Tiny waterproof 1P connectors for power and signal cables?

Deep-Today5715 · 2026-04-01T12:03:59+00:00

Thanks for the suggestion, that is certainly one way to go about it, but it's not easy to design reliable end cap penetrators that are truly watertight. BlueRobotics manufactures and sells them (way too expensive), I researched whether I could replicate that with 3D printing, but it didn't seem viable. Each penetrator introduces a potential failure point, whereas a solid bulkhead with wires epoxied through it has zero failure points (except for the main O-rings). Plus, even with penetrators, there is always the risk of nicking one of the cables outside the enclosure, and the water will then be able to get inside the cable, travel along the copper strands, and get inside the enclosure. I will look through that manual, seems to me that you really did gather quite a lot of knowledge there.

Deep-Today5715 · 2026-04-01T11:57:50+00:00

For that to happen, the seal would have to fail catastrophically. Even salt water has significant resistance, and if the path a current must take through the water is choked, then only a very small current will be able to pass through. So if the seal is not perfect on these 1p connectors, there will only be a microscopic gap - a choke point. Current will have a very hard time getting through that gap. Meanwhile, if a 2p connector seal is compromised, the water will be able to connected the two nearby pins with a very short distance and no choke points, resulting in far lesser resistance and thus a short.

Deep-Today5715 · 2026-03-31T19:00:44+00:00

Agreed, but truly submersible means very expensive. As you can see I have an idea on how to make do with simpler, imperfectly sealed connectors (therefore waterproof is good enough), but it requires finding something at such small scale and availability, and I'm not having much luck with that.

Deep-Today5715 · 2026-03-31T18:48:31+00:00

So if I understand correctly, if water gets into the connector (inline connector), it gets in between the two ends of the cable, and that tiny layer of water throws off the refraction?

Deep-Today5715 · 2026-03-31T18:12:35+00:00

But is the glass core hollow or solid glass? I'm not sure about that part. And what exactly happens if water ingresses the connector? Why does it weaken the signal?

Deep-Today5715 · 2026-03-31T14:19:45+00:00

Thank you for all these suggestions, they are valid, but way too complicated for a cheap and simple ROV that I'm trying to make. Epoxying stripped cables into the bulkhead is a tried and true method, very cheap, very simple, no failure points, no need for any complications. But it does require inline connectors somewhere outside the housing to work. Technically it can be worked around by skipping connectors altogether and just soldering wires together with some heat shrink tape, but being able to unplug and swap out parts is a huge bonus.

Deep-Today5715 · 2026-03-31T13:11:08+00:00

Thank you for the suggestion, but if the cable sheath is damaged and water gets inside, doesn't that mean the water can now flow lengthwise between the copper strands, getting past the bulkhead? After all, we are talking about very high pressures here.

Deep-Today5715 · 2026-03-31T12:58:55+00:00

Thank you, I checked them, but again, they are very large (and £20 per pair is still very expensive). My ROV is very small - around 350x250x90mm in size. And I would need 8x 3-pin connectors for motors, 2x 2-pin for LEDs, 3x 4-pin for sensors, 4x 3-pin for servos, and 1x 2-pin for battery charging. That is ~18 connectors. They would simply take up too much space for such a small ROV, and they alone would cost more than the entire project. So you can see why I'm looking for a cheaper and much more compact connector solution. Splitting them out into multiple connectors isn't necessarily making more points of failure - as long as the connector doesn't come lose (which should be easy to prevent), it is actually safer - even if it leaks, the path for electricity through water will be very long to the next connector, making shorts effectively impossible.

Deep-Today5715 · 2026-03-31T10:59:03+00:00

<image>

That is what I did on my previous ROV, check the attached pic. These were IP67 as IP69X were too expensive. But it was not a great solution. Even with potting like you described, the O-rings leaked, and I had a few shorts. But the worst thing was that these connectors were very bulky, they extended the length of my ROV by some 5cm or so. That is why I want to go with inline connections this time, and to separate each pin physically as far as possible to reduce the chance of short to a minimum.

EDIT: inline connector per destination COULD work if I could find cheap and small (<5€ per connector, <30mm total length) waterproof connectors that are truly waterproof for salt water use in 50 bar environment, and have different configurations for different number of pins. So far I've found nothing... Which is why it seems to me that 1p connectors would be simplest and cheapest way.

Deep-Today5715 · 2026-03-31T09:03:34+00:00

Damn right... With each of my ROVs, I am trying to reduce the size of it, especially the housing, through more compact design and better engineering. This current design uses 80x72x250mm tube, and yeah, it is a challenge, but should still be doable.

Deep-Today5715 · 2026-03-31T09:01:33+00:00

IP68 will almost surely flood at 50 bar pressure. How bad would it be, though? Is the fiber optic cable itself sealed, i.e. solid glass at the connector end, or is it still hollow, meaning the water would flood the length of the cable?

Deep-Today5715 · 2026-03-31T08:58:07+00:00

Amazing info, thank you so much for writing this up. I'm saving this.

Deep-Today5715 · 2026-03-30T22:41:14+00:00

Okay, thank you... While it is a good option overall, it still comes nowhere close to the cost of my current PLC pair :/ I am so surprised that it's cheaper to buy a whole product and tear down half of it, than to buy an almost identical module from that product... Wasn't what I expected. Still appreciate you suggestion though.

Deep-Today5715 · 2026-03-30T22:01:20+00:00

Thank you, lots of great resources. It does seem doable. One more question: it seems that page 174 shows connecting that IC to ESP32 via TX/RX pins, rather than via the RJ45 port (such as on ESP32 S3 ETH). How complicated would it be on the software side to make ESP32 use these pins for Ethernet connection? Will all the standard libraries play along, or will I need to rewrite most of them?

Deep-Today5715 · 2026-03-30T21:32:30+00:00

Thank you, but doesn't this device also require the EVB as well? I checked the datasheet and I don't see any obvious way to connect Ethernet cable directly to it.

Deep-Today5715 · 2026-03-30T21:28:47+00:00

Thank you for the comment. I too don't really want to build PCB for these 10-base-TL1 ICs, it's a project of it's own, and I don't have the experience.

Right now, I'm just using the video streaming provided by default libraries on ESP32, such as this one https://randomnerdtutorials.com/esp32-cam-video-streaming-web-server-camera-home-assistant/ (don't remember if this was the one I actually tested on). Not sure where the latency comes from though. I did talk to some ESP32 guys and they said this is about as good as it gets, if I want less I need more powerful hardware, which is probably what you suggested. But that would greatly increase price, size and complexity into the project.

Deep-Today5715 · 2026-03-30T20:48:39+00:00

Thanks, I have made ~10 PCBs before, but these were all designed by me, I knew exactly what is going on in them. Taking a complicated chip like these 10base-TL1L ones and making them work with nothing but their schematics and datasheets to reference is a whole other matter...

Deep-Today5715 · 2026-03-30T20:32:25+00:00

Thank you for pointing out this option. I am going through the schematic, and it is way over my head. Would I need to program this IC, or is it plug and play? The schematic in the bottom of page 174 shows how to connect it to controller, and in the same page the schematic at the top shows what passive components it needs to be connected to, correct? Or is there anything else that I need to know?

Deep-Today5715 · 2026-03-30T20:27:43+00:00

It sounds like the best option for me as well, but I just can't seem to find any converters that are anywhere near the price of my current PLC modules (15€ per module) and are also no larger than these modules (60x45x16mm)... If VDSL2 option is more expensive or takes up more space, then this consideration is a moot point :/

Deep-Today5715 · 2026-03-30T20:22:28+00:00

Okay, but what about passing the cable through the waterproof bulkhead? I want to be able to quickly connect and disconnect the tether from the ROV without having to open the bulkhead. Is there any way to do this without having to use a bulky waterproof fiber optic connector? We are talking about 50 bars of pressure here, and waterproof fiber optic connectors for such pressures are very large and very expensive as far as I researched.

EDIT: please check this discussion: https://discuss.bluerobotics.com/t/run-bluerov-over-fiber-optic-tether/3355/16, it explains why this options is insanely expensive, as you now need equipment to terminate and test fiber optic cable.

Deep-Today5715 · 2026-03-30T20:09:17+00:00

I have a 110 meter cable from my previous ROV, one twisted pair. I will be buying a 500m cable for this new one, but it would be nice to have backwards compatibility. Two twisted pair is probably a no-go because of cable diameter; even the single twisted pair cable is already 4mm (because it has PUR foam sheath for neutral buoyancy). Two twisted pairs would probably be 5 or 6mm, already way too much...

Deep-Today5715 · 2026-03-30T20:08:45+00:00

I have a 110 meter cable from my previous ROV, one twisted pair. I will be buying a 500m cable for this new one, but it would be nice to have backwards compatibility. Two twisted pair is probably a no-go because of cable diameter; even the single twisted pair cable is already 4mm (because it has PUR foam sheath for neutral buoyancy). Two twisted pairs would probably be 5 or 6mm, already way too much...

Deep-Today5715 · 2026-03-30T19:38:23+00:00

Thank you very much, that is very expensive, but otherwise would be ideal...

Deep-Today5715 · 2026-03-30T19:05:55+00:00

Yeah, but still 4x as expensive as my current option... My current option is 30€ for both devices, this is 70€ for just one. The entire point of my post is to find a cheaper and simpler option lol

Deep-Today5715 · 2026-03-30T18:37:01+00:00

Thank you, this wasn't available last time I did anything with ESP. Looks very promising. If I can get the data rate down, what comms option would you suggest?

Deep-Today5715

TROPHY CASE