5 ms·

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking f

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

BoorishBears 7y ago
How do you spec a fuse for out of spec usage? What's stopping me from connecting a strand of magnet wire between both sides?
- jakeogh 7y ago
  A consumer does not solder USB connectors together with magnet wire. Power plug compatibility which relies on software for fire safety is a bad idea.
  - BoorishBears 7y ago
    Ok? But the kind of supplier willing to under-design cables will gladly do stuff that's barely a step up? I literally don't understand your proposed alternative unless you're saying all cables should be spec'd to handle the max amount of voltage... in which case people would still under-design. If the fuse is designed to keep cables for some voltage X from going up in flames, how will it keep cables for some voltage X-Y from going up in flames while also allowing Voltage X, when both are in spec?
wlesieutre 7y ago
You can plug a 5 amp rated extension cord into a residential plug on a 15A breaker and the breaker won’t protect you from overloading the cable with 15A. So yes, those sorts of light duty cables have their own fuse to prevent this. But I really would not trust all the no-name vendors flooding the market with shitty USB cables to include correct safety measures in all of their cables, so requiring cables to specifically request higher power levels seems like a better precaution to rely on in this case.
- deleted 7y ago
  [deleted]
tjohns 7y ago
(a) A fuse only prevents over-current based on the port's rating, not the cable's. It wouldn't help here. (b) USB-C has several modes of operation. The thinner cables aren't under-speced in the lower-tier modes. They're perfectly fine for powering a mouse or carrying low-speed (USB 2.0 class) data. But not for charging a laptop, or other high current / data-rate uses.
jhbhjjhvhjkgh 7y ago
No, what the spec does is say that if the cable doesn't have a max rating, it'll top out at 5V (and .5a, I believe). Then, it does negotiation with the cable and the device to insure that it can provide the voltage the device needs. And yes, PSUs MUST negotiate voltage or be 5V only and all USB-C devices must accept at least the 5V voltage.

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

BoorishBears 7y ago

How do you spec a fuse for out of spec usage? What's stopping me from connecting a strand of magnet wire between both sides?

jakeogh 7y ago
A consumer does not solder USB connectors together with magnet wire. Power plug compatibility which relies on software for fire safety is a bad idea.
- BoorishBears 7y ago
  Ok? But the kind of supplier willing to under-design cables will gladly do stuff that's barely a step up? I literally don't understand your proposed alternative unless you're saying all cables should be spec'd to handle the max amount of voltage... in which case people would still under-design. If the fuse is designed to keep cables for some voltage X from going up in flames, how will it keep cables for some voltage X-Y from going up in flames while also allowing Voltage X, when both are in spec?

wlesieutre 7y ago

You can plug a 5 amp rated extension cord into a residential plug on a 15A breaker and the breaker won’t protect you from overloading the cable with 15A. So yes, those sorts of light duty cables have their own fuse to prevent this. But I really would not trust all the no-name vendors flooding the market with shitty USB cables to include correct safety measures in all of their cables, so requiring cables to specifically request higher power levels seems like a better precaution to rely on in this case.

deleted 7y ago
[deleted]

tjohns 7y ago

(a) A fuse only prevents over-current based on the port's rating, not the cable's. It wouldn't help here. (b) USB-C has several modes of operation. The thinner cables aren't under-speced in the lower-tier modes. They're perfectly fine for powering a mouse or carrying low-speed (USB 2.0 class) data. But not for charging a laptop, or other high current / data-rate uses.

jhbhjjhvhjkgh 7y ago

No, what the spec does is say that if the cable doesn't have a max rating, it'll top out at 5V (and .5a, I believe). Then, it does negotiation with the cable and the device to insure that it can provide the voltage the device needs. And yes, PSUs MUST negotiate voltage or be 5V only and all USB-C devices must accept at least the 5V voltage.