Waterproof connectors - any suggestions?

So over the holidays I ordered some mini-banana jacks and plugs from Mouser. Tonight I filled one of the jacks with water, put a little silicone grease on the plug, and had no problem inserting it into the jack. Contact resistance was unmeasurable.

I think this might be a viable option for electrically attaching the tether to the ROV (it will need a strain relief, of course, for the mechanical attachment). I'll bring some of the plugs/jacks to Saturday's build day to see how the jacks might fit onto the ROV itself.

Seems like a decent idea. The question I have about any of these "wire through potting" schemes is how well can you actually seal against water water wicking between the insulation and the wire, especially as one moves to greater depths? (I think this is what you are calling the "water jacket" effect.)

Perhaps this idea would work best if you actually stripped away some of the insulation on the wires where they're running through the potting, so the potting material would be in direct contact with the wire. If the wire for this short length was solid (as opposed to stranded) you should get a good seal.

Great!! Looking forward to seeing it.

Yea, the hosing effect is a serious concern, especially with the twisted pair.

I've done exactly what you suggest: strip away some of the insulation in the potted pass through just in case.

A user on the homebuildrovs forum has also used banana connectors: http://www.homebuiltrovs.com/rovforum/viewtopic.php?f=18&t=815&start=30

The subconn/seaconn needs lubrication because of the friction of rubber agains rubber, but also to give the rubber a better sealing.

The sealing principle on the connectors are 2-3 small grooves in rubber on the pin, and the inside of the female plug has an smaller diameter where the pin has grooves - thus making a principle of 2-3 oring seals per connector pin(!)

The mc series has 2 groves, and the larger ones has 3.

Hi Guys,

I'm all very new to OpenROV so please excuse any ignorance on my part.

is there any merit in having a lazer transmitter/receiver as the connection, thereby reduce the risk of a through hull connection?

See 'A simple laser communicator'.

Regards

James

On the OpenROV there are allready 11 wires going trough the hull in addition to the two communication wires, so it would not help that much to reduce from 13 to 11.

but i really like the laser communicator, i havent seen something like that before. genius!

Hi,

nice idea... BUT at least in Germany's lakes you normally have a visability between 0 to 15 meters :-)

Best regards

- Tobi

Hi folks,

Thanks for the replies.

The idea I have been considering regarding the Laser comms system is that we still utilise the tried and trusted ROV umbilical.

The main reason for keeping it, is that if all fails, we still have a rudimentary retrieval system to get the ROV back topside.

However, I’m a great believer in failsafe, and reducing failure, whether it is in components or risk.

The general idea is that the ROV end of the umbilical terminates with a Laser & photodiode housing, this housing has a simple connection to a translucent window on the hull of the ROV, data is transmitted and received through the translucent window, thereby removing a through hull connection. If the laser housing can be encased in polycarbonate, this would give us a watertight housing that could be machined.

If the ROV umbilical end housing onto the ROV hull has a simple connection that can be released in the event of an emergency i.e. comms failure, power failure, umbilical snag/entrapment, then we have a method of detaching the ROV from its umbilical and allow it to free access to topside. A small CO2 cartridge and stored SMB (as used by divers) or bladder that can be activated by trigger mechanism that could disconnect the umbilical as it is deployed.

Just food for thought, as with most projects, we could end up over engineering/complicating the project.

Might add it to my build, if I end up using a camera housing as a hull. In the rear is a small viewport, which would be good for optical communication window (via plastic fiber optic). Any fewer holes in the “boat” is good in my book. Also, as far as going umbilical free, could go with an audio modem- I saw one for a dive computer that could locate other divers (with same computer) using audio modems communicating with a base station to give relative gps position (using triangulation, guessing)!

You should use dielectric grease in the fitting, if water makes it in it will be repelled. You can get it at orielly’s or autozone.

I like it! Instead of a laser, why not just an IR X-mitter/receiver combo? Attach it to an IR invisible port on the side of your ROV and the signals get sent through this MODEM window. Much more reliable than trying to make physical contact through the hull.

The decision to make would be whether the expense of the additional translation and hardware is worth the hassle of potting/sealing your ROV.

Great idea though.

Hi,

nice idea but IR-signal is absorbed by water!

-Tobi

I was thinking that an IR transmitter and receiver could be mounted right inside and right outside a window so there would basically be nothing between them but the glass/plastic (no water). This way the tether terminates at the outside of the ROV window and the IR TX/RX device in the ROV would be the modem inside the ROV.

I would imagine the task of sealing a small window would be a lot easier than sealing wire penetrations around each and every strand of every conductor.

Ah, now I got it!

This could work for sure... nice idea!

-Tobi

Hi there.

They don't fit the cheap part of the spec, but, LEMO V series connectors are used in Military / Space / Subsea work. They maybe costly, but ultimately less costly than a flooded / dead ROV

LEMO Specs

I'm planning on using these connectors for my OpenROV when I get back home from deployment and get around to ordering one:

http://wet-connect.com/index.html

They have wet connectors and bulkhead connectors. Not cheap at $40-80 but they look like they will do the trick. They also have triple-pole connectors for connecting servos outside the pressure tube.

Hey we have these on one of our ROV’s at work and they work great! Also WOODHEAD MOLEX has a special like of waterproof connectors that I just used on a prototype to power a motor arm that we have to take off all the time. I only ever work to depths of about 50’ so I don’t know if it would do the trick. But for shallow stuff the WOODHEAD connectors are great.

Sorry I couldn’t find a link

I just posted this Tether disconnect
Has a link to the connector I use for my tether.

Hi David,

You can research more underwater connectors at www.anekonnect.io

The site is an information repository for underwater connectors and does not sell them, but if you contact them, they will put you in touch with distributors near you to get those connectors.

They have a good visualization of all commonly available underwater connectors and have a good cable design wizard. Hope you find what you are looking for.