Designing a ROV similar to Harry Bohm’s ROV design allows the ROV to maneuver adequately underwater. Harry Bohm’s model is constructed using a PVC pipe frame, three DC motors, and football floats, and a polyester mesh. (Bohm) Minor adjustments to Harry Bohm’s design were made prior to construction of the actual ROV. The football floats, provide the ROV with positive buoyancy, were substituted with ½’’ foam insulation; the polyester mesh was completely removed from the ROV design. The two 2 ½’ PVC pipes used to assembly the ROV frame were cut using PVC pipe cutters. Below is a diagram of MIT’s sea perch ROV frame.
Figure 1: The diagram (above) displays the length of the PVC pipes necessary for constructing the ROV frame. [2]
Upon completion of the ROV frame, three 12v DC motors were waterproofed and mounted onto the ROV frame. The materials used to properly waterproof the motors were electrical tape, three film canisters, toilet bowl wax, and petroleum jelly. All motors were wrapped with electrical tape covering all exposed section, excluding the motor shafts. Approximately 14’’ of multi-purposed wire was soldered onto each motor terminal. The #6 x ½” PHPH MS (Phillip machine screw) pierced the center of the film canisters, both the top and bottom. Clumps of toilet bowl wax were inserted into the film canisters, until the canisters were partially filled.
The motors were forced into the film canisters, and connected to the 12v battery. This task was completed with virtually no effort. Toilet bowl wax was applied over the motor terminals, and the wires ran through the cap of the canister. Motors were mounted onto the ROV frame by drilling the #6 x ½’’ PHPH MS (Phillip Machine Screw) into the mounting bracket. Displayed on the photo below
Figure 2: Solder the motor wires to the 15’ 8 wire cable; write down the color for each connection. Once all the wires are labeled test the motors using the 12v battery, to insure all the motors are operational.Drill three holes on top of the project box with the ¼’’ drill bit. Use the notes on the motor wire colors that were taken earlier to connect the pairs of motor wires to the same switch. It’s also smart to test if the switches work properly before soldering the wires together, repeat this process for the other switches. After you’ve soldered the motor wires to the switches re-screw them to the control box. Now take the 10’ 22 AWG wire and cut about 3’ of the wire off; use the scissor to separate the 4 wires and run them through the other hole in the control box. After putting the wires through the hole in the control box, strip about a 3’’ off the 4 wires; twist the black and white wires and red and green wires together. Next take the brown wires that are soldered onto the middle terminals of each switch and connect one to each pair of 22 AWG wires, make sure you connect the brown wires the same way for all the switches. Test the switches again but instead of putting the brown wires on the battery, take the other end of the 22 AWG wire and divide them with the scissor just like the other end. When the four wires are separated, don’t separate them completely, strip about 3’’ from each wire; now twist the red and green wire and the black and white wires together. Use the alligator clippers to keep the wires on the battery and test each switch. Then solder the multi-purpose wires onto the positive and negative 22 AWG wires and screw the wires onto the alligator clippers. Now seal the control box with the nails provide in the control box or just wrap electrical tape. [10]
Figure 3: Completed and operational ROV unit.
Solar energy is a type of renewable energy that is harnessed from the sun (photons). The solar energy is converted to electricity using solar cells. These solar cells are created from pure silicon, which is then doped with other elements, causing the solar cell have a positive and negative side. The negative side of the solar cells absorbs photons, this causes electrons from the negative side of the solar cell to be knocked off and flow toward the positive side of the solar cell. This flow creates an electrical current which may be harnessed for used. Solar cells are constructed from this simple concept and the result is energy that is applicable to all electrical appliances.
Solder the solar cells together, on a flat and smooth surface. Use rosin core solder that is pre-flux and buss ribbon to solder the stringers together. For charging the 12v lead-acid battery used to power the ROV, twenty-five solar cells must be wired in complete series [5].
Figure 4: Solar cells are soldered together carefully shift the cells onto the plexiglass and silicon sealant on the solar cells then place the other sheet of plexiglass over the solar cells.
Figure 5: Cut aluminum c-channels connected around plexiglass.
Drill holes through the positive and negative wires (Bus Ribbon) on the back side of the solar panel. Then solder on the copper wire to the bus ribbon exposed by the holes. Run the wires diagonally across the frame of the panel, meeting at the center of the panel and down to the edge of the panel. Drill two small holes in the side of the small project box and two large holes on top. Take the project box and seal it onto the bottom edge of the solar panel, also use the sealant to hold the terminal inside the project pox into place. Shown in the photo above
Run the wires from the panel into the project box and terminal and tighten the screws on the top of the terminal. Run the copper wire through the project box and solder them onto each banana jack, screw the two wires into the other end of the terminals. Cut 5’ of heavy duty wires then solder the 5v diodes into the wires. Strip part of the heavy duty wire and solder onto the banana plugs, and on the other end of the wire attach the alligator clippers.
The purpose of this experiment is to determine whether the operation time of the ROV will be affected by the solar panel/battery combination. When testing the ROV use a stop watch to record the overall operation time, and anemometer to record wind speeds of each motor. The purpose for the anemometer is to further compare the results of the ROV battery and solar panel/battery combination. Make sure the ROV is in an area where it can be monitored throughout the day and moved if necessary. For the test with the solar panel/battery combination place the panel facing toward the sun, and connect the alligator clippers to the 12v battery. After the sunset the solar panel and ROV were taken inside and the test was resumed the next day.
