Sun Tracking Solar Panel

Hi Everyone!  My name is Karina, and I am a rising junior at Castilleja School.  For my starter project I built an Ultrasonic Parking Sensor.  This circuit alerts the driver if their car is getting too close to another object.  Unfortunately this circuit had a defective part, so I decided to do another starter project.  My second starter project was a Laser Target.  This circuit turns on LEDs when I shine a laser on it.

For my intensive project I built a sun tracking solar panel, which is a mechanism that is designed to make solar panels follow the sun throughout the day and adjust to the different angles of the sun rays throughout the year.

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Documentation:

Bill of Materials: KGupta BOM

Arduino Code: Arduino Code

My Completed Sun Tracking Solar Panel: 

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For my final video, I made my motor rotate one revolution every 24 hours instead of 3 revolutions per minute. I was initially going to use gear ratios to control the number of revolutions per unit of time for my solar panel, but after doing gear ratio calculations, I realized that my gear ratio was 1:43,500.  So instead I used Pulse Width Modulation (PWM) on an Arduino. PWM did not actually make my solar panel rotate at a slower rate, but it can give one that illusion.  PWM simply turned my motor on and off extremely quickly, so it looked like it was moving constantly but at a slower speed.  So, when I wanted to make my motor even slower, I increased the ratio of the percentage of time the motor was off/on per revolution. This made the motor appear to be moving at a slower speed, even though it was the same speed the whole time.

Here is my final video:

My Second Milestone:

For my second milestone, I finished the mechanical design for my project. There are two major systems for my project. The first one allows my solar panels to follow the sun in a 24-hour period.  At midnight, my solar panels face the ground. As the sun rises, the solar panels rotate upward around a shaft. By the afternoon, when the sun is completely above you, the solar panels are face up, and then continue rotating with the sun until it sets. At midnight, the solar panels will be face down again and will have completed a full rotation. I used a DC geared motor to rotate these solar panels. The motor is below the solar panels, and there is a gear on the motor’s shaft. There is another gear directly above the motor’s gear that is on the shaft with the solar panels. These two gears mesh, causing the shaft and the solar panels to rotate.

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My second major mechanism allows the solar panels to adjust to the different angles of the sun rays when they strike the Earth. For example, in June, the sun rays hit the surface at almost 90 degrees.  So, the solar panels should be completely flat so that the sun rays strike the solar panels perpendicularly. However, in December, the angle between the sun rays and the surface is extremely narrow.  In order for these sun rays to continue to hit the solar panel at a 90 degree angle, the angle of the solar panels must adjust to ensure that they are absorbing the maximum amount of energy as possible from the sun. I have created a “sliding mechanism” that allows the solar panels to change angles each month. There are two pieces of wood that extend from the wooden frame of my solar panels that have magnets glued to them. I then have a two-foot iron rod standing up that attaches to the magnets of my two pieces of wood. This allows one side of my solar panels to slide up and down the iron rod, which changes the angle of my solar panels.

I researched what the angles of my solar panel should be each month depending on the angle of the sun rays.  I then used simply trigonometry to determine how high the solar panel would have to slide up the rod to be that given angle.  I also learned that the solar panels did not slide up the iron rod in a linear path, but in an arch shape. So, instead of using an “L-bracket” to attach my iron rod to the base of my mechanism, I needed to use a hinge to allow the solar panel to move with the iron rod in an arch shape.

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I also completed the base for my mechanism.  The biggest challenge I had when designing the base was figuring out how I was going to allow one side of my solar panel to slide up the iron rod while keeping the frame of my solar panel connected to the base.  I solved this problem by connecting two pieces of wood together with a hinge.  I then connected my wooden frame to one of these wood pieces, while the other one was connected to my base.  This allowed the wooden frame to move up and down, but still stay attached to the base.

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Here is my video:

My First Milestone:

For my first milestone, I built a wooden frame for my solar panels.  The wooden frame surrounds both of my solar panels and joins them together so that they can move as one unit.  I also drilled a hole through the sides of my wooden frame and put a 1/4” shaft through the holes.  This shaft allows the solar panels to rotate.

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I also finished the electrical component of my project. First, I connected the two solar panels in parallel sequence to double their current.  Then I used a multimeter to test whether there was current flowing through my solar panels so that I could potentially charge a battery with them.  Because my multimeter had a reading of 8.25 volts, I knew there was current.  This is because voltage measures the potential difference between two points and the work done per unit of charge to get from the two points that I connected my multimeter to.  So, if there was a reading of 8.25 volts, then there must be current flowing through the solar panels.

Here is my video

Ultrasonic Parking Sensor:

The Ultrasonic parking sensor can detect objects from a given distance, and it and will trigger a buzzer if the object exceeds that given distance. This device has two ultrasonic sensors. The first sensor will emit a sound wave that will bounce back on an object (another car, curb, etc). This sound wave is then received by the other sensor on the opposite end of the circuit. This sound wave is converted into energy, and its voltage corresponds to the different wavelength and frequency of the sound wave, which is dependent on the distance of the object from the car. If this voltage exceeds the breakdown threshold of the zener diode, then the current can continue to flow through the circuit, and it will trigger the buzzer. If the object is further away, the voltage of the sound wave may not exceed the breakdown threshold, and so the buzzer will not alert the driver.

Laser Target:

The Laser Target uses a laser to turn on LEDs. The most important device of this circuit is the CDS. The CDS has a very high resistance that decreases as light intensity increases. So, when a laser shines on the CDS, the light intensity lowers the resistance enough so that current can flow through the circuit and light up the LEDs. I also used a transistor that acts as an off/on switch. I also used a lot of parts in this project that I used in my ultrasonic parking sensor project such as resistors, capacitors, and potentiometers.

Here is my video

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