this post was submitted on 26 Dec 2024
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There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.

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[–] MargotRobbie 336 points 6 days ago (14 children)

If you want a more detailed explanation, USB-C is a small connector that was designed primarily for data transfer, extended power range delivery (240w) was essentially hacked on to the standard. Electricity arcing between the contacts on the connector is the biggest challenge with this hack, since the contacts are small and very close together, which could burn out the circuit board and start fires. For EPR to work safely, there needs to be a lot of extra components on the circuit board/female connector side, which there simply isn't enough space for on an f2m extension cable.

As for why USB-C cables are so short, it's simply a matter of physics, carrying high speed data over larger distances would result in higher losses and requires thicker conductors and more shielding, which is why you don't see USB4 Gen3 cables over 1 meter unless they are optical, and longer "charging cables" are only rated at USB 2.0 speeds, because more often than not they don't even have the USB 3.x data pins on their connector.

[–] Agent641 101 points 6 days ago (1 children)

You are a brilliant woman of many talents, Margot Robbie!

[–] MargotRobbie 95 points 6 days ago (1 children)

That's esteemed Academy Award nominated character actress Margot Robbie to you!

Also, thank you.

[–] [email protected] 3 points 3 days ago (1 children)
[–] MargotRobbie 3 points 3 days ago

I would say more like a Harley Quinn.

[–] [email protected] 12 points 5 days ago* (last edited 5 days ago) (1 children)

It's amazing for a "standard" that there can be so many non-standard ways to do it. Your explanation is great and just reminded me that cable tester tools are a really good idea to have at home. There was one in Kickstarter earlier this year, I think, that was a really smart idea. I don't recall what it was nqmed though. Maybe you have heard of it? I'll see if I can find it.

Regardless, there are some devices that really need a specific type of usb-c cable to function properly and/or not burn the circuitry. (i.e. Nintendo Switch, the original release model (though, they may have fixed it in later hardware revisions))

Edit: Found it! That cable tester that I was referring to was called the BLE CaberQU. I think it is a really neat idea.

[–] [email protected] 1 points 17 hours ago

Nice! I’ve wanted a tool exactly like that many times. I’ll back it and see.

The closest I could find before were essentially pin to pin continuity checkers, which are useful for telling if a cable is PD only, 2.0 vs 3.x, or has a line break, but most of those can be eyeballed, otherwise metered. So these just checkers just add precision and speed to something you already know how to do.

The runner ups were the (now ubiquitous) inline inductive energy trackers, because they can tell you a bit more about the gauge of the wires in the cable which can be important, especially high amperage 5v like pi 4.B

But to test quality of shielding for high rate data transfer, DP and PCI-E tunneling, etc., the only option was manually user testing with adequately powerful devices.

[–] [email protected] 18 points 6 days ago (2 children)

I have this cable: https://www.spigen.com/products/arcwire-usb-c-to-usb-c-cable-pb2202

It's 2 meters long, 240 watts and supports Thunderbolt 4/USB 4 (40 gbps).

I couldn't test the 240 watts charging as I don't have any device pulling more than 100 watts, but the Thunderbolt 4 part definitely works.

Apple sells a 3 meter Thunderbolt 4 cable (albeit limited to 100 watts of power) that isn't optical either (I think there's some special circuitry in the plugs though).

[–] MargotRobbie 29 points 6 days ago (2 children)

You're right. Those are active cables which I forgot to mention earlier that have special circuits that amplify signals, but are also a lot more expensive as a result.

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[–] flames5123 14 points 5 days ago (4 children)

$90 for a cable and it’s not even braided is wild to me.

[–] stoicmaverick 6 points 5 days ago

I prefer not braided. Both for cables and hair. More of a ponytail kinda guy myself.

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[–] [email protected] 17 points 6 days ago (1 children)

I don't seem to be able to upvote this twice.

[–] MargotRobbie 47 points 6 days ago (1 children)

You could always buy more copies of "Barbie" on Blu-ray for Christmas.

Just saying.

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[–] [email protected] 8 points 5 days ago

I'm glad someone is smart cause I sure ain't

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[–] [email protected] 206 points 6 days ago (20 children)

Anybody care to sum this up for people who can’t watch videos?

[–] WraithGear 338 points 6 days ago* (last edited 6 days ago) (28 children)

So a standard cable needs to be chipped to show its rating to the device, its not that the device can pull what it wants or can get, but the cable itself tells it what it can supply. Extension cables can’t do that, because it doesn’t know what it’s plugged into, and that would be if they even bothered to put a chip in. They instead piggy back off the chip for the main cable. The problem comes when you you have a 240 watt cable hooked up to a cheap 120 watt cable, with the device being told it can push 240, and starts to super heat the extension cable

[–] [email protected] 88 points 6 days ago (2 children)

Brilliant thanks

5 sentences that inexplicably need a 9 minute video to say

Fuck YouTube

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[–] [email protected] 37 points 6 days ago (3 children)

This sounds solvable, doesn't it? Have the extension cable have a chip saying it can do X at maximum, then compare with whatever is to be extended and communicate the minimum of both upstream. Might not become a sleek cable-like design, but would extend the 240W cable with the extender safely staying at 120W

[–] [email protected] 83 points 6 days ago (5 children)

That's an active extension cable, which is essentially a single port USB hub.

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[–] [email protected] 28 points 6 days ago (2 children)

Heh heh heh. Wait till you dive into the world of "That $15 cable costs 12c to make."

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[–] FourPacketsOfPeanuts 33 points 6 days ago

Soon on Amazon..

1m USB-C CABLE HEATER!! 0.99c

($5.99 shipping)

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[–] [email protected] 25 points 6 days ago* (last edited 6 days ago) (18 children)

Going to take a wild guess and say the same reason you shouldn’t chain extension cords. USB can carry over 200w these days.

[–] [email protected] 26 points 6 days ago (3 children)

the same reason you shouldn’t chain extension cords.

what if I don't know that either

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[–] AnUnusualRelic 67 points 6 days ago (1 children)

I'll have you know that I've been using a 2m extension on my deck power supply for a while and haven't had any fires to speak of. Almost none actually.

[–] [email protected] 15 points 6 days ago (1 children)
[–] rob_t_firefly 45 points 6 days ago (1 children)
[–] [email protected] 12 points 5 days ago* (last edited 4 days ago)

This is my ship, HMS Can't Possibly Sink Again IV

[–] [email protected] 1 points 2 days ago

Usually if a thing is not allowed, there is a good reason for it. Unfortunately many people seem to ignore that because they don't know or understand the reason.

[–] [email protected] 15 points 5 days ago (1 children)

USB-C somehow managed to be the worst "standard." Hopefully the next big USB port doesn't allow for so much variance. I don't see why a specific wattage and data transfer rate isn't included in the specification. I can scarcely believe they managed to standardize it so well that I can plug the wrong cord into a port and break something.

[–] [email protected] 19 points 5 days ago* (last edited 5 days ago)

Per the video, the usb-c connector on the cable has a chip that communicates the maximum current that it can safely pass. By plugging it into a lesser rated usb extension cable, that assertion is now wrong, potentially dangerously wrong if enough current is sent that the wires in the extension overheat.

[–] dual_sport_dork 49 points 6 days ago* (last edited 6 days ago)

Technically extension cables were not part of the original USB spec, either, but that did not prevent oodles of them from appearing pretty much instantly. They solved a problem, there was a need, and thus they happened.

I.e. there never was supposed to be any such thing as a passive male USB-A to female USB-A cable, and yet pretty much every little MP3 player from 2001 to about 2005 came with one regardless.

[–] BombOmOm 23 points 6 days ago (9 children)

Seems negligent to not include extension cables in the spec. Lots of hubs have too short of cables, or one needs to expose a plug somewhere other than where the PC is.

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[–] asbestos 25 points 6 days ago (1 children)

I never wondered about this, but it makes sense now. Off topic but man, the dry mouth noises he makes inbetween sentences are driving me crazy…

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