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designing marine electronics

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JohnH

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May 19, 2005, 2:53:51 PM5/19/05
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Hey all,

Anyone have any experience with embedded marine electronics? I have a
product I'm developing which might be exposed to salt spray, sun, rain,
splash and the worst a marine environment can dish out. It will be above
decks and could be subject to a good bath.

Is the solution a gasketed enclosure? That and / or dipping the board in
some kind of sealer?


Leon Heller

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May 19, 2005, 5:27:33 PM5/19/05
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"JohnH" <johnh...@gmail.com> wrote in message
news:CuWdnQ6FW6j...@comcast.com...

An IP68 enclosure and connectors are what you need.

Leon
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Paul E. Bennett

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May 19, 2005, 6:09:36 PM5/19/05
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JohnH wrote:

Firstly, become familiar with IEC 60529 which deals with the degrees of
protection afforded by electrical enclosures.

Having been involved in a sonar fish design we had a number of issues about
proper sealing faces and special threads to ensure that the electronics
would stay dry. The weakest points will always be where you need to break
out of the enclosure with a cable connection. Proper feedthrough design
would help the most in this respect.

If you make the enclosure a pressure vessel you could always pressurise the
containment with dry nitrogen gas to ensure that the innards stayed dry.
Alternatively, on the presumption that you didn't need to make adjustments
after closing up, you could always pot the electronics in potting compound.

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Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
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Robert Scott

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May 19, 2005, 8:25:25 PM5/19/05
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On Thu, 19 May 2005 23:09:36 +0100, "Paul E. Bennett"
<p...@amleth.demon.co.uk> wrote:


>Alternatively, on the presumption that you didn't need to make adjustments
>after closing up, you could always pot the electronics in potting compound.

True, but even this is not trivial. Most potting compounds do not
bond with the insulation on wires. Also, you need to clean the board
exceptionally well before potting because any acid residue will
migrate along the potting boundary and attach the traces. And some
potting compounds expand so much they will lift surface-mount
components off the board.


-Robert Scott
Ypsilanti, Michigan

Mark Borgerson

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May 19, 2005, 10:34:56 PM5/19/05
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In article <CuWdnQ6FW6j...@comcast.com>, johnh...@gmail.com
says...
I've been doing electronics for oceanographers for many years now. The
basic rule is: Separate the electricty and the seawate (or even
the salt spray). Do not rely on board coatings or such. Put your
electronics in a waterproof enclosure if it will be out on deck.
Use waterproof connectors it the device will be out on deck.
The connectors will cost you about $50 to $100, so it is an
issue that will require good engineering.

Mark Borgerson

Mark Borgerson

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May 19, 2005, 10:37:07 PM5/19/05
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In article <428d2dd7...@news.provide.net>, no-...@dont-mail-me.com
says...
Potting your electronics also requires careful attention to thermal
design if your product dissipates more than a few Watts. Fault
diagnosis and repair also becomes a non-starter.


Mark Borgerson


Not Really Me

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May 20, 2005, 10:54:15 AM5/20/05
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"Mark Borgerson" <mborg...@comcast.net> wrote in message
news:MPG.1cf6eca7e...@news.comcast.giganews.com...

If you're not running off your own batteries or AC, be careful with ships
power. It can be extremely noisy and have a wide range and huge transients.
Devices I have worked on were usually spec'ed for 10-48 VDC, which is a
tough range to handle with small switching supplies.

Scott


Kevin D. Quitt

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May 20, 2005, 12:49:30 PM5/20/05
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You can never be too safe. A company I worked for produced three large
power converters for Naval use, each in a 6' enclosure approp[riate for the
environment. A swabbie decided the units needed cleaning, and he turned off
the converters, opened the doors, hosed them down with sea water, then
closed the doors and turned them back on. The enclosures were such that not
only was he not harmed, but he was not even aware of the damage he caused -
until a little later.

Good thing he wasn't in the army - it would have taken him a while to pay
for the replacement of the units.


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Kevin D Quitt USA 91387-4454 96.37% of all statistics are made up

JohnH

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May 20, 2005, 12:53:17 PM5/20/05
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Thanks, all, for the replies. You've all been quite helpful!


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