Step 1: Design
The first ROV was built by Steve of Homebuilt ROVs. His website has numerous ROV designs as well as links to other ROV websites. He also incorporates several How To instructions in his site. I found this site to be invaluable in building my ROV, and would recommend it to anyone interested in building their own
The second ROV was built be Jason Rollette at Rollette.com His design is a little different but still very effective.
For my ROV I decided on a large center tube with two smaller tube located on either side, slightly underneath the center tube.
Step 2: Frame
After some testing, I found that the screw plugs leak, so I switched over to rubber end caps that have a band clamp to secure them.
Step 3: Thrusters
I used 4 Rule 1100 GPH bilge Pumps, 2 for forward, backward and turning, and 2 for up and down.
Step 1: Cut off all of the white housing of the bilge pump, but be careful not to cut into the red motor housing
Step 2: Use a screwdriver to pry off the impeller, the blue thing to expose the motor shaft.
Step 3: I use a prop adapter for an airplane to attach the propeller to the shaft. It has a set screw, and I just tightened the nut against the threaded hub on the prop to lock it in position. I had to re-thread the prop adapter because it was a little too big. As a extra precaution, i used thread locker to seal the assembly together.
Since the threads did not line up, I was forced to re-tap the prop adapter. Although it seemed straightforward, it took considerable time to do it correctly.
Step 4: Navigation
In the picture, the four wires in the silver casing will go to the surface and interface with the computer to show me which direction I am facing. I am writing a program that will rotate an image of the robot to show direction. However, this might take a while so for now I might just use the LEDs
For a tilt compensated compass, check out this one at Sparkfun. It is definitely top of the line, but also carries a huge price tag
EDIT: I removed this because of its inability to maintain a steady heading. This is most likely due to the tilt that the compass couldn't handle, along with the magnieting interference.
Step 5: Camera
I went with a 30$ color camera from Spark Fun. It has an RCA output that I will attach to my computer. Here it is attached to a mount ready to be installed.
The PC card connects to the camera via RCA, and also came with a program to view and capture the video feed
Step 6: Lights
I attached the LEDs to a stand I made out of an L bracket to hold the in the center of the viewport. to make it easier to change, I bolted them to a aluminum strip so that they an be adjusted or replaced
The pictures do not show how bright these things really are. After looking for a second at one, I had spots in my vision
Step 7: Control: ROV Side
Alternatively you could use relays to switch the motors on and off. this is not as good as full range control, but it is much simpler and straightforward. At Homebuilt ROVs, Steve used relays to control the Seafox, and he has a good guide to assembling any number of relay controlled motors.
This is one of the 4 speed controllers I am using for the thruster control
Step 8: Power
Step 9: Control: Surface
I wanted full analog control with out using a microcontroller, so I decided on ESCs, Electronic Speed Controllers. These should be familiar to everyone who has a model plane or car. I needed reversing speed controllers, and stumbled across some at Bane Bots. They are plugged into the Reciever inside the ROV, and the antenna is attached to one of the Cat 5 wires. From there I used my Hitec Remote control with the appropriate crystal and frequency.
The light are controlled by a switch that is operated by a servo. The compass has yet to be set up, but I think I might just use a bunch of LEDs instead of trying to interface it with my laptop.
EDIT: I have since upgraded my control system using an Arduino microcontroller and a servo controller. I will post my results a soon as I finish sea trials.
Step 10: Tether
This is plenum rated Cat 5, meaning that it can be pulled through walls using a fishtape. The covering is tightly shrunk and has a thin nylon cord inside that helps distribute the load over the entire cable. This makes it more durable and reduces that chance that I damage the cable from load stress.
I will need to add floats to the cable because it will probably sink due to its weight.
The connector I used is a Bulgin Buccaneer Ethernet connector. It makes it easier to transport the ROV by separating the cable and the robot. Bulgin tests their connector thoroughly, and this is supposedly rated to 30ft for 2 weeks and 200ft for a few days. As I am planning on going no more that 100, this is well within the limits.
Step 11: Testing
I will try to post some videos in the near future to show how this thing works in the water