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Mechanical & Electrical Design
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When designing the system’s mechanical and electrical components, we gained inspiration from many commonplace items around us, the first of which was a windshield wiper. The device that performs the cleaning of the solar panel is a windshield wiper to wipe laterally across the panel. The wiper is attached to a “carriage” that moves back and forth across the width of the solar panel. To accomplish this sideways motion, the carriage uses a mechanism nearly identical to that of a 3D printer’s Z axis (height control). Another inspiration was from Radio Control (RC) cars and planes. We used a battery from an RC car to store energy from the solar panel and to power our system. Thanks to that battery, the sensor and the cleaning system can receive power even when the sun is not shining. One last source of inspiration comes from some models of CNC lathes (a computer-controlled manufacturing device). When the lathe powers on, it has a carriage that moves through its full range of motion in order to position itself. The machine is able to identify when it has reached its range limit when it comes in contact with a limit switch. We then used this idea for our system to recognize when the carriage and wiper has reached the limit of its range and needs to reverse its direction of travel.
Software Design
We used C-based Arduino for the code for Sol Sweeper project. For the code, we used four digital pins that connected to two limit switches and two relay pins. For the directional change, we created a variable called "dir" to determine the direction of which the motor should be spun. "dir" was given either "1", "2", or "3" corresponding to clockwise direction, counter-clockwise direction, or stationary. The value of "dir" was changed according to the digital value that was read from the limit switches. Code was written in a way for the carriage to go from one end to the other, come back, and have a delay of 6 hours using the delay method in Arduino. For the future code, we are looking to find a way to conserve energy while the Arduino enters the delay of 6 hours.
How It Works
The Sol Sweeper harvests energy from the sun via a single solar panel. The solar panel charges an onboard battery, which then powers an Arduino that dictates when the solar panel cleaning cycle should begin. In future designs, it would be ideal to have more than one solar panel to provide more power to the Arduino, cleaning system, and marine sensor because currently, the Arduino consumes the majority of the power generated from the panel. When connecting the solar panel to the battery, we had to use a charge controller so that power from the solar panel could only flow to the battery. This is necessary because, without it, power could flow from the battery to the panel, which could severely damage the panel. When the buoy is turned on, the Arduino sends power to a system of electrical relay switches, which then deliver power to a motor. Since we only used one motor, the relay switches have to control the polarity of the motor. When one relay is turned on, the motor spins clockwise with one wire being powered and the other wire being grounded. When the second relay is turned on, the motor spins counter-clockwise, and the powered and grounded wires are switched. This motor turns a lead screw, which moves a wiper blade laterally across the solar panel to clean it. When the wiper reaches the edge of the solar panel, it hits a limit switch. The Arduino detects that the limit switch has been hit, then reverses the direction of rotation of the motor via the relay switches. This reversal causes the lead screw to be spun in the opposite direction, which causes the wiper blade to move back across the solar panel in the opposite direction. When the wiper has reached the other side of the solar panel, it hits a second limit switch. When the Arduino detects that this switch has been hit, it stops the motor and a delay method in the Arduino code begins a timer for six hours. Once the six hours have passed, the cleaning cycle will begin again.
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