Control: I used a joystick to control the side thrusters. The joystick was wired like shown at homebuiltrov.com. Two separate SPDT switches control the up/down thruster and the motor for the camera tilt. A simple switch will be used to turn on the LED lights. The camera will be powered all the time. The thrusters and camera tilt motor will be connected to SPDT relays to allow forward, backward, and tilt movement. Homebuiltrov.com has a diagram with DPDT relays. But I used SPDT relays. The wiring is a little less complicated. Also I think they are easier to find. Many thanks to Hugo at hugonutz.com for his help with this. Two relays are needed for each motor. I used these relays but not the harnesses due to lack of room. They are not waterproof so I put hot glue along the seams then poured wax on top of that. Making the relays waterproof is just in case since I made the tube they are in waterproof also. They are glued on top of the 24v to 12v reducer. That slides into the 4" PVC tube. It turned out to be easier to wire than I thought it would. And using the bigger relays made soldering much easier. All of the wires were soldered onto the copper wire protruding through the end plate.
UPDATE: I don't like the joystick. It is good for 4 directions (forward, back, left, right). But it is not easy to engage two motors at the same time (i.e. left forward, right reverse). So I am going to use two more SPDT momentary switches for the left and right thrusters. It will be more intuitive for me to navigate that way.
The control box is just a plastic container that fits inside the cooler. It also holds the little TV I use to display the video from the ROV. The box has another quick disconnect for the tether and a power receptacle for the power from the batteries.
UPDATE: I don't like the joystick. It is good for 4 directions (forward, back, left, right). But it is not easy to engage two motors at the same time (i.e. left forward, right reverse). So I am going to use two more SPDT momentary switches for the left and right thrusters. It will be more intuitive for me to navigate that way.
The control box is just a plastic container that fits inside the cooler. It also holds the little TV I use to display the video from the ROV. The box has another quick disconnect for the tether and a power receptacle for the power from the batteries.