Encapsulating to allow immersion in water

Other Hardware Motors, Mechanics, Power and CNC
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I have put question this under mechanical as I think this is the best location.

I will be testing some LED transmission under water, about 1m or so initially (see my question IR type remote control - using blue LEDs).

I am wary that a waterproof enclosure may leak, to mitigate and minimise risk of water damage to my circuit I propose to encapsulate all the electronics except for protruding LEDs (and maybe the top of a display.

I also want to be able to remove the encapsulant and modify the circuit.

In the past I have successfully used epoxy encapsulation for an electrometer design and for some instrumentation undergoing harsh environmental stress. These were permanent encapsulations, no way could the encapsulant be removed to modify the circuit.

I am thinking that I could wrap the circuit in a layer of plastic; cling film or a plastic bag and encapsulate in paraffin wax. Paraffin wax melts at <60C, so would not thermally stress the electronics either in the casting or the removal.

I would be interested in anyone has any experience of doing this or thoughts as to how successful it may be.

Thanks, Steve

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Then find or build a better enclosure. The easiest way to ensure no water leaks is to pressurize the air in the enclosure.
Please decide on the length of time you need under water. You can make things water resistant, but can never make something completely water proof for an extended period of time That will help you in determining what you actually need. Be aware that the greater the number of wires, etc. to the project, the greater the change of leaking. Best to have NO wires connecting your project to the rest of the world.
Consider how cameras were used in the past in under water.
Your only concern should be the exposure of the LED epoxy covering to the water. What physical design of the LED are you using?

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There are underwater camera housings... a few are not very expensive

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Hello Paul,

There will be NO wires breaking the enclosure's intergrity; IR through the clear walls and later wireless charging of the batteries.

Initially the time under water will be short - just long enough to perform my testing. But I intend to extend the time and depth significantly later. I also want to extend the idea to other items.

I am wary of leaking waterproof enclosure as I have electrical items that are purportedly water resistant and intended to be immersed - but they all seem to leak eventually and fail. :frowning:

I have a SCUBA camera, the instructions for it and other similar cameras require that the seals are cleaned fastiduiously to ensure their integrity.

I do not understand your question:

[quote="Paul_KD7HB, post:2, topic:961144"]
Your only concern should be the exposure of the LED epoxy covering to the water. What physical design of the LED are you using?
[/quote] Please elucidate. I am using 5mm LEDs.

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I have one with a camera in it.

Its form is not great for what I want to do and as I said to Paul,

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I can't be bothered, I photograph walrus instead. :slight_smile:
But seriously, consider, it's a sign that any underwater enclosure will be like that.

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Exactly, which is why I am considering encapsulation, so there are no joints to be concerend about for leaks.

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Have you verified that your IR will pass the plastic?
There are many types of LED encapsulation. Some are completely flat and surface mounted. Others are epoxy enclosed with lenses as part of the epoxy covering. Others are similar, but flat on the end.

Do not combine the terms water resistant and water proof. I am sure you already know the difference. Most things marked as water proof are in reality water resistant. Potting compounds advertised as being water proof are in reality just very water resistant.
Have you considered the heat generated by your LEDs? I am sure you have.
Good luck.
Paul

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Yes, those nice people at Hammond advised me. I was surprised that Polycarbonate allows IR transmission. I did a very simple test using my mobile phone's camera and a TV remote control.

5mm domed.

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If I use paraffin wax (candle wax) then I know that is impervious to water. One aspect I am wholly unsure of, is whether the wax will adhere to the components. Or will it permit water to creep underneath the wax and therefore allow corrosion or electrical degradation; i.e shorting.

Not explicitly. There is no spec for the IR LED (they were low cost, £1.20 for 100) . Working on an assumption that a TV type remote control puts 10mA to 20mA through an LED, the power dissipation is very low, 15mW to 30mW. Even if I drive 100mA the instantaneous power is <150mW. I will have a low mark-space ratio, so I do not expect much heat to be generated.

Thank you for all your thoughts, Paul :slight_smile:

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The power dissipation is low because the duty cycle is low. But the current when on is quite high.
Are your IR LEDs clear or black? I have discovered that my trail cameras which use IR LEDs for night photos actually show red for an instant before they switch to IR. That is why most of the IR LEDs you see are black, so the initial red light is not allowed to pass to the outside.

Finally, the only heat sinking for normal LEDs is through their wire leads. Be sure to allow for that in your design.
Good luck,
Paul

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