ROV single line digram - request for help


first of all, am not that much experince the filed of electronics and electrical staff! So ecxuse my words and my slow understanding. However; i’ll do it and i’ll show you that.

First of all; I bought the BlueROV and some other accessories and things well received. But before starting the assembly exercise; i’ve read alot of articles and got some confused. I’ve summrized what i understand in the attached single line digram. Is it correct the way of communication in the single line digram?

The second thing; is it possiable to have the battery above the water (Part of the control box) for easy replacment if the battery low charge? If yes how to supply power to the ROV under the water?

The third thing; subsea light and pressure sensor where to connect them?


That’s it for now and thank you.

Hi Saeed,

First question - I’ve attached a quick picture of how I’ve wired up the Fathom-S boards for my build that should help you set yours up. A laptop connects to the topside Fathom-S board via the USB connector, and your joystick connects to that laptop. The video display is separate from the laptop and connects via the RCA connector on the topside Fathom-S board.

Second question - No, not that I’m aware of, but Rusty can answer this better than I can.

Third question - The pressure sensor connects to the I2C connector on the Pixhawk. I’m not sure where the lights connect but I’m sure Rusty can answer that for you.


The ROV-side interface board in the store only has a single (serial) connection to the pixhawk, the power interface has been removed in this version compared to Paul’s board. I am working on a diagram now. The subsea light red and black wires will need to be connected directly to the battery, and a female header or servo plug will need to be attached to the signal wire and connected to the pixhawk aux pins.

Here are some possible connection diagrams.


I’ve been working on putting together wiring diagrams as well. They are still in progress but I’ve attached the current version.

As far as sending power goes, there is not a good way to connect a battery on the surface. Due to the voltage drop through the tether, this is relatively challenging.

I hope this helps.



Dear Paul,

really thank you.

Dear Jacob,

Your digram made my life easy!

Thank you.

Dear Rusty;

what’s the easiest way to calculate the voltage drop? And what’s the acceptable drop limit?

Moreover, in your diagram the lights connected directly to the battery. Is it still controllable by through the Pixhawk as ON/OFF?

last question; can i display the camera on the same laptop screen am connecting my gamepad controller to it?

Thank you Rusty for your continues support.

Here is a handy calculator for voltage drop: Electrical Cable Voltage Drop Calculator

With 24V batteries, 10 meter tether, and 16 gauge copper wire, if you pull 50A (2 T200s running full power), the voltage drop is 13V and you have 11 V at the end:

Also, the camera output on the tether interface is NTSC analog video, so it doesn’t come through qgc. For video to show up on qgc you need to connect to a companion computer with an Ethernet link between the computer and the fish.


well, i’ll try to find a way to resolve the battery issue.

For the camera output; please can you check this list (in the below link) and advise me the best selection(s) will suit the purpose.


@Saeed - I can’t claim that this is the “best” video recorder, but this is the one I’m using and it seems to work fairly well:

The voltage drop issue is one of the biggest problems we deal with when designing an ROV. The two options are to either supply power locally, as the BlueROV does with on board batteries, or from topside, as most commercial ROVs do. There are advantages and disadvantages to both. It’s really up to you.

Personally, I’ve chosen to use on board batteries in my current design. I typically operate in fairly shallow water (less than 40 meters) and for fairly short periods (4 hours or less) so for my purposes batteries work best. The other advantage are that using on board batteries is often less expensive to build and can be safer (topside power often means you use very high voltages).

But it really depends on what you want to accomplish, what your budget is, and your own personal preference.


@Paul, as we used to say on the boat … it is not the voltage that kills you it is the current. Running AC down the line and rectifying it locally is not that bad of an idea. You have much lower losses with AC power over the long haul. Just ask Edison why he lost the power battle.

@Harold - True, but I wouldn’t recommend using AC down the tether for an amateur builder. In fact, I’m not aware of any mini ROV manufacturers who use AC power down the tether. No doubt it could be done, but there would be some serious obstacles to overcome.

@paul, sorry am not looking for a recorder. Am looking for getting the Video on my mac screen where my gamepad controller connected. So everything will be on 1 laptop screen.

Hopefully its clear.

Going to Jacob reply # 7890; he wrote “<u><i>The subsea light red and black wires will need to be connected directly to the battery, and a female header or servo plug will need to be attached to the signal wire and connected to the pixhawk aux pins</i></u>”

couldn’t not understand it fully. Is it possiable to have a single line digram showing the subsea light connections to the battery and pixhawk so i can understand it perfectly?

I know i kept asking alot :frowning: but it’s just this time guys and then i’ll dive alone :stuck_out_tongue:

@Saeed - I’ve used one of these before:

Several companies make similar or identical units and the price is super cheap. The problem some people had with them was software drivers. I’d do my homework before buying ones.

Am still inquiring about the subsea light connections. Can i see single line digram?

appreciate your continues support.

Hi Saeed,

We don’t have a diagram with all wires shown, but on the Lumen light, you connect the ground and power (black and red) wires to the battery directly and the yellow signal wire is connected to the signal pin on the Pixhawk.

Does that help?



cristal clear. Am going to start the connections and will let you know the results.