Upload
reagan-anguish
View
218
Download
1
Tags:
Embed Size (px)
Citation preview
Forward Until Dark
NXT Light Sensors
NXT Light Sensors
• How does the Light Sensor detect brightness?
• The Light Sensor shines a red light on the surface below it and reports how much of that light is reflected back.A bright surface will reflect a lot of light and give a high reading. A dark surface will reflect less light and give a low reading.
Forward Until Dark Program
Establishing The Threshold
• On the NXT – Select the View Mode– Select Reflected Light– Select Port 3
• Position the robot over the surface to be read by the light sensor as shown in the next two slides
Establishing The Light Threshold
Establishing The Dark Threshold
Calculating The Threshold
Motor Block One Details
Light Sensor Block Two Details
Motor Block Three Details
Test Your Robot
Forward Until Light
Forward Until Light Light Sensor Block Two Details
Wait for the Light Sensor on Port 3 to get a Light reading
Light = Light Sensor value>Threshold value
Test Your Robot
Calculating Thresholds Quiz
Would the robot classify the following Light Sensor readings as Light or Dark?
a. Sensor = 15 with Threshold = 40
b. Sensor = 55 with Threshold = 40
c. Sensor = 49 with Threshold = 56
d. Sensor = 15 with Dark = 10 and Light = 30
e. Sensor = 55 with Dark = 43 and Light = 62
Calculating Thresholds Quiz Answers
a. Sensor = 15 with Threshold = 40Sensor value is less than Threshold therefore it is darkb. Sensor = 55 with Threshold = 40Sensor value is greater than Threshold therefore it is lightc. Sensor = 49 with Threshold = 56Sensor value is less than Threshold therefore it is dark
Calculating Thresholds Quiz Answers
d. Sensor = 15 with Dark = 10 and Light = 30The threshold is (10+30)/2=20 The Sensor Value is less than Threshold, therefore it is Dark. Intuitively - the Sensor value is closer to Dark than Light,
therefore it is dark e. Sensor = 55 with Dark = 43 and Light = 62 The threshold is (43+62)/2=52 The Sensor Value is greater than Threshold, therefore it is Light. Intuitively - the Sensor value is closer to light than dark. Therefore it is light.