SF30/D altitude or distance sensor

The SF30/D is a single-beam laser altimeter and rangefinder from LightWare Optoelectronics for unmanned aircraft. It measures the distance to the ground or to an obstacle with a time-of-flight laser and reaches 200 m, which makes it a height-above-ground sensor for UAV landing, terrain following and obstacle detection, and a ranging element for mapping systems.

The sensor measures distance and speed with time-of-flight, so the reading does not depend on the colour or texture of the target or on the angle of incidence of the beam. LightWare states that it is virtually immune to background light, wind and noise. Fast single-pulse measurement with first and last pulse detection is also documented for altitude readings over water, a surface where many ranging sensors struggle.

The main figures: measuring range 0.2 to 200 m on a white wall in daylight; resolution 1 cm; accuracy of plus or minus 10 cm; update rate configurable from 49 up to 20,000 readings per second. The high rate lets a flight controller filter the data, or lets a scanning mechanism build 2D SLAM maps or 3D images. The laser is 905 nm, Class 1M, with a beam divergence below 0.2 degrees and an optical aperture of 51 mm. Class 1M means the beam must not be viewed through binoculars or other optics.

Mounting and power: the open-frame unit measures 30 x 56.5 x 50 mm and weighs about 30 g, with a 35 g figure on the datasheet excluding cables. Supply is 4.5 to 5.5 V DC at about 250 mA, and the operating temperature range is -10 to +50 degrees C. The unit has no IP rating, so the installation has to protect it from dust and water.

Interfaces cover most flight controllers and companion computers: a serial port (3.3 V logic, 921,600 baud by default), I2C (3.3 V, default address 0x66), micro USB for configuration and firmware updates, an analog output of 0 to 2.048 V proportional to distance, an alarm output that signals when the distance falls below a preset value, and a synchronisation pulse that marks the laser flash. Settings are changed with the LightWare Studio application, and an API repository supports host software. Typical uses are altitude hold, automatic landing, terrain following and obstacle sensing on multirotors, helicopters and fixed-wing UAVs.