[PSUBS-MAILIST] camera

Sun Apr 12 14:07:16 EDT 2020

I am curious whether you could encapsulate a small camera in a product like this:

https://www.mgchemicals.com/products/potting-compounds/epoxy-potting-compounds/832wc-epoxy-encapsulating-potting-compound

...and still retain acceptable image clarity. Likely you would have to vacuum cure the epoxy to even have a shot.

Sean

-------- Original Message --------
On Apr. 12, 2020, 12:01, Sean T. Stevenson via Personal_Submersibles wrote:

> Tapered threads are not a good idea in brittle plastics, because it is very easy to over torque pipe thread fittings and cause the plastic to crack.
>
> I use a lot of NPT threads, but acrylics and other brittle polymers are one application in which I stick to straight threads with O-ring seals (i.e. SAE O-ring boss), or through-hole bulkhead fittings with gaskets. You might get away with NPT threads in acetal (Delrin) or HDPE, but I wouldn't expect to reliably in PMMA (acrylic).
>
> Sean
> -------- Original Message --------
> On Apr. 12, 2020, 10:37, Brian Cox via Personal_Submersibles wrote:
>
>> I was thinking about putting some pipe threads ( 1/2" npt)   into a thick piece of acrylic,  I've avoided doing this up til now but I see an application for it,  I"m worried there could be some issues with cracking the acrylic ,   does anyone have any experience doing this ?  I might be better off just drilling a hole and putting a bulkhead fitting in.
>>
>> Brian
>>
>> --- personal_submersibles at psubs.org wrote:
>>
>> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
>> To: Ian Juby via Personal_Submersibles <personal_submersibles at psubs.org>
>> Subject: Re: [PSUBS-MAILIST] camera
>> Date: Sun, 12 Apr 2020 11:54:16 +0000 (UTC)
>>
>> Hi Ian,
>> When I started playing around with LED lights and testing them for pressure resistance, I was shocked at how much pressure the electronic components can withstand.  I have tested a small LED board to 3,000 psi and it survived. This is what leads me to think a cheap backup camera can handle the pressures.  The picture quality really is not too important when you just want situational awareness.
>> If anyone want to mess with this, I am happy to pressure test one in an acrylic enclosure.
>> Hank
>>
>> On Saturday, April 11, 2020, 10:05:44 AM MDT, Ian Juby via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>> While I have not yet personally tried this (I'll be conducting experiments like this once I get my pressure test tank built, able to generate controlled hydraulic pressures), what Hank mentioned may work. This will depend entirely on the camera you intend to use. I have not been following this thread, so please forgive me if I'm speaking about things in ignorance.
>> Because lenses are involved, you'd have to be sure to get the mineral oil throughout everywhere - including in between the lenses of the camera (depending on the camera you're using). If the camera has mechanical zoom, then you won't be able to use it because there is multiple lenses which move and change position relative to each other. It would literally be like a miniature hydraulic cylinder in there, with pistons moving in opposite directions - the mechanics of the camera just wouldn't be able to do it because it's trying to fight hydraulic pressures.
>> Also, mineral oil has a different density than air or water, and so the optics will get thrown off because the lenses are designed to work in air. The index of refraction in water, oil and air are all different - which is why your eyes don't work well underwater. So the mineral oil is going to throw off the focal length of the lenses. If it's a pinhole camera, I think you might be alright, but I haven't done the math and the physics, just so you know. lol This may change in refraction may cause bizarre effects like a permanent zoom or permanent out of focus. And that's the part I haven't done the math and physics on, nor the experiments. I could be wrong on this, but I don't believe any ROV's have oil-filled camera housings, and I expect it's for these reasons.
>> However, with regards to the electronics of the camera itself, the mineral oil is an insulator (as you guys already know obviously) so there won't be electronic interference, however the hydrostatic pressure of the water is being transferred to the camera housing, which is compressing and transferring hydrostatic pressure to the camera parts through the mineral oil - including the electronics. Most electronics can withstand enormous pressures so you're probably alright. Just keep it in mind - again it depends on the camera you intend to use, and the components that camera has. You'll notice a lot of deep submersible ROV designers literally fly by the seat of their pants on this one: they just stick the electronic components they want to use into a pressure test vessel and crank the pressure until they hear something crack.  :D
>> Most microchips wind up with an air pocket inside their plastic housing, overtop the silicone chip itself. CCD's have their silicone chip surface exposed, but I'm unsure about possible air cavities behind the silicone chip. Any cavities can collapse under pressure or the liquid can leach along the leads into the plastic housing. In both cases, it probably wouldn't matter if you've immersed it all in mineral oil because it's an insulator. However, if the mineral oil gets enough hydrostatic pressure to force oil along the leads and into the air pocket inside the microchip, it can fracture the chip case when the outside pressure is removed because now the interior has excessive pressure stored up inside. Again, this may or may not cause a problem if it's immersed in oil. You might just wind up with a fully-functioning microchip that has a cracked case.
>> Lots of electronics for deep ROV's are literally just potted or painted circuitboards out in the open water and just relying on the physical strength of the components to withstand the extreme hydrostatic pressure.
>>
>> What I have seen suggested with ROV cameras though is optical-clarity potting (i.e., clear casting acrylic). Again, whether or not you could do this would depend entirely on the camera - if it's got a moveable lens, then you've got a problem because the cast plastic would lock the lens. You'd have to figure out some way of casting everything but leaving an air space around the lens portion.
>>
>> Okay, enough random thoughts for now.
>> Ian
>>
>> On Sat, Apr 11, 2020 at 11:09 AM Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>> That could be interesting  ,  the mineral oil I use is crystal clear.
>>>
>>> Brian
>>>
>>> --- personal_submersibles at psubs.org wrote:
>>>
>>> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
>>> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
>>> Subject: [PSUBS-MAILIST] camera
>>> Date: Sat, 11 Apr 2020 11:21:18 +0000 (UTC)
>>>
>>> Brian, I have thought about putting a camera in an oil filled housing like I do with my lights.  You could put the camera in an acrylic tube same as the light.  Fill with clear oil and the view would not be distorted because it is oil filled.  I am convinced the camera would take the pressure just fine.  A worthwhile experiment, because you would avoid making complicated 1atm housings.
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