Chapter 4: Reading Sensors

This chapter was all about the different sensors available for the NXT. The chapter starts out by saying the differences between the new NXT and the old NXT. On the new NXT, there are 4 sensor ports rather than 3 and it features a different cable which locks into place. The next part is about the touch sensor. It is the simplest sensor of all. Not much has changed from the old version except for the studless connections. The touch sensor can tell if its pressed, released or bumped. The most common use for the touch sensor is as a bumper. The bumper can be made to be open and then be pressed when it runs into something, or it can be closed all of the time and released when something presses it. The next sensor was the light sensor. The light sensor detects ambient light and measures its intensity. With this sensor, you must set a threshold for it to work properly. This was shown in previous blog posts. The light sensor can measure two different types of light, reflected light (from an emitted beam from the sensor), or ambient light. Using the reflected light, you can tell what color your robot is going over or how far away a color is from the sensor but not both at the same time. you can do this because different colors reflect different amounts of light. An application of ambient light that we did was line following. If you combine the light sensor with a lamp brick, you can make a photoelectric cell which can tell if the light is interrupted. The next sensor is the ultrasonic sensor. This sensor emits a high frequency ultrasonic sound which bounces off objects and is received again and the time taken for this to happen tells the sensor, how far an object is. An advantage of ultrasonic sensors is its ability to work in the dark. Using this sensor, you can tell the robot to stop or perform an action when it approaches something that is ______ inches/cm away. The last sensor is the rotation sensor. This sensor is built into the motor. With the motors in the NXT, they can detect when going over rough terrain. For example, if your NXT is going straight, and you press down on one of the wheels, that wheel will speed up to compensate. This is a new feature in the NXT.