pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

8 mm × 5

37.0 × 20.0

RC (digital)

3.5 mA

14 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 40 mm. This version features high-performance, low-current QTRX sensors with lenses.

Pinout diagram of a QTRX-MD-xRC Reflectance Sensor Array.

QTRX-MD-05RC Reflectance Sensor Array, front and back views.

QTRX-MD-05RC Reflectance Sensor Array dimensions.

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: 5

Sensor pitch: 8 mm

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

Max board current: 14 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: 40 mm

Weight: 1.9 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 is the FemtoBuck, a small-size single-output constant current LED driver. Each FemtoBuck has the capability to dim a single high-power channel of LEDs from 0-350mA at up to 36V while the dimming control can be either accessed via PWM or analog signal from 0-2.5V. This board is based off of the PicoBuck LED Driver, developed in collaboration with Ethan Zonca, except instead of blending three different LEDs on three different channels the FemtoBuck controls just one.

For the FemtoBuck, we’ve increased the voltage ratings on the parts to allow the input voltage to cover the full 36V range of the AL8805 driver. Since the FemtoBuck is a constant current driver, the current drawn from the supply will drop as supply voltage rises. In general, efficiency of the FemtoBuck is around 95%, depending on the input voltage. On board each FemtoBuck you will find two inputs for both power input and dimming control pins and an area to install a 3.5mm screw terminal. Finally at either side of the board you will find small indents or “ears” which will allow you to use a zip tie to secure the wires to the board after soldering them down. This version of the FemtoBuck is equipped with a small solder jumper that can be closed with a glob of solder to double the output current from 330mA to 660mA.

Life has its ups and downs, so why not measure them? The MPL3115A2 is a MEMS pressure sensor that provides Altitude data to within 30cm (with oversampling enabled). The sensor outputs are digitized by a high resolution 24-bit ADC and transmitted over I2C, meaning it’s easy to interface with most controllers. Pressure output can be resolved with output in fractions of a Pascal, and Altitude can be resolved in fractions of a meter. The device also provides 12-bit temperature measurements in degrees Celsius.

This breakout board makes it easy to prototype using this tiny device by breaking out the necessary pins to a standard 0.1" spaced header. The board also has all of the passive components needed to get the device functioning, so you can simply connect it to something that talks I2C and get to work!

Features

1.95V to 3.6V Supply Voltage, internally regulated by LDO

1.6V to 3.6V Digital Interface Supply Voltage

Fully Compensated internally

Direct Reading, Compensated

Pressure: 20-bit measurement (Pascals)

Altitude: 20-bit measurement (meters)

Temperature: 12-bit measurement (degrees Celsius)

Pressure: 20-bit measurement (Pascals)

Altitude: 20-bit measurement (meters)

Temperature: 12-bit measurement (degrees Celsius)

Programmable Events

Autonomous Data Acquisition

Resolution down to 1 ft. / 30 cm

32 Sample FIFO

Ability to log data up to 12 days using the FIFO

1 second to 9 hour data acquisition rate

I2C digital output interface (operates up to 400 kHz)

The SparkFun BME280 Atmospheric Sensor Breakout is the easy way to measure barometric pressure, humidity, and temperature readings all without taking up too much space. Basically, anything you need to know about atmospheric conditions you can find out from this tiny breakout. The BME280 Breakout has been design to be used in indoor/outdoor navigation, weather forecasting, home automation, and even personal health and wellness monitoring.

The on-board BME280 sensor measures atmospheric pressure from 30kPa to 110kPa as well as relative humidity and temperature. The breakout provides a 3.3V SPI interface, a 5V tolerant I2C interface (with pull-up resistors to 3.3V), takes measurements at less than 1mA and idles less than 5µA. The BME280 Breakout board has 10 pins, but no more than six are used at a single time. The left side of the board provide power, ground, and I2C pins. The remaining pins which provide SPI functionality and have another power and ground, are broken out on the other side.

Note: The breakout does NOT have headers installed and will need to purchased and soldered on yourself. Check the Recommended Products section below for the type of headers we use in the Hookup Guide!

Features

Operation Voltage: 3.3V

I2C & SPI Communications Interface

Temp Range: -40C to 85C

Humidity Range: 0 - 100% RH, =-3% from 20-80%

Pressure Range: 30,000Pa to 110,000Pa, relative accuracy of 12Pa, absolute accuracy of 100Pa

Altitude Range: 0 to 30,000 ft (9.2 km), relative accuracy of 3.3 ft (1 m) at sea level, 6.6 (2 m) at 30,000 ft.

Incredibly Small

The SHT15 Breakout is an easy to use, highly accurate, digital temperature and humidity sensor. This board has been fully calibrated and offers high precision and excellent long-term stability at low cost. The digital CMOSens® technology integrates two sensors and readout circuitry on one single chip. All you need is two lines for 2-wire communication, and you’ll have relative humidity and temperature readings to help you sense the world around you!

The two sensors built into the SHT15 have been seamlessly coupled to a 14bit analog to digital converter and a serial interface circuit resulting in superior signal quality, fast response time, and a strong resistance to external disturbances. Additionally, the on board SHT15 features a 0-100% RH measurement range with a temperature accuracy of +/- 0.3°C @ 25°C. There are only four pins that need to be hooked up in order to start using this sensor in a project. One for VCC, one for GND, and the two data lines SDA and SCL.

Features

Operating Voltages: 2.4V min - 5.5V max

2 factory calibrated sensors for relative humidity & temperature

Digital 2-wire interface (Not I2C, but similar)

Measurement range: 0-100% RH

Absolute RH accuracy: +/- 2% RH (10…90% RH)

Repeatability RH: +/- 0.1% RH

Temp. accuracy: +/- 0.3°C @ 25°C

Precise dewpoint calculation possible

Fast response time

Low power consumption (typ. 30 µW)

The Si7021 is a low-cost, easy-to-use, highly accurate, digital humidity and temperature sensor. This sensor is ideal for environmental sensing and data logging and perfect for build a weather stations or humidor control system. All you need are two lines for I2C communication, and you’ll have relative humidity readings and very accurate temperature readings as a bonus!

There are only four pins that need to be hooked up in order to start using this sensor in a project. One for VCC, one for GND, and two data lines for I2C communication. This breakout board has built-in 4.7KΩ pullup resistors for I2C communications. If you’re hooking up multiple I2C devices on the same bus, you may want to disable these resistors.

Features

0.6" x 0.6"

This is a very small infrared 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.

This is the SparkFun RGB and Gesture Sensor, a small breakout board with a built in APDS-9960 sensor that offers ambient light and color measuring, proximity detection, and touchless gesture sensing. With this RGB and Gesture Sensor you will be able to control a computer, microcontroller, robot, and more with a simple swipe of your hand! This is, in fact, the same sensor that the Samsung Galaxy S5 uses and is probably one of the best gesture sensors on the market for the price.

The APDS-9960 is a serious little piece of hardware with built in UV and IR blocking filters, four separate diodes sensitive to different directions, and an I2C compatible interface. For your convenience we have broken out the following pins: VL (optional power to IR LED), GND (Ground), VCC (power to APDS-9960 sensor), SDA (I2C data), SCL (I2C clock), and INT (interrupt). Each APDS-9960 also has a detection range of 4 to 8 inches (10 to 20 cm).

Features

Operational Voltage: 3.3V

Ambient Light & RGB Color Sensing

Proximity Sensing

Gesture Detection

Operating Range: 4-8in (10-20cm)

I2C Interface (I2C Address: 0x39)

The SparkFun Soil Moisture Sensor is a simple breakout for measuring the moisture in soil and similar materials. The soil moisture sensor is pretty straight forward to use. The two large exposed pads function as probes for the sensor, together acting as a variable resistor. The more water that is in the soil means the better the conductivity between the pads will be and will result in a lower resistance, and a higher SIG out.

To get the SparkFun Soil Moisture Sensor functioning all you will need is to connect the VCC and GND pins to your Arduino-based device (or compatible development board) and you will receive a SIG out which will depend on the amount of water in the soil. One commonly known issue with soil moisture senors is their short lifespan when exposed to a moist environment. To combat this, we’ve had the PCB coated in Gold Finishing (ENIG or Electroless Nickel Immersion Gold). We recommend either a simple 3-pin screw pin terminal or a 3-pin jumper wire assembly (both can be found in the Recommended Products section below) to be soldered onto the sensor for easy wiring.

Note: Check the Hookup Guide below for assembly and weatherproofing instructions as well as a simple example project that you can put to together yourself!

Get Started with the Soil Moisture Sensor Guide

This is the SparkFun “Time-of-Flight” Range Finder, a sensor board for the VL6180 distance sensor. Unlike most distance sensors that rely on reflected light intensity or reflected angles to determine range, the VL6180 uses a precise clock to measure the time it takes light to bounce back from a surface. This affords the ToF Range Finder and VL6180 a great benefit over other methods because it can be much more accurate and more immune to noise. Does this technology sound familiar? Well it should, it’s the same means cellphones use to detect when the caller is holding their phone to their ear.

The VL6180 is actually a 3-in-1 package that combines an IR emitter, a range sensor, and an ambient light sensor together for you to easily use and communicate with via an I2C interface. The ToF Range Finder is very similar to its breakout cousin with a few important differences. What sets this board apart is this sensor is equipped with an on-board 2.8V regulator, which means if you were to plug in a voltage higher than 2.8V it will be shifted down without worry of damaging your board! Another thing to note is the form factor of the sensor itself. Many small robotics platforms have integrated hole patterns for the long time favorite Sharp IR sensor line. This allows the VL6180 Sensor to be a near drop-in replacement for most Sharp sensors.

Note: Though the datasheet states the VL6180 measures an absolute range of up to 10cm, we have successfully tested it up to 25cm. The more you know.

Features

2.8V Regulator - Provides the required 2.8V for the sensor

I2C Level Shifter - Provides logic level conversion from 2.8V to VCC

3-in-1 Module

IR Emitter

Range Sensor

Ambient Light Sensor

IR Emitter

Range Sensor

Ambient Light Sensor

Measures absolute range up to 10cm

Gesture Recognition

I2C Interface

Two Programmable GPIO

Sharp Sensor Board Layout

The SparkFun XBee Explorer Regulated takes care of the 3.3V regulation, signal conditioning, and basic activity indicators (Power, RSSI and DIN/DOUT activity LEDs). It translates the 5V serial signals to 3.3V so that you can connect a 5V (down to 3.3V) system to any XBee module. The board was conveniently designed to mate directly with the SparkFun Arduino Pro series of boards for wireless bootloading and USB based configuration.

This unit works with all XBee modules including the Series 1 and 2, standard and Pro versions. Plug an XBee into this breakout and you will have direct access to the serial and programming pins on the XBee unit and will be able to power the XBee with 5V.

This board comes fully populated with 3.3V regulator (5V max input), XBee socket, four status LEDs, and level shifting. In the latest revision the diode level shifter is replaced with a more robust MOSFET level shifter. This board does not include and XBee module. XBee modules sold below.