Pololu Digital Distance Sensor with Pulse Width Output, 300cm Max, Side-Entry Connector

Overview

Pololu Digital Distance Sensor with Pulse Width Output, 300cm Max, Side-Entry Connector, sensor-side view.

Pololu Digital Distance Sensor with Side-Entry Connector, back view with 3-pin JST SH-style cable (cable not included).

This compact sensor makes it possible to measure the distance of objects up to about 300 cm (120″) away using a simple digital pulse width interface (similar to a hobby servo control signal). It uses a short-range lidar module to precisely measure how long it takes for emitted pulses of infrared, eye-safe laser light to reach the nearest object and be reflected back, allowing for 2 mm resolution. As long as the sensor is enabled, it takes continuous distance measurements and encodes the ranges as the widths of high pulses, which can then be timed by a microcontroller using a single digital input.

A camera with no IR filter shows the infrared light emitted by a Pololu Digital Distance Sensor.

The relationship between measured distance d (in mm) and pulse width t (in µs) is as follows:

     ``d = (4 text( mm)) / (1 text( µs)) * (t  – 1000 text( µs))``

     ``t = 1000 text( µs) + (1 text( µs)) / (4 text( mm)) * d ``

The timing uncertainty is approximately ±5%. As objects approach the sensor, the output pulse width will approach 1.0 ms, while an object detected at 300 cm will produce a 1.75 ms pulse width. The sensor uses a pulse width of 2.0 ms to indicate no detection. The pulse period T ranges from around 30 ms to 33 ms, depending on the proximity of the detected object.

The maximum detection range depends on object reflectivity and ambient lighting conditions. In our tests, the sensor was able to reliably detect a wall out to around 300 cm away, a white sheet of paper out to around 170 cm, and a hand out to around 100 cm. The following graph shows the measured distances of three units versus their actual distances from a variety of targets at several different ranges:

Please note that while this sensor can detect objects to within about 1 mm of the sensor face, the effective minimum distance it can measure is around 4 cm, so objects closer than 4 cm might result in an inaccurate measurement.

This sensor features a side-entry 3-pin male JST SH-style connector that works with our 3-pin JST SH-style cables. A functionally identical version is also available with 0.1″-pitch through-holes instead of a connector.

Specifications

• Operating voltage: 3.0 V to 5.5 V
• Current consumption: 30 mA (typical) when enabled, 0.4 mA when disabled
• Maximum range: approximately 300 cm (120″) (for high-reflectivity targets in good ambient conditions; lower-reflectivity targets or poor ambient conditions will reduce the maximum detection range)
• Minimum range: 4 cm (for accurate measurement); < 1 mm (for detection)
• Update rate: 30 Hz to 33 Hz (33 ms to 30 ms period)
• Field of view (FOV): 15° typical; can vary with object reflectance and ambient conditions
• Emitter: eye-safe, 940 nm invisible Class 1 VCSEL (vertical cavity surface-emitting laser)
• Output type: digital pulse width
• Connector: side-entry 3-pin male JST SH-style that is compatible with our 3-pin JST SH-style cables
• Dimensions: 0.9″ × 0.35″ × 0.22″ (22.9 × 8.9 × 5.6 mm); see the dimension diagram (290k pdf) for more information
• Weight: 0.02 oz (0.5 g)

Using the sensor

Three connections are necessary to use this module: VIN, GND, and OUT. These pins are accessible through the board’s 3-pin male JST SH-style connector, which is compatible with our 3-pin JST SH-style cables. When used with our cables, the red wire connects to VIN, the black wire connects to GND, and the white wire connects to OUT. The VIN pin should be connected to a 3 V to 5.5 V source, and GND should be connected to 0 volts. The OUT pin drives low (0 V) when an object is being detected and it drives high (to the VIN level) when an object is not being detected. It is weakly pulled high when the sensor is disabled or waiting for its first reading to complete after power-up. A red LED on the back side of the board also lights whenever an object is detected.

The board has an optional ENABLE pin that can be driven low to put it into a low-power state that consumes approximately 0.4 mA. This pin can be accessed through a via or its neighboring surface-mount pad on the back side labeled “EN” on the silkscreen. The ENABLE pin is pulled up to VIN, enabling the sensor by default.

The board has one mounting hole intended for use with #2 or M2 screws.

Arduino program for reading pulse width output

This is a simple Arduino sketch that reads the output of the Pololu Distance Sensor with Pulse Width Output, 130cm Max and displays the measured distance in millimeters.

// Example Arduino program for reading the Pololu Distance Sensor with Pulse Width Output, 130cm Max

// Change this to match the Arduino pin connected to the sensor's OUT pin.
const uint8_t sensorPin = 2;

void setup()
{
  Serial.begin(115200);
}

void loop()
{
  int16_t t = pulseIn(sensorPin, HIGH);

  if (t == 0)
  {
    // pulseIn() did not detect the start of a pulse within 1 second.
    Serial.println("timeout");
  }
  else if (t > 1850)
  {
    // No detection.
    Serial.println(-1);
  }
  else
  {
    // Valid pulse width reading. Convert pulse width in microseconds to distance in millimeters.
    int16_t d = (t - 1000) * 2;

    // Limit minimum distance to 0.
    if (d < 0) { d = 0; } 
 
    Serial.print(d);
    Serial.println(" mm");
  }
}

micro:bit MakeCode program for reading pulse width output

We have also created a MakeCode example program for the BBC micro:bit single-board computer that demonstrates how to read and convert the output of the Pololu Distance Sensor with Pulse Width Output, 300cm Max. The program’s output can be viewed in the MakeCode device console, which also plots the readings on a graph. You can open the program in the micro:bit MakeCode editor by clicking this link or the picture below.

Jumper settings (irs17a/irs17b)

The board features four surface-mount configuration jumpers that determine its operation mode. Different versions of the Pololu Digital Distance Sensors ship with the appropriate jumpers pre-populated with 0 Ω resistors. These resistors can be desoldered from the populated spots or solder bridges can be added across the unpopulated spots to convert one sensor version into another. This sensor can be converted into any other irs17a/irs17b version as listed in the following table. (For more information about how the different output types work, see the product pages for representative versions.)

irs17a/irs7b jumper settings
Item #		Description	Maximum range(1)	Hysteresis	Resolution	Minimum update rate	Jumper settings (4321)
no connector	side-entry connector
#4066	#5480	Digital output, 25cm	25 cm	50 mm	-	100 Hz	0000
#4067	#5481	Digital output, 50cm	50 cm	50 mm	-	100 Hz	0001
		Digital output, 75cm	75 cm	50 mm	-	100 Hz	0010
#4069	#5483	Digital output, 100cm	100 cm	50 mm	-	100 Hz	0011
		Digital output, any detect	~130 cm	-	-	100 Hz	0100
#4071	#5485	Pulse width output, 130cm max	~130 cm	-	1 mm (= 0.5 µs)	100 Hz (110 Hz max)	0101
		Digital output,125cm	125 cm	50 mm	-	30 Hz	1000
		Digital output,150cm	150 cm	50 mm	-	30 Hz	1001
		Digital output,175cm	175 cm	50 mm	-	30 Hz	1010
#4077	#5491	Digital output, 200cm	200 cm	50 mm	-	30 Hz	1011
		Digital output, any detect	~300 cm	-	-	30 Hz	1100
#4079	#5493	Pulse width output, 300cm max	~300 cm	-	2 mm (= 0.5 µs)	30 Hz (33 Hz max)	1101
Note 1: Effective range depends on object reflectivity and ambient lighting conditions.

Item numbers in this table indicate versions that we offer for sale as standard products, but we can manufacture the other versions on demand (or even make sensors with custom firmware for you). If you are interested in customization, please contact us.

The Pololu Digital Distance Sensor family

We have several versions of Pololu Digital Distance Sensors with different ranges, operating modes, and connector options:

Digital output (does not provide distance measurement)
Item #		Maximum range(1)	Minimum range	Minimum update rate	Jumper settings (4321)	PCB ID	Price
no connector	side-entry connector
#4050		5 cm	< 5 mm	145 Hz	0000	irs16a	$19.95
#4052		10 cm	< 5 mm	115 Hz	0010
#4054		15 cm	< 5 mm	95 Hz	0100
#4066	#5480	25 cm	< 1 mm	100 Hz	0000	irs17a/b	$24.95
#4067	#5481	50 cm	< 1 mm	100 Hz	0001
#4069	#5483	100 cm	< 1 mm	100 Hz	0011
#4077	#5491	200 cm	< 1 mm	30 Hz	1011
Note 1: Effective range depends on object reflectivity and ambient lighting conditions.

Pulse width output (provides distance measurement)
Item #		Maximum range(1)	Minimum range(2)	Resolution	Minimum update rate	Jumper settings (4321)	PCB ID	Price
no connector	side-entry connector
#4064		~50 cm	1 cm	3 mm	50 Hz	1110	irs16a	$19.95
#4071	#5485	~130 cm	4 cm	1 mm	100 Hz	0101	irs17a/b	$24.95
#4079	#5493	~300 cm	4 cm	2 mm	30 Hz	1101
Note 1: Effective range depends on object reflectivity and ambient lighting conditions. Note 2: Objects closer than the minimum distance can still be detected, but the measured distance might be inaccurate. The minimum detection range is < 5 mm for irs16a boards and < 1 mm for irs17a/b boards.

These are the output graphs for the digital output versions that just report if an object is in their detection range:

The output graph is a bit different for the versions that use a pulse width to encode the measured distance. The output for these versions is similar to hobby servo control signals and is shown below as a function of time:

Comparison to Sharp Digital Distance Sensors

The Pololu Digital Distance Sensors have nearly the same form factor and pinout as our carrier boards for the Sharp/Socle GP2Y0D8x digital distance sensors. They are available in the same 5 cm, 10 cm, and 15 cm ranges, in addition to longer ranges of up to several meters. This means they can be used as replacements for these older modules, which are based on sensors from Sharp/Socle that are no longer in production, and the longer-range versions can serve as upgrades that provide enhanced detection and measurement capabilities. The sensors on these newer units are much thinner than the Sharp modules, so the zero-range point is approximately 7 mm closer to the PCB, and the beam angle of the newer units is wider. The pictures below show side-by-side comparisons of the two: