LW20/C altitude or distance sensor

The LW20/C is a microLiDAR laser altimeter and distance sensor from LightWare Optoelectronics for drones and other unmanned vehicles. It is a single-beam, time-of-flight laser rangefinder in an IP67 housing that measures the distance to a surface up to 100 m away, used as a height sensor for altitude measurement, terrain following and landing, and as a forward-facing range sensor for obstacle detection.

The sensor sends a rapid series of 905 nm laser pulses and times the reflections. It measures from 0.2 m to 100 m on a 70% albedo target of 0.9 x 0.9 m in sunlight, with a resolution of 1 cm. The update rate can be set from 48 to 5000 readings per second. The setting changes the accuracy: it is +/- 5 cm at rates below 500 readings per second and +/- 10 cm above that rate, so slower rates suit precise height keeping and scanning, while faster rates give a better detection range for forward-looking obstacle avoidance. The beam divergence is below 0.5 degrees and the optical aperture is 12.7 mm. The maker states that the measurement is not affected by the colour or texture of the target or by the angle of incidence. The laser is Class 1M for eye safety.

For integration, the sensor measures 30 x 20 x 43 mm and weighs 19.5 g including its cable. It takes a supply of 4.5 to 5.5 V, with a typical current of 85 mA and below 200 mA at start-up. It has a serial UART and an I2C interface with 3.3 V TTL levels that tolerate 5 V, and a servo driver. The default serial setting is 115200 baud, and the default I2C address is 0x66. A Pixhawk adapter is supplied with each unit, and a USB adapter, breakout board, DroneCAN adapter, ABS mounting brackets and an aluminium stand kit are accessories. Settings are made in the LightWare Studio software. The operating temperature range is -20 to +60 degrees C.

Advanced functions add to the single distance reading. The first and last pulse feature reports more than one target in the field of view, which helps with measurements through foliage or dust. A small digital servo on the onboard servo driver can steer the beam for scanning and mapping. An alarm channel gives two live status outputs when an object is closer than user-set distances and angles.

The product carries IP67, CE and RoHS3 approvals and complies with NDAA Section 848; the maker also states that it is Blue UAS listed. Typical applications are altitude hold and terrain following for multirotors and fixed-wing UAVs, precision landing, forward obstacle detection and sense-and-avoid, and SLAM-type mapping with a servo-driven scan.