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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #11  
Old 11-26-2010
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We're doing the marine electronics thing. The best way we've discovered to make stuff water/bomb proof is encapsulation epoxy.

(Looking around to see if the moderators are watching..)

Here's an example..


We use aluminum or delrin molds. We like delrin better. The trick is to solder m/f standoffs to the PC board then use these to bolt the pc board into the mold. Pour in the resin, let it kick and the mounting screws end up being your contacts.

Another example, from my past life is the water injection valve for performance boats : Injection valve construction.

There's also potting boxes you can get from different electronic houses. We've used those as well. Put in your electronic goodies and pour the resin in filling up to the top.

A potting box example would be (Also from Banderlog) :



These are nice because here is no tooling to develop. Just choose size fits your stuff.

If you ned to pass a wire out of a resin block you will need some kind of protection for where it passes out of the block. A simple way to do this is with heat shrink. A few layers of heat shrink makes a nice cushion for this.

Heat shrink cushion.



Expresspcb.com, they are the bomb! We use them for everything. Really tough to beat their service.

Anyway, hope this helps.

-jim lee
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Last edited by LeftCoast; 12-03-2010 at 03:40 PM.
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Old 12-03-2010
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Left Coast, could you expand a bit on epoxy encapsuation and potting process? So the product you picture has standoffs that are soldered to pads on the board that serve as your connections? Do you literally fill that box with epoxy?

Do you have a suggestion for potting epoxy? When I googled it I was flooded with possibilities and most of them seemed expensive in small quantities. Also what about the thermal properties of the encapsulation. For power applications it seems that encapsulation would be an issue.

Thanks, Chris
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Old 12-03-2010
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One other idea is using a pair of high efficiency flashlights as spreader lights. In the battery comparment you'd put a small DC-DC converter to drop 12V to 3-5V depending on the flashlight chosen.

High end flashlights have the latest in LED technology (usually its a generation or two ahead of other markets including marine), are rugged, weigh almost nothing, and I think the spread of light would be just about right to illuminate the decks from spreader height.

This example puts out 174 lumens with 700mA at 3V. That would be only about 0.25A, 3W of 12V input
Quark 123, S2 Edition 4Sevens.Com


As others mention, this and any other ideas assume you can't find something suitable off the shelf. And I agree, you'd prefer to only do this in non-critical applications (currently my spreader lights don't work, so I think that applies) and have a backup. That said, this site supports a lot of do-it-yourself work in areas that are arguably more critical than electrical.
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Old 12-03-2010
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Here's the PCB



Here's the mold



And yes, we just pour the mold full once the PC board has been screwed down in there. To hurry things along we cook it at 120 deg. for about an hour or so. Then, pull out the screws, pop out the part, trim, clean add stickers. Vola! There you go. A waterproof electronic thingy.

Our resin currently comes from : EFI polymers

Our contact for the epoxy rep. : Potting solutions
Jim Halstrom (303) 617-3094

Resin : 20203-5
Hardener : 50015

These are for roughly 5 gallon amounts. I don't know how small they will go. Your cured resin will be on the order of $5.25 / lb.

Thermal properties:

Some resins are better than others. We used to use an epoxy from Dolphs, it had better heat sinking than what we are using today, I'm not really sure how much better. Dolphs is harder to come by on the west coast so we switched. One trick is to bolt down a heat sink plate to the mold along with the connections. This way you can have the heat wicked out if that becomes an issue.

Our stuff, seeing its for people sitting an anchor, is -really- low power and we do every thing possible not to waste any in heat. (Notice the power supply? Digital not analog, doesn't get hot.) Meaning, there is very little heat to wick out, so its never a problem. My brother on the other hand designed stuff for driving small to very large electric motors. Heat was always an issue. Designing for external heat sinks, extra large power hookups that doubled as heat sinks, etc. etc. There's a million ways to deal with it.

So that's everything I know. Hope it helps!

-jim lee
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Old 12-03-2010
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Awesome, thanks. Got it now - your product is resin. I had thought it was a delrin enclousure filled with resin. I was confused by your use of the term mold at first.

Yep that looks like an express PCB. So not much chance of re-working those boards is there...
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Actually sometimes you mold a part, like the stereo on my first post. Sometimes you just purchase a "potting box" put your stuff in that and pour the resin in on top of it. Potting boxes are really popular in the automotive world.

And yes, once they are potted, there' in there for good. Rework is not going to happen.

Now for doing LED things? Clear Urethane is the ticket.

-jim lee
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Old 07-20-2012
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Re: Custom Electronic Design

I have an interest in learning electrical and electronics, and an old sailboat I am trying to upgrade -- my passion. BTW phone support from Blue Sea is appalling; I got a lecture on "not starting boat fires from DIY efforts" instead of help. I asked them what I buy to split a 12volt circuit pair into 2 circuits (stern/bow nav lights) -- see I have no low-level experience, nowhere to learn it! I learn "higher level" from books/online/etc, so I can now design and draw circuits, program Arduino, and all sorts of fun stuff... but can someone tell me how to learn this lower-level parts-and-wires hands-on Marine DC so I'll know what parts to purchase and how to connect 'em?
I'll split off a set of 24-hour circuits for various purchased and home-grown alarms, that could be lots of fun. First I need to remove old unused wires and replace old "spade paddlewheel" terminal blocks.... remove a stack of connectors on the power post. How do I get the education for this?
I'm in Washington but not in Seattle. Where's "Marine MAKER of B'ham" club?
Thanks!
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Old 07-20-2012
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Re: Custom Electronic Design

Forgot what I started to say, is thanks for this set of posts, which I found so illuminating.
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Old 07-20-2012
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Re: Custom Electronic Design

Post specific questions here and search sailnet using google by adding "site:sailnet.com" at the end of the search. You can find lots of posts about splicing two wires. Mostly it comes down to using a small terminal strip or just jamming two wires in a butt splice (that's what I did for the Nav lights). They make specific butt splices for 2:1 connections but you don't necessarily need it.

Otherwise I recommend the very good books by Nigel Calder.
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Old 07-22-2012
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Re: Custom Electronic Design

Quote:
Originally Posted by RobertKWFL View Post
Yeah, by "deck lights" I meant courtesy lights for boarding at night, certainly not navigation lights. Sorry if I used the wrong terminology. Even for non-critical systems I would have a hard wired backup. I enjoy building things, but don't like taking unnecessary risks.
Perhaps I'm missing something here.

Lights need power.

Power comes from wires, NOT wireless.

The I/O function is called a switch, and is placed in the WIRE.


So? What's the "beauty" of a wireless switch.

Other than the "complexity?"
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