Homebuilt ROVs Forum

Hey,

Doing the MATE this year as well! Good luck to everyone else.

I have a small problem. I'm using two Arduinos, one on shore to act as a relay between the computer and the ROV arduino. This is, surprisingly, after a bit of programming, working extremely well. I'm using A3959s to power the bilge motors, and everything's fine and dandy above water.

However, I simply have no idea how to water proof a control system like this. The A3959s release a significant amount of heat, as I have 7 of them. I'm currently thinking of buying a metal box with a cover, and putting thermal paste on the A3959s, then pasting them to the bottom of the case, and potting the whole thing with epoxy. The nice thermal contact with the metal bottom, and the fact that the metal bottom will be touching cool water might help.

But I simply have no faith in my potting skills. And water proofing skills. And those ICs cost a pretty buck. :p.

Any criticisms?

Go to either Radio Shack or your local electronics store, or if you don't have one check the Internet, for relay/power supply heat sinks. These may very well be heavy, but if you are concerned about the heat problem, this might be the way to go.

As for waterproofing, your idea sounds good. If you are worried about mixing the potting epoxy, use the kind that comes mixed in a tube. It isn't hard at all!

SkubaGEEB to the rescue!

Have you considered mineral oil.
It is non conductive and will both water proof and dissipate heat.

any water that manages to get in will just sink straight to the bottom the box and away from your electronics which are now submerged in oil.
and as fare as pressure goes if your box is full of oil there is no compressible air space to allow water to get in.
your idea of using the thermal paste will be replaced by the oil and your whole box will then act as the heat sink, oil drawing heat from the circuits, box drawing heat from the oil and so on, especially if you go with the metal box option.
the only real downside is that once the oil is on your electronics its not coming off again, but if you were willing to pot them with epoxy the I guess this would not be a problem anyway, plus this also allows you to remove them and use them again in the future or just allow easy access.
also there is no heating or mixing needed.
Good luck
SkubaGEEB out :mrgreen:

Nice, ScubaGEEB, nice..

I think using oil could improve the "waterproofness" of any ROV. A possible problem is that the camera vision will become blury, and therefore I am looking for a very clear oil. Coconut oil is very clear, but has anyone got any better alternatives?

If I am for instance servicing the ROV, how am I going to clean up this oil (or "this mess", I was tempted to say..) You could degreaser, but that would maybe harm the electronic components. I will check that out with some electronics professionals.

The oil idea is not necessarily recommended for use with cameras for the reasons you mentioned,(not to say that you coudnt) so if your camera is in the same housing as the rest of your electronic you may need to try a different option (you should also be aware of any focusing optics too, ie moving parts and viscus fluids don't always play well together).
But for other electronics it should be ok.
As for servicing issues, is it any easier to do after covering them with wax or potting them in epoxy......not really.
There are as I know solvents and degreasers made for use on electronic but I can't comment on their effectiveness or if they are safe to use.

SkubaGEEB :mrgreen:

MagicHat wrote:Nice, ScubaGEEB, nice..

I think using oil could improve the "waterproofness" of any ROV. A possible problem is that the camera vision will become blury, and therefore I am looking for a very clear oil. Coconut oil is very clear, but has anyone got any better alternatives?

If I am for instance servicing the ROV, how am I going to clean up this oil (or "this mess", I was tempted to say..) You could degreaser, but that would maybe harm the electronic components. I will check that out with some electronics professionals.

You could use esso marcol 82 for the oil that is what is used in the navy.

If you have to do maintenance you could use contact cleaner here is a link:

http://www.mcmaster.com/#electrical-com ... rs/=cwu6hp

Markol transfers heat well and with the reduced heat load the electronics work better.

This is a tried and true method.

Thank you very much Seadragon! Well, if they use it in the navy I think it's good enough for me

Now I live in Norway, so where do you think I would be most likely to find some Marcol 82 oil? At the gas station or a drug store, perhaps?

Will a normal contact cleaner do the same work as the one you linked to?

It is always good to know that things are real life stress tested

You can also use Drakeol 32.
some of the contact cleaners may not be good for electronics. that one I linked to we use every day at my present job to get different oils of the control cards for the machines.
In Norway I think you can get markol or drakeol from any supplier to the pharmicuetical industry.

Hope that helps.

I have a video buoy from my sub that houses a 900MHz transmitter that gets REALLY hot and requires heatsinking so I housed the buoy in a cast aluminium case. The transmitter is clamped to the case with heatsink compound and since the case is in the water, it is a VERY effective heatsink - it doesn't even get warm in the water. The case is thick enough to be drilled and tapped for mounting screws and a little thread compound on the screws ensures no oozing through the threads. The inexpensive cast aluminium cases (through electronic suppliers) are not gasketed but it is a simple matter to make a gasket.

Just a thought.....