How does my cellphone detect moisture in its USB port?

[berkeman]

I had a shift outdoors yesterday where it was raining off and on. I was mostly under EZ-Up tents, but was out in the rain a little and there was plenty of moisture blowing in the air from the foggy conditions.

Part-way through the day, after the rain had let up for a few minutes, I happened to see a notice on my Google Pixel 6 cellphone similar to this one:

https://candid.technology/liquid-or-debris-in-usb-port-pixel/

I'd never seen something like that before (and was happy that it was reporting that all was okay), but it got me wondering how the phone can detect when some moisture gets into the type-C USB port. Does it look at leakage current between the 5V and Ground pins, or some other characteristic between the other lines in the type-C connector? I've worked mostly with circuitry for type-A and micro-USB connectors, and not so much with type-C, so maybe this is a feature of type-C only?

https://medium.com/@leung.benson/usb-type-c-s-configuration-channel-31e08047677d

Thanks for any insights.

 

[Drakkith]

I think there's a moisture sensor in the port. Per Samsung:

Devices with a waterproof rating of IP68 and above (most of the Galaxy series) are equipped with a moisture detection sensor to prevent water damage to the device.

I assume the same is true for other brands.

 

[DaveC426913]

Oh, that's an easy one.
Your phone is powered by the magic of electricity! It's a little known fact that water conducts electricity!

_{Follow me for more pro-tips.}[EDIT: OK, Drakkith's answer may be more useful.]

 

[berkeman]

LOL goofball Dave.

 

[berkeman]

I think there's a moisture sensor in the port. Per Samsung:

Devices with a waterproof rating of IP68 and above (most of the Galaxy series) are equipped with a moisture detection sensor to prevent water damage to the device.

I assume the same is true for other brands.

Thanks Drak. Link?

 

[Drakkith]

Here you are.

 

[berkeman]

Here you are.

Fantastic! Thanks Drak. So it's not a feature that is built-in with generic USB-C ports, but an additional detection device in the USB-C port of these devices. Cool stuff.

 

[Drakkith]

That is my understanding, yes.

 

[DaveE]

It must be an impedance measurement between the pins, since it recovers quickly. Other sensors (magnetoresistive, etc.) take longer to recover. They are also an extra part to add into a tight space. An integrated microcontroller could do the impedance measurement.

Phones also have permanent sensors for warranty purposes, both visual and electronic.
https://appleinsider.com/articles/1...ove_water_sensors_for_detecting_iphone_damage

 

[berkeman]

Phones also have permanent sensors for warranty purposes, both visual and electronic.
https://appleinsider.com/articles/1...ove_water_sensors_for_detecting_iphone_damage

That patent seems more to be for water intrusion into the interior, rather than moisture entry into the USB connector, no?

 

[DaveE]

That patent seems more to be for water intrusion into the interior, rather than moisture entry into the USB connector, no?

yes, exactly. A one time thing.
You won't find anything from Apple about impedance measurement, it's as old as vacuum tubes.

Which reminds me of a marketing guy that wanted me to patent a different, but similar, thing for lasers. I laughed and told him I stole it from a guy, who stole it from another guy, who copied it from a book, etc...

 

[sophiecentaur]

Fantastic! Thanks Drak. So it's not a feature that is built-in with generic USB-C ports, but an additional detection device in the USB-C port of these devices. Cool stuff.

It shows what they can do when they want to. BUTTTTTT how come they don't slow down the processor when my iPhone gets nearly hot enough to burn my leg?

 

[berkeman]

BUTTTTTT how come they don't slow down the processor when my iPhone gets nearly hot enough to burn my leg?

It's doing updates or something. There was a piece in the news in the last week or two...

 

[berkeman]

Whelp since @sophiecentaur is skeptical, here you go: https://www.moneysupermarket.com/mobile-phones/guides/stop-iphone-overheating/

 

[sophiecentaur]

Hmm. If I’m clever enough to take all the measures they describe then so is my iPhone. Power dissipation is as much related to clock speed as anything and the stupid machine could warn me about heavy use.
The annoying thing is that it feels like thermal runaway. No excuse imo.

 

[berkeman]

Especially if you keep it in your front pocket... Yeowie!