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Recently Samsung came out with the new Galaxy and Edge phones which are advertised as IP68 rated.The mircro USB ports on these phones are completely exposed, yet are still IP68 rated. My question is, how do you achieve a water resistant rating on these ports while still exposing these pins to the potential of a short circuit?

The only thing i can think is that the phone will use some kind of smart circuitry too prevent it going into USB host mode and supplying any voltage when exposed to water. Or prehaps some kind of special nano coating around the charge port?

Figure 1 - Example of waterproof exposed port

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  • \$\begingroup\$ Does it behave as a USB host? I thought it was just a USB device. \$\endgroup\$ – Roger Rowland Apr 9 '16 at 7:58
  • \$\begingroup\$ Most new android phones use USB OTG which allows it to either act as host or device depending on how the last pin on the USB cable use is configured \$\endgroup\$ – user3095420 Apr 9 '16 at 8:00
  • \$\begingroup\$ Ok, so would it be possible for a short circuit from any water to prompt the phone to switch to host mode, or does it rely on a correctly wired USB cable? \$\endgroup\$ – Roger Rowland Apr 9 '16 at 8:01
  • \$\begingroup\$ Yes, in fact shorting the 5th pin to ground (these pins are right next to each other ) will cause the port to act as USB host and supply 5V and having the potential for a short circuit \$\endgroup\$ – user3095420 Apr 9 '16 at 8:10
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    \$\begingroup\$ It's likely checking for the ID pin AND changes in D- and D+. Some devices will shut off the power output if it doesn't sense any draw after period of time. It also likely has short circuit detection. \$\endgroup\$ – Passerby Apr 9 '16 at 8:18
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The new S7 phones with IP68 ratings seem to include a moisture sensor in the usb port. It will prevent charging if it detects any moisture. It's reportedly very sensitive.

Undoubtedly, this is also used to shut off any potential USB-OTG output, if the phone supports full OTG support. Not all phones have OTG, and if those that do, many do not power the port, requiring a y cable and external power. The S7 phones support full OTG, and even have a OTG adapter in the box (for migrating from an old phone. Neat).

Standard techniques like short circuit detection would still apply, and likely enabled by which-ever usb switching IC or PMIC Samsung is using (likely in-house based on my S5 generation device).

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According to Cnet, the newest Samsung s7 isint totally waterproof, but is still a big step from Apple's iPhone 6.

It shouldn't be submerged at all (just like other phones), and Samsung technically lied about its waterproof rating, since it should be Ip67 instead of it's advertised IP68.

The phone tries to keep water out of all it's ports with a water sensor which, when it senses water, shuts off that port, for exampke, if you use USB OTG with the phone and it falls into water, it will shut off right away.

Hope that helped!

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