Wet Connector


#1

I'd just like to preface this post with the acknowledgement that I know next to nothing about electricity. There's a positive and a negative, that's about the limit of my understanding of it.

As it stands the tether and motor connections are placed through the endcaps into the e-chasis housing and then potted into place with epoxy. Personally I see this as a bit of a limitation to easy repair and modifying of the ROV.

I am looking into making a wet connector (I think other people are doing this as well) and have started to document the process to see if anyone else has any bright ideas.

My idea is best explained through a high quality 3D rendering. But I don't have one of those so a "paint" sketch will have to do.


I began by taking two male bullet connectors, removing the insulation, placing them back to back and soldering them together. But I forgot to take pictures of that, my bad.

Then I put these new custom connectors through a bottle cap and epoxyed them into place.


I attached some female bullet connects onto what would be the "Wet" side and attached a 12v lamp to the wires for testing purposes.


I hooked the whole thing up to some bench power and got some numbers.

3v - 0.82A and 12v - 1.63A readings on the PSU with everything dry.

2.96v and 11.82v on my Multimeter taken across the lamp with everything dry.

I hot glued the cap back on the bottle, cut the bottom of the bottle off and filled it with water.


I also put the probes from a multimeter in the water just for the hell of it.


And I got some more numbers.

11.98v - 1.63A reading on the PSU with both filtered water and salt water.

The readings across the lamp were 11.86v with both filtered and salt water.

0.4v on the multimeter probes with filtered water.

0.2v on the multimeter probes with salt water.

What does this all mean?

I don't really know.


#2

Hey Owen,

Interesting idea! Before getting into the best way to make use of your multimeter, what is it that you're trying to test for? If the mechanical aspects of this all seem to be fine (that is, nothing is leaking!) then I would imagine you're interested in if the way you've attached wires to the "wet side" of the connector provides good enough insulation so that that nothing will short in salt water.

I can suggest some ideas about how you might be able to test for this sort of a thing with a multimeter if you like, but first, would you clarify that that's what you're interested in??

I love your write up and photos so far- keep that up!

Eric


#3

Hi Eric,

Yes I'm trying to measure for any shorting across the "wet" side of the connectors.


#4

Ah- okay. So I think the best way to do this would be to make some *very* salty water (the more salt you add, the more conductive it will be), then apply a voltage (the higher the voltage, the more detectable it will be but be safe!) to one of your conductors. Put your multimeter in DC Voltage detection mode and ground one of the probes. With the part of the connector you hope is waterproof in the water, place the other probe in the water nearby, and see if you can detect voltage in the water. If you detect an appreciable voltage, you've got a short. You can do this for both conductors to test each.

~E



#5

One other configuration would be to have both + & - from the DC Supply into the water.

Use your setup that you did and attached the + & - to the pins in the bottle cap then submerse the pins in the salt water with nothing attached to the pins. use your multi meter and measure the current that may pass through either the + or - leads through the salt water. If your PS is variable start at low voltage then crank it up watching the current meter. You can then calculate the resistance of the salt water between the two pins. knowing how much current travels between the two pins is the key.