I guess he learned that step 1 should be using the ohmmeter and step 2 should be plugging it into hundreds of dollars of equipment.
Bad USB-C cable destroys laptop
61–70 of 146 posts
Re: Bad USB-C cable destroys laptop
#62TL;DR; USB-C cable had GND tied to Vbus and Vbus tied to GND (opposite as it should be) Honestly, I'm surprised that this isn't something that thelaptop and other such USB adapters aren't equipped to deal with. This is only slightly worse in my book than a USB adapter being fried from shorting the Vbus and GND pins together
Electrical faults are just a fact of life. Wires fray, cables get tugged, or are miswired from the factory. And you just know that sooner or later some genius is gonna jam a butter knife in there for the hell of it. The basic USB spec requires that all ports be protected with a small self-resetting polyfuse for exactly this reason. I don't know if the Type-C or USB 3.1 specs includes something similar - I would assum…
This was an A-C cables, which means it was used to charge the laptop, not to power something from the laptop.
Current limiting doesn't magically protect powered devices from voltage reversal (-5V instead of +5V), so both the laptop and power delivery analyzer went poof.
They may have taken enough current to trip charger's current limiter, but then it was a bit too late.
Re: Bad USB-C cable destroys laptop
#63Re: Bad USB-C cable destroys laptop
#64Earlier quoted context omitted.
Sure, but the magnitude of that cost matters a lot. You were saying a dollar or two in raw materials to protect against 100W, now you're saying three or four cents. A few cents to protect hundreds of dollars in equipment from electrical faults seems worthwhile to me.
That makes sense from the consumer's point of view. But imagine you're a manufacturer, producing USB device controller chips by the million. Would you really be willing to spend tens of thousands of dollars to protect against a failure mode that can only happen due to some other company's extreme negligence?
Yes, but of course it doesn't matter what I think.
It's not abnormal to add protection that isn't needed when everything works properly. As noted elsewhere, the USB spec already requires resettable overcurrent protection, for example.
Re: Bad USB-C cable destroys laptop
#65Earlier quoted context omitted.
I don't want to be a broken record, but you're right, not a tall order, but no it's unreasonable on account of cost. It's impossible for USB C to be hooked up backwards by its mechanical design, so why guard against it? The high-side transistor to prevent reverse polarity faults could be 3 to 4 cents in manufacturing cost! It's also not trivial to make sure that transistor trips fast enough to prevent all your low-vo…
Sure, but the magnitude of that cost matters a lot. You were saying a dollar or two in raw materials to protect against 100W, now you're saying three or four cents. A few cents to protect hundreds of dollars in equipment from electrical faults seems worthwhile to me.
Sorry I was not clear in my comments. The dollar solution is for some type of crowbar circuit. This is the most robust solution.
The 3-4 cents is for specifically, reverse polarity protection when somehow, a -5V differential is applied to device power inputs.
This cheaper solution only narrowly addresses this particular power fault, and no others.
Re: Bad USB-C cable destroys laptop
#66Earlier quoted context omitted.
I was playing with a FTDI (a clone :D) and an Arduino and accidentally mixed up VCC and GND from an external power source. I only realised because Minicom was failing to connect to the device. Then I realised what I had done, I tried removing it from the USB port and putting it back in, but it wouldn't work. I then tried a mouse too, but that wasn't working either. Thinking I'd killed a USB port on my Mac (well there…
Use ... a ... hub. If you're doing lab work, it's really easy to get weird potentials on various lines. I almost never plug anything like an Arduino directly into my laptop without a powered hub in between. I assume I'm a klutz. So, I take steps to minimize the damage when something happens.
Anyone have a hub to recommend? I have a hub which I bought for cheap on eBay which I use on my desk for keyboard, mouse and similar but would not trust that hub to offer much if any in way of voltage protection so I'd like to know about safe hubs for lab use.
Re: Bad USB-C cable destroys laptop
#67Earlier quoted context omitted.
It's not the standard that's bad, it's the actual wiring of it. That's akin to saying: The US power grid is a bad standard because I wired up my house wrong and it burned down.
It seems more like saying: The US power grid is a bad standard because I wired up my house wrong and it burned the power station down.
How so? The charger was fine (I presume, it's not mentioned either way), the charged device got fried.
Re: Bad USB-C cable destroys laptop
#68The item appears to have been removed from amazon now. Clicking the link to the item[1] on the review page leads to a 404. [1]: https://www.amazon.com/SurjTech%C2%AE-Standard-Adapter-Devic...
Question is, did they pull it for real or did they only do so to relist it without having that review show up?
Re: Bad USB-C cable destroys laptop
#69I guess he learned that step 1 should be using the ohmmeter and step 2 should be plugging it into hundreds of dollars of equipment.
Do you really test each USB cable you buy like that?
Re: Bad USB-C cable destroys laptop
#70His review has 1,120 positive votes out of 1,121; I don't think I have seen anything get near that high with just one 'unhelpful' vote.
https://www.amazon.com/review/R2XDBFUD9CTN2R/ref=cm_cr_rdp_p...