LIGHT-FOLLOWING ROBOT

EGGN 383 Final ProjectJacob DubinskyTyler Scott

Overview• Mobile platform that determines and drives towards the

direction of strongest light• If an obstacle is in the way, redirects and then resumes

following the light

Hardware• Arduino Uno• 4 Photoresistors• 4 10kΩ resistors• Two wheels with attached DC Motors and Rotary

Encoders• H-Bridge• Proximity Sensor• Platform

Schematic

Software Overview• Arduino Uno – ATMega328P• Registers instead of built in functions (digitalWrite(),

analogRead(), etc)• Interrupts• Analog Read• PWM

• Subsumption Architecture• Avoid obstacles has highest priority (lowest layer)

Interrupt Registers

Interrupt Registers

• Set INT# bit to enable interrupts on pin INT#

• Set I bit to enable global interrupts

Analog Read Registers

Analog Read Registers

PWM Registers

PWM Registers

Source (Register Slides 6-11): http://www.atmel.com/Images/doc8161.pdf

Phase-Corrected PWM

Source: http://www.cs.washington.edu/education/courses/csep567/10wi/lectures/Lecture7.pdf

Pseudo Code – Light FollowingInitialize PWM to 1kHz on pins D5,D6,D9,D10Initialize A/D converters on A0-A3Input capture on D2,D3 with interruptsLoop:Check analog valuesDetermine new directionCheck the speed of wheelsChange speed of wheels with PWMD5 = PWM D6 = 0 for left wheel forwardD9 = PWM D10 = 0 for right wheel forward

Interrupt:Calculate speed of right wheel

Interrupt:Calculate speed of left wheel

Pseudo Code – Obstacle AvoidanceLoop: // same loop as previous; broken up for readability// Read proximity voltageVproximity = ReadAnalog(ProximityPin)// Check if closer than 15 cm (1.75 V) to an obstacleIf(Vproximity > 1.75 V)Allow vehicle to turn, do not allow it to move forward

elseFollow light // loop in last slide

Questions?