Potting compound for building a tank light

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tvizk
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Potting compound for building a tank light

I’m building a Convoy M1 with Luxeon MZ and a FET driver and I’m thinking of potting it as well to make it a tank light. I’ve also been reading a lot on BLF about potting compounds but a lot of the posts are a couple years back. My question is what potting compound would be good for this? My main reason of potting is just for durability, not so much for heatsinking, although that would be a plus. I know most would mix some epoxy with silicon carbide powder but I would prefer it without since I’m not from the US and shipping would be a pain. Are there any alternatives or can I just pot with bare epoxy?

Lightbringer
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You have a tank!?

Wheredya park it overnight?

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

tvizk
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Lightbringer wrote:
You have a tank!?

Wheredya park it overnight?

Right in front of my house facing my neighbor.

Jtm94
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If I remember correctly you want to avoid acetic acid because it can react poorly with components on the driver, but other than that I know very little about what’s usable and what isn’t Sad

tvizk
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Jtm94 wrote:
If I remember correctly you want to avoid acetic acid because it can react poorly with components on the driver, but other than that I know very little about what’s usable and what isn’t Sad

Yes, I’ve read about that. It’s mostly because that would corrode the components from what I’ve read. I’ve seen most posts about potting and many are mainly doing it for heatsinking to drive their lights harder but non talk about potting for durability. Those that do never show or talk about the process of potting. Sad

everydaysurvivalgear
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What about using hot glue?

I used it on a bunch of those solar outdoors lights to keep out water.

Macka17
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Hi.
I’ve done a couple of my torches and it seems to work.

Hardware Store. “ Ceramic Epoxy”. It’s white. Comes in a 2 x tube mixer. and takes a few hrs to set. NOT a 5 min mixture. I add enuff to cover base driver and partially UP the components, Not fully cover them. You won’t get them out again It’s PERMANENT.. but you can see if you’ve cooked them etc. I did an original old C8 with Q5 chip in there first. then threw it against a brick wall and onto the ground half a doz times. Well dented. and cracked glass. But the light still worked incl the switching. L.M.H.Flash. etc. So Potting seems to give more electrical stability.
tvizk
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everydaysurvivalgear wrote:
What about using hot glue?

I used it on a bunch of those solar outdoors lights to keep out water.

I’m quite sure that’s not going to do it. Hot glue melts at a fairly low temp and it’s going to melt when the light is on for long periods of time.

Macka17
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Above.. YEP….

Tried on a $2.50 Speshul yrs ago.
everydaysurvivalgear
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Macka17 wrote:
Hi.
I’ve done a couple of my torches and it seems to work. Hardware Store. “ Ceramic Epoxy”. It’s white. Comes in a 2 x tube mixer. and takes a few hrs to set. NOT a 5 min mixture. I add enuff to cover base driver and partially UP the components, Not fully cover them. You won’t get them out again It’s PERMANENT.. but you can see if you’ve cooked them etc. I did an original old C8 with Q5 chip in there first. then threw it against a brick wall and onto the ground half a doz times. Well dented. and cracked glass. But the light still worked incl the switching. L.M.H.Flash. etc. So Potting seems to give more electrical stability.

Even without potting mix a 7135 driver will take a beating no issues. It has nothing to big sticking out to break of. You see the most issue with boost and buck drivers.

tvizk
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Macka17 wrote:
Hi.
I’ve done a couple of my torches and it seems to work. Hardware Store. “ Ceramic Epoxy”. It’s white. Comes in a 2 x tube mixer. and takes a few hrs to set. NOT a 5 min mixture. I add enuff to cover base driver and partially UP the components, Not fully cover them. You won’t get them out again It’s PERMANENT.. but you can see if you’ve cooked them etc. I did an original old C8 with Q5 chip in there first. then threw it against a brick wall and onto the ground half a doz times. Well dented. and cracked glass. But the light still worked incl the switching. L.M.H.Flash. etc. So Potting seems to give more electrical stability.

Hmm, thanks for the info. I’ll try to look for that. I’ve seen the abuse the PFlexPro lights take and was inspired to make one myself. Would be nice if it could be used on a 12 gauge once potted. It’s always much more satisfying when you have something you built.

everydaysurvivalgear
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tvizk wrote:
everydaysurvivalgear wrote:
What about using hot glue?

I used it on a bunch of those solar outdoors lights to keep out water.

I’m quite sure that’s not going to do it. Hot glue melts at a fairly low temp and it’s going to melt when the light is on for long periods of time.

You can get low / high temp glue. I think the low temp melts at around 80 degrees Celsius shouldn’t be much of an issue?

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Macka17 wrote:
Hi.
I’ve done a couple of my torches and it seems to work. Hardware Store. “ Ceramic Epoxy”. It’s white. Comes in a 2 x tube mixer. and takes a few hrs to set. NOT a 5 min mixture. I add enuff to cover base driver and partially UP the components, Not fully cover them. You won’t get them out again It’s PERMANENT.. but you can see if you’ve cooked them etc. I did an original old C8 with Q5 chip in there first. then threw it against a brick wall and onto the ground half a doz times. Well dented. and cracked glass. But the light still worked incl the switching. L.M.H.Flash. etc. So Potting seems to give more electrical stability.

Macka17, the only thing that’s really popping out in my search is porcelain chip repair 2-part epoxy, does that sound right?
I’d be fine just putting some JB Weld or any old 2-part on there but I don’t have the depth of knowledge a lot of these folks have and you’ve actually used this with no ill effects.
Somebody was talking about acid or something eating away at components and then I realize this is beyond my scope.
I’d hate to click the switch when I really needed some light and get nothing!
I once dropped a light, it quit working, something rattling around inside. Potting is a great option if possible.

tvizk
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Also, I wonder if some epoxy putty like waterweld would work? It would be much easier to work with since it doesn’t flow.

Macka17
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YEP. Bought to repair a china thingy of Missus’s Grandma. 7 pieces. fitted purrfect.

SHHH. Does good job, She ain’t noticed it yet. Over 150 yrs old luckily the breaks occurred between the glazed colouring so All white and blending.

I use it on boards to locate and stabilise all the little bits and their solder.
No Shaking loose or dry joint tricks.
Rather than protecting the internals of individual parts.

Agro
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I would recommend simply silicone thermal glue. Not as tough against direct damage as epoxy, but still pretty tough and inside the light there should be no difference.
Thermally it should be better.
And if you screw something up or some component blows – you can remove it.

tvizk
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Agro wrote:
I would recommend simply silicone thermal glue. Not as tough against direct damage as epoxy, but still pretty tough and inside the light there should be no difference. Thermally it should be better. And if you screw something up or some component blows – you can remove it.

Do you have any brand to recommend? Might be a dumb question but it will cure like silicone and not so much like caulk right? I might get some Fujik to try.

Enderman
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I don’t know about any brands but I would recommend something that’s not just for waterproofing but also thermally conductive because there will be no air touching your components, so you need the potting compound to move heat away rather than insulate it.

Agro
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tvizk wrote:
Agro wrote:
I would recommend simply silicone thermal glue. Not as tough against direct damage as epoxy, but still pretty tough and inside the light there should be no difference. Thermally it should be better. And if you screw something up or some component blows – you can remove it.

Do you have any brand to recommend? Might be a dumb question but it will cure like silicone and not so much like caulk right? I might get some Fujik to try.


No. I have Kafuter K-5024K and don’t recommend it because it separated into fractions, one white and thick and the other watery and translucent. I mix it up a bit before application and it works for me, but that’s not how it should work. I’ve seem many people recommend Fujik.
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Enderman wrote:
I don’t know about any brands but I would recommend something that’s not just for waterproofing but also thermally conductive because there will be no air touching your components, so you need the potting compound to move heat away rather than insulate it.

Isn’t air a thermal insulator already?

Tom Tom
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Oh dear, has it never occurred to you to search for “potting compound” ?

The proper stuff for the job.

Now, if you live in the UK, you can have almost anything available, in a couple of days, because we still do serious electronics here, and have a robust supply chain (for now).

E.g. https://uk.rs-online.com/web/c/adhesives-sealants-tapes/adhesives-glues/...

If you want to try to bodge things up with totally unsuitable “cheap” (not actually, when they fail) materials, maybe from a DIY warehouse, particularly any cheap silicones (more thermal insulator than conductor) that smell of vinegar and will corrode everything, eventually, well, you’ve got it wrong.

The thing is, that mixing up a batch of a good potting compound, even in a small sachet, is expensive, and you had better be prepared to use it wisely, which means more than just one hobby experiment. If this interests you, then you will need to do your own research, choose the materials that work for you, are available, and that you can afford (i.e. not only delivered in 1Kg tubs MOQ, like the professional ones).

Develop your own methods, experiment, don’t expect to get it right first time, or have your hand held.

Edit: did I also mention time and temperature ? Fundamental.

And it is mostly unnecessary, except for those of us who have an application for an assembly that can survive extreme G-force, repeatedly. Some do, and will pay for that assurance.

Jack Kellar
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Tom Tom wrote:
And it is mostly unnecessary, except for those of us who have an application for an assembly that can survive extreme G-force, repeatedly. Some do, and will pay for that assurance.

Pretty sure the OP wants to use his torch as a shotgun light, so extreme G-force survival is necessary for him.

tvizk
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Tom Tom wrote:
Oh dear, has it never occurred to you to search for “potting compound” ?

I wouldn’t be asking if I actually found an answer. I live in SEA, which means it’s way harder to look for things like this and most of the time the only way is to ship from China since shipping from Euro or US is a pain. I’ve dug up all the old BLF posts as well about potting and non of them talk about making a light durable and most of them talk about heatsinking so I wanted to make sure.

Tom Tom wrote:
mixing up a batch of a good potting compound, even in a small sachet, is expensive

Yes, I do know that real potting compounds are pricey, which is also one of the main reason why I’m asking as well.

Tom Tom wrote:
And it is mostly unnecessary, except for those of us who have an application for an assembly that can survive extreme G-force, repeatedly.

Well, I would want to use it as a weapon light if it worked, so..

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I live in SEA Question
It would a little help, if you can tell us in which country do yo live.

In generall any epoxy glue without reinforcement particles should do the job.
I potted a lot uf switched buck/boost drivers with frequency up to 1.2MHz! without problems.

Today I buy epoxy for large jobs per kg, since its a fraction in price. (25 – 30 usd/kg)

Jack Kellar
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SEA = SouthEast Australia?

Macka17
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True.
With Marine epoxy being slightly flexible in relation to rigid/crackable in extremes STD Epoxy blends.
We used to “stiffen” it up with Talcum powder to give it some body, and just watered down with 50/50% thinners for soaking in before top layers.
(I had 2 x Timber yachts.)
Preserving carved Teak and Mahogany mainly.

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tvizk wrote:
Well, I would want to use it as a weapon light if it worked, so..

I’ll have a think about this. What do you actually have available ? I have no idea about what is common in SEA ?

You need to be looking at either elastomer’s that set (electronic materials mostly).

Or rigid stuff like acrylic and epoxy resins with fillers (boat building). Which, I would not recommend as a starting point, if heavy recoil is involved.

Don’t touch the silicone RTVs unless they are really good ones. Dow Corning etc. Not tubes from the DIY warehouse.

tvizk
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Most of the hardware stores here carry mostly chinese stuff or stuff from the US (local Ace Hardware) which is not going to be cheap, obviously. So I just mostly depend on chinese sites like banggood, aliexpress and the others. I found some Arctic Alumina thermal adhesive locally but holy shit it costs USD$45 for 5g.

I just ordered some Fujik to try it out though so I’ll see how it goes when it’s here.

EDIT: Just for some context on why I keep saying it’s hard to find things here, I used to do some work that requires the material and hardware be imported from the US, which is the only place available. Heck, even painter’s tape is a god damn hassle to look for. Yea, painter’s tape. My local Ace Hardware sells that for USD$20.

tvizk
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Macka17 wrote:
True. With Marine epoxy being slightly flexible in relation to rigid/crackable in extremes STD Epoxy blends. We used to “stiffen” it up with Talcum powder to give it some body, and just watered down with 50/50% thinners for soaking in before top layers. (I had 2 x Timber yachts.) Preserving carved Teak and Mahogany mainly.

Honestly, I’m not very confident in using epoxy or waterweld to pot the M1 that I’m going to build since I have a feeling it’s going to get pretty hot with the Luxeon MZ on a FET driver and also bypassed springs. Just worried I’ll insulate the thermal path. I can probably try that in another light I have to see how well it works though.

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If you’re thinking about using a silicone-based material, put a little on a piece of cardboard and see if you can smell vinegar (also known as acetic acid). If you smell vinegar, don’t use it, it’ll corrode your electronics.

A lot of the cheap silicones produce acetic acid as a by-product when curing. That’s especially true for the ones you’ll see in a DIY store.

There are better silicones that produce non-corrosive by-products like alcohol or acetone, but you’d need to make sure they didn’t come in contact with anything that might be susceptible to degrading or dissolving in those solvents. Not usually a problem with electronic stuff, but just so you know.

I’ve never potted anything, so unfortunately I can’t recommend any particular potting material to use. I just wanted to add some detail on the silicone possibility.

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Jack Kellar wrote:
Enderman wrote:
I don’t know about any brands but I would recommend something that’s not just for waterproofing but also thermally conductive because there will be no air touching your components, so you need the potting compound to move heat away rather than insulate it.

Isn’t air a thermal insulator already?

It’s a fluid though so it cools by convection.
Air will keep components on a pcb much cooler than covering them with some non-conductive plastic or material.

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