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Laser Distance Sensor Array (v1)

Three laser time-of-flight distance sensors, facing left, forward and right at 90° to each other. It gives your robot millimetre distance readings to walls and obstacles, for example in RoboCup Junior Rescue Maze or for positioning on a Soccer field.

At a glance

  • Measures: distance to the nearest surface, in three directions
  • Connects to: LEGO® SPIKE™ Prime hub, any port (shows up as a colour sensor)
  • Firmware: LaserArrayFirmware from the AdvancedBotWorks library
  • Shop: advancedbotworks.com

Channel outputs

Channel Meaning Range Units Notes
Red (R) Left distance about 40 – 3600 mm
Green (G) Front distance about 40 – 3600 mm
Blue (B) Right distance about 40 – 3600 mm

How far it can see depends on the light and the surface

The sensors run in the VL53L1X's long distance mode. ST's datasheet figures for this mode (measured with a 100 ms timing budget):

Target Dark Bright ambient light
White (88% reflective) up to 360 cm about 73 cm
Mid grey (54%) up to 340 cm about 69 cm
Dark grey (17%) up to 170 cm about 68 cm
  • Ranging error: ±20 mm in the dark, ±25 mm in ambient light.
  • Below 4 cm, a target is detected but the distance isn't accurate.
  • The ABW firmware uses a shorter, 50 ms timing budget, so real-world maximum range may be a little lower than these figures. Measured ABW figures are to come.

Quick start

  1. Mount the array with the middle sensor facing your robot's front.
  2. Plug the cable into any hub port.
  3. Read R, G and B (see Getting started). Hold a book in front of each sensor and watch its value change.

Example code

Add the More Sensors extension, then use Color Sensor red for the left distance, green for the front and blue for the right. All values are in millimetres.

from hub import port
import color_sensor, runloop

async def main():
    while True:
        left, front, right, _ = color_sensor.rgbi(port.A)
        print("L", left, "mm  F", front, "mm  R", right, "mm")
        if front < 100:
            print("Wall ahead!")
        await runloop.sleep_ms(50)

runloop.run(main())

Specifications

Physical
Dimensions TBC mm
Weight TBC g
Sensor directions Left, front, right (90° apart)
Mounting Fits the LEGO® stud/pin grid (hole spacing TBC)
Cable Attached cable with SPIKE Prime connector, length TBC

Electrical
Supply From the SPIKE hub port
Current draw TBC (measured). The three VL53L1X sensors alone draw about 48 mA typical while ranging (16 mA each, ST datasheet)
Microcontroller Microchip ATSAMD21G18A (ARM Cortex-M0+, 48 MHz)
Distance sensors 3 × ST VL53L1X time-of-flight laser sensors (940 nm, Class 1 laser, eye-safe)
USB USB port on the board for firmware updates (see Updating firmware)

Performance
Distance mode Long (VL53L1X), 50 ms timing budget
Range (ST datasheet, long mode) Up to 360 cm in the dark (white target); about 70 cm in bright ambient light. See the table above
Minimum distance 4 cm
Ranging error (ST datasheet) ±20 mm (dark), ±25 mm (ambient light)
Resolution 1 mm
Field of view 27° cone per sensor
Update rate About 20 Hz per sensor (TBC). A fixed, documented rate is planned
Surfaces Works on most opaque surfaces. Very dark, shiny or transparent surfaces can give poor readings

In the box

  • 1 × Laser Distance Sensor Array with attached SPIKE Prime cable

Mounting

The array fits the LEGO® stud/pin grid. Mount it so that nothing on the robot blocks the three sensor windows, and keep the windows clean.

Mounting diagram coming soon.

Firmware

Known limitations

  • Bright sunlight and other infrared light greatly reduce the maximum range in long distance mode (to under 1 m in strong ambient light).
  • Glass, mirrors and very dark matte surfaces may give wrong or no readings.
  • Each sensor measures within a 27° cone, not a single point, so a surface at an angle or a narrow object can affect the reading.

Revision history

Version Date Changes
v1 2025-03 First release (firmware library 2.0.0)

Still to confirm

  • Dimensions, weight, hole spacing and cable length
  • Current draw
  • Measured range and accuracy on ABW hardware (with the 50 ms timing budget, under competition lighting)
  • Measured update rate (the firmware requests about 30 Hz, but the sensor's default timing gives about 20 Hz)
  • What's reported when no surface is in range or a reading fails