USB stick short circuit

Discussion in 'hardware' started by Arcanez, Jan 13, 2014.

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  1. Arcanez

    Arcanez Registered Member

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    hey

    I just plugged in a usb stick into the front Panel of my Computer. The usb stick has the shape of a key which I carry with my bunch of keys. Also I have a Lian Li Aluminium case. So when I plugged in the usb stick I noticed a Little spark between the usb port and the stick and then the Computer shut off immediately. I could't turn it back on for quiet a while. I unplugged everything and just tried to turn it back on and it worked. I checked all the usb ports of the Computer and they all seem to work correctly. Now I'm still afraid that something could still have been damaged.

    I think the short circuit occured because of my Aluminium case combined with the bunch of keys hanging around the usb port.

    My PSU is a Seasonic X-Series 560W Gold. Case is a Lian Li PC9F

    Now have I been lucky or could there be any Problem later on caused by the short circuit??

    Front Panel of my PC:

    http://www.beckpc.ch/images/product_images/popup_images/5215_2.jpg

    USB Stick:

    http://m.ua/jpg_zoom1/138703.jpg
     
    Last edited: Jan 14, 2014
  2. Bill_Bright

    Bill_Bright Registered Member

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    What you experienced was ESD - electro-static discharge and if it happened inside your case, you could EASILY have destroyed your CPU, RAM, and/or motherboard too!!! :eek:

    HOPEFULLY [fingers crossed] what happened is the excessive voltage (potentially into the 30 or 40,000s of Volts!!!!!) on the chassis (case) "ground" was detected by your PSU as a power fault, and the PSU shutdown out of self-preservation. The PSU then remained in a "fault" status until you reset it by unplugging.

    Note standard ATX power supplies are required to supply +5Vsb standby voltage to several points on the motherboard when simply plugged in (and, if optional switch is present, the master power switch on the back of the supply is set to on).

    ESD control is critical around ESD sensitive devices - which includes high-density integrated circuits (ICs) like processors, memory modules, and the like. An electro-static discharge (static shock) so tiny it is well below the threshold of human awareness can EASILY and TOTALLY destroy these devices. That is, you can destroy a CPU, for example, with a static shock so small that humans are not even aware a shock occurred - we cannot see it, feel it, or hear it, but it is like taking a blowtorch to the device.

    I suspect what happened is when you pulled the USB device out of your pocket, you generated a high "potential" (voltage) static electricity charge in your body. Then when you moved the tip of the USB device in close to the case, the distance between the charged device (you) and Earth (case ground) became short enough for the potentials (charge) to jump (arc) to Earth - the path of which is through the case chassis, through the power supply and to Earth via the PSU power cord.

    So how do you prevent this from happening again - easy! The hard part is making a habit of it. All you need to do is touch the case (preferably bare metal) with your extended finger first - so you and case ground are zapped and not the device, or circuits in a port/connection.

    FYI - because ESD is so sneaky (silent destructive force) it is critical all users get into the habit of discharging static in their body before touching the computer, and ESPECIALLY before reaching inside the opened computer case for any maintenance or cleaning. And again, touching bare (not painted, or otherwise covered) metal of the case is best.

    What is important is YOU the user and the computer MUST be "at the same potentials". When at the same potential, there is no "difference in potential". And when no "difference in potential", there can be NO discharge.

    If all is working fine, I suspect all is okay and just consider yourself lucky and lessoned learned. Personally I might be hesitant to try that USB device in my computer again because it may have been damaged.

    Also, just as a precaution, I recommend you get a (and every home should have one) AC Outlet Tester just to make sure your wall outlet is properly wired. I recommend one with a GFCI (ground fault circuit interrupt) indicator as it can be used to test bathroom and kitchen outlets too. These testers can be found for your type and voltage outlet, foreign or domestic, at most home improvement stores, or even the electrical department at Walmart.
     
  3. TheKid7

    TheKid7 Registered Member

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    I had a similar thing happen to me last year at work. I was wearing a fleece jacket and I quickly removed the fleece jacket followed by starting to insert a USB 3.0 Flash Drive in a back USB 2.0 port on my Dell Office PC. There was a large static spark which jumped between the USB Flash Drive and the back I/O panel of the PC. The PC immediately shutoff. I restarted the PC, and the PC came back with no issues and is still functioning OK today.

    I am now more careful when wearing and taking off my fleece jacket. I touch something metal before touching a PC.
     
  4. Bill_Bright

    Bill_Bright Registered Member

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    You might have easily had 50,000 volts built up in you! Every one is different of course, but generally the threshold for human awareness is around 3,000 volts of static. Anything less than that and we cannot detect it, even if looking, listening and feeling for it.

    But things like CPUs and GPUs - devices that have billions (with a "b") transistors in the space of postage stamp - can be damaged with static voltage potentials as low as 30 volts - even when the current (amperes) is infinitesimally small.

    Unfortunately, just squirming in our chairs can generate destructive static potentials - especially when ambient humidity is very low. For this reason, the use of a anti-static wrist-strap is a good idea (if you can remember to put it on and properly attach it to chassis ground).
     
  5. Arcanez

    Arcanez Registered Member

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    It happened yesterday after I came back from evening School. I fetched my bunch of keys which I had in my jacket's pocket and immediately tried to connect the usb key into the usb port on the front Panel. I think the pc hadn't even booted completely into Windows when I tried to plug in the usb key.

    Now I don't see anything weird going on with the Computer. Everything seems to work properly. So in order to prevent this from Happening once again you say that I have to touch the pc case before plugging in a usb device?

    Also I would like to know if there are any security measures against such short circuits. I mean a Mainboard should have protection against such ESD built in. Endusers really shouldn't be able to damage a Mainboard or similar components by just plugging in a crappy usb device.

    If this ESD had fried my Computer it would have been such a pity since I have some pretty expensive components installed.:thumbd:
     
  6. Bill_Bright

    Bill_Bright Registered Member

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    YOU (the user) are the security measure. You must ensure your computer is properly assembled and the wall outlet properly wired to "minimize" any chance of damage. You can only minimize, not absolutely prevent.

    It does, sort of. It depends on where the discharge is introduced. If your charged body zooms in close to a memory module, the discharge may run through the memory module to the mainboard, then out through ground - destroying the memory along the way.

    Since you introduced the static on the exterior of the case, the voltage likely stayed in the chassis and went out through the ground wire of the PSU.
     
  7. Arcanez

    Arcanez Registered Member

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    Thanks for your Explanation. I think a Major Problem is my Aluminium case and the fact that the pc case stands under my desk and it's very hard to see the usb port on the front Panel so you Kind of scratch with the tip of the usb stick on the case until you find the usb port to plug it in. I plugged in a usb cable into the back of the pc which is about 1m Long and I think I will plug the usb key in there if needed.
     
  8. Bill_Bright

    Bill_Bright Registered Member

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    Actually, being an aluminum case may have saved you here. Aluminum is a much better conductor than steel so much of the voltage may have traveled harmlessly through the case instead of through any of the circuits.
    Yeah, with any connection, it is best to align the two sides visually first. You might consider buying a hub that you can place on your desk.
     
  9. bo elam

    bo elam Registered Member

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    Thanks for this tip, Bill. I always put my hand on the case before inserting or removing a USB drive so the flash drive goes in and out smoothly but never thought about the problem that static current can cause to a PC. A lot of times when I shake hands with someone or touch something, I feel the static so this thing described by Arcanez could happen to me. I guess putting my hand on the case has kept me safe from this danger.

    Bo
     
  10. Bill_Bright

    Bill_Bright Registered Member

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    No doubt touching the case with your finger tip before making contact with another device is a good habit to get into. But we must remember that static buildup begins again immediately. So frequent, or better yet, constant contact if best.
     
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