Build a small hobby grade ROV for an underwater robotics competition


#1

Background
I’m trying to build a small hobby grade ROV for an underwater robotics competition held at the university I’m studying. And I have used eight brushed dc motors each of which consumes 8A on full load.

The whole system might consume about 75-80A at maximum usage. But we are pretty sure that we are not running all motors at the same time at full load and hence average current usage would be around 50-65A.

I have included eight 12V 8Ah SLA batteries(http://www.kynix.com/Product/605.html) inside our ROV and hope it might run for like one and a half hour at most on average.

Problem

One of the issues I’m having right now is with designing a PCB layout where wires from eight batteries are merged onto the PCB Board.

Please note that I’m not an electronics/electrical engineering student that I do not have proper and solid knowledge on power circuits and calculating thermal dissipation.

I just don’t want to be a dumbass letting the PCB burns into smoke and flame from overheating. I am afraid that might happen when the amount of current stated above have to be passed through the plate.

I have space limitation and maximum dimension of the PCB for the distribution panel should not exceed 6"x6" dimension.

Above is the overview of the power supply and distribution concept for the ROV. After the summation of total current usage and wattage, to a shocking moment, it’s around 1kW and 80A of DC 12V. Is it such a high usage of power in sense of power circuits? I never had an experience with circuits that use over 12V 35A. I’m afraid that I might be wasting a lot of power. But my ROV is a bit big in size, about 3’x2’x1.5’ dimension of steel structure. But I’m pretty sure we are going to operate only four motors at the same instance and at 70% of full load at max. So I guess 50A is maximum for normal operation conditions.

Question

My question is

  1. How should I design my pcb for power distribution purpose only?
  2. Shall I use a typical thick PCB or a copper block with heatsink?
  3. Is the total overall power usage huge and not suitable?
  4. Your advice on making things better.

Thanks A Lot!!!


#2

I also am not an electrical engineer but that power consumption is HUGE! The only way I can see that kind of amp flow is with relays on a power board and controls on your PCB. I have a number of questions for you:

Why is ypour unit so heavy? If this is supposed to be a “small hobby grade ROV” why not downscale and use PVC pipe or aluminum conduit for the frame?

Have you even looked at the OpenROV 2.X series? These are "small hobby grade ROV"s that use light weight but dependable ESC motors that do not require waterproof encapsulation.

I suggest you spend some time in the Forum and you will find many ideas that you may be able to adapt to your needs.

Best wishes and good luck.


#3

When the voltage is raised to 48V, the problem will be very simple. It is not difficult to choose the motor of the 48V.