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In my project I need fairly long (up to 5 meters) shielded cabling that has compact 4 pin connectors (will be used in a noisy environment). As I understand the shield of the cable should connect to the connector, which connects the shielding to the header, which is grounded on the PCB. I believe that a good choice here would be RJ45, but the size of the connectors is excessive.

From an electrical engineer's point of view, would it be acceptable to implement USB or microUSB ports for an application which has nothing to do with the actual USB protocol? Would this decision cause problems if it would become a commercial product? The cables are for connecting digital sensors to a controller.

Suggestions for alternatives to USB connectors are also welcome.

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    \$\begingroup\$ One day a customer came to me with this little story: He bought some heating regulation gadgets that go onto your radiator valve directly and control it. And they had usb connectors. So he wondered if instead of with the build in UI, he could connect his laptop somehow. He tried and the gadget was immedeately dead. What happened was that it directly took whatever came down the line and wrote it into its flash... \$\endgroup\$ – PlasmaHH Nov 17 '15 at 11:57
  • \$\begingroup\$ Try RJ18 - like RJ45 only smaller - often used for phone handset connections \$\endgroup\$ – Icy Nov 17 '15 at 12:03
  • \$\begingroup\$ @PlasmaHH - I get the message, it wouldn't be for home consumers, though. \$\endgroup\$ – I have no idea what I'm doing Nov 17 '15 at 12:09
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    \$\begingroup\$ @Icy - I like those very much, but the price almost induced a heart attack. I'd need quite a few of those and the price of the connectors alone will vastly outweigh the price of the rest of the device. \$\endgroup\$ – I have no idea what I'm doing Nov 17 '15 at 12:20
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    \$\begingroup\$ @IhavenoideawhatI'mdoing -- be careful about turning this into a shopping question. "Is a USB connector good here?" is fine -- "what else should I use" is not. Try chat \$\endgroup\$ – Scott Seidman Nov 17 '15 at 13:42
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This depends on your situation, and what the failure modes of plugging a USB cable into your device would be. When people see a USB connector, people want to plug a USB cable into it. A decade of user experiences confirms this behavior as valid. If it makes no difference, and your device can laugh at 5V coming in on the USB pin, and you won't kill someone's laptop in the process, you should be OK, but your users might get confused.

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  • \$\begingroup\$ It wouldn't be targeted at home users which might not resist the temptation to plug a mouse to it or try plugging it to a computer, but I'd make sure 5V wouldn't fry the sensor. Other than that, would this not be unprofessional for some reasons? \$\endgroup\$ – I have no idea what I'm doing Nov 17 '15 at 12:12
  • \$\begingroup\$ Don't get me wrong - I'm not endorsing the approach, which I don't care for very much. It's begging for mistakes to happen, and doesn't show much regard for user experience. When you can anticipate errors and confusion in design stages, and don't fix it, yes, that's unprofessional. \$\endgroup\$ – Scott Seidman Nov 17 '15 at 12:17
  • \$\begingroup\$ Alright. Do I have alternatives that do not double the price of the device? \$\endgroup\$ – I have no idea what I'm doing Nov 17 '15 at 12:25
  • \$\begingroup\$ If it's for consumer electronics, you should double the price of your device. On my workplace, we use USB connector for UART signals, but it is safe to plug it to USB (it has no effect), and it's only for internal use. As a matter of fact, it was designed to be restricted to internal use, but some customers use it for debug (on B2B market. The end user never see a single USB connector). \$\endgroup\$ – Jacen Nov 17 '15 at 12:36
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    \$\begingroup\$ @IhavenoideawhatI'mdoing connectors being notoriously expensive is common, yes. In our products they often end up being the most expensive part (on it's own), so we try to reduce the number of them wherever possible. \$\endgroup\$ – Arsenal Nov 17 '15 at 13:58

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