Need Advice on Waterproofing

[bobskinner]

Hi everyone,

I just joined this forum, I have been reading a bit on here the last while and thought I would join. The deciding factor was so I could ask for some assistance from what seems to be an awesome knowledge base here on this forum.

I have searched for quite some time and have not found any answers. I could very well be doing a poor job of searching but I honestly don't know what key words to be using anymore...

The concept is by no means complicated and I hope it has a simple solution.

I intend soldering a 5mm white LED to the ends of 2 lengths of regular pieces of wire, plastic insulated (one positive and one negative) the circuit is not a concern and the waterproofing of that is also taken care of but I need to waterproof the connections at the base of the LED. I do not wish to put the LED in a housing and intend for it to be directly exposed to salt water. It does not have to be overly robust but a bit of flex in the insulation might not be bad.

First question is the plastic insulation around the wire waterproof (found on most electrical wires, not sure what it's called)

And then more importantly, what would be the most simple and effective way to waterproof the connection between LED and wires? I have been considering a bead of epoxy, liquid electrical tape or other glue around the base of the LED running to a little ways past where the insulation of the wire starts. If this is a reasonable idea, what would be the best glue or other insulation substance that I can use, my knowledge in glues is too limited to know what might be a good choice?

I hope I'm making sense. I don't mind feeling stupid if someone is willing to point out a solution I might have overlooked, or even point me in the right direction to making a more effective search for the solution.

Thanks in advance for any assistance.

Bob

 

[LukeA]

Silicone caulk.

 

[crazedmodder]

Use liquid electrical tape or a potting compound (epoxy for sealing electronics). MG Chemicals make potting compounds, you can pick some up from http://www.mouser.com. Potting compound is more for filling than for coating though. I don't recommend caulking as I've heard some issues with it and I wouldn't risk it. Probably apply crappy too.

 

[bobskinner]

Thanks for the replies guys,

I have considered the silicone caulk, but my concerns were the application and the acetic acid that some caulks give off eating away the copper or wires. I believe there is silicone available that does not have this negative side effect but application of it still seems a bit of a challenge, working with such a small area.

How does potting compound differ from regular waterproof epoxy besides the price tag? I also only need a small amount.

Liquid electrical tape seems like a reasonable plan, I just wasn't sure as to how durable/resistant it would be to salt water and it's adhesion capabilities to the base of a diode. Then I have to figure out where to buy it as I'll be in South Africa for a few months and only return to the States Mar/Apr 09.

Thanks again for the responses.

Bob

 

[TigerhawkT3]

You can get aquarium sealant. I'm looking right now at a package of "DAP" brand sealant. It says it's "harmless to fresh and saltwater fish," so hopefully it won't harm LEDs.

 

[CampingLED]

Then I have to figure out where to buy it as I'll be in South Africa for a few months and only return to the States Mar/Apr 09.

Bob

Call me when you arive!

 

[bobskinner]

TigerHawkT3,

Thanks for the suggestion, I had a look the MSDS of that product and sadly it appears to give of acetic acid also, which I believe is the culprit that damages the copper/metal.

I am still open to suggestions if anyone has any advice or experience.

It seems as though this little project of mine is quite tiny compared to what is mostly going on on this forum. All the talk of 1+Amp LEDs where I'm just playing with some teeny 20mA ones... They are sufficient for my purposes though but I am definitely looking to play with some of the bigger LEDs in the future, too many projects going on right now though.

Bob

 

[CampingLED]

What is that black stuff called that Gene uses on the Malkoffs? It may work. Will it also not work if you first use heat shrink around the exposed wires / connection before you cover it?

 

[crazedmodder]

Thanks for the replies guys,

I have considered the silicone caulk, but my concerns were the application and the acetic acid that some caulks give off eating away the copper or wires. I believe there is silicone available that does not have this negative side effect but application of it still seems a bit of a challenge, working with such a small area.

How does potting compound differ from regular waterproof epoxy besides the price tag? I also only need a small amount.

Liquid electrical tape seems like a reasonable plan, I just wasn't sure as to how durable/resistant it would be to salt water and it's adhesion capabilities to the base of a diode. Then I have to figure out where to buy it as I'll be in South Africa for a few months and only return to the States Mar/Apr 09.

Thanks again for the responses.

Bob

I don't know how liquid electrical tape would hold up to salt water though. Hmm I think potting compound would be best. I think the differences between potting compound and regular epoxy is that the compound is actually made to encapsulate things (I guess it will get into all the spaces and leave nowhere for water to enter) whereas normal epoxy is for bonding things. Also, it's not conductive, some epoxies have metal in them for strength (or so I believe). The potting compounds aren't that pricey, the thermally conductive ones are expensive though.

CampingLED has a good idea, you can use waterproof heatshrink to cover up to as close to the LED as you can, then maybe seal the bottom with a potting compound or epoxy?

 

[RalphStirling]

You can get waterproof heatshrink with an adhesive lining
that melts and flows around your connection when you shrink
the tubing. Put a piece around each wire/LED leg, shrink those,
and then put a larger piece around the LED base and over both
wires. Never tried it in salt water, but if it isn't immersed too long
it should work OK. You could do some experimenting before you
take it into the field.

Here is one source for the tubing:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=EPS2018-ND

-- Ralph

 

[outer limits]

I would also recomend the heat srink with the internal glue. It is very good stuff, used for underground cables and joines exposed to the weather. You can get thin or thick wall heat skink depending upon the amount of physical abuse you expect. But I would not use a thicker one to cover the led but just a small drop of epoxy to make sure on water touches the bare wires.