You tell it what to do and when to do it.

Did you ever wonder how we get robots to “understand” and do what we want them to do? How does the telephone answering machine know when to answer the phone and record the message?  What makes the electric door open when we walk in front of it?  How does it know we’re there? And what about that remote control car we love to play with?  What makes it back up, turn, go forward, or stop when we say so?

It all lies in control.  Every robot needs to be told what to do.  When you set up control of the robot, you need three factors working together:
1. INPUT
The information that comes from the robot’s sensors.
2. PROGRAM
The instructions or set of rules you give a robot to follow.
3. OUTPUT
The action the robot takes, usually involving motors (movement), lights, or sound.

Input.- When you use the remote control to program your VCR, you send input via infrared signals that tell the VCR that it’s time to take a particular action.

Program.- The program (also known as the “algorithm”) is the robot’s set of instructions.  In this case, we are programming (or instructing) the VCR to record our favorite television show for an hour.

Output.- Finally, we look at the output, which means the action we want the robots to take.  Here , the action is to turn the VCR recorders on at the start of the hour, and off at the end of the hour.  We can hear the motors moving inside the VCR as it begins to record.  We may also see certain lights come on to indicate the VCR is taking action.  The control loop is complete as the VCR records our television show.

How robots come to their senses.

All robots have sensors, which provide input for the robot.  Some of these sensors are much like our own senses in the way they “see” and “feel.”  For instance, any switch or button that turns on the power of an appliance is a touch sensor.  It responds when it “feels” the pressure of your touch.

You will find many different kinds of sensors at work in robots.  Refrigerators use touch sensors to turn on and off the light inside when the door is closed.  Telephone answering machines have a circuit that measures voltage and indicates that the phone is ringing.  Ovens and toasters use temperature sensors to control the amount of heat produced by heating coils.

Similar robotic systems may differ in the sensors they use to get the job done.  Some automatic lights, such as outdoor floodlights, may use motion detectors to activate the when someone approaches.  Others may use a light sensor to gauge when it becomes dark and turn on the light.

Programs for robotic control can be as simple and purely mechanic as turning a switch to begging a set of actions such as when you press the “Reheat” touchpad on your microwave to heat up your dinner.  Or they can be as complicated as the computer-based programs found in automatic cameras on NASA space rovers.

Did you know that the human body has a visual sensor, a touch sensor, a sound sensor and a smell sensor?  We commonly call them an eye, a hand, an ear, and a nose.

The program that controls a robot relies on several factors:

• The type and number of sensors used
• Where the sensors are placed
• The potential outside stimuli
• The combinations of resulting actions

The RCX is a Lego microcomputer.  It is the brain behind any robotic system built with Lego bricks, motors, and sensors.

The RCX allows you to build a system of control over your robots and robotic systems.  Three sensors at a time can take input from the environment.  The sensors are touch, light, *rotation, *temperature, and the infrared receiver on the RCX itself.

You program the RCX using simple icon-based programming language.  The program instructions for the robotic system are downloaded from your desktop computer using an infrared transmitter.

The RCX can now control output, the lights, sounds, robotic motors attach to the mechanical parts, or infrared signals sent to other RCXs.

Because the RCX itself is a microcomputer, your robotic systems act independently of the computer.  You can build anything from a light-sensitive intruder alarm for your intelligent house to a rover that can follow a trail or play basketball.