pitch × sensors

size(mm)

output

max current

optimalrange

LED

board

8 mm × 2

13.0 × 20.0

analog

3.5 mA

5 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-MD-02A 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: 2

Sensor pitch: 8 mm

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

Max board current: 5 mA

Output format: analog voltages (0 V to VCC)

Optimal sensing distance: 10 mm

Maximum recommended sensing distance: 30 mm

Weight: 0.7 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

8 mm × 2

13.0 × 20.0

RC (digital)

3.5 mA

5 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-MD-02RC 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: 2

Sensor pitch: 8 mm

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

Max board current: 5 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: 0.7 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 a simple board that no one really needs but it sure comes in handy. If you’ve ever tried to hook up an FTDI to something only to realize you need to swap the TX and RX, maybe you could use this board. Sure, you can grab some jumper wires and make your own, but this little crossover board makes it much easier.

The board has a set of headers going in and a set going out. The TX and RX lines are swapped so you can connect it to a Bluetooth Mate and configure it without having to swap the pins coming from your FTDI.

This small synchronous switching step-down (or buck) regulator takes an input voltage from 4 V to 36 V and efficiently reduces it to 3.3 V. The board measures only 0.7″ × 0.7″ yet delivers a typical continuous output current of up to 2.6 A and features reverse voltage protection. Typical efficiencies of 85% to 95% make this regulator well suited for powering moderate loads like sensors or small motors. An optional shutdown pin enables a low-power state with a current draw of around 20 μA to 350 μA, depending on the input voltage, and a power-good output indicates when the regulator cannot adequately maintain the output voltage.

The D24V22Fx family of step-down voltage regulators generates lower output voltages from input voltages as high as 36 V. They are synchronous switching regulators (also called switched-mode power supplies (SMPS) or DC-to-DC converters) with typical efficiencies of 85% to 95%, which is much more efficient than linear voltage regulators, especially when the difference between the input and output voltage is large. These regulators can typically support continuous output currents of over 2 A, though the actual available output current is a function of the input voltage and efficiency (see the Typical efficiency and output current section below). In general, the available output current is a little higher for the lower-voltage versions than it is for the higher-voltage versions, and it decreases as the input voltage increases.

These regulators have a typical quiescent (no load) current draw of around 1 mA, and an enable pin can be used to put the boards in a low-power state that reduces the quiescent current to approximately 5 µA to 10 µA per volt on VIN.

The modules have built-in reverse-voltage protection, short-circuit protection, a thermal shutdown feature that helps prevent damage from overheating, and a soft-start feature that reduces inrush current.

Several different fixed output voltages are available:

Several alternatives are available for this product.

Select from the options below and click “Go” to find a particular version.

Close

Alternatives available with variations in these parameter(s): output voltage Select variant…

The different voltage versions of this regulator all look very similar, so you should consider adding your own distinguishing marks or labels if you will be working simultaneously with multiple versions. This product page applies to all versions of the D24V22Fx family.

The D24V22Fx family is intended to replace our older D24V25Fx family of step-down voltage regulators. The two designs have the same size and similar current capabilities and input voltage ranges, but they do not have the same pinout and are based on different internal circuits, so there are fundamental differences in operation. In particular, these newer D24V22Fx regulators have much lower dropout voltages and provide a “power good” signal, and the newer design allows for higher output voltages (e.g. 12 V).

Input voltage:

4 V to 36 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 36 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

4 V to 36 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 36 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

Fixed 3.3 V, 5 V, 6 V, 7.5 V, 9 V, or 12 V output (depending on regulator version) with 4% accuracy

Typical maximum continuous output current: >2 A

Typical efficiency of 85% to 95%, depending on input voltage, output voltage, and load

Switching frequency: ~400 kHz

Integrated reverse-voltage protection, over-current protection, over-temperature shutoff, and soft-start

1 mA typical no-load quiescent current; this can be reduced to approximately 5 µA to 10 µA per volt on VIN by disabling the board

“Power good” output indicates when the regulator cannot adequately maintain the output voltage

Compact size: 0.7″ × 0.7″ × 0.31″ (17.8 mm × 17.8 mm × 8 mm)

Two 0.086″ mounting holes for #2 or M2 screws

Connections

These buck regulators have five main connection points for five different electrical nodes: power good (PG), enable (EN), input voltage (VIN), ground (GND), and output voltage (VOUT). The board also features a second ground connection point off the main row of connections that might be convenient for applications where you are soldering wires directly to the board rather than using it in a breadboard.

The input voltage, VIN, powers the regulator. Voltages between 4 V and 36 V can be applied to VIN, but for versions of the regulator that have an output voltage higher than 4 V, the effective lower limit of VIN is VOUT plus the regulator’s dropout voltage, which varies approximately linearly with the load (see below for a graph of dropout voltages as a function of the load).

The output voltage, VOUT, is fixed and depends on the regulator version: the D24V22F3 version outputs 3.3 V, the D24V22F5 version outputs 5 V, the D24V22F6 version outputs 6 V, the D24V22F7 version outputs 7.5 V, the D24V22F9 version outputs 9 V, and the D24V22F12 version outputs 12 V.

The regulator is enabled by default: a 270 kΩ pull-up resistor on the board connects the EN pin to reverse-protected VIN. The EN pin can be driven low (under 1 V) to put the board into a low-power state. The quiescent current draw in this sleep mode is dominated by the current in the pull-up resistor from EN to VIN and by the reverse-voltage protection circuit, which altogether will draw between 5 µA and 10 µA per volt on VIN when EN is held low. If you do not need this feature, you should leave the EN pin disconnected.

The “power good” indicator, PG, is an open-drain output that goes low when the regulator’s output voltage falls below around 85% of the nominal voltage and becomes high-impedance when the output voltage rises above around 90%. An external pull-up resistor is required to use this pin.

Pololu Step-Down Voltage Regulator D24V22Fx with included hardware.

Pololu Step-Down Voltage Regulator D24V22Fx, bottom view.

The five main connection points are labeled on the top of the PCB and are arranged with a 0.1″ spacing for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. Either the included 5×1 straight male header strip or the 5×1 right angle male header strip can be soldered into these holes. For the most compact installation, you can solder wires directly to the board.

Pololu Step-Down Voltage Regulator D24V22Fx, side view.

The board has two 0.086″ (2.18 mm) diameter mounting holes intended for #2 or M2 screws. The mounting holes are at opposite corners of the board and are separated by 0.52″ (13.21 mm) both horizontally and vertically. For all the board dimensions, see the dimension diagram (204k pdf).

Typical efficiency and output current

The efficiency of a voltage regulator, defined as (Power out)/(Power in), is an important measure of its performance, especially when battery life or heat are concerns. This family of switching regulators typically has an efficiency of 85% to 95%, though the actual efficiency in a given system depends on input voltage, output voltage, and output current. See the efficiency graph near the bottom of this page for more information.

The maximum achievable output current is typically over 2 A, but this depends on many factors, including the ambient temperature, air flow, heat sinking, and the input and output voltage.

Typical dropout voltage

The dropout voltage of a step-down regulator is the minimum amount by which the input voltage must exceed the regulator’s target output voltage in order to ensure the target output can be achieved. For example, if a 5 V regulator has a 1 V dropout voltage, the input must be at least 6 V to ensure the output is the full 5 V. Generally speaking, the dropout voltage increases as the output current increases. See the “Details” section below for more information on the dropout voltage for this specific regulator version.

The graph below shows the typical efficiency of the 3.3 V D24V22F3 regulator as a function of the output current:

Since the regulator’s input voltage must be at least 4 V, dropout voltage is not a consideration for this 3.3 V version.

During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.

People often buy this product together with:

This small synchronous switching step-down (or buck) regulator takes an input voltage of up to 36 V and efficiently reduces it to 5 V. The board measures only 0.7″ × 0.7″ yet delivers a typical continuous output current of up to 2.5 A and features reverse voltage protection. Typical efficiencies of 85% to 95% make this regulator well suited for powering moderate loads like sensors or small motors. An optional shutdown pin enables a low-power state with a current draw of around 20 μA to 350 μA, depending on the input voltage, and a power-good output indicates when the regulator cannot adequately maintain the output voltage.

The D24V22Fx family of step-down voltage regulators generates lower output voltages from input voltages as high as 36 V. They are synchronous switching regulators (also called switched-mode power supplies (SMPS) or DC-to-DC converters) with typical efficiencies of 85% to 95%, which is much more efficient than linear voltage regulators, especially when the difference between the input and output voltage is large. These regulators can typically support continuous output currents of over 2 A, though the actual available output current is a function of the input voltage and efficiency (see the Typical efficiency and output current section below). In general, the available output current is a little higher for the lower-voltage versions than it is for the higher-voltage versions, and it decreases as the input voltage increases.

These regulators have a typical quiescent (no load) current draw of around 1 mA, and an enable pin can be used to put the boards in a low-power state that reduces the quiescent current to approximately 5 µA to 10 µA per volt on VIN.

The modules have built-in reverse-voltage protection, short-circuit protection, a thermal shutdown feature that helps prevent damage from overheating, and a soft-start feature that reduces inrush current.

Several different fixed output voltages are available:

Several alternatives are available for this product.

Select from the options below and click “Go” to find a particular version.

Close

Alternatives available with variations in these parameter(s): output voltage Select variant…

The different voltage versions of this regulator all look very similar, so you should consider adding your own distinguishing marks or labels if you will be working simultaneously with multiple versions. This product page applies to all versions of the D24V22Fx family.

The D24V22Fx family is intended to replace our older D24V25Fx family of step-down voltage regulators. The two designs have the same size and similar current capabilities and input voltage ranges, but they do not have the same pinout and are based on different internal circuits, so there are fundamental differences in operation. In particular, these newer D24V22Fx regulators have much lower dropout voltages and provide a “power good” signal, and the newer design allows for higher output voltages (e.g. 12 V).

Input voltage:

4 V to 36 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 36 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

4 V to 36 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 36 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

Fixed 3.3 V, 5 V, 6 V, 7.5 V, 9 V, or 12 V output (depending on regulator version) with 4% accuracy

Typical maximum continuous output current: >2 A

Typical efficiency of 85% to 95%, depending on input voltage, output voltage, and load

Switching frequency: ~400 kHz

Integrated reverse-voltage protection, over-current protection, over-temperature shutoff, and soft-start

1 mA typical no-load quiescent current; this can be reduced to approximately 5 µA to 10 µA per volt on VIN by disabling the board

“Power good” output indicates when the regulator cannot adequately maintain the output voltage

Compact size: 0.7″ × 0.7″ × 0.31″ (17.8 mm × 17.8 mm × 8 mm)

Two 0.086″ mounting holes for #2 or M2 screws

Connections

These buck regulators have five main connection points for five different electrical nodes: power good (PG), enable (EN), input voltage (VIN), ground (GND), and output voltage (VOUT). The board also features a second ground connection point off the main row of connections that might be convenient for applications where you are soldering wires directly to the board rather than using it in a breadboard.

The input voltage, VIN, powers the regulator. Voltages between 4 V and 36 V can be applied to VIN, but for versions of the regulator that have an output voltage higher than 4 V, the effective lower limit of VIN is VOUT plus the regulator’s dropout voltage, which varies approximately linearly with the load (see below for a graph of dropout voltages as a function of the load).

The output voltage, VOUT, is fixed and depends on the regulator version: the D24V22F3 version outputs 3.3 V, the D24V22F5 version outputs 5 V, the D24V22F6 version outputs 6 V, the D24V22F7 version outputs 7.5 V, the D24V22F9 version outputs 9 V, and the D24V22F12 version outputs 12 V.

The regulator is enabled by default: a 270 kΩ pull-up resistor on the board connects the EN pin to reverse-protected VIN. The EN pin can be driven low (under 1 V) to put the board into a low-power state. The quiescent current draw in this sleep mode is dominated by the current in the pull-up resistor from EN to VIN and by the reverse-voltage protection circuit, which altogether will draw between 5 µA and 10 µA per volt on VIN when EN is held low. If you do not need this feature, you should leave the EN pin disconnected.

The “power good” indicator, PG, is an open-drain output that goes low when the regulator’s output voltage falls below around 85% of the nominal voltage and becomes high-impedance when the output voltage rises above around 90%. An external pull-up resistor is required to use this pin.

Pololu Step-Down Voltage Regulator D24V22Fx with included hardware.

Pololu Step-Down Voltage Regulator D24V22Fx, bottom view.

The five main connection points are labeled on the top of the PCB and are arranged with a 0.1″ spacing for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. Either the included 5×1 straight male header strip or the 5×1 right angle male header strip can be soldered into these holes. For the most compact installation, you can solder wires directly to the board.

Pololu Step-Down Voltage Regulator D24V22Fx, side view.

The board has two 0.086″ (2.18 mm) diameter mounting holes intended for #2 or M2 screws. The mounting holes are at opposite corners of the board and are separated by 0.52″ (13.21 mm) both horizontally and vertically. For all the board dimensions, see the dimension diagram (204k pdf).

Typical efficiency and output current

The efficiency of a voltage regulator, defined as (Power out)/(Power in), is an important measure of its performance, especially when battery life or heat are concerns. This family of switching regulators typically has an efficiency of 85% to 95%, though the actual efficiency in a given system depends on input voltage, output voltage, and output current. See the efficiency graph near the bottom of this page for more information.

The maximum achievable output current is typically over 2 A, but this depends on many factors, including the ambient temperature, air flow, heat sinking, and the input and output voltage.

Typical dropout voltage

The dropout voltage of a step-down regulator is the minimum amount by which the input voltage must exceed the regulator’s target output voltage in order to ensure the target output can be achieved. For example, if a 5 V regulator has a 1 V dropout voltage, the input must be at least 6 V to ensure the output is the full 5 V. Generally speaking, the dropout voltage increases as the output current increases. See the “Details” section below for more information on the dropout voltage for this specific regulator version.

The graphs below show the typical efficiency and dropout voltage of the 5 V D24V22F5 regulator as a function of the output current:

During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.

People often buy this product together with:

This small synchronous switching step-down (or buck) regulator takes an input voltage of up to 38 V and efficiently reduces it to 5 V. The board measures only 0.7″ × 0.8″, but it allows a typical continuous output current of up to 5 A. Typical efficiencies of 85% to 95% make this regulator well suited for high-power applications like powering motors or servos. High efficiencies are maintained at light loads by dynamically changing the switching frequency, and an optional shutdown pin enables a low-power state with a current draw of a few hundred microamps.

The D24V50Fx family of step-down voltage regulators generates lower output voltages from input voltages as high as 38 V. They are switching regulators (also called switched-mode power supplies (SMPS) or DC-to-DC converters) with typical efficiencies between 85% and 95%, which is much more efficient than linear voltage regulators, especially when the difference between the input and output voltage is large. The available output current is a function of the input voltage and efficiency (see the Typical Efficiency and Output Current section below), but the output current can typically be as high as 5 A.

At light loads, the switching frequency automatically changes to maintain high efficiencies. These regulators have a typical quiescent (no load) current draw of less than 1 mA, and the ENABLE pin can be used to put the boards in a low-power state that reduces the quiescent current to approximately 10 µA to 20 µA per volt on VIN.

The modules have built-in reverse-voltage protection, short-circuit protection, a thermal shutdown feature that helps prevent damage from overheating, a soft-start feature that reduces inrush current, and an under-voltage lockout.

Several different fixed output voltages are available:

Several alternatives are available for this product.

Select from the options below and click “Go” to find a particular version.

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Alternatives available with variations in these parameter(s): output voltage Select variant…

The different voltage versions of this regulator all look very similar, so you should consider adding your own distinguishing marks or labels if you will be working simultaneously with multiple versions. This product page applies to all versions of the D24V50Fx family.

For lower-power applications, please consider our D24V25Fx family of step-down voltage regulators; these are slightly smaller, pin-compatible versions of this regulator with typical maximum output current of 2.5 A.

Side-by-side comparison of the 2.5A D24V25Fx (left) and 5A D24V50Fx (right) step-down voltage regulators.

Two larger, higher-power, 5 V versions of this regulator are also available: one with a typical maximum output current of 6 A, and the other with a typical maximum output current of 9 A. The higher-power versions also have a few additional features, like a “power good” signal and the ability to lower their output voltage, and they include optional terminal blocks for easy removable connections.

Input voltage:

4.5 V to 38 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 38 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

4.5 V to 38 V for the version that outputs 3.3 V

[output voltage + dropout voltage] to 38 V for output voltages of 5 V and higher (see below for more information on dropout voltage)

Fixed 3.3 V or 5 V (depending on regulator version) with 4% accuracy

Typical maximum continuous output current: 5 A

Integrated reverse-voltage protection, over-current protection, over-temperature shutoff, soft-start, and under-voltage lockout

Typical efficiency of 85% to 95%, depending on input voltage and load; the switching frequency automatically changes at light loads to maintain high efficiencies

Typical no-load quiescent current under 1 mA; can be reduced to 10 µA to 20 µA per volt on VIN by disabling the board* Compact size: 0.7″ × 0.8″ × 0.35″ (17.8 mm × 20.3 mm × 8.8 mm)

Two 0.086″ mounting holes for #2 or M2 screws

Connections

This buck regulator has five connection points for four different connections: enable (EN), input voltage (VIN), 2x ground (GND), and output voltage (VOUT).

The input voltage, VIN, powers the regulator. Voltages between 4.5 V and 38 V can be applied to VIN, but for versions of the regulator that have an output voltage higher than 4.5 V, the effective lower limit of VIN is VOUT plus the regulator’s dropout voltage, which varies approximately linearly with the load (see below for graphs of dropout voltages as a function of the load).

The output voltage, VOUT, is fixed and depends on the regulator version: the D24V50F3 version outputs 3.3 V and the D24V50F5 version outputs 5 V.

The regulator is enabled by default: a 100 kΩ pull-up resistor on the board connects the ENABLE pin to reverse-protected VIN. The ENABLE pin can be driven low (under 0.6 V) to put the board into a low-power state. The quiescent current draw in this sleep mode is dominated by the current in the pull-up resistor from ENABLE to VIN and by the reverse-voltage protection circuit, which will draw between 10 µA and 20 µA per volt on VIN when ENABLE is held low. If you do not need this feature, you should leave the ENABLE pin disconnected.

Pololu 5A Step-Down Voltage Regulator D24V50Fx with included hardware.

Pololu 5A Step-Down Voltage Regulator D24V50Fx, bottom view.

The five connection points are labeled on the top of the PCB and are arranged with a 0.1″ spacing for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. Either the included 5×1 straight male header strip or the 5×1 right angle male header strip can be soldered into these holes. For the most compact installation, you can solder wires directly to the board.

Pololu 5A Step-Down Voltage Regulator D24V50Fx, side view.

The board has two 0.086″ mounting holes intended for #2 or M2 screws. The mounting holes are at opposite corners of the board and are separated by 0.53″ horizontally and 0.63″ vertically.

Typical efficiency and output current

The efficiency of a voltage regulator, defined as (Power out)/(Power in), is an important measure of its performance, especially when battery life or heat are concerns. This family of switching regulators typically has an efficiency of 85% to 95%, though the actual efficiency in a given system depends on input voltage, output voltage, and output current. See the efficiency graph near the bottom of this page for more information.

The maximum achievable output current is typically around 5 A, but this depends on many factors, including the ambient temperature, air flow, heat sinking, and the input and output voltage.

Typical dropout voltage

The dropout voltage of a step-down regulator is the minimum amount by which the input voltage must exceed the regulator’s target output voltage in order to ensure the target output can be achieved. For example, if a 5 V regulator has a 1 V dropout voltage, the input must be at least 6 V to ensure the output is the full 5 V. Generally speaking, the dropout voltage increases as the output current increases. See the “Details” section below for more information on the dropout voltage for this specific regulator version.

Switching frequency and behavior under light loads

The regulator generally operates at a switching frequency of around 600 kHz, but the frequency drops when encountering a light load to improve efficiency. This could make it harder to filter out noise on the output caused by switching.

The graphs below show the typical efficiency and dropout voltage of the 5 V D24V50F5 regulator as a function of the output current:

During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.The over-current limit of the regulator operates on a combination of current and temperature: the current threshold decreases as the regulator temperature goes up. However, there might be some operating points at low input voltages and high output currents (well over 5 A) where the current is just under the limit and the regulator might not shut off before damage occurs. If you are using this regulator in an application where the input voltage is near the lower limit and the load could exceed 5 A for sustained periods (more than five seconds), consider using additional protective components such as fuses or circuit breakers.

People often buy this product together with:

This power distribution board is designed specifically for the Romi chassis as a convenient way to access the chassis’s battery power and pass that on the rest of the electronics that make up your robot. It has slots for soldering directly to the chassis’s battery contacts offers reverse voltage protection, several power switching options, and easy access to the various power busses. Just add your own motor drivers, microcontroller, and sensors to complete your Romi robot.

This power distribution board is designed specifically for the Romi chassis as a convenient way to access the chassis’s battery power and pass that on to the rest of the electronics that make up your robot. The board features reverse voltage protection and the patented latching circuit from the Pololu pushbutton power switch, providing a compact, solid-state power switch for your robot that can be controlled with a momentary pushbutton: one push turns on power and another push turns it off.

The board has a small pushbutton already installed and offers convenient points for connecting external pushbutton or tactile switches in parallel. It also offers several alternate pushbutton connection options that result in push-on-only or push-off-only operation, and additional inputs enable further power control options like allowing your robot to turn off its own power. Alternatively, the board can be reconfigured to disable the pushbutton circuit and give control to the small installed slide switch.

The board’s power buses are accessible through a set of 0.1″-spaced pins that are compatible with standard 0.1″ male and 0.1″ female headers, and also through a larger set of holes that are compatible with 3.5mm-pitch terminal blocks (you can combine a 2-pin block and a 3-pin block into a single 5-pin block that spans the three power holes and two ground holes).

Two 1/4″ #2-56 screws and two #2-56 nuts are included for mounting the board to the Romi chassis.

Power Distribution Board for Romi Chassis.

Motor Driver and Power Distribution Board for Romi Chassis.

Installation

Power Distribution Board for Romi Chassis with included hardware.

Power Distribution Board for Romi Chassis on a black chassis.

Before installing the power distribution board on a Romi chassis, you should solder any headers, terminal blocks, wires, or other connectors you plan to use on the board (not included). Please read the rest of this page carefully to determine what additional connectors you might want and where they should be installed.

It is possible to remove the board from the chassis later to solder additional connections, and some of the through holes can be soldered through the slots in the chassis while the board is mounted, but soldering beforehand is easier and avoids the risk of inadvertently melting the chassis with your soldering iron.

The four battery terminals should be soldered to the board after it is mounted on the chassis, as described in the chassis assembly instructions. You will be able to remove the board and battery contacts from the chassis as a single piece after soldering.

Once your you have soldered your through-hole connections to the power distribution board, please follow the instructions given in the Pololu Romi Chassis User’s Guide to finish assembling the chassis, mounting the control board, and soldering in the battery contacts. (The diagrams in those instructions show assembly with the larger Romi 32U4 Control Board, but the same steps apply for the smaller power distribution board.)

Power switch circuit

By default, the on-board pushbutton can be used to toggle power: one push turns on power and another turns it off. Alternatively, a separate pushbutton can be connected to the BTNA and BTNB pins and used instead. Multiple pushbuttons can be wired in parallel for multiple control points, and each of the parallel pushbuttons, including the one on the board itself, will be able to turn the switch on or off. The latching circuit performs some button debouncing, but pushbuttons with excessive bouncing (several ms) might not function well with it.

For proper pushbutton operation, the board’s slide switch should be left in its Off position. (Sliding the switch to the On position will cause the board power to latch on, and the switch must be returned to the Off position before the board can be turned off with the pushbutton.)

Alternatively, to disable the pushbutton, you can cut the button jumper labeled Btn Jmp; this transfers control of the board’s power to the on-board slide switch instead. A separate slide or toggle switch can be connected to the GATE pin and used instead.

More advanced control options are available through the button connection pins and four control inputs:

Power distribution

The diagram below shows the layout of the power distribution buses and access points on the board.

VBAT is connected to the battery contact labeled BAT1+ and provides a direct connection to the battery supply. By default, VBAT is the high side of all six of the chassis’s AA battery cells in series, although this can be reconfigured with the battery jumper (see below).

VRP provides access to the battery voltage after reverse-voltage protection.

VSW is the battery voltage after reverse protection and the power switch circuit.

VREG is not connected to anything by default, but along with the adjacent ground and VSW pins, the VREG pins provide a good place to connect an optional voltage regulator. For example, adding a D24V5F5 step-down regulator would make a regulated 5 V supply available for a microcontroller and other electronics on your chassis.

BAT2+ provides access to the high side of two AA cells in series. This can be useful if you reconfigure the board to provide two separate battery supplies as described below.

Battery supply configuration

The power distribution board’s default configuration provides battery power, VBAT, from all six of the chassis’s AA cells in series (nominally about 7.2 V with rechargeable batteries or 9 V with alkaline batteries). However, the board’s battery jumper, labeled Bat Jmp, allows you to reconfigure the battery connections to provide two independent supplies: BAT1, with 4 cells in series (nominally 4.8 V rechargeable or 6 V alkaline), and BAT2, with 2 cells in series (nominally 2.4 V rechargeable or 3 V alkaline). Cutting the connection between the BAT1− and BAT2+ pads separates the two sets of batteries, and using solder to bridge the BAT1− and GND pads establishes a common ground between the two new supplies.

Warning: Do not bridge the BAT1− and GND pads without first disconnecting BAT1− from BAT2+. Failing to do so could create a short circuit across the BAT2 batteries.

Simplified schematic diagram

This schematic is also available as a downloadable pdf (110k pdf).

In addition to the power distribution board, we have a few other boards designed to mount onto a Romi chassis:

The Motor Driver and Power Distribution Board for Romi Chassis adds motor drivers and a more versatile power circuit (including a 5 V switching regulator); just add a microcontroller and sensors to build a Romi robot.

The Romi 32U4 Control Board turns the Romi chassis into an integrated robot platform. In addition to the same motor drivers and power circuit found on the motor driver and power distribution board, the Romi 32U4 board includes an on-board ATmega32U4 microcontroller, a number of other peripherals and sensors, and interfaces for an optional LCD or Raspberry Pi.

People often buy this product together with:

This is a very simple board that takes a 6-12V input voltage and outputs a selectable 5V or 3.3V regulated voltage. All headers are 0.1" pitch for simple insertion into a breadboard.

Input power can be supplied to either the DC barrel jack or the two pin header labeled + and -. Output power is supplied to the pins labeled GND and VCC. Board has both an On/Off switch and a voltage select switch (3.3V/5V).

The two sets of four GND and VCC holes are spaced such that when connected to our Basic Breadboard both power busses will be powered.

Note: Headers are not supplied. You will need to supply your own headers to connect this board to a breadboard. Check below for some breakaway header strips.

Features

6-12V input voltage via barrel jack or 2-pin header

3.3V or 5V regulated output voltage

800mA Operating Current

ON/OFF switch

Output voltage select switch

Power status LED

PTC fuse protected power

5.5x2.1mm center positive barrel jack

2.15x0.65"

This is the newest revision of our FTDI Basic. We now use a SMD 6-pin header on the bottom, which makes it smaller and more compact. Functionality has remained the same.

This is a basic breakout board for the FTDI FT232RL USB to serial IC. The pinout of this board matches the FTDI cable to work with official Arduino and cloned 3.3V Arduino boards. It can also be used for general serial applications. The major difference with this board is that it brings out the DTR pin as opposed to the RTS pin of the FTDI cable. The DTR pin allows an Arduino target to auto-reset when a new Sketch is downloaded. This is a really nice feature to have and allows a sketch to be downloaded without having to hit the reset button. This board will auto reset any Arduino board that has the reset pin brought out to a 6-pin connector.

The pins labeled BLK and GRN correspond to the colored wires on the FTDI cable. The black wire on the FTDI cable is GND, green is DTR. Use these BLK and GRN pins to align the FTDI basic board with your Arduino target.

There are pros and cons to the FTDI Cable vs the FTDI Basic. This board has TX and RX LEDs that allow you to actually see serial traffic on the LEDs to verify if the board is working, but this board requires a Mini-B cable. The FTDI Cable is well protected against the elements, but is large and cannot be embedded into a project as easily. The FTDI Basic uses DTR to cause a hardware reset where the FTDI cable uses the RTS signal.

This board was designed to decrease the cost of Arduino development and increase ease of use (the auto-reset feature rocks!). Our Arduino Pro and LilyPad boards use this type of connector.

Note: We know a lot of you prefer microUSB over miniUSB. Never fear, we’ve got you covered! Check out our FT231X Breakout for your micro FTDI needs!

This is the newest revision of our FTDI Basic. We now use a SMD 6-pin header on the bottom, which makes it smaller and more compact. Functionality has remained the same.

This is a basic breakout board for the FTDI FT232RL USB to serial IC. The pinout of this board matches the FTDI cable to work with official Arduino and cloned 5V Arduino boards. It can also be used for general serial applications. The major difference with this board is that it brings out the DTR pin as opposed to the RTS pin of the FTDI cable. The DTR pin allows an Arduino target to auto-reset when a new Sketch is downloaded. This is a really nice feature to have and allows a sketch to be downloaded without having to hit the reset button. This board will auto reset any Arduino board that has the reset pin brought out to a 6-pin connector.

The pins labeled BLK and GRN correspond to the colored wires on the FTDI cable. The black wire on the FTDI cable is GND, green is CTS. Use these BLK and GRN pins to align the FTDI basic board with your Arduino target.

This board has TX and RX LEDs that make it a bit better to use over the FTDI cable. You can actually see serial traffic on the LEDs to verify if the board is working.

This board was designed to decrease the cost of Arduino development and increase ease of use (the auto-reset feature rocks!). Our Arduino Pro boards and LilyPads use this type of connector.

One of the nice features of this board is a jumper on the back of the board that allows the board to be configured to either 3.3V or 5V (both power output and IO level). This board ship default to 5V, but you can cut the default trace and add a solder jumper if you need to switch to 3.3V.

Note: We know a lot of you prefer microUSB over miniUSB. Never fear, we’ve got you covered! Check out our FT231X Breakout for your micro FTDI needs!

The smallest and easiest to use serial conversion circuit on the market! This board has one purpose in life - to convert RS232 to TTL and vice versa (TX and RX). This will allow a microcontroller to communicate with a computer. Shifter SMD is powered from the target application and can run at any voltage! That’s right - power the board at 5V and the unit will convert RS232 to 5V TTL. Power the board at 2.8V and the Shifter board will convert RS232 to 2.8V CMOS TTL. Includes two indicator LEDs for TX and RX. Runs from 300bps up to 115200bps.

This version comes with no DB9 connector attached. Useful for field installations and projects where RS232 serial is coming from something other than a DB9 cable.

Features

1.2x1.1"

If you need to charge LiPo batteries, this simple charger will do just that, and do it fast! The SparkFun USB LiPo Charger is a basic charging circuit that allows you to charge 3.7V LiPo cells at a rate of 500mA or 100mA. It is designed to charge single-cell Li-Ion or Li-Polymer batteries.

The board incorporates a charging circuit, status LED, selectable solder jumper for 500mA or 100mA charging current, external LED footprint, USB input, two pre-installed JST connectors for SYS OUT and BATT IN, and (back by popular demand) a barrel jack connector.

There is also a ‘SYS OUT’ with a pre-installed JST connector which allows you to connect the charging circuit directly to your project so you don’t need to disconnect the charger each time you want to use it.