Solar Tracker

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Solar Tracker

• Where is the light at?

Website http//web.engr.oregonstate.edu/ernsts/me
chatronics/ Members Steven Ernst, Hansang Ko,
David Jensen, and Jon Mueller Special Thanks
to Kevin Gatimu, Takahiro Yamakawa, and Matt
Knudson
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What is it?

• The solar tracker responds to the light intensity
  to situate the solar panel in an optimal location
  for capturing solar rays.

• With the usage of three photo-voltaic sensors,
  the ATmega128 AVR board (microcontroller)
  controls the actuators so the solar panel will
  always point in the direction of the brightest
  light source.

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Finalized Parts List
Parts used only (excluding testing equipment)

• Motor Controller Board
• Atmega128 AVR Board
• TekBot charger board
• 3 Photoresistors
• Male Female Headers
• Shrink Wrap
• Wire and Solder
• 2 Actuators (Motors)
• Plastic Sheets
• Resistors

4
Lets see it work!

• Show video here
• Video should show
• Moving left, then change direction to move right
• Moving up, then change direction to move down
• Covering left sensor and moving up and down,
  covering right sensor and moving up and down.

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How did we make it?

• Design Process
• Generate idea
• Device to optimize solar rays
• Design physical layout
• Continuous rotating base
• Maximum angle rotation
• Enclosed electronics
• Design code layout
• Identify what the code must do
• Break down processes into specific functions with
  inputs and outputs
• Optimize design and restructure layouts
• Based on complete detailed overview, make
  necessary changes to the design.
• Build the project
• Sequentially code the project
• Sample circuit first

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Physical Design Facts
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Programming Diagram Tree
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Programming Facts

• Functions
• int getSensorInput(int sensorChoice)
• void sendMotorOutput(int motorChoice, int
  motorDirection, int motorSpeed)
• int compareSensors(int sensorA, int sensorB)
• void controlBaseMotor(void)
• void controlAngleMotor(void)
• void angleLimit(int motorDirection)
• void PWM_init()
• int pwmRate(int sensorA, int sensorB)
• void change_motor_speed(int motorChoice, uint8_t
  motorSpeed)

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Testing

• Step by Step design
• Motor Torque Debugging

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Cool Facts / Extras

• Variable PWM Actuator Control With the use of a
  PWM signal, the user has flexibility to
  independently and dynamically adjust the speed of
  each actuator.
• Sensor Variability Sometimes a sensor can be
  covered up due to unforeseen affects. Fortunately
  the solar tracker can account for this when
  adjusting the angle sensor. If the left sensor is
  covered, the right sensor is utilized to compare
  with the upper sensor and vise versa.
• Semi - Infinite Rotation Our sleek mechanical
  design provides us with a base that can
  continuously rotate in a single direction without
  being limited by physical parameters.

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What would we change?

• Include motors with encoders to code in more
  bells and whistles.
• Optimizing Hardware
• Self-Charging Design

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Documentation
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Conclusions

• A special offer just for you , buy one today and
  well knock off 100.00
• Only 199.99 while supplies last

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Code (Header)

• define motorForward 1
• define motorBackward -1
• define motorOff 0
• define topSensor 101
• define leftSensor 102
• define rightSensor 103
• define baseMotor 110
• define angleMotor 111 // the larger the
  sensitivity range, the longer the sensors will be
  off
• define sensitivity 0
• define TRUE 1
• define FALSE 0

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Code (PWM)

• //PWM code
• define F_CPU 16000000UL //CPU speed in hertz
• include ltavr/io.hgt
• include ltstdlib.hgt
• include "light.h
• //PWM frequency (16,000,000)/(1 (799 1))
  20kHz
• uint16_t TOP_value 799
• /
  /
• /
  change_motor_speed
  /
• /Change the speed of motor according to the
  current duty cycle setting /
• /OCR1A and OCR1B are calculated from TOP_value
  and duty cycles /
• /OCR1A and OCR1B are updated at the end of the
  function /
• /
  /
• void change_motor_speed(int motorChoice, uint8_t
  motorSpeed)
• if(motorChoice baseMotor)
• OCR1A TOP_value motorSpeed / 100 //PORTB
  PIN5 output
• else if (motorChoice angleMotor)
• OCR1B TOP_value motorSpeed / 100 //PORTB
  PIN6 output

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Adjustable Speed Code

• //This adjusts the speed the motors will rotate
  based upon the percent difference between the two
  inputted sensors
• int pwmRate(int sensorA, int sensorB)
  if(((float)getSensorInput(sensorA) /
  (float)getSensorInput(sensorB) gt (1
  sensitivity)) ((float)getSensorInput(sensorA)
  / (float)getSensorInput(sensorB) lt (1 -
  sensitivity)))
• int maxSpeedRange 0.25 //difference
  percentage scaled to 1
• int mediumSpeedRange 0.2 //difference
  percentage scaled to 1
• int minSpeedRange 0.15 //difference
  percentage scaled to 1
• int maxSpeed 60 //expressed as percentage out
  of 100
• int mediumSpeed 50 //expressed as percentage
  out of 100
• int minSpeed 40 //expressed as percentage out
  of 100
• //If the difference between the two is greater
  than maxSpeed, then it returns the highest
  percentage desired
• if(((float)getSensorInput(sensorA) /
  (float)getSensorInput(sensorB) gt (1
  maxSpeedRange)) ((float)getSensorInput(sensorA)
  / (float)getSensorInput(sensorB) lt (1 -
  maxSpeedRange)))
• return(maxSpeed)
• //If the difference between the two is greater
  than mediumSpeed but less than maxSpeed, then it
  returns the medium percentage desired
• else if(((float)getSensorInput(sensorA) /
  (float)getSensorInput(sensorB) gt (1
  mediumSpeedRange)) ((float)getSensorInput(sens
  orA) / (float)getSensorInput(sensorB) lt (1 -
  mediumSpeedRange)))
• return(mediumSpeed)
• //If the difference between the two is greater
  than minSpeed but less than mediumSpeed, then it
  returns the lowest percentage desired
• else if(((float)getSensorInput(sensorA) /
  (float)getSensorInput(sensorB) gt (1
  minSpeedRange)) ((float)getSensorInput(sensorA)
  / (float)getSensorInput(sensorB) lt (1 -
  minSpeedRange)))
• return(minSpeed)

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Code (Main)

• int main()
• //Initialize PWM settings
• PWM_init()
• while(1)
• angleLimit(angleMotorDirection) controlBaseMot
  or()
• angleLimit(angleMotorDirection) controlAngleMo
  tor()
• return 0

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Code (getSensorInput)

• //Determines which sensor to get data from and
  returns that data.int
• getSensorInput(int sensorChoice)
• DDRF ((1ltlt0)(1ltlt2)(1ltlt4)) //sets PortF
  pins0,2,4 to zero one means output pins, zero
  means input pins
• switch (sensorChoice)
• case topSensor //Top Sensor plugs into PORT F,
  PIN 0
• ADMUX (1ltltREFS1)(1ltltREFS1)
• ADCSRA (1ltltADEN)(1ltltADSC)(1ltltADPS2)(1ltltADPS1)
  (1ltltADPS0)
• while(bit_is_clear(ADCSRA,ADIF)) //loops while
  interrupt flag not set (while it is zero)
• ADCSRA (1ltltADIF) //set interrupt flag to
  1
• return ADCW //returns raw sensor value
• break
• case leftSensor //Left Sensor plugs into PORT
  F, PIN 2
• ADMUX (1ltltREFS1)(1ltltREFS1)(1ltltMUX1)
• ADCSRA (1ltltADEN)(1ltltADSC)(1ltltADPS2)(1ltltADPS1)
  (1ltltADPS0)
• while(bit_is_clear(ADCSRA,ADIF)) //loops while
  interrupt flag not set (while it is zero)
• ADCSRA (1ltltADIF) //set interrupt flag to
  1
• return ADCW //returns raw sensor value
• break
• case rightSensor //Right Sensor plugs into PORT
  F, PIN 4

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Code (sendMotorOutput)

• //Determines which motor to send an output to and
  what direction should be sent.void
• sendMotorOutput(int motorChoice, int
  motorDirection, int motorSpeed)
• DDRE (1ltltPE0)(1ltltPE4) //sets PortE pins0,4
  to one one means output pins, zero means input
  pins
• switch (motorChoice) //Port E Pin 0 connects
  to baseMotor direction pin
• case baseMotor
• if (motorDirection motorForward) // Sets
  PortE Pin0 to 1 (high) this outputs to the
  direction pin on the motor controller
• PORTE (1ltltPE0) //Sets motor speed using PWM
  this outputs to the enable pin on the motor
  controller
• change_motor_speed(baseMotor, motorSpeed)
• else if (motorDirection motorBackward) //
  Sets PortE Pin0 to 0 (low) this outputs to the
  direction pin on the motor controller
• PORTE (1ltltPE0) //Sets motor speed using
  PWM this outputs to the enable pin on the motor
  controller
• change_motor_speed(baseMotor, motorSpeed)
• else //Set motor speed using PWM this
  outputs to the enable pin on the motor
  controller
• change_motor_speed(baseMotor,0)
• break //Port E Pin 4 connects to baseMotor
  direction pin
• case angleMotor
• if (motorDirection motorForward
  angleLimitForward FALSE) // Sets PortE Pin4
  to 1 (high) this outputs to the direction pin on
  the motor controller

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Code (compareSensors)

• int compareSensors(int sensorA, int sensorB)
• if(((float)getSensorInput(sensorA) /
  (float)getSensorInput(sensorB) gt (1
  sensitivity)) ((float)getSensorInput(sensorA)
  / (float)getSensorInput(sensorB) lt (1 -
  sensitivity)))
• if ((getSensorInput(sensorA) -
  getSensorInput(sensorB)) gt 0)
• return(motorForward)
• else
• return(motorBackward)
• //If the sensors are within the sensitivity
  range, then motorOff is returned.
• else
• return(motorOff)

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Code (controlBaseMotor and controlAngleMotor)

• //sends a motor output, determined by
  compareSensors function, to the base motor
• void controlBaseMotor(void)
• sendMotorOutput(baseMotor, compareSensors(leftSens
  or, rightSensor))
• //sends a motor output, determined by
  compareSensors function, to the angle motor
• void controlAngleMotor(void)
• int brighterSensor rightSensor
• //if-else statement ensures the topSensor is
  compared to the smaller voltage (brighter).
• if (getSensorInput(leftSensor) lt
  getSensorInput(rightSensor))
• brighterSensor leftSensor
• sendMotorOutput(angleMotor, compareSensors(topSens
  or, brighterSensor))

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Code (angleLimit)

• //if an input switch is set, then the angle motor
  is turned of and a limit flag is set
• //Port D Pin 0 and 4 are default to 1 when
  pressed, they are zero (limit becomes TRUE)
• void angleLimit(int motorDirection)
• DDRD ((1ltlt0)(1ltlt4)) //sets PortD pins0,4 to
  zero one means output pins, zero means input
  pins
• if (motorDirection motorForward
  bit_is_clear(PIND,0)) sendMotorOutput(angleMoto
  r, motorOff)
• angleLimitForward TRUE
• else if (motorDirection motorBackward
  bit_is_clear(PIND,4))
• sendMotorOutput(angleMotor, motorOff)
• angleLimitBackward TRUE