Sentry System Multiple Sensors See Teacher Guide for printing instructions

Opening Activity Partner with the person next to you. The person on the left (“A”) will read the column on the left below, silently to him or herself The person on the right (“B”) will read the column on the right out loud Person A on the left will try to answer questions about both Go to the next slide when ready…

Opening Activity Read this column silently to yourself: A robot is a machine with the capability to Sense, Plan, and Act. This means, first of all, that it can Sense important things about its environment. It can then Plan what it should do, based on that information. Lollipops are delicious. Finally, it can Act to carry out that plan. These three things together make a robot capable of more complex and useful tasks than an ordinary machine. While Person B reads this out loud: ( Person A don’t look! ) On October 8, 2005, twenty-three robotic vehicles lined up at the starting gate for the DARPA Grand Challenge. These were vehicles of all shapes and sizes, outfitted with special sensors and software to allow them to drive on their own, with no human operators. These would compete to travel more than 100 miles of rough desert terrain in order to win a $2 million prize.

Opening Activity Answer the following questions. Left column What three defining capabilities of a robot were discussed in the left column? In what order were the three discussed? What sentence did not belong in that column? Right column What was the name of the event described in the right column? What was special about the vehicles in this event? What was the prize?

Opening Activity Multiple Inputs and Interference Reading and listening are very difficult to do at the same time because both tasks demand the attention of the same area of the brain Robots have a similar problem Many sensors, only one program to watch them all You might have tried switching back and forth quickly between reading and listening This doesn’t tend to work very well for people But it works fine for computers, because they can do it very quickly, and don’t forget what they had been doing before

Watching One Sensor How to watch a sensor A Switch Block is set to watch the sensor, and based on what it sees, do different things Example: Touch Sensor Touch Sensor Switch checks value of sensor Beep if pressed Be silent if not pressed Wait For Blocks, Sensor Blocks, and Loops are also used to check sensors, depending on how you want to use them Beep if Pressed Check the touch sensor; if it is pressed, make a sound… do nothing otherwise

Watching More Than One Sensor “At the same time” A robot can’t actually do more than one thing “at the same time” It can do things in order so quickly that you can’t tell the difference Therefore, you can’t technically watch more than one sensor “at the same time” However, you can check several sensors in order so quickly you can’t tell the difference Look and Listen Check the Ultrasonic Sensor and the Sound Sensor one after another (use picture alerts instead of sounds so the Sound Sensor doesn’t get confused)

Multiple Sensors: Technical Review The Sensors Switches Loops

Touch Sensor Detects physical contact Tells you: 1 if touched 0 if not touched Poke, Poke? The cross axle probe inserted into the end of the Touch Sensor contact increases its effective range

Sound Sensor Detects Sound Tells you: Amplitude (volume) of sound Low numbers = quiet High numbers = loud Can be confused by sounds of different frequencies (pitch) Listen Carefully The Sound Sensor can detect many sounds, from gentle vibrations to jarring collisions

Light Sensor Detects light intensity Tells you: The intensity of light detected Low numbers = dark High numbers = light Light on the front can be turned on or off Light the Way The light sensor in Reflected Light mode shines its own light out and measures the amount that bounces back

Ultrasonic Sensor Detects distance Tells you: Distance to a surface or object in front Indicates a distance in cm or inches Ro-Bat The Ultrasonic Sensor uses the same basic principle for detecting distance as cave-dwelling bats do.

The Rotation Sensor is built into the Interactive Servo Motors Detects rotation of the motor axle Tells you: Amount the axle has rotated in degrees or full rotations Rotational position of an attached piece* Linear position of an attached piece* Rotato Chips The Rotation Sensor is built into the Interactive Servo Motors * If you also know the initial position and how the piece is attached, you can calculate this

Sensor Switch Block Switch Blocks… allow the program to observe a value, and choose between different paths of code to follow, based on the observed value. Sensor Switch Blocks… check a specified sensor to determine which group of blocks to run. Keep Your Distance Based on the value of the Ultrasonic Sensor, this Switch will either move backward (if the sensor value is less than the threshold), or move forward (if the sensor value exceeds the threshold)

Infinite Loop The Loop Block runs the blocks inside it over and over again, until a certain stopping condition is met. The infinite loop or “forever” loop has no stopping condition, and therefore will repeat the blocks inside over and over, forever. Back and Forth The loop causes the robot to repeat the forward-then-back motion forever

Summary Humans and robots both have trouble paying attention to more than one input at a time Robots can get around the problem by checking sensors quickly and repeatedly Your sentry needs to watch more than just one sensor in order to detect many different kinds of hazards In this Investigation, you will learn how to program the sentry to watch for multiple problems using different sensors “at the same time”