Pololu Distance Sensor with Pulse Width Output, 300cm Max

A digital microcontroller pin can be used to time the length of each high pulse, which encodes the measured distance. The sensor works over an input voltage range of 3.0 V to 5.5 V, and the 0.1″ pin spacing makes it easy to use with standard solderless breadboards and 0.1″ perfboards.

Note: The maximum range of 300 cm is only achievable for high-reflectance objects in good ambient conditions. Lower-reflectivity targets or poor ambient conditions will reduce the maximum range.

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.

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

     d=4 mm1 µs⋅(t –1000 µs)d=4 mm1 µs⋅(t –1000 µs)

     t=1000 µs+1 µs4 mm⋅dt=1000 µs+1 µs4 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.