The Light Sensor is a device that can be connected to the Lego Mindstorm NXT Brick. It collects information on light intensity, which can be used to direct robotic sequences ambient light intensity and/or reflected light intensity.
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The function of the NXT Light Sensor is to detect the intensity of light received by the photo-resistor. It is measured as a percentage where 0% indicates complete darkness and 100% is complete brightness. There are two modes: Active light sensing (reflected light intensity) and Passive light sensing (ambient light intensity). For the reflected light intensity mode, red light is emitted from the LED, which is situated below the photo-resistor (please refer to Figure 1 below). The photo-resistor picks up the light intensity of the reflected red light. Please note that the sensor should be ideally be located close to the surface to be measured, but not touching it. On the other hand, the passive light sensing mode detects ambient light (light from the environment) instead of the reflected red light.
About the Light Sensor
||Video of Keith's successful execution||
Figure 1: Front view diagram of the NXT light sensor
About our robot - "Keith"
Our robot, Keith, has been assigned the task of drawing a straight line when he is in a light-coloured area, and stop moving and drawing when he has reached the darker zone. To see him in action, please click on the video below.
Investigation
A Lego Mindstorm project that uses the light sensor:
Industrial application of a light sensor:
Keith, powered by the NXT Brick, is instructed to move when he sees a high light intensity, and to stop moving when a change to a dark intensity is detected by its beautiful light sensor. The light sensors transmit an electrical signal to Keith's "brain", which determines the movement of the wheels. Meanwhile, at the back of Keith is a pen that produces ink on the paper when it moves. As a result, as Keith moves straight ahead, a straight line is left behind on the paper. This kind of function is extremely useful in artworks and design, where artists may need to draw specific lines in different patterns of light intensity.
This robot created by "nxtprograms" follows a black (dark) line. The NXT light sensor, indicated above the red light reflection, looks for a preset light intensity level, and is instructed to move on the black line. The robot then continues its motion forwards, until the light intensity changes. As can be seen from the video, the robot accurately follows the path indicated.
In the industry, carts can be a very useful form of transportation, especially involving heavy weights/oversize items over large distances. Rails constructed in the ground tend to take up a lot of space, so a contrasting line of different luminosity painted on the ground can allow efficient transportation. The technology used is similar to the line tracking Lego Mindstorms project on the left, where the robot's motion is determined by the path in which it follows.
Meet Keith!
As can be seen from the video, Keith can successfully draw a straight line and stops when he encounters a dark zone with a different light intensity.
