high and then measuring the time for the output voltage to decay. The typical sequence for reading a sensor is:

QTR-1RC output (yellow) when 1/8" above a black line and microcontroller timing of that output (blue).

QTR-1RC output (yellow) when 1/8" above a white surface and microcontroller timing of that output (blue).

Turn on IR LEDs (optional).

Set the I/O line to an output and drive it high.

Allow at least 10 μs for the sensor output to rise.

Make the I/O line an input (high impedance).

Measure the time for the voltage to decay by waiting for the I/O line to go low.

Turn off IR LEDs (optional).

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

With a strong reflectance, the decay time can be as low as a few microseconds; with no reflectance, the decay time can be up to a few milliseconds. The exact time of the decay 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 sensors. If lower-frequency sampling is sufficient, you can achieve substantial power savings 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 125 mA to 13 mA.

These reflectance sensor arrays maintain a constant current through their IR emitters, keeping the emitters’ brightness constant, independent of the supply voltage (2.9 V to 5.5 V). The emitters can be controlled with the board’s CTRL pins, and the details of the control depends on the array size and density:

HD units with 5 or more sensors and MD units with 11 or more sensors have two emitter control pins: CTRL ODD and CTRL EVEN. By default, these are connected together with a 1 kΩ resistor and pulled up, turning on all the emitters by default and allowing them to be controlled with a signal on either pin, but the CTRL ODD and CTRL EVEN pins can be driven separately for independent control of the odd-numbered and even-numbered emitters.

MD units with 3-10 sensors also have two emitter control pins since these are made by only populating every other sensor on an HD board, but only the CTRL ODD pin will have an effect on these versions (it is not possible to independently control alternate emitters).

HD units with 4 or fewer sensors and MD units with 2 or fewer sensors have a single CTRL pin that controls all of the emitters.

Driving a CTRL pin low for at least 1 ms turns off the associated emitter LEDs, while driving it high (or allowing the board to pull it high) turns on the emitters with the board’s default (full) current, which is 30 mA for “QTR” versions and 3.5 mA for “QTRX” versions. For more advanced use, the CTRL pin can be pulsed low to cycle the associated emitters through 32 dimming levels.

Demo of IR LED dimming and independent even/odd control on the QTR-HD-07x (as seen through an old digital camera that can see IR).

Demo of IR LED dimming and independent even/odd control on the QTRX-HD-07x (as seen through an old digital camera that can see IR).

To send a pulse, you should drive the CTRL pin low for at least 0.5 μs (but no more than 300 μs), then high for at least 0.5 μs; (it should remain high after the last pulse). Each pulse causes the driver to advance to the next dimming level, wrapping around to 100% after the lowest-current level. Each dimming level corresponds to a 3.33% reduction in current, except for the last three levels, which represent a 1.67% reduction, as shown in the table below. Note that turning the LEDs off with a >1 ms pulse and then back on resets them to full current.

For example, to reduce the emitter current to 50%, you would apply 15 low pulses to the CTRL pin and then keep it high after the last pulse.

pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

4 mm × 3

13.0 × 20.0

RC (digital)

3.5 mA

9 mA

10 mm

This array of IR LED/phototransistor pairs is great for precisely identifying changes in reflectance (like line detection). It operates from 2.9 V to 5.5 V and offers dimmable brightness control independent of the supply voltage. In general, the closer the object, the higher the contrast between light and dark readings, but high-reflectance objects are generally detectable out to around 30 mm. This version features high-performance, low-current QTRX sensors with lenses.

QTRX-HD-03RC Reflectance Sensor Array dimensions.

Dimensions: 13.0 × 20.0 × 3.0 mm (see the dimension diagram (1MB pdf) for more details)

Operating voltage: 2.9 V to 5.5 V

Sensor type: QTRX

Sensor count: 3

Sensor pitch: 4 mm

Full-brightness LED current: 3.5 mA (independent of supply voltage)

Max board current: 9 mA

Output format: digital I/O-compatible signals that can be read in parallel as timed high pulses

Optimal sensing distance: 10 mm

Maximum recommended sensing distance: 30 mm

Weight: 0.8 g

These reflectance sensors feature a linear array of infrared emitter/phototransistor pair modules in a high-density (4 mm pitch) or medium-density (8 mm pitch) arrangement, which makes them well suited for applications that require detection of changes in reflectivity. This change in reflectivity can be due to a color change at a fixed distance, such as when sensing a black line on a white background, as well as due to a change in the distance to or presence of an object in front of the sensor. A variety of sensor counts and densities is available so you can pick the ideal arrangement for your application. Since the outputs are all independent, you can connect just some of the channels to attain an irregular or non-standard sensor spacing.

Unlike our original QTR sensor modules, these units have integrated LED drivers that provide brightness control independent of the supply voltage, which can be anywhere from 2.9 V to 5.5 V, while enabling optional dimming to any of 32 possible brightness settings. For high-density (HD) modules with five or more sensors and medium-density (MD) modules with eleven or more sensors, there are separate controls for the odd-numbered and even-numbered LEDs, which gives you extra options for detecting light reflected at various angles. See the “Emitter control” section below for more information on using this feature.

Two different sensor options are available, denoted by “QTR” or “QTRX” in the product name. The “QTR” versions feature lower-cost sensor modules without lenses while the “QTRX” versions feature higher-performance sensor modules with lenses, which allow similar performance at a much lower IR LED current. You can see the two different sensor styles in the pictures below of the 4-channel modules:

QTR-HD-04A Reflectance Sensor Array.

QTRX-HD-04RC Reflectance Sensor Array.

We also have several single-channel modules with the “QTRXL” designator that offer extra-long range by using the QTRX-style sensor module with higher current through the emitter.

Each sensor option is available in two output types: an “A” version with analog voltage outputs between 0 V and VCC, and an “RC” version with outputs that can be read with a digital I/O line on a microcontroller by first setting the lines high and then releasing them and timing how long it takes them to read as low (typically anywhere from a few microseconds to a few milliseconds). The lower the output voltage or shorter the voltage decay time, the higher the reflectance. The following simplified schematic diagrams show the circuits for the individual channels:

Schematic diagrams of individual QTR sensor channels for A version (left) and RC version (right). This applies only to the newer QTRs with dimmable emitters.

Our Arduino library makes it easy to use these sensor modules with an Arduino or compatible controller by providing methods for controlling the emitters, calibrating the module, and reading the individual sensor values from either the A or RC versions. It also has a method specifically for line-following applications to compute the location of the line under the array.

Note: Unlike most of our products, these sensor arrays do not ship with any headers or connectors included, so you will need to supply your own or solder wires directly to the board to use it. See our selection of male headers, female headers, and pre-crimped wires for various connector options.

Each sensor on the A versions outputs its reflectance measurement as an analog voltage that can range from 0 V when the reflectance is very strong to VCC when the reflectance is very weak. The typical sequence for reading a sensor is:

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 logic threshold.

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.

QTR-1A output 1/8" away from a spinning white disk with a black line on it.

QTR-1A output 3/8" away from a spinning white disk with a black line on it.

Each sensor on the RC versions requires a digital I/O line capable of driving the output line high and then measuring the time for the output voltage to decay. The typical sequence for reading a sensor is:

QTR-1RC output (yellow) when 1/8" above a black line and microcontroller timing of that output (blue).

QTR-1RC output (yellow) when 1/8" above a white surface and microcontroller timing of that output (blue).

Turn on IR LEDs (optional).

Set the I/O line to an output and drive it high.

Allow at least 10 μs for the sensor output to rise.

Make the I/O line an input (high impedance).

Measure the time for the voltage to decay by waiting for the I/O line to go low.

Turn off IR LEDs (optional).

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

With a strong reflectance, the decay time can be as low as a few microseconds; with no reflectance, the decay time can be up to a few milliseconds. The exact time of the decay 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 sensors. If lower-frequency sampling is sufficient, you can achieve substantial power savings 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 125 mA to 13 mA.

These reflectance sensor arrays maintain a constant current through their IR emitters, keeping the emitters’ brightness constant, independent of the supply voltage (2.9 V to 5.5 V). The emitters can be controlled with the board’s CTRL pins, and the details of the control depends on the array size and density:

HD units with 5 or more sensors and MD units with 11 or more sensors have two emitter control pins: CTRL ODD and CTRL EVEN. By default, these are connected together with a 1 kΩ resistor and pulled up, turning on all the emitters by default and allowing them to be controlled with a signal on either pin, but the CTRL ODD and CTRL EVEN pins can be driven separately for independent control of the odd-numbered and even-numbered emitters.

MD units with 3-10 sensors also have two emitter control pins since these are made by only populating every other sensor on an HD board, but only the CTRL ODD pin will have an effect on these versions (it is not possible to independently control alternate emitters).

HD units with 4 or fewer sensors and MD units with 2 or fewer sensors have a single CTRL pin that controls all of the emitters.

Driving a CTRL pin low for at least 1 ms turns off the associated emitter LEDs, while driving it high (or allowing the board to pull it high) turns on the emitters with the board’s default (full) current, which is 30 mA for “QTR” versions and 3.5 mA for “QTRX” versions. For more advanced use, the CTRL pin can be pulsed low to cycle the associated emitters through 32 dimming levels.

Demo of IR LED dimming and independent even/odd control on the QTR-HD-07x (as seen through an old digital camera that can see IR).

Demo of IR LED dimming and independent even/odd control on the QTRX-HD-07x (as seen through an old digital camera that can see IR).

To send a pulse, you should drive the CTRL pin low for at least 0.5 μs (but no more than 300 μs), then high for at least 0.5 μs; (it should remain high after the last pulse). Each pulse causes the driver to advance to the next dimming level, wrapping around to 100% after the lowest-current level. Each dimming level corresponds to a 3.33% reduction in current, except for the last three levels, which represent a 1.67% reduction, as shown in the table below. Note that turning the LEDs off with a >1 ms pulse and then back on resets them to full current.

For example, to reduce the emitter current to 50%, you would apply 15 low pulses to the CTRL pin and then keep it high after the last pulse.

Your power supply problems just got SUPER SOLVED! This 3.3V Buck Converter Breakout board is great for supplying power to low voltage circuits from a single Li-Ion cell battery or USB power.  This chip provides up to 600-mA load current across the entire input voltage range of 3.5 to 5.5V.  Great for your portable project, we made this "pin compatible" with the LM1117-3.3V TO-220 chip so you can swap it in for better performance (90-95% efficiency!) There's also an ENable pin, tie it low to shut down the output completely.

There's a 2-MHz fixed-frequency in PWM mode and PFM mode extends the battery life by reducing the current during light load or standby operation.

Comes with a fully assembled and tested breakout board.  We also include header to plug it into a breadboard.

PowerBoost is the perfect power supply for your power-hungry portable project! This little DC/DC boost converter module can run from 1.8V batteries or higher, and convert that voltage to 5.2V DC for running your 5V projects. With a beefy 4A DC/DC converter, it can give you 1A+ from as low as 2V. Like our popular 5V 1A USB wall adapter, we tweaked the output to be 5.2V instead of a straight-up 5.0V so that there's a little bit of 'headroom' long cables, high draw, the addition of a diode on the output if you wish, etc. The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone while preventing icky brown-outs during high current draw because of USB cable resistance.

The PowerBoost 1000 has at the heart a TPS61030 boost converter from TI. This boost converter chip has some really nice extras such as low battery detection, 4A internal switch, synchronous conversion, excellent efficiency, and 700KHz high-frequency operation. Check out these specs!

Synchronous operation means you can disconnect the output completely by connecting the ENable pin to ground. This will completely turn off the output

4A internal switch means you can get 1000mA+ from as low as 1.8V, 1500mA+ from 2 NiMH or Alkaline batteries, and at least 2000mA from a 3.7V LiPoly/LiIon battery or 3 NiMH/Alkalines. Just make sure your batteries can actually supply the required 2-4A, OK?

Low battery indicator LED lights up red when the voltage dips below 3.2V, optimized for the most common usage of LiPo/LiIon battery usage

On-board 1000mA charge-rate 'Apple/iOS' data resistors. Solder in the included USB connector and you can plug in any iPhone or iPod for a speedy 1000mA charge rate. Works with iPads, both mini and 'classic' type.

Full breakout for battery in, control pins and power out

90%+ operating efficiency in most cases (see datasheet for efficiency graphs), and low quiescent current: 5mA when enabled and power LED is on, 20uA when disabled (power and low batt LED are off)

Great for powering your robot, Arduino project, single-board-computer such as Raspberry Pi or BeagleBone! Each order comes with one fully assembled and tested PCB, a loose 2-PH JST jack, a 2-pin Terminal block and a loose USB A jack.

If you are powering your project from USB, solder the USB A jack in (a 3-minute soldering task). Then choose either JST for input (JST is often used for our LiIon batteries, but the connector is only rated for 2A) or a terminal block. 

The 1000 version comes with a 2-pin terminal block so you can solder it to the output spot where the USB jack would go. Or don't solder any connectors in for a more compact power pack and go with 22AWG wires soldered directly in.

Note: The terminal blocks included with your product may be blue or black.

PowerBoost 1000C is the perfect power supply for your portable project! With a built-in load-sharing battery charger circuit, you'll be able to keep your power-hungry project running even while recharging the battery! This little DC/DC boost converter module can be powered by any 3.7V LiIon/LiPoly battery, and convert the battery output to 5.2V DC for running your 5V projects.

If you dont need the 1A battery charger, smart load-sharing, or 1A iOS resistors, check out the Powerboost 500CLike our popular 5V 1A USB wall adapter, we tweaked the output to be 5.2V instead of a straight-up 5.0V so that there's a little bit of 'headroom' for long cables, high draw, the addition of a diode on the output if you wish, etc. The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone while preventing icky brown-outs during high current draw because of USB cable resistance.

The PowerBoost 1000C has at the heart a TPS61090 boost converter from TI. This boost converter chip has some really nice extras such as low battery detection, 2A internal switch, synchronous conversion, excellent efficiency, and 700KHz high-frequency operation. Check out these specs!

Synchronous operation means you can disconnect the output completely by connecting the ENable pin to ground. This will completely turn off the output

2A internal switch (~2.5A peak limiting) means you can get 1000mA+ from a 3.7V LiPoly/LiIon battery. Just make sure your battery can handle it!

Low battery indicator LED lights up red when the voltage dips below 3.2V, optimized for LiPo/LiIon battery usage

Onboard 1000mA charge-rate 'iOS' data resistors. Solder in the USB connector and you can plug in any iPad, iPhone or iPod for 1000mA charge rate.

Full breakout for battery in, control pins and power out

90%+ operating efficiency in most cases (see datasheet for efficiency graphs), and low quiescent current: 5mA when enabled and power LED is on, 20uA when disabled (power and low batt LED are off)

To make this even more useful, we stuck a smart load-sharing Lipoly charger on the other side. The charger circuitry is powered from a microUSB jack, and will recharge any 3.7V/4.2V LiIon or LiPoly battery at 1000mA max rate. There's two LEDs for monitoring the charge rate, a yellow one tells you its working, a green one lights up when its done.

Since the built-in battery charger has load-sharing, it will automatically switch over to the USB power when available, instead of continuously charging/draining the battery. This is more efficient, and lets you charge-and-boost at the same time without any interruption on the output so its fine for use as a "UPS" (un-interruptable power supply).

Just be aware that the charge rate is 1000mA max, and there's some inefficiency during the boosting stage, so make super sure that the USB adapter you're using to charge with is high quality, can supply 2A and has thick power wires. This one from Adafruit is ideal and has been tested, lower quality ones will not act well due to the voltage drop on the wires or droop on the power supply. This is especially true if you're actually drawing 1000mA out of the PowerBoost 1000C, the MCP73871 maxes out at 1.8A.You do have to always have a LiPo plugged into manage the load spikes, it's not optional!

This charger-booster is great for powering your robot, Arduino project, single-board-computer such as Raspberry Pi or BeagleBone! Each order comes with one fully assembled and tested PCB and a loose USB A jack. If you are powering your project from USB, solder the USB A jack in (a 3-minute soldering task). If you would like to use a terminal block, pick up a 3.5mm 2pin block here and solder to the output spot where the USB jack would go. Or dont solder anything in for a more compact power pack.

If you're trying to figure out how much current your project is using, check out the CHARGER DOCTOR!

You may get an off-white or black JST connector.

PowerBoost 500C is the perfect power supply for your portable project! With a built-in battery charger circuit, you'll be able to keep your project running even while recharging the battery! This little DC/DC boost converter module can be powered by any 3.7V LiIon/LiPoly battery, and convert the battery output to 5.2V DC for running your 5V projects.

If you need a 1A battery charger, smart load-sharing, and 1A iOS resistors, check out the Powerboost 1000C

Like our popular 5V 1A USB wall adapter, we tweaked the output to be 5.2V instead of a straight-up 5.0V so that there's a little bit of 'headroom' for long cables, high draw, the addition of a diode on the output if you wish, etc. The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone while preventing icky brown-outs during high current draw because of USB cable resistance.

The PowerBoost 500C has at the heart a TPS61090 boost converter from TI. This boost converter chip has some really nice extras such as low battery detection, 2A internal switch, synchronous conversion, excellent efficiency, and 700KHz high-frequency operation. Check out these specs!

Synchronous operation means you can disconnect the output completely by connecting the ENable pin to ground. This will completely turn off the output

2A internal switch (~2.5A peak limiting) means you can get 500mA+ from a 3.7V LiPoly/LiIon battery. We had no problem drawing 1000mA, just make sure your battery can handle it!

Low battery indicator LED lights up red when the voltage dips below 3.2V, optimized for LiPo/LiIon battery usage

Onboard 500mA charge-rate 'iOS' data resistors. Solder in the USB connector and you can plug in any iPhone or iPod for 500mA charge rate. Not suggested for large iPads.

Full breakout for battery in, control pins and power out

90%+ operating efficiency in most cases (see datasheet for efficiency graphs), and low quiescent current: 5mA when enabled and power LED is on, 20uA when disabled (power and low batt LED are off)

To make this even more useful, we stuck a MicroLipo charger on the other side. The charger circuitry is powered from a microUSB jack, and will recharge any 3.7V/4.2V LiIon or LiPoly battery at 500mA max rate. There's two LEDs for monitoring the charge rate, a yellow one tells you its working, a green one lights up when its done. You can charge and boost at the same time no problem, without any interruption on the output so its fine for use as a "UPS" (un-interruptable power supply) for a low-current draw device. Just be aware that the charge rate is 500mA max, so if you're drawing more than ~300mA continuously from the 5V output side, the battery will slowly drain since the charge rate is less than the dis-charge rate.

Great for powering your robot, Arduino project, single-board-computer such as Raspberry Pi or BeagleBone! Each order comes with one fully assembled and tested PCB and a loose USB A jack. If you are powering your project from USB, solder the USB A jack in (a 3-minute soldering task). If you would like to use a terminal block, pick up a 3.5mm 2pin block here and solder to the output spot where the USB jack would go. Or don't solder anything in for a more compact power pack.

Each order comes with a fully assembled and tested PowerBoost 500C + USB jack. Does not come with a Lipoly or LiIon battery, but we have tons in the shop, just pick one with more than 500mAh of capacity. Also doesn't come with the nice iPhone or charger cable. You can also grab a switch that can be soldered in to create an output on/off switch. Be sure to read our lovely tutorial for details, schematics, and more!

If you're trying to figure out how much current your project is using, check out the CHARGER DOCTOR!

This is the SparkFun MOSFET Power Control Kit, a breakout PTH soldering kit for for the RFP30N06LE N-Channel MOSFET. This kit is extremely simple to assemble with only 10 pins to solder. If you are looking for a little more control over projects that require a little more power than normal but need a better way than your breadboard, this kit is perfect for you

Included in each kit is a SparkFun MOSFET Power Control PCB, two screw terminals (one 2-pin and one 3-pin), a 10k resistor, and a single RFP30N06LE MOSFET. What we really like about this particular MOSFET is that it’s very common and offers very low on-resistance with a control (gate) voltage that is compatible with any 3-5V microcontroller or mechanical switch. This allows you to control high-power devices with very low-power control mechanisms.

Note: While the MOSFET is rated to 60V 30A, the circuit board traces are only rated to 3.5A.

Includes

1x SparkFun MOSFET Power Control PCB

1x RFP30N06LE MOSFET

1x 2-pin screw terminal

1x 3-pin screw terminal

1x 10k resistor

Convert just about any battery pack to 5V with VERTER - our fresh new Buck-Boost power converter. VERTER can take battery voltages from 3-12VDC and output a nice 5V DC, which makes it a perfect universal power supply for your portable project! Where Verter really shines is when you have a battery or power range that can fluctuate a lot, or you don't know what you'll end up using.

It operates smoothly over the 3-12V range, moving from a boost converter (3-5V in) to a buck converter (5-12V in) on the fly. Please note! This chip can do both, but it really works better as a buck converter than a boost. If you need a full 500mA out, it will struggle as it gets down to 3V and the output will sag to about 4.8V (which is still within standard USB power specs). If you only need something to boost a voltage up to 5V and you want it to be really good at it, check out our PowerBoost series, which excel at that.

Like our popular 5V 1A USB wall adapter, we tweaked the output to be 5.2V instead of a straight-up 5.0V so that there's a little bit of 'headroom' long cables, high draw, the addition of a diode on the output if you wish, etc. The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone while preventing icky brown-outs during high current draw because of USB cable resistance.The VERTER has at the heart a TPS63060 boost converter from TI. This buck-boost converter chip can handle a wide range of voltages (3-12V) and has some really nice extras such as power good output, 2A internal switch, synchronous conversion, excellent efficiency, and 2.2MHz high-frequency operation. Check out these specs!

Synchronous operation means you can disconnect the output completely by connecting the ENable pin to ground. This will completely turn off the output

2A internal switch means you can get out 500mA from as low as 3V, and at least 1000mA from inputs as high 12V

On-board 500mA charge-rate 'Apple/iOS' data resistors. Solder in the included USB connector and you can plug in any iPhone or iPod for 500mA charge rate. Not suggested for iPad (which really needs 1A charge rate).

Full breakout for battery in, control pins and power out

90%+ operating efficiency in most cases (see datasheet for efficiency graphs), and low quiescent current: 5mA when enabled and power LED is on, 20uA when disabled (power and low batt LED are off)

Great for powering your robot, Arduino project, single-board-computer such as Raspberry Pi or BeagleBone from a wide variety of inputs. We especially like it for use with 4 x AA batteries, which can range from 7V for fresh alkalines down to 4V for nearly-dead rechargeables. If you're only going to be using voltages higher than 6V, we recommend our UBEC step-down. If you're only going to be using voltages under 5V, check out the PowerBoost 500 which has much better boosting capability

Each order comes with one fully assembled and tested PCB, 2 pin terminal block, and a loose USB A jack. If you are powering your project from USB, solder the USB A jack in (a 3-minute soldering task). If you would like to use a terminal block, pick up a 3.5mm 2pin block here and solder to the output spot where the USB jack would go. The terminal block goes on the input side, so  you can easily connect and disconnect a battery pack. Or don't solder anything in for a more compact power pack. 

Note: The terminal block included with your product may be blue or black.