USB device can destroy most PCs

Den fredag den 9. september 2016 kl. 16.54.14 UTC+2 skrev DemonicTubes:

boost converter charging some capacitors to a few 100 volts and discharge into the USB pins

-Lasse

Question is of course what it will destroy... probably the USB port it has been plugged into, maybe the neighboring USB ports that share the same chip, but how much else?

And how long until manufactures protect the port against overvoltage, rendering this toy useless?

ectricity.aspx

and a few largish caps.

ched too. What method do you think is used to accomplish this here?

ge

Never, it cost too much. And the thing doesn't give an overvoltage, but a undervoltage (-100V or so) .

Bye Jack

I wonder if the key is that it blasts the data pins, as the +5V and GND pins are most likely protected.

What made you come to that conclusion, Jack?

As others have mentioned, it's a high voltage generator.

However, if you really want to see the laptop belch fire, just take a USB cable, chop off one end, and replace the connector with an AC power plug[1]. Insert the USB connector into the target computer, the other end in the wall receptacle, and no more computer. I would build one of these but suspect that I might try it just to see what would happen.

One of my friends attached a USB flash drive to the end of a large plastic syringe. He demonstrates it to the clueless by plugging it into a computah and pulling on the plunger thus "sucking" the data out of the computah. Amazingly, there are often a few believers.

A 5.1v zener from each pin to ground should cover both those cases. Maybe combine with a series resistor or polyfuse.

Have a look at the capacitance requirements, if signal integrity is to be assured. 1pF is too much!

I damaged a USB hub and a Microchip programmer/debugger while testing an SCR trigger circuit that had 120 VAC on it. Now I have a USB isolator I can use when working on such "dodgy" circuits.

Not this, but similar:

This is what I have:

Cheaper versions:

Paul

I see this as nothing but a destructive device.

Drug dealers,spies,etc may want them to quickly destroy evidence.

Andy

Well, depending on the thermal mass of the zener. I note the capacitors appear to be 1825 size. A typical part might be a 0.68uF 250V unit. These could store 22mJ, and five could store 0.1 joule.

A common HBM, or human body model (see AoE pages 200 and 804) has a 100pF cap charged to 1.5kV. That's only 0.1mJ, or 1/1000 of the USB killer's potential energy delivery. This means that USB inputs provided with protection for the HBM are likely not prepared to withstand the USB killer. That could be true even if they had say 100x HBM protection.

Most zeners short when damaged, but a severely- excess discharge could blow past that failure mode.

I doubt it would be effective for that. Even if it contrived to burn out the hard-disk electronics, the disk itself would still be readable.

Perhaps for an SSD, but on the whole I doubt the damage would extend that far into the PC anyway. Kill the USB port, no doubt, but that's probably all.

Sylvia.

With the required physical access, there are more effective ways. A mallet into the motherboard for example.

This device is useful for vandals, but that's about all.

Sylvia.

I read that the thing does not blow most Apple devices. Apparently they have done enough to protect against this.

I can't help but wonder, if it's true, how they pull that off. As others have pointed out, zener protection doesn't fully make sense.

You can get a TVS designed for fairly high energy surges. Here is one that is rated for 5 VDC operation and can handle surges of 43 amps, with peak power of 400W, for about 20 cents.

The chart shows it can handle 400 watts for 1 mSec, or 0.4 Joules. That's about 4x the estimated energy of the USB killer:

Paul

But would the capacitance of something like that make it unusable on the data pins?

yep, I beleive the limit for USB3 is 1pf, USB2 10pf