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Solar Tracking Project
• Team Members:
–
–
–
–
–
Cristian Ruvalcaba
Ken Seal
David Clark
Mark McKinley
Richard DeJarnatt
Mark McKinley
• Project Lead
• Time Management
• Budget Analyst
Richard DeJarnatt
• Parts Manager
• Lead Photographer
Cristian Ruvalcaba
• Web Designer
• Asst. Photographer
David Clark
• Report Editor
Ken Seal
• Presentation Design
Tracking the Sun
• Why have a solar cell that tracks the
movement of the sun?
– Stationary solar cells do not collect all of the
direct sunlight that is available to them.
Stationary Solar Cell Limitation
• The Stationary Solar Cell is subject to the
movement of the sun.
Path of
the Sun
Angle of
Incidence
Stationary Solar Cell
Stationary Solar Cell
• By taking the cosine of the angle of incidence over
180 (the path of the sun in the sky) we find that the
solar cell is not gathering 100% of the direct sunlight
throughout the day.
• The
efficiency
can be
found by
adding
the area
under the
curve.
Stationary Solar Cell
• The stationary solar cell is most effective at
gathering sunlight when the angle of
incidence is zero or within a few degrees.
• This occurs only for a short period every day
when the sun is directly over the solar cell.
• The solution for this problem is to move the
solar cell to meet the sun and lessen the
angle of incidence to near zero throughout the
day.
Tracking Solar Cell
• The ability to move the solar cell to receive
the most direct sunlight would allow for the
light gathering efficiency of the cell to be at
a maximum level.
• The angle of incidence would be kept near
0 for the entire duration that the sun was
visible to cell.
Determining the Position of the Sun
• A dual cell photo sensor will be used to
translate the position of the sun into two
separate signals.
Photo Sensor
Signals Generated from the Dual
Photo Sensor
• Shadows are caused by the moving sun
on the dual panel photo sensor.
Amplifying the Differential Signal
• The two signals from the dual cell photo
sensor will then be sent to a differential
amplifier.
• The signal from the differential amplifier
will vary from 0 to 5 VDC.
The Sun
Dual Cell
Photo
Sensor
Differential
Amplifier
Analog to
Digital
Converter
Microcontroller Programming
Solar
Micro-
Cell
•
Differential
Signal
Controller
PWM
Motor
Controller
Signal
Micro-Controller
Analog
Signal
– Inputs:
• Analog signal 0-5v from solar cell amplification circuit
• Analog signal 0-5v from DC motor
– Outputs:
• PWM motor signal
– Dual Microchip Development
• Microchip PIC chip
– Cheap – Around $1
– Uses assembly language for programming
• Motorola Free scale 16 bit processor
– More expensive - $10
– Uses assembly and C programming languages
DC
Power
Motor
Control Strategies
Solar
Cell
•
MicroDifferential
Signal
Controller
PWM
Motor
Controller
DC
Power
Motor
Signal
Analog
Signal
Problem: Correct error from solar cell:
– PID Solution
• Proportional, Integral, Derivative
• Too Complex for following something that moves as slow as sun
– Threshold Control System
• As the error breaks a set “Threshold” for error the microcontroller sends the
signal to move the motor to correct.
• This is simple and allows the system to be in a energy efficient sleep mode.
• This is our feedback loop.
– Limit Control
• Limit the maximum amount the motor can rotate so that there is no
mechanical damage.
PWM to H Bridge
• Receives a Pulse Width Modulated signal from
microcontroller
• Transforms duty cycle to voltage
– High duty cycle – positive voltage
• Motor runs forward
– Low duty cycle – negative voltage
• Motor runs backwards
H Bridge
• Receives Voltages and Control Signals
• Control Signals energize motor to turn in
appropriate direction
• And at correct speed
Overview
• Why use the tracker?
• The heart of the design
• The brain of the design
• The limbs of the design
Questions…