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Simple ROV waterproof cameras

3 attempts to build simple and cheap waterproof ROV cameras

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I tried to build three different camera. The camera hardware was essentially the same, but the waterproofing was different:

1. Marine grade heat shrink tubing
2. Waterproof flashlight
3. Waterproof GoPro case.

I wanted to see if I could build a simple, waterproofed, composite video camera which could be used in ROV competitions like MATE. The camera components need to be easy to acquire, cheap to buy, and simple to put together. I particularly wanted to look at using higher-resolution imaging than found on a "standard" waterproof car backup cameras common at competitions.

I came up with this design. It consists of a FPV composite video camera (populate for drone flying), and a video balun to convert the output of the camera to a balanced signal we can transmit over normal wires (no coax required).

The tricky bit is sealing the electronics from the water.

Design 1: My first design encased all the electronics in marine grade heat shrink tubing, but this design didn't seal well enough. [Fail]

Design 2: The second design uses a pre-purchased waterproof flashlight which has been hollowed out and the camera installed. [Success]

Design 3: The third design uses a pre-purchased waterproof GoPro case. Instead of putting a GoPro inside, I put the video camera. [Success]

Files:

Camera mount designs: http://bit.ly/2drxVC4

GoPro Mount.stl

GoPro camera mount

Standard Tesselated Geometry - 26.25 kB - 09/28/2016 at 20:43

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Flashlight Mount.stl

Flashlight camera mount

Standard Tesselated Geometry - 22.74 kB - 09/28/2016 at 20:42

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View all 8 components

  • Design 3: Camera mounting

    Tim Wilkinson09/28/2016 at 20:37 0 comments

    Mounting the camera in the GoPro box is a little trickier. The easiest solution was to 3d print a mount which fits snuggly inside the box and has a hole to mount the camera. The design is here http://bit.ly/2drxVC4.

    The design has legs to stabilize the mount inside the box and keep the lens a fixed distance from the box surface.

    Here is the final result with the camera and video balun inside the GoPro box.


  • Design 3: Overnight water test

    Tim Wilkinson09/28/2016 at 16:35 0 comments

    Unfortunately the GoPro case is just a tiny bit big to go into the 10ft pool, so I had to put it in the hot tub - only about 2ft deep. Overnight the case maintained its integrity with >1000 MOhm resistance.

  • Design 3: Cheap GoPro case

    Tim Wilkinson09/28/2016 at 01:57 0 comments

    When I was looking for waterproof cases I bought two: a waterproof flashlight and a cheap GoPro waterproof case (about $15). With the success of Design 2 (flashlight), it's time to try out Design 3.

    The GoPro case is a rather splendid little transparent cube, with enough space inside to accommodate the camera and the video balun. The case unclips making the internals easy to access. There are a couple of waterproofed buttons which are used to trigger a GoPro camera ... if one were inside, and by removing one of these I was able to pass the 4-wire tether from outside to in. I had originally feared I would have to drill the case but this was better.

    Unfortunately this hole was far too small to accommodate a waterproof gland (as I'd used in the flashlight design), but the cable still needed to be waterproofed. As much as I wanted to avoid it, I used Marine Epoxy to fill the space around the wire on the outside of the case, and so make a waterproof (but permanent) seal.

    The design of the case made this sealing very simple - the hole allowing the wires into the case was small enough for 4 wires but no so big to allows the epoxy to drip in, and the outside of the case had a circular wall while held the epoxy on the outside making a good seal. It wasn't design for this, but it really couldn't have been better.

    Once this is dry, it will go into the water for a first test.

  • Design 2: Mounting the camera in the tube

    Tim Wilkinson09/27/2016 at 19:24 0 comments

    For the Design 2 build, I decided not to put the camera in the tub until I'd completed all the underwater tests (in an attempt to not break the camera this time). That done, I now needed to mount the camera. To do this I laser cut (I'm useless with a scalpel) two circular mounts out of card stock (designs are here: http://bit.ly/2drxVC4)

    The camera is screwed into the center of the discs, the outer sits on the lip of the tube.

    When the top is screwed back on, the camera is held in place.

    Now back into the pool to make sure the the seals are still good.

  • A little glue

    Tim Wilkinson09/27/2016 at 19:11 0 comments

    As an aside to this camera build I've found that the wires, soldered to the camera PCB, are very fragile and easily break-off. I suggest applying a little glue (I used gel superglue) to provide better strain relief.

  • Design 2: Three days later

    Tim Wilkinson09/27/2016 at 01:24 0 comments

    I've been out of town, but I left the camera in its 10' pool while I was away. Three days later, and the megohm meter reads > 1000 MOhms. I'm happy.

  • Design 2: Morning check

    Tim Wilkinson09/23/2016 at 16:56 0 comments

    A quick check of the camera this morning and the megohm meter is still reading > 1000 MOhms - looks like all the seals are good!

  • Design 2: Waterproof flashlight

    Tim Wilkinson09/23/2016 at 06:04 0 comments

    The electronics of this design appear sound, but the first design failed at depth to keep the water out. So, on to design two.

    A commenter suggested I look at converting a waterproof flashlight to contain the camera, and this seems like a fabulous idea. Waterproof flashlight are cheap on eBay, but there's always a questions of how "waterproof" they really are. Are some searching I found a $10 flashlight rated to 80ft on Amazon (https://smile.amazon.com/Flashlight-Flashlights-Submarine-Waterproof-Underwater/dp/B01K6K69R6).

    The internals are easily removed; I just needed to get the cabling into it without ruining the waterproof seal.

    I'm attempting to do this without potting or epoxy, so I chose to use a cheap cable gland. I drilled a hole in the base of the tube

    And inserted the gland and wires

    At this point it became obvious that this wiring was not going to work. In Design 1 I had water wicking between the wires and into the camera. This design would suffer the same problem. Time to change the wiring.

    This time I used some cheap 4-core phone cable. This has an outer shield which would waterproof the internal wires and provide a single surface for the cable gland to grip. However, there was a mismatch between the diameter of the wire the size of the cable gland (an M12 - the smallest I had). To fix this I used some 1/4" marine heat shrink tubing to thicken the wire where it entered the gland.

    And here's the final assembly

    Visually the seal looks good.

    Back in the 10ft water tube and the megohm meter showed a resistance >1000 MOhms. Now to leave it overnight and test tomorrow.

  • Overnight failure

    Tim Wilkinson09/20/2016 at 18:46 0 comments

    I tested the camera after it had been immersed in the 10' pool overnight, and it still works. However, the megohm meter now reads < 10MOhms which is an electrical failure. So where's the problem? In turns out that the front of the camera is not seal as well as it could be - in fact that's kind of obvious from the photos when you look at them. I needed to find a better, but simple, way to seal this part.

  • Electrical testing: Megaohms

    Tim Wilkinson09/20/2016 at 05:33 0 comments

    The final test for the camera is to make sure it's electrically insulated. Of course, if it's waterproof it should also be electrically insulated; but there are degrees to which that might be true. Just as waterproofing is only good to a certain depth, insulation can be measured.

    It's difficult to know a good measure of insulation but >100 Mega Ohms is suggested as as a lower limit. To test this I used a Supco M500 Insulation Tester (megohmmeter). With the camera submerged, I connected one lead to the positive power cable at the end of my cables, and put the other connectors in the water. My meter measured the resistance as > 1000 Mega Ohms; 10x the lowest acceptable level.

    Success!

    It's worth noting that if this test had failed in a significant way, the camera electronics would likely be fried. But then, if this test had failed, the electronics would eventually get wet and fry anyway.

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Discussions

SuperSexyTime wrote 09/26/2019 at 13:45 point

Hello Tim, we need some assistance with the wiring on the go-pro mount camera.    

  Are you sure? yes | no

Mark Farver wrote 09/20/2016 at 22:28 point

Why not let someone else solve the issue?  Waterproof flashlights sell for as little as $4 US.  Remove the light, drill a hole for the cable and install camera.   Or if that is too expensive, maybe a plastic bottle?  If you don't want to use glue or silicon for the cable exit look for "gland nuts" which serve as both a strain relief and water proofing

https://www.aliexpress.com/item/CREE-Q5-1200-Lumens-Aluminum-alloy-Cree-led-Torch-Zoomable-Cree-Waterproof-LED-Flashlight-Torch-Light/32531688306.html

https://www.aliexpress.com/item/10-Pcs-Plastic-PG9-Waterproof-Cable-Stuffing-Glands-Connectors-With-Lock-nuts/32693485764.html?

  Are you sure? yes | no

Tim Wilkinson wrote 09/20/2016 at 23:17 point

I like that idea a lot. Looking at various waterproof flashlights I do wonder how many are actually waterproof rather than water resistant. I'm going to hunt down a cheap diving light and see if that can be used. Thanks.

  Are you sure? yes | no

jlbrian7 wrote 09/23/2016 at 18:23 point

 This would probably work at the depths you are talking about.  http://www.pelicancasesforless.com/p-12240-pelican-2010-sabrelite-led-flashlight.aspx?gclid=Cj0KEQjwpZO_BRDym6K_nMye7cEBEiQAVA7RaNKuXv0yJ0hJzwcxFROIjJIG-0q896Pa6amMF46Ea54aAgMk8P8HAQ.  

And if you want I can post a picture of the dive camera's we used in the gulf, but this is what was inside. 

https://www.amazon.com/Kingmak-800TVL-Bullet-Outdoor-Weatherproof/dp/B01CFYA3M8/ref=sr_1_3?ie=UTF8&qid=1474654838&sr=8-3&keywords=small+bullet+camera

Just wrap black electric tape around it so that it fits snuggly in the enclosure.

Also, we would send 24v down the line, and use an lm7812 inside the enclosure to bring the voltage down.  I never saw a problem with the video going through over 300' of tether coming back either.

You can also put a healthy coating of rtv around the cable gland where it mates with the housing, and that will be compliant enough to let you make repairs if necessary, but if you want something more permanent, then you shouldn't have any trouble with this https://www.google.com/search?q=scotchcast+splice+kit&safe=off&source=univ&tbm=shop&tbo=u&sa=X&ved=0ahUKEwjHhLbrj6bPAhXBwj4KHe8jCokQsxgIHg&biw=1280&bih=918#spd=3119971423440707056, other than the mess it makes anyway.

  Are you sure? yes | no

Martin wrote 09/20/2016 at 08:16 point

For the electrical insulation test I would suggest to connect all leads together, not only the positive. So you can not have any internal potential difference on the electronics in any case.

  Are you sure? yes | no

Tim Wilkinson wrote 09/20/2016 at 14:55 point

Thanks - didn't think of that. Do you think all leads would be better, or just the +ve and -ve?

  Are you sure? yes | no

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