LED light & salt water/waterproof battery container

Hi,

I have made a small LED light consisting of 2 AAA batteries, a switch, resistor and an LED.

Does anyone know what will happen if this is frequently splashed or even submerged in salt water?

I know that salt water is conductive. I presume that when submerged current will short circuit. What will the affects of this be? Will it drain my battery, does anyone know how quick this will happen? Will it be like a direct short? Will I damage the LED? Will I get corrosion? Could I put a sacrificial anode in my system to direct the corrosion to a particular point?

The light is to be used as a blacklight for a compass on my sea Kayak. So when it is rough it is likely that there will be a lot of water frequently splashing the deck. And if I capsize The whole thin will be submerged.

I have been unable to think of a way to waterproof the light. I considered encapsulating the whole thing in a ball of silicone, this presents problems when I need to change the battery. I have tried in vain to get a waterproof battery holder. There is limited space under my compass, just enough for a double AAA battery pack placing the battery pack in a film canister will not work. I need to find out if the problems I will experience will out waterproofing will outweigh the hassle of re encapsulating the whole thing in a ball of silicone every time I need to change the battery.

Any suggestions will be welcome.

Sean

Reply to
Sean Bartleet
Loading thread data ...

A UV LED that runs on three volts? They typically take much more -

3.6 to 4.0 so three cells are often used for 4.5 or you could use a lithium type cells. (3 volts per cell)

It will drain your batteries over a period of hours but the major problem will be corrosion / electrolysis - use once throw away.

I may eat the leads away but the led itself is well protected

Sacrificial anode won't work - the voltages produced by a zinc anode will be much less than the 3+ volts you have. The zincs only work on metals when there's no additional source of voltage.

They do make an active system where the anode is an electrode fed by a battery and electronics that adjusts the voltage to protect the metal parts - but that's not really going to work for you and is too complicated.

I do a lot of kayaking (going today - winds gusting to 30 perfect kiteyaking weather)

I also do a lot of underwater electronics work.

The easiest ways to waterproof electronics . . .

For prototypes and for total submersion I like to pot the stuff in paraffin wax. Once a design is finalized it will get potted in epoxy. LED's can poke through the surface of the epoxy or polyester resin - they might be visible through the epoxy or resin, but most resins don't tolerate UV light and turn yellow or pit when exposed to the elements day in and day out.

Metal (steel cans) solder sealed with a backfill of mineral oil are another good technique. Glands (wire-through) connections are via something called a feedthrough capacitor that can be soldered to the can and water proofed with some varnish. The oil provides crush protection, a good dielectric insulator, and helps achieve neutral buoyancy.

For serious stuff that needs a window I use PVC plumbing pipe and seal with RTV and/or O rings. Those get backfilled with dry nitrogen and a coating of varnish on the electronics.

Best easiest way for someone with limited electronics experience, would be to pot the circuitry in wax, epoxy, or polyester. Use a rechargeable battery and pot that too. (use a battery with solder tabs or solder directly to it - don't use a battery holder) For a switch you can use a reed switch close to the surface of the potting compound with a magnet that slides into place to turn the light on.

That still leaves two connections that will be exposed. Use a pair of brass tabs in the potting compound and coat them with solder. Lead corrodes slowly in salt water and can easily be replenished with just the touch of a soldering iron.

The two wires (tabs) will be going to the rechargeable battery and will cause it to discharge when coated with spray or submerged. That can easily be remedied with a small silicon diode (one way valve for electricity).

If you do a lot of electronics, building an inductively coupled charger would be a neat trick (the way some medical implants are recharged).

An easy technique is to just buy a small waterproof 3-4 cell flashlight and modify it to hold a UV LED.

Or . . . give up the idea of UV and use cheap disposable LED pen lights.

Use chemical light sticks? Not UV but real handy when kayaking on a dark night with a buddy. My wife and I use them on a string necklace. When she's in the lead she flips her light to the back and I wear mine on the front.

Taped to the paddle shafts the movement makes them easier to spot at a distance or over the swells.

--
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
 Click to see the full signature
Reply to
default

Electric toothbrushes charge the same way, as you probably are aware.

Thomas

Reply to
Zak

X-No-archive: yes On Sun, 4 Dec 2005 18:11:38 +1000, "Sean Bartleet" used recycled pixels to say:

A cheap water proof $5 LED pen light from Walmart does the trick for me, but then again, there's no fun in that!

------------------------------------------------ Autobot This Spammers!

mailto:postmaster@127.0.0.1 (to reply to actual address, dispense the dots before and after sirname.

Reply to
The Alien

Wasn't aware. Thanks, will check one out sometime.

--
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
 Click to see the full signature
Reply to
default

I am wondering about how important the light is to your safety. Do you need to have it working at night? And does it mean you might be paddling to your doom in the wrong direction if it fails?

If safety is a factor, then some back up might be the way to go - ie a couple of those $5 pens just in case your other solution(s) fail while you are paddling in the dark/fog etc

David

The Alien wrote:

Reply to
quietguy

Everyone,

Thanks for the replies, I really appreciate the suggestions.

The LED I have was sold as a Cat No Z 4074 3600med 5mm Ultrabright Red LED. The specifications state a typical voltage of 1.8, 2.4 max. I am not sure what a UV LED is.

I will look into the various suggestions made, much appreciated.

Quietguy, I guess that I will have the moon (some of the time) and a flashlight as backup. I will look into the $5 pens.

Sean

Reply to
Sean Bartleet

From your post "The light is to be used as a blacklight for a compass on my sea Kayak,"

A "BLACKlight" is an Ultra Violet light, Green Blue White and UV require more voltage than Red.

I thought you had a fluorescent compass card and wanted it to glow with a UV light . . . I guess you meant "back light?"

--
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
 Click to see the full signature
Reply to
default

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.