pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

4 mm × 9

37.0 × 20.0

analog

3.5 mA

22 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 and separate controls for the odd and even emitters. 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 40 mm. This version features high-performance, low-current QTRX sensors with lenses.

Pinout diagram of a QTRX-HD-xA Reflectance Sensor Array.

QTRX-HD-09A Reflectance Sensor Array, front and back views.

QTRX-HD-09A Reflectance Sensor Array, front and back views.

Dimensions: 37.0 × 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: 9

Sensor pitch: 4 mm

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

Max board current: 22 mA

Output format: analog voltages (0 V to VCC)

Optimal sensing distance: 10 mm

Maximum recommended sensing distance: 40 mm

Weight: 2.1 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.

This super small mono amplifier is surprisingly powerful - able to deliver up to 2.5 Watts into 4-8 ohm impedance speakers. Inside the miniature chip is a class D controller, able to run from 2.0V-5.5VDC. Since the amp is a class D, its very efficient (over 90% efficient when driving an 8Ω speaker at over half a Watt) - making it perfect for portable and battery-powered projects. It has built in thermal and over-current protection but we could barely tell it got hot. There's even a volume trim pot so you can adjust the volume on the board down from the default 24dB gain. This board is a welcome upgrade to basic "LM386" amps!The A+ and A- inputs of the amplifier go through 1.0uF capacitors, so they are fully 'differential' - if you don't have differential outputs, simply tie the Audio- pin  to ground. The output is "Bridge Tied" - that means the output pins connect directly to the speaker pins, no connection to ground. The output is a high frequency 250KHz square wave PWM that is then 'averaged out' by the speaker coil - the high frequencies are not heard. All the above means that you can't connect the output into another amplifier, it should drive the speakers directly.Comes with a fully assembled and tested breakout board. We also include header to plug it into a breadboard and a 3.5mm screw-terminal blocks so you can easily attach/detach your speaker. You will be ready to rock in 15 minutes! Speaker is not included, use any 4 ohm or greater impedance speaker.

Output Power: 2.5W at 4Ω, 10% THD, 1.5W at 8Ω, 10% THD, with 5.5V Supply

50dB PSRR at 1KHz

Filterless design, with ferrite bead + capacitors on output.

Fixed 24dB gain, onboard trim potentiometer for adjusting input volume.

Thermal and short-circuit/over-current protection

Low current draw: 4mA quiescent and 1uA in shutdown mode

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

For precision temperature sensing, nothing beats a Platinum RTD. Resistance temperature detectors (RTDs) are temperature sensors that contain a resistor that changes resistance value as its temperature changes, basically a kind of thermistor. In this sensor, the resistor is actually a small strip of Platinum with a resistance of 100 ohms at 0°C, thus the name PT100. Compared to most NTC/PTC thermistors, the PT type of RTD is much most stable and precise (but also more expensive) PT100's have been used for many years to measure temperature in laboratory and industrial processes, and have developed a reputation for accuracy (better than thermocouples), repeatability, and stability. 

However, to get that precision and accuracy out of your PT100 RTD you must use an amplifier that is designed to read the low resistance. Better yet, have an amplifier that can automatically adjust and compensate for the resistance of the connecting wires. If you're looking for a great RTD sensor, today is your lucky day because we have a lovely Adafruit RTD Sensor Amplifier with the MAX31865 breakout for use with any 2, 3 or 4 wire PT100 RTD!

If you have a PT1000 RTD, please visit this page to purchase a version of this board with the reference resistor for 1000-ohm RTDs

We've carried various MAXIM thermocouple amplifiers and they're great - but thermocouples don't have the best accuracy or precision, for when the readings must be as good as can be. The MAX31865 handles all of your RTD needs, and can even compensate 3 or 4 wire RTDs for better accuracy. Connect to it with any microcontroller over SPI and read out the resistance ratio from the internal ADC. We put a 430Ω 0.1% resistor as a reference resistor on the breakout. We have some example code that will calculate the temperature based on the resistance for you.

We even made the breakout 5V compliant, with a 3.3V regulator and level shifting, so you can use it with any Arduino or microcontroller.

Each order comes with one assembled RTD amplifier breakout board. Also comes with two 2-pin terminal blocks (for connecting to the RTD sensor) and pin header (to plug into any breadboard or perfboard). A required PT100 RTD is not included! (But we stock them in the shop). Some soldering is required to solder the headers and terminal blocks to the breakout, but it's an easy task with soldering tools.

Please note: this does not include an RTD sensor! Also, the terminal blocks included with your product may be blue or black

This tiny audio amplifier is based on the Texas Instruments TPA2005D1. Its efficient class-D operation means low heat and long battery life. It can drive an 8-Ohm speaker at up to 1.4 Watts; it won’t shake a stadium, but it will provide plenty of volume for your audio projects.

The fully-differential inputs are safe for floating audio signals such as from our MP3 Shield, and can also be connected to ground-referenced signals as well. A shutdown input is provided to save power when the amplifier is not being used, and a solder jumper and header are provided to connect a volume-control potentiometer (not included).

Note: The amplifier’s class-D design outputs a 250kHz PWM-like signal that is restored to an analog voltage in the speaker’s coil. This is what makes the amplifier so efficient, but because of the switching frequency, you should keep the amplifier as close to the speaker as possible to minimize possible interference.

Features

Extremely efficient class-D amplifier

1.4W into 8 Ohms

2.5V to 5.5V supply

Fully differential audio inputs, can be ground-referenced as well

Shutdown input with pullup and LED-follows-shutdown circuitry

PTH pads provided to change gain resistors if desired (see datasheet for details)

Solder jumper and header allow addition of a 10k volume control potentiometer (not included)

This incredibly small stereo amplifier is surprisingly powerful - able to deliver 2 x 2.1W channels into 4 ohm impedance speakers (@ 10% THD). Inside the miniature chip is a class D controller, able to run from 2.7V-5.5VDC. Since the amp is a class D, it's incredibly efficient (89% efficient when driving an 8Ω speaker at 1.5 Watt) - making it perfect for portable and battery-powered projects. It has built in thermal and over-current protection but we could barely tell it got hot. This board is a welcome upgrade to basic "LM386" amps!The inputs of the amplifier go through 1.0uF capacitors, so they are fully 'differential' - if you don't have differential outputs, simply tie the R- and L- to ground. The outputs are "Bridge Tied" - that means they connect directly to the outputs, no connection to ground. The output is a ~300KHz square wave PWM that is then 'averaged out' by the speaker coil - the high frequencies are not heard. All the above means that you can't connect the output into another amplifier, it should drive the speakers directly.Comes with a fully assembled and tested breakout board with 1.0uF input capacitors. We also include a dual mini DIP switch for setting the amplifier gain on the fly, 3.5mm screw-terminal blocks so you can easily attach/detach your speakers, and some header in case you want to plug it into a breadboard. You will be ready to rock in 15 minutes! Speakers are not included, use any 4 ohm or 8 ohm impedance speakers.

Output Power: 2.1W at 4Ω, 10% THD, 1.4W at 8Ω, 10% THD, with 5V Supply

PSRR: 77 dB typ @ 217 Hz with 6 dB gain

Designed for use without an output filter, when wires are kept at under 2"-4" long

Four pin-selectable gains: 6dB, 12dB, 18dB and 24dB. Select with the onboard switches or by setting the G0 and G1 breakout pins (see schematic for breakout board showing gain pin settings for details)

Excellent click-and-pop suppression

Thermal shutdown protection

Independent channel shutdown

Low current draw: typ 6mA quiescent and 1.5uA in shutdown mode

Check out the tutorial for more details!

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

Stereo 2.8W Class D Audio Amplifier (8:55)

A mini class D with AGC and I2C control? Yes please! This incredibly small stereo amplifier is surprisingly powerful. It is able to deliver 2 x 2.8W channels into 4 ohm impedance speakers (@ 10% THD) and it has a i2c control interface as well as an AGC (automatic gain control) system to keep your audio from clipping or distorting.If you don't want to use I2C to control it, it does start up on with 6dB gain by default and the AGC set up for most music playing. We do suggest using it with a microcontroller to configure it, however, since its quite powerful. Settings are not stored in the chip, so you'll need to adjust any gain & AGC amplification settings every time the amp is powered up.Inside the miniature chip is a class D controller, able to run from 2.7V-5.5VDC. Since the amp is a class D, it's incredibly efficient (89% efficient when driving an 8Ω speaker at 1.5 Watt) - making it perfect for portable and battery-powered projects. It has built in thermal and over-current protection but we could barely tell if it got hot. This board is a welcome upgrade to basic "LM386" amps!The inputs of the amplifier go through 1.0uF capacitors, so they are fully 'differential' - if you don't have differential outputs, simply tie the R- and L- to ground. The outputs are "Bridge Tied" - that means they connect directly to the outputs, no connection to ground. The output is a ~300KHz square wave PWM that is then 'averaged out' by the speaker coil - the high frequencies are not heard. All the above means that you can't connect the output into another amplifier, it should drive the speakers directly.Comes with a fully assembled and tested breakout board with 1.0uF input capacitors. We also include 3.5mm screw-terminal blocks so you can easily attach/detach your speakers, and some header in case you want to plug it into a breadboard. Speakers are not included, use any 4 ohm or 8 ohm impedance speakers.Our awesome tutorial and Arduino library will let you set the AGC configuration (you can also just turn it off), max gain, and turn on/off the left & right channels all over I2C! You will be ready to rock in 20 minutes!

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

Stereo 2.8W Class D Audio Amplifier - I2C Control AGC - TPA2016 (6:10)

Pump up the volume with this 20W stereo amplifier! This slim little board has a class D amplifier onboard that can drive 2 channels of 4-8 ohm impedance speakers at 20W each. Power it with 5-12VDC using the onboard DC power jack and plug stereo line level into the 3.5mm stereo headphone jack and jam out with ease. Since it's class D, its completely cool-running, no heat sinks are required and it's extremely efficient - up to 93% efficiency makes it great for portable or battery powered rigs.We like the MAX9744 amplifier at the heart of this board because its very easy to use, but it also has both analog and digital volume control capability. Use a single 1KΩ pot (we include one) to adjust volume analog-style. Or hook it up to your favorite microcontroller and send I2C commands to set 64-steps of volume amplification.Some great stats about the MAX9744:

Power from 4.5V-14V DC voltage

Up to 93% efficient (88-93% typical)

20mA quiescent current (or put into shutdown for 1uA quiescent)

Up to 29.5dB max gain

Use DC or AC coupled line-level input, up to 3Vpp

Filterless Spread-Spectrum Modulation LowersRadiated RF Emissions from Speaker Cables

20W Stereo Output (4Ω, VDD = 12V, THD+N = 10%)

Low 0.04% THD+N

Integrated Click-and-Pop Suppression

Short-Circuit and Thermal-Overload Protection

We took this lovely chip and wrapped it up into a breakout for you, with polarity-protection, jacks and terminal blocks, i2c level shifting, and a spot to solder in a volume pot.Each order comes with one MAX9744 breakout board with all surface-mount parts fully assembled and tested. We also include 3 x 2pin and 1 x 3pin terminal blocks, a 470uF power filter capacitor and 1KΩ trim pot. To use this board, a little soldering is required to attach the terminal blocks and other components, but its fairly easy and expect it should take less than 15 minutes. Check out our detailed tutorial for assembly instructions and overall usage

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

This incredibly small stereo amplifier is surprisingly powerful - able to deliver 2 x 3.7W channels into 3 ohm impedance speakers. Inside the miniature chip is a class D controller, able to run from 2.7V-5.5VDC. Since the amp is a class D, its incredibly efficient (over 90% efficient when driving an 8Ω speaker at over a Watt) - making it perfect for portable and battery-powered projects. It has built in thermal and over-current protection but we could barely tell it got hot. This board is a welcome upgrade to basic "LM386" amps!The inputs of the amplifier go through 1.0uF capacitors, so they are fully 'differential' - if you don't have differential outputs, simply tie the R- and L- to ground. The outputs are "Bridge Tied" - that means they connect directly to the outputs, no connection to ground. The output is a 360KHz square wave PWM that is then 'averaged out' by the speaker coil - the high frequencies are not heard. All the above means that you can't connect the output into another amplifier, it should drive the speakers directly.Comes with a fully assembled and tested breakout board with 1.0uF input capacitors. We also include header to plug it into a breadboard, 3.5mm screw-terminal blocks so you can easily attach/detach your speakers, and a 2x4 header + jumper to change the amplifier gain on the fly. You will be ready to rock in 15 minutes! Speakers are not included, use any 3ohm or greater impedance speakers. 

Output Power: 3.7W at 3Ω, 10% THD, 1.7W at 8Ω, 10% THD, with 5V Supply

Passes EMI limit unfiltered with up to 12 inches (30 cm) of speaker cable

High 83dB PSRR at 217Hz

Spread-Spectrum Modulation and Active Emissions Limiting

Five pin-selectable gains: 6dB, 9dB, 12dB, 15dB and 18dB. Select with a jumper or by setting the G and G' breakout pins (see schematic for breakout board showing gain pin settings for details)

Excellent click-and-pop suppression

Thermal and short-circuit/over-current protection

Low current draw: 2mA quiescent and 10uA in shutdown mode

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