USB Drop camera


I am building a vehicle that requires an underwater USB drop camera. I am using the Low-Light HD USB Camera (same as BlueROV) which is fitted inside a small acrylic cylinder, and I need to connect it to the Raspberry Pi3 inside the electronics enclosure. However my main issue is the cable, because the USB connectors cannot pass through the penetrators, so I need to trim the cable, weld it and reconnect it. I did this and despite the cable having continuity it does not work.

Am I missing something? Is there any advice I can take in order to trim USB cables and reconnect them?

It is worth noting that if I trim/weld/connect it once it works, but if I do it on both ends of the cable it does not work.

Hi @Alex_UJI1,

Given this, is there any chance you connected the wires incorrectly on the second end? If possible I’d recommend you do a continuity check with a multimeter to see if each wire has good electrical connectivity to where it is supposed to go :slight_smile:

More generally, what kind of cable are you putting between the two enclosures? Presumably it’s something water proof?

Hello Eliot,

I am using a subconn cable.

This works:

However when I use the subconn cable like this, it does not work:

I have checked continuity and the multimeter reads 5V throughout the cable. I also made sure that every cable had continuity so I am not sure what can be the problem here.

How long is the subcon tether? USB 2 can work up to ~30 m and USB 3 can work up to 18m. Perhaps you need a 5 pin connector and use one of the pins for shielding?

You likely don’t maintain the proper twisting through those connectors for it to work properly. Try getting a cat 5 rated connector (just because its twisted pairs)…or cut up a USB extension cable and use the Wetlink penetrators.


That’s with an active/repeater cable - for a single passive USB 2.0 cable length is limited to ~5m (source).

From the USB 2.0 specification (section 6.1) high-speed and full-speed cables should have a twisted pair for the signal wires (as @Outland suggested), and also shielding (as @FairweatherIT suggested). Given you have quite a long cable, which most likely has straight wires and no shielding, it’s not too surprising that it’s having signal issues.

This makes it seem like the cable would only need to be quite short - would you be able to describe your setup in some more detail? It seems a little odd to be using SubConn bulkheads and connectors for this unless the setup is going very deep, and given the costs I’d probably expect a connector on one end and a penetrator on the other.

You might want to look into Cobalt Connectors - @damonblue has previously mentioned that they offer USB-compatible bulkheads and cables :slight_smile:

Hello everyone,

Thanks for your replies.

It is 1.5m long.

I am building a surface vehicle. The camera just needs to be “hanging” from the vehicle 1.5m into the water. I am using SubConns because it seemed the better solution given the equipment and materials we have available at the moment.

I did not know about the existance of the Cobalt Conenctors I will look into the them, because they seem to provide a better solution and as you said they are not as costly as the SubConns.

I will also try @Outland 's advice and use twisted pairs and I will try to get the wetlink penetrators.

I will update this thread once I have tried the proposed solutions.

Have a nice day!

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Hello, just saw this! Cool project by the way!

Yes, as the others recommend using a USB extender is your best bet! I’ve done custom work before for a customer using our exploreHD USB ROV Camera with a USB extender from Amazon. We used an SLA printer to print a custom mold of the USB extender’s inners and filled it with epoxy :slight_smile:

The results worked great, with a 10 meter extension to standard USB 2.0. If you want, we can ship out the SLA mold for you!

Let me know!

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My experience is to use a USB 3 extension cable. I’ve done a 30 meter connection between a USB 3 hub and a host laptop. It worked well in transferring images from two usb 3 cameras to the laptop. You can cut the cable and use subconn connecters in between (I didn’t use it though).

Can’t see how the cable is sealed. I assume that the case was printed using some clear material, and then the extender was inserted? And the whole extender and two cable connections were fully sealed by some clear epoxy? Thanks.

Yes that is correct! It uses an SLA printer rather than FDM which prints in resin. This removes any kind of gaps that are known with FDM prints.

I’ve had issues before when I tried making the camera wires longer. I soldered maybe 20 or 30cm and that was enough for things to stop working properly. I’m not really sure why.

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I notice that on the stock camera, you guys twist the data lines and power lines together. In USB 2.0, the pairs are not differential so there is no purpose in doing that. Proper shielding is the best way to extend the range of USB 2.0 cables.

Hello everyone,

We bought two 8-pin Cobalt Series Bulkead Connectors as @EliotBR suggested. One connector for the electronics enclosure and one for the camera enclosure. We also bought the corresponding double-ended cable.

We choose the 8-pin connector because it is the one that has twisted pairs, and following the advice provided in this post it was recommended to use twisted pairs. The 6-pin hybrid also has 2 twisted pairs however it was out of stock at the moment we placed the order.

I welded the twisted pairs of the Cobalt connectors to the USB connectors, however I was having the same issues as before. After asking around, one of our colleagues suggested that the welding might be adding some resistance to the wires, and this is totally what was happening. Too many welding points across the cables was adding enough resistance to disrupt the signal! @williangalvani might be having this same issue.

The solution:

We built the JST connector for the camera and the USB connector that goes to the Raspberry using the wires of the Cobalt connector, this way we don’t weld the cable at any point. It works really well!. The cable is 1m long and we haven’t had any issues so far.

What remains to be tested is if this can work with the 4-pin Cobalt connector (i.e the untwisted wires), but I don’t think we will try to test this.

Again, thanks everyone for your advices and have a nice day!


Hi Alejandro,

Are you using a USB 3 cable for your camera? I have a similar problem at the moment where I need to connect my USB camera in one enclosure to the raspberry pi in another enclosure. I’m wondering if your solution will work for my application.