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. Stationary Solar Cell Angle of Incidence Path of the Sun

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. Dual Cell Photo Sensor Differential Amplifier Analog to Digital Converter The Sun

Microcontroller Programming Micro-Controller –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 Solar Cell Differential Signal Micro- Controller Motor Controller DC Motor PWM Signal Power Analog Signal

Control Strategies 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. Solar Cell Differential Signal Micro- Controller Motor Controller DC Motor PWM Signal Power Analog Signal

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…