Underwater robots are essential tools in modern ocean exploration. They play an important role in the offshore oil and gas industry, the defense sector, maritime search and rescue, oceanographic research, underwater archaeology, and environmental monitoring.
Other applications of remotely operated vehicles (ROVs) include monitoring underwater habitats, observing fishes and other organisms, exploring deep-sea environments, investigating shipwrecks, and studying areas too dangerous for humans, such as active underwater volcanoes.
Depending on the application, ROVs come in a variety of shapes and sizes. All of them have some common features: flotation so that the ROV is neutrally buoyant, ballast to keep the robot from rolling over, propulsion to move up and down, side to side, and backward and forward, control to perform certain tasks, power to operate motors, video cameras, and other equipment, and navigation to keep track of the robot.
Let’s now look at how to build an underwater robot.
What you need
- Water container (bathtub, large laundry tub, etc.) at least 18 inches deep
- Model boat propeller
- 6 or 12 volt DC motor
- One or two 6 volt batteries
- Plastic coat hanger
- Epoxy glue
- Two pieces of AWG stranded wire or telephone wire, each about five feet long
- Electrical tape
- Two film canisters with lids
- Twelve nails or ¼ inch diameter bolts to use as weights
- Hot glue gun
- Wire cutters
- Optional: Hand drill and drill bit of the same diameter as the motor shaft
How to build
1. Place the propeller on the motor’s shaft. Drop a small amount of epoxy glue on the end of the shaft before installing the propeller if it is loose on the shaft. If the shaft is too long for the hole in the propeller, use a hand drill with a small drill bit and enlarge the hole slightly.
2. Make sure the coat hanger’s hook is pointing down. Tape the motor to the hook’s inside in a way that the propeller is in an upward position.
3. Tape the two film canisters to the upper part of the coat hanger, with lids on.
4. Attach enough weights to the lower parts of the coat hanger (near the hook) so that it floats just beneath the water’s surface.
5. Both ends of each wire should have about an inch of insulation removed.
6. Twist one end of each wire onto the motor’s terminal. Use the hot glue to keep the wires in place if necessary.
7. Twist the wires to make a single cable.
8. Tape each wire’s other end to a popsicle stick/chopstick, allowing the bare wire end to hang over the stick’s end.
9. Connect two 6-volt batteries in series if you’re using a 12-volt motor: Remove about one inch of insulation from both ends of a 12-inch piece of #28 AWG wire. Twist one end of the wire around one battery’s negative terminal and the other end of the wire around the other battery’s positive terminal.
10. Test dive. Connect one wire’s bare end to one battery terminal and the other wire’s bare end to the other battery terminal. Reverse the wires on the battery terminals and see what happens if the propeller spins but does not sink. If your ROV continues to float, you may need to add more weight.
Warnings
- A wire should never be connected directly between the two terminals of a battery. The wire will quickly become extremely hot, potentially causing a fire or serious burns!
- This activity should not be done in saltwater because everything will short out, and your motor will be destroyed.
- If you’re removing insulation from wires with a knife, be careful! Roll the knife over the wire to cut the insulation but not the wire by placing it on a cutting board. Make sure your fingers aren’t in the way of the blade!
