Does anyone have any suggestions on what to encapsulate these with? So far I'm looking at http://www.mgchemicals.com/products...ar-epoxy-encapsulating-potting-compound-8322/ These will be under water.
Encapsulating ?
- Thread starter mnm99
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mds82
Enlightened
If you don't mix the 2 party epoxy correctly it might not dry correct and then you just ruined your entire project. an o-ring and a glass cover might be safer.
I would love to do that. I'm trying how to figure that out. I don't have a machine shop. Still researching.... I also bought small 22mm domes for my 12 watt Luxeon M's. I don't know what i want to do with that also yet. Maybe I do a test pot on scrap first.
Steve K
Flashlight Enthusiast
I would plan for a few failures before you get to something that works.
There are other sources for encapsulants. Some suppliers that I'm familiar with are:
http://www.ellsworth.com/Encapsulants/Epoxy/
http://www.masterbond.com/
you might also check with distributors such as Digi-key, Mouser, Newark Electronics, Allied Electronics... they might carry a wider variety of products.
I've worked with conventional potting/encapsulants, and learned that keeping moisture out isn't easy. Getting the potting to bond to the walls of the housing, the electronic components, and any wires going through the potting can be a huge challenge. While the potting may initially stick to the other stuff, a number of thermal cycles can pull it away, creating capillary paths between the potting and walls or wires. Water will creep through these paths and cause corrosion that could cause a failure months later.
Proper preparation of the surfaces of the wall or wires can be tricky and require careful attention. I've been amazed at what I've seen done to prepare a molded plastic part to get it to bond to potting. It was well beyond what a hobbyist could do. I suspect that the potting/encapsulant supplier can provide info on the techniques required to properly prep the surface for your housing.
There are other sources for encapsulants. Some suppliers that I'm familiar with are:
http://www.ellsworth.com/Encapsulants/Epoxy/
http://www.masterbond.com/
you might also check with distributors such as Digi-key, Mouser, Newark Electronics, Allied Electronics... they might carry a wider variety of products.
I've worked with conventional potting/encapsulants, and learned that keeping moisture out isn't easy. Getting the potting to bond to the walls of the housing, the electronic components, and any wires going through the potting can be a huge challenge. While the potting may initially stick to the other stuff, a number of thermal cycles can pull it away, creating capillary paths between the potting and walls or wires. Water will creep through these paths and cause corrosion that could cause a failure months later.
Proper preparation of the surfaces of the wall or wires can be tricky and require careful attention. I've been amazed at what I've seen done to prepare a molded plastic part to get it to bond to potting. It was well beyond what a hobbyist could do. I suspect that the potting/encapsulant supplier can provide info on the techniques required to properly prep the surface for your housing.
DIWdiver
Flashlight Enthusiast
I'd say that material looks good. Several important characteristics, it has all of them:
simple to mix
optically clear
designed for electronics (shown being poured over LEDs!)
excellent resistance to salt water
Assuming the back side is sealed to the transom, and the wires come out there, into a 'dry' area, the encapsulant only has to seal to the aluminum.
Speaking of wire, it's almost impossible to prevent water travelling down the inside of the wire. Many dive lights have had double floods where the head leaks and water travels through the cord to the battery pack, or vice versa. It's very important to keep the insulation intact and the ends dry.
simple to mix
optically clear
designed for electronics (shown being poured over LEDs!)
excellent resistance to salt water
Assuming the back side is sealed to the transom, and the wires come out there, into a 'dry' area, the encapsulant only has to seal to the aluminum.
Speaking of wire, it's almost impossible to prevent water travelling down the inside of the wire. Many dive lights have had double floods where the head leaks and water travels through the cord to the battery pack, or vice versa. It's very important to keep the insulation intact and the ends dry.
Have you ever tried silicon sealant inside heat shrink to seal the cable ends?
Not sure if it would work, just an idea, you may have already tried it, not anywhere near my field of expertise.
Norm
Steve K
Flashlight Enthusiast
I've used that in some products at work. It's been a while, but IIRC it was called "sealed wire". There was a "blob" of silicone sealant every few inches. It did work well. I had seen some of our designs where water wicked up the strands and caused corrosion on the circuit board. I think we got our sealed wire from Judd. http://www.juddwire.com/
I ordered a few IP connectors, but I don't think they will work due to size. If I drill a tight hole to run the wire in and encapsulate it do you think water will get into the lights around the wire? I'm not sure how good the encapsulations work. If you look at Loomis design it looks like he just ran the wires in the housing then encapsulated everything. Click on the light and look close. Also is he using just a large block of aluminum for a heat sink?
https://loomisled.com/shop/2-24-led-flush-mount-boat-transom-lights-12-14-5-vdc-charging-battery/
https://loomisled.com/shop/2-24-led-flush-mount-boat-transom-lights-12-14-5-vdc-charging-battery/
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What do you think LoomisLED did for sealing the water out? It looks like the leds are encapsulated and that's it. The wire just runs down the side.
I picked up some of this yesterday. http://www.mgchemicals.com/products...ar-epoxy-encapsulating-potting-compound-8322/ It was over $100 a qt so I hope it seals good.
Steve K
Flashlight Enthusiast
when I look at that picture, the thing that grabs my attention is that the LEDs and wires are all hand soldered together. Is this built in someone's basement?? ... by someone who never heard of a circuit board?
I don't suppose there is a photo showing where the wires exit the housing? It would be interesting to see how they get the wires out. A gland, perhaps? Or is it just a hole, and they pour the potting in through that hole?
Regarding the price of $100 per quart for the encapsulant... I'm not surprised. Potting is always expensive, at least when I've checked prices. Making a housing that is fully sealed can be pricey too, so it's not easy to decide which is easier and more cost effective.
edit: when I go to the LoomisLED web page for this light, I do get the feeling that these guys don't really know what they are doing.
http://loomisled.com/shop/2-24-led-flush-mount-boat-transom-lights-12-14-5-vdc-charging-battery/
The housing is made of PVC, so there's no obvious way to get the heat out. Their description of the heatsinking is:
"The leds are embedded in a crystal clear waterproof epoxy and heat sinked to a large block of aluminum surrounded by pvc with an acrylic window and military spec silver coated Teflon wire"
The large block of aluminum must be that gray slab that the LEDs are sitting on. Do the designers understand that if the aluminum doesn't have a way to get the heat out of the housing, then all that the aluminum is doing is ensuring that all of the LEDs will be at the same temperature as they overheat?
Just amazing... my impression is that they have no idea of what they are doing. How long have these designs been in production?
I don't suppose there is a photo showing where the wires exit the housing? It would be interesting to see how they get the wires out. A gland, perhaps? Or is it just a hole, and they pour the potting in through that hole?
Regarding the price of $100 per quart for the encapsulant... I'm not surprised. Potting is always expensive, at least when I've checked prices. Making a housing that is fully sealed can be pricey too, so it's not easy to decide which is easier and more cost effective.
edit: when I go to the LoomisLED web page for this light, I do get the feeling that these guys don't really know what they are doing.
http://loomisled.com/shop/2-24-led-flush-mount-boat-transom-lights-12-14-5-vdc-charging-battery/
The housing is made of PVC, so there's no obvious way to get the heat out. Their description of the heatsinking is:
"The leds are embedded in a crystal clear waterproof epoxy and heat sinked to a large block of aluminum surrounded by pvc with an acrylic window and military spec silver coated Teflon wire"
The large block of aluminum must be that gray slab that the LEDs are sitting on. Do the designers understand that if the aluminum doesn't have a way to get the heat out of the housing, then all that the aluminum is doing is ensuring that all of the LEDs will be at the same temperature as they overheat?
Just amazing... my impression is that they have no idea of what they are doing. How long have these designs been in production?
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Two problems, one that this epoxy is very hard. Because of that it both stresses the LEDs, and does not move at all when the wires move (or their exteriors shrink/expand ).
It will bond very good to some things and not to others. Watch the wire type you use. You will want marine wire ... Make sure this bonds to it. Epoxy is good, but lots of stuff it does not bond too including many plastics.
It will bond very good to some things and not to others. Watch the wire type you use. You will want marine wire ... Make sure this bonds to it. Epoxy is good, but lots of stuff it does not bond too including many plastics.
Steve K
Flashlight Enthusiast
a couple of observations about the photo of the LoomisLED light..
1. do I see bubbles in the encapsulant? This is a common issue when potting electronics. Getting rid of the bubbles is a bit of an art. I've seen cases where the device was placed on a vibrating platform after pouring the potting, with the idea that this would shake the bubbles loose. I've also seen cases where a vacuum was drawn.... it's not clear to me why that would knock the bubble loose. The air is already under pressure from the potting.... does slightly reducing the pressure above the potting make much difference?
2. The gray stuff under the LEDs may be an adhesive thermal pad, and the plate that everything is mounted to could be aluminum. The thermal pad just makes it harder to get heat from the LED to the aluminum, but the large aluminum disc would have a better chance of getting some heat transferred through the PVC housing. Regardless... there are 24 LEDs tightly packed, and presumably they are all dissipating close to 3 watts. Let's just say at least 50 watts is dissipated... that's a lot of heat to get out of a thick plastic housing. I'd love to see some temperature measurements of that aluminum plate.
1. do I see bubbles in the encapsulant? This is a common issue when potting electronics. Getting rid of the bubbles is a bit of an art. I've seen cases where the device was placed on a vibrating platform after pouring the potting, with the idea that this would shake the bubbles loose. I've also seen cases where a vacuum was drawn.... it's not clear to me why that would knock the bubble loose. The air is already under pressure from the potting.... does slightly reducing the pressure above the potting make much difference?
2. The gray stuff under the LEDs may be an adhesive thermal pad, and the plate that everything is mounted to could be aluminum. The thermal pad just makes it harder to get heat from the LED to the aluminum, but the large aluminum disc would have a better chance of getting some heat transferred through the PVC housing. Regardless... there are 24 LEDs tightly packed, and presumably they are all dissipating close to 3 watts. Let's just say at least 50 watts is dissipated... that's a lot of heat to get out of a thick plastic housing. I'd love to see some temperature measurements of that aluminum plate.
Thanks for your input. The potting compound was cheap compared to Masterbond. I called this morning and was told they don't sell to the public and there product was $600 an ounce! wow. I guess he is trying to remove the heat out of the back being that it is open to the water. I'm no engineer , but like to figure things out. My design I was figuring would dissipate heat better, but I don't like the aluminum exposure to the salt water all that much. I was going to try the same thing, but using (4) 12w led's or only 12 of the 3w. What would you suggest on the heat sinking?
Not to gang up on the OP, but I agree with you Steve. I too noticed things such as: no ESD precautions, poor quality solder joints, difficult design, and poor implementation.
To put a positive spin back on this thread. All the issues can be corrected by listening to those the OP asked for help and maybe taking a mechanical design class and getting a soldering certification.
No one can do it all. That's why even small business hire professionals.
I appreciate you input. This is a small project I was going to take on. If I had time I would take classes if I could. If I'm in over my head I may stop here buying materials now. I'm only around $150 into it. Considering Transom lights go for $500 and up I wanted to take a shot. Does my design look any better? One of my problems is getting the wire in the housing without leaking. The smallest IP fitting won't fit.
Oh give me a break.
The thermal design method is good. With water passing over the aluminum behind the LEDs, it's going to run cool.
Soldering could be better ... Sure, but a course? ... How about just practice ...and smaller wire that's easy to work with. Worst issue is usually not enough heat not from using too much.
Complicated ... A bit but who cares its a one off not a production model.
Real issue is maintaining the seal around the wires. If this is transom mounted you may be better with a compression fit tube of welded tube from the front through the back and through the transom.
Keep plugging.
Steve K
Flashlight Enthusiast
well, my comments were regarding the LoomisLED, and their website says that the housing is completely PVC. They don't have any aluminum anywhere near the water. It does reduce concerns about corrosion, but with a distinct reduction in heat transfer.
For the OP's design, I like the idea of an aluminum housing that the LEDs get mounted to. It would require some very robust paint or other treatment, and I don't know anything about that stuff. Maybe some epoxy based paint?
Steve K
Flashlight Enthusiast
I've seen electronics that were designed to be continuously submerged, and one of them did pot the electronics and simply run the wires directly out of the potting. Two factors were important in making the design successful... one was that they knew how to treat the wire insulation to get the potting to stick to it. The other was to have a long length of wire in the potting between the electronics and the point where the wires exited the potting. Even if the wires did pull away from the potting in some places, it was unlikely to do this over the whole length of potted wire.
Teflon insulation seems like the worst thing to try to get potting to stick to, though (just my guess). The potting manufacturer should be able to comment on this, as well as recommend wire insulation and/or any processes that improve the bonding between the potting and the insulation. This is an issue that manufacturers struggle with constantly (based on my experience), so be prepared to do a lot of research, run a bunch of experiments, and be prepared for a number of failures. This should be cheaper than giving refunds to all of your customers after their lights leak after 12 months of use.
