VisionSensor.md

December 22, 2021 ยท View on GitHub

Color & Distance Sensor

Mode subscriptions

Sensor has number of different modes to subscribe.

Colors that are detected are part of COLORS map (see LED section). Only several colors are possible to detect: BLACK, BLUE, CYAN, YELLOW, RED, WHITE. Sensor does its best to detect best color, but only works when sample is very close to sensor.

Distance works in range of 0-10 inches, with ability to measure last inch in higher detail.

Simple example of subscribing to sensor:

from pylgbst.hub import MoveHub, VisionSensor
import time

def callback(color, distance):
    print("Color: %s / Distance: %s" % (color, distance))

hub = MoveHub()

hub.vision_sensor.subscribe(callback, mode=VisionSensor.COLOR_DISTANCE_FLOAT)
time.sleep(60) # play with sensor while it waits   
hub.vision_sensor.unsubscribe(callback)

Subscription mode constants in class VisionSensor are:

  • COLOR_INDEX - use callback(color)
  • DISTANCE_INCHES - use callback(color) measures distance in integer inches count
  • COUNT_2INCH - use callback(count) - it counts crossing distance ~2 inches in front of sensor
  • DISTANCE_REFLECTED - use callback(reflected) where reflected is float value from 0 to 1
  • AMBIENT_LIGHT - use callback(luminosity) where luminosity is float value from 0 to 1
  • COLOR_RGB - use callback(red, green, blue) - each value corresponds to a color channel
  • COLOR_DISTANCE_FLOAT - default mode, use callback(color, distance) where distance is float value in inches

Two specific constants are used with methods to act on the sensor:

  • set_color(color) and SET_COLOR mode - allow to change the color of the sensor RGBLED. COLOR_BLACK and COLOR_NONE turns the LED off
  • set_ir_tx(ir_code) and SET_IR_TX mode - allow to send IR code for PowerFunctions receiver

Access to sensor measures

The following attributes are available, they correspond to the modes described above.

from pylgbst.hub import MoveHub

hub = MoveHub()
print("Color:", hub.vision_sensor.color)
print("Distance:", hub.vision_sensor.distance)
print("Reflected light:", hub.vision_sensor.reflected_light)
print("Luminosity:", hub.vision_sensor.luminosity)
print("Detection count:", hub.vision_sensor.detection_count)
print("RGB channels:", hub.vision_sensor.rgb_color)