ROV custom build: seeking comments on my plan for the electrical / electronics


#1

Hi all.

I am planning an ROV build project. Planning on making various aspects of this project an educational experience for my kids.

My goals are:

  • expose them to a wide variety of physics
  • keep the materials price low
  • make the project relatively simple

I have been reading up on a lot of different design ideas. The attached image is what I think is the most reasonable way to achieve my goals (for a 100 ft max fresh-water dive).

Here is a diagram of the electrics / electronics:
yellow vertical line separates items in the boat v.s. items on the ROV
other lines indicate wires

Open questions in my mind:

  • Will CAT 5E transmissions work well for the distances discussed?
    o 100 ft USB->ethernet->USB extension cable
    o 100 ft 12volt transmission for motor power (from a car battery in the boat)
    o 100 ft timing for usb operation of Webcam, and controller

  • Do I need a separate, higher gauge line for 12volt electrical (for propulsion)? Or should I find an unused couple of wires in the CAT 5E cable?

  • I assume that PWM control is far better than on-off switches for the navigational motors (in terms of operational accuracy)

  • I assume a cheap servo that I waterproof is the cheapest way to operate the claw (even if that means replacing the servo every now and then when it finally gets water logged.

  • instead of the PWM controller, I could instead use an Arduino or a Rasp PI…

  • some programming is required to control the propulsion and grabber servo via the laptop

FWIW: I was thinking about using something like the basic Sea Perch design for the structure of the vehicle.

Thanks
-Ray


#2

A few thoughts -

I would recommend testing your USB plan early. I’ve never had any luck with the USB-over-ethernet boxes and webcams, but I’m prepared to believe they are not all created equal and that one might work.

Power - yes you’re going to need a larger gauge cable. When I started my own build I was going to feed power to my ROV from a topside battery but ultimately gave up when I realized the gauge of the cable I’d need to get enough current down it. Take a look at the 12V table here (http://www.solar-electric.com/wire-loss-tables.html - admittedly for solar but still useful) to get an idea of the wire gauge you’ll need.

You can buy waterproof servos (Hitec do some), although they’re only a bit waterproof - good enough for a pool but no idea how well they are at significant depth. I have some of these on my ROV but haven’t stress tested them yet.

Hope this helps.


#3

Very useful info, Tim. Thank-you!