Another Brilliant Rumination - Waterproofing LED Flashlight Projects

LED's will eventually wick water up into the dies, ruining the bond wires. I've saw this happen to LED 3rd brake lights.

Why not just encapsulate your project, with Liquid Electrical Tape, or the stuff you dip tools in to insulate the handles. If there is a heat issue, make a heat riser that passes thru the plastic. Check out boat trailer supply/ repair.

Luck; Ken

In article , snipped-for-privacy@sbcglobal.net mentioned...

Thanks for the info. I was supposing that the exposure time to the water would be short because it would dry out soon after being exposed. And with a short exposure time, the amount of water getting inside the LEDs would be minimized, and their lifetimes would not be shortened considerably. But you may have pointed out a weak spot that could be a problem if the water stayed for a long time. Or if the water had salt in it from the streets, where salt is used to get rid of snow. Fortunately in SOuthern California, that's not a problem.

The liquid goop sounds like a good idea. But the problem is that if you have an open frame, and dip only part of it in the goop, then there is still a problem with water wicking up the wires where they enter the goop. So it would be best to cover the whole framw with goop. But then every time I need to change batteries, I would have to cut away the goop where the batteries are. And regoop it afterwards.

But one thing that I had planned to do is use rechargeable Ni-MH AA cells for this open frame light. If I installed the cells permanently and added a jack to recharge the batteries, it would allow me to encapsulate the whole thing in goop. The only problem is to keep the goop out of the on/off switch and the charging jack.

I bought a forever flashlight that uses a reed switch and magnet to turn it on. I've got a lot of small reed switches, and I could use such a system to replace the switch. But the reed switches I have are very low current and might fail if I tried to switch a few hundred mA of battery current. I might be able to get it to work by just switching the base of the driver transistor off. The trick is to get some kind of sliding mechanism for the magnet, with a detent like a slide switch so it stays at one end or the other.

Thanks for the info.

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wrote in

tins,

resistant.

They're

in

the

it's

the

some

wires.

heat

It is watertight, originally designed to seal the wires and connectors of a boat trailer. (BTW "Goop" is a trade name for a product series that includes some for this purpose. The "Liquid Electrical Tape" is a different approach.)

So it would be best to cover the whole framw with

...

Use petroluem jelly rather than automotive grease.

Even if it is fairly clean to start with, your water will soon get salty from electrolysis, and when it dries will deposit salts. Then whenever is gets damp it will absorb water, conduct, and corrode some more. I've seen flood-damaged industrial equipment fail this way months after the event. Even condensation does it, which is cleaner than rainwater.

This corrosion will apply equally well to copper, bronze or stainless steel, You need gold or platinum wiring to prevent it!

When I get a water damaged (or once, toffee contaminated) PCB to repair, my first action, to everyone's horror, is to wash it. It's the only way to get rid of the salts. I do bake it out thoroughly before applying any bias. And they do work afterwards.

Tim Jackson Industrial electronic engineer

OK - You should get alot of answers on making it waterproof... but now make it float for boating uses. Then make an LED fishing bobber for night fishing. Extra credit if the LED changes colors when you get a bite.

~Tom in Mn

I had the water concern too regarding a bicycle speed logger I built into an Altoid Sours tin last month. I put a super bright red LED into the prototype to give visual verification that wheel rotations were being sensed (I was afraid the shock and vibe of riding would shake the circuit to pieces). I drilled and filed a small window in the lid ... the center of the "O" in Altoids ... and RTVed behind it an oval sliver of acetate sheet. Probably polystyrene would have worked just as well but I didn't want to sacrifice a parts drawer . I didn't even try to waterproof the lid itself. Electron routes stayed dry through two rain storms, though I'm certain this would not have been the case if the tin had been upside down.

By the way, have you housed one of your steel-melting LED flashlights in a round Altoids Sours tin? I haven't seen one posted.

In article , snipped-for-privacy@nojunkmail.com mentioned...

The first one I made was aluminum and this latest one is brass, and both would sink like an anchor if dropped in water. But I made it clear in the OP that I was not concerned about that, that I was asking about waterproofing against rain water.

Thanks for the ideas tho.

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Cool! Someone else finds a use for an Altoids tin!

Problem is that the LEDs have to be directed in one direction, so putting them on the round edge would be a real problem. They would have to be mounted on a flat surface. And the batteries just don't fit well into a round tin. There would be a large amount of unused space where nothing much would fit because of the curve.

I'll (re)post a pic of the Coffee Mints tin light I made recently to the ABSE newsgroup. There's almost no space left inside after three AAA cells, three LEDs w/ 3 resistors, and a switch are stuffed inside. It's about as small as one could make it in that shape. I really didn't need to glue anything because there's so little space that things don't move around inside.

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In article , tim@tim- jackson.co.uk mentioned...

I bought something almost as good as toffee. I got a spray can of goop, the handle grip stuff that you put on pliers handles and screwdrivers, etc. I'm going to go outside and give my open frame light a couple coats to see how it works. I'm not going to spray the battery holder, but most everything else. The goop is clear, so it should allow me to see the innards somewhat. I'll post later on the results, maybe a pic if it comes out okay.

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The battery is probably the component that will fail soonest when wet. It's got a small gap across the seal, and will rapidly corrode.

On Sat, 29 Nov 2003 04:24:03 -0800, Watson A.Name - "Watt Sun, Dark Remover" Gave us:

If you use an RTV encapsulant, you get the opportunity to service the device in the future as it will shear easily under pressure.

If you use a hard epoxy, it will work well, but be rendered all but totally unserviceable.

Make the design such that any silicon elements that exhibit heat in the design will be on the outboard edge of the "case" for conduction cooling purposes.

The hard bricks conduct better as a monolithic block than the RTV typically does. If you use gold terms for the battery contacts, you can use external battery "packs" that you construct to attach to it. Long term non-corrosion there. Or use car ignition points, which are platinum plated, an even better non-oxidating metal than is gold.

In article , Watson A.Name - "Watt Sun, Dark Remover" mentioned...

Well, I went outside and gave the open frame light many spray coats of "Rustoleum Grip & Guard". I'm very disappointed with the results. I had laid two layers of black electrical tape on the brass frame to keep the circuit board from shorting against the brass. After a few coats, the topmost layer began to swell up from the xylene, naphtha, and acetone in the goop, so I had to pull that layer out. Then after several more coats, the bottom layer of electrical tape started to swell and curl up, so I had to pull that out, too.

But even after many coats, with some drying between coats like it said on the can, I still could not get the coating to build up on the surfaces. It was more like the consistency of crankcase oil, and most of it flowed down to the bottom of the brass case. Almost none of it stayed on vertical surfaces. It's a mystery to me how this stuff is supposed to cover the handles of a pliers, where there is no flat surface.

I think I should have bought the dipping can, where the handles are dipped into the goop. I don't know how I would apply the thick stuff, I would probably have to pour it in and try to keep it from running out with some tape and plastic sheet.

Altogether this has been an excellent time waster. Not much accomplished with the goop.

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I work with projects that are waterproof to depth in salt water. For some stuff I've used mineral oil in sealed tins with solder-in feed through caps to use in place of cable glands. Waterproofing to hundreds of feet is easy that way.

In others I use paraffin wax as used in candle making to waterproof the circuitry yet leave it easy to repair or modify. For higher temperatures - the candle making hobbyists add steric acid or chopped polyethylene to the mix to raise the melting point.

Drive the moisture off by baking the circuitry if possible before potting.

Casting in epoxy or polyester resin works well where exposure to temperature and weather are factors in mature designs. Paint protects the surface from UV, sun, light.

Dipping the circuit boards in poly urethane varnish is great for milder weatherproofing. Even the new water-based poly varnishes work well. Heat the circuit and the varnish is sucked into the small spaces while it sits in the tank for a few minutes and cools.

Switches are reed types where practical. There are various types of potentiometer nuts with built in rubber seals already on the market and rubber boots for switches.

Where a design has to be sealed in a container but left open (applications where a window for a camera, or meters must be visible) it is important to remove all moisture before sealing so condensate won't plague you when the temperature drops. I bake out a quantity of silica gel in a large tin, then let it cool while covered. I introduce the device to the tin and leave it 24 hours for the desiccant to soak up the moisture, then seal it using RTV silicone rubber.

Access to a vacuum oven is nice - pressure cooker adapted to withstand vacuum and a small vacuum pump will work. Great for sucking out the air and moisture from a potting project.

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In article , R75/ snipped-for-privacy@defaulter.net mentioned...

Thanks for the good advice. I've all but given up on the goop spray, as I posted in my other followup. I looked at the stuff a short while ago, and the spot under the circuit board still had not dried, and when I tipped it, it started to flow out. And the stuff that was dried was thin, not a thick covering as I had expected, as I've seen on pliers handles. At this rate, it'll take most of a can to coat just a small device like this. Most of the spray evaporated as the solvents dissipated. I think I had much better luck using hot glue, even tho it can't stand up under heat. Epoxy doesn't stick well to the metal tins, but RTV does a good job. I may end up using RTV over everything.

I might add that the standard way to waterproof flashlights is to enclose them in a metal or plastic tube, and use O-rings at every joint. This works fine, and is a reasonably cost effective way to do it. Since the device can have air inside, it might float if it has enough air. But I wasn't interested in that; just a simple quick way to waterproof. But this goop spray has wasted too much of my time already. Thanks again.

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[snip]

It shouldn't be too difficult to find some inexpensive, o-ring sealed incandescent flashlights, used or new. Just throw out the bulb/reflector assembly and install an LED array and drive circuitry on a round PCB in its place. The switch and battery housing are already taken care of for you.

Here's an interesting project: make a selectable white/red/laser pointer flashlight. Maybe throw in a xenon strobe while you're at it for MOB rescue while boating.

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Yeah, been there, done that. I converted at least 8 of the cheapo four AA cell flashlights with the rubber coated hand grip to hold 3 LEDs.

Well, why not throw in an AM/FM radio, etc... ;-)

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Don't forget the cheeze grater ;)

Tim

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In article , snipped-for-privacy@charter.net mentioned...

Righ.. I gave the open frame light another coat of spray yesterday morning, and it still wasn't dry in the evening. After all the coats, I still haven't managed to get it to fill the 2 to 3 mm void between the circuit board and the brass. I was hoping to at least get the board bedded in the goop, so that it would stay put. It's not going anywhere, but I had expected more from this spray goop, and I'm disappointed. It has not built up a coat that is thick enough to use for the grips on a pliers handle for example. It would take a week or more of sprays, with 24 hours wait between them, to build up a somewhat acceptable thickness. It's a big waste of time, IMHO.

I tried to switch the toggle switch and it was stuck. Apparently the goop managed to seep inside. I wiggled it around and got it to work, but it doesn't toggle as good as it did before. But the LEDs light up, and that's the main concern.

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