Today’s Agenda 1.Scribbler Program Assignment 1.Project idea due next class 2.Program demonstration due Wednesday, June 3 2.Attendance & lab pair groupings 3.Robots –Sensors –Input / Output 4.Lab 10 with Scribbler Robot

Dead Reckoning is HARD Move Forward indefinitely Pause for 5 seconds Stop Move Forward for 5 seconds Pause for 0.2 seconds

Urban Challenge Sensors GPS Cameras Radar LiDar Light Detection and Ranging Odometer Gyroscope

Scribbler Sensors 1.Obstacle sensor 2.Stall sensor 3.Light sensors 4.Line sensors

Flashes the right infrared (IR) emitter –If the center IR detector sees the IR light reflected back, it reports an object on the right Flashes the left IR emitter If the center IR detector sees the IR light reflected back, it reports an object on the left Obstacle Sensor

Scribbler’s Headlights If obstacle on left turn right Else If obstacle on right turn left Else go straight

Obstacle Sensor Tips Infrared light reflects best off of shiny, light- colored surfaces; it is absorbed by dull, dark colored surfaces The Obstacle sensors work best at detecting objects 3” to 8” away Obstacle sensors are far from perfect, have a backup plan in case of collision –Obstacle sensors do not work at very close range (distances of 2 inches or less)

Stall Sensor The Scribbler’s stall sensor can tell when the motors are running but the wheels are not turning freely 0 or 1 (i.e. the Scribbler is stuck )

Go Forward until Stuck! Move Forward indefinitely Do While { Pause 0.2 seconds // Moving Forward } Stop END Program

Go Forward until Stuck! Move Forward indefinitely Do forever If Then Stop End Program Else Pause 0.2 seconds // Moving Forward

Stall Sensor Tips The Stall sensor detects if the robots has bumped against something – Navigation by bumping into things. This is similar to a person entering a dark room and then trying to feel their way by touching or bumping slowly into things. The Stall sensor is Binary : there is no way to tell if the bump was on the left or right

Stall Sensor Tips #2 The motor must be running for Scribbler to stall –Use Move Forward indefinitely –Move Forward for 1 second will not work Every time you issue a Move instruction, the Stall sensor resets itself –For best results, insert a short pause after every Move instruction before checking the Stall sensor

The Scribbler has three photoresistor light sensors on front of the robot –The center sensor looks straight ahead –The other two sensors look 30 degrees to each side. Their positioning allows Scribbler to use its photoresistors to navigate towards or away from light Light Sensors

Do forever Pause for 0.2 seconds If Then Move Forward for 1 second Else If Then Turn Left for 1 second Else If Then Turn Right for 1 second Else // no light – do nothing END Follow the Light

Light Sensor Tips There appears to be a lot of leakage of light into the Scribbler robot –Use SCP’s Sensor Monitor to get a feeling for Scribbler’s light sensor readings You can cover Scribbler completely with its white box to block out all light –The sensors should read near zero

On the bottom of Scribbler are – two Infrared Emitters and – two Infrared Detectors These allow Scribbler to see a dark line on a light background Line Sensors

Move Forward indefinitely Do forever If Then Stop End Program END

Line Sensor Tips Line sensors are binary sensors: –0 is white –1 is black – Other colors are detected as either white or black For best results, Use white paper with thick black lines (at least one inch) Line sensors are precisely positioned and work best on a smooth, hard, flat surface

Scribbler I/O Input Sensors –Infrared obstacle sensor –Stall sensor –Three photoresistor light sensors –Two infrared Line sensors Red reset button Output Motors &Wheels Three LED’s Speaker

Button Press If Then LED: OFF, ON, ON Else If Then LED: OFF, ON, OFF Else If Then LED: ON, ON, ON