I got elecrecuted from EOS 300D !!!

[shay_ohayon]

Hi All,

 

I was ready to take a snap using my EOS digital Rebel today, and got

close to the LCD screen when my nose accidently touched something,

and I got electercuted by a small current. Apperantly, it I touced

the handle of my tripod's head (Manfrotto 486 RC2). It was a small

current which you cannot feel with your hand (too much resistance).

When I checked this further, I discovered that the reason was my USB

cable, which was connected between my laptop and my camera. When I

unplugged it, it stopped.

What I understand from this is that Canon decided to connect the

tripod screw socket to their ground cable ?!?!?

 

Oh well, I learned my lesson.

 

Shay

[lex_jenkins]

Technically speaking, electrocution is execution by electricity. You survived. Did the camera?

[mag_miksch]

plastic people

[jimstrutz]

My sincerest condolences to your family & friends. I think you should consider writing your last Will and Testament while you can still type. Someone will probably want that 300D. Do you have a preference to the disposition of your remains? :)

 

Not sure why you got shocked, but you can be very sure that the tripod screw is attached to the electrical ground within the camera. I would think that would be the norm.

[shay_ohayon]

Both of us survived. However, I think I will try to ground my tripod somehow (maybe add a wire which touches the ground?)

[miles_feigenbaum___dallas_]

WOW, Its a SHAYme to hear this shocking story! You must have purchased the GREY market version as they were shipped without the neoprene with kevlar weave booties and mittens that are known insulators for this safety precaution. On the upside, though, you won't need to order your viagra for the next two months...

[craig_gillette]

I think you've got a problem there. It's been too long since one of my "responsibilities" was electronics safety so I can't say for certain why or how but I doubt you should be getting shocked by a device powered by your usb cable. While I don't think there's anything too dangerous, I'm inclined to think it's more likely to damge the gear than you.

[Ed_Ingold]

It sounds like you have a leakage from them mains to the ground in your laptop. That needs attention. Start by reversing the wall plug, but you may have to replace the power supply as well, and/or have your laptop checked and repaired.

 

Leakage is hard to test. The impedance of a digital voltmeter is very high, and can read line voltage from nearly anything due to capacitative or magnetic induction. You need to know the leakage current, but you can fry your voltmeter if you're not careful. The current should be very low - less than 1 mA. You can begin to feel 5 mA and 75 mA can kill you.

 

The body of the camera is always "ground" with regard to external connections, like the flash. Strapping the tripod to ground won't solve the problem. It might make the camera safer to use, but it might fry something too.

[basscheffers]

Sounds more like a not properly grounded computer rather than a problem with the camera Canon can be blamed for!

[todd_west]

Odds are it's not so much the laptop as the laptop power supply. Was the laptop plugged into AC? If so, does the power supply have a two prong plug or three prong where it attaches to the wall? How many prongs on the supply's laptop connector? Knowing which tripod, the kind of flooring it was on, and what sort of shoes you were wearing would help too.

 

Usually, this kind of stuff happens with two wire supplies, since the laptop ground is isolated from earth ground and therefore floats. Unless unusual ground topologies are used (not the case here) cables tie the computer ground to the ground of the plugged in device, so the camera's chassis ground---and, by extension, the tripod socket---is held at the same potential as the laptop ground. There's usually a few hundred volts of ground bounce between laptop ground and mains ground as the capacitive coupling through the power supply causes the laptop voltages to oscillate as a function of the mains supply cycle. The resulting charge buildup causes ESD events when another conducting object such as your nose comes into proximity. This is one of the reasons why most newer laptops use supplies with three prong plugs which route mains green wire ground to the laptop chassis.

[shay_ohayon]

Hmm.

My laptop was connected to AC power supply. The connector is three pin plug. I was barefoot (I know my father always told me not to handle electronic devices without shoes, but this was my CAMERA!!!)

[tom_christiansen]

As Todd points out, this is most likely a leakage current issue related to the AC power supply being used. The reason you don't feel it with your hand but do feel it with your nose is probably that the density of nerve endings on your hands is much lower than on your nose (although, I'd have to consult a physiology book to verify this claim).

<p>

I doubt this was an ESD (ElectroStatic Discharge) event. ESD is what you get when you pet your cat on a dry winter day. Little blue sparks between you and the kitty (which seriously annoys most cats!) Everything charges up to some voltage level. Just sitting in front of a CRT monitor or TV will cause a few kV of electrostatic build-up on you (or any items in front of the CRT). ESD is actually a huge problem in the semiconductor industry. Losses of more than 25 % of parts during manufacturing due to ESD or EOS (Electrical Over-Stress) have been reported in literature [Wagner, 1993]. Some say it's more like 20 % for ESD [Vinson, 1998].

<p>

I bet the leakage current is to blame for this. Here's the scoop:<br>

There's a small but finite capacitance between you and the electrical system (including ground) of you house. <br>

The power supply for your laptop is a switchmode power supply. A switchmode power supply works by rectifying the mains power, chopping it up, and sending it through a transformer. (This is in very general terms. If you want to know more, I suggest picking up a copy of R.W. Erickson, <em>Fundamentals of Power Electronics</em>, Chapman & Hall, 1997). The switching (chopping up of the mains power) happens at a relatively high frequency (typically anywhere from 20 kHz - above the audible range for humans - to the low MHz range). The transformer has some parasitic capacitance between input and output. This is just a result of having two transformer windings sitting close on the transformer bobbin. <br>

So the circuit is now as follows: [Mains power] - [paracitic capacitance of power supply transformer] - [you (via laptop, camera)] - [capacitance between you and ground] - [building ground]. Note that the system is driven at the switching frequency of the switchmode power supply. Also note that the impedance of a capacitor decreases with increasing frequency. In other words, you might not get much of a shock from the 60 Hz mains with above system. But at the switching frequency of the power supply, the capacitive coupling becomes significant. That's why you feel a buzz on your nose when you touch the tripod with it...

<p>

The question now becomes what to do about it. I doubt grounding the laptop will do much. If the shock is indeed caused by capacitive coupling, then proper grounding likely won't make much of a difference - unless the grounding creates a preferred current path to ground, which may or may not be the case. For some markets, the manufacturer is required by law to install mains filters which would yield a preferred current path for capacitively coupled currents, but in many cases the spots for these filter components are simply left unpopulated. It's a matter of money (as usual). If the manufacturer knows there is no testing agency to verify the existence of a mains filter, it can save a buck or two by omitting the parts... If you break the law but nobody is around to catch you in the act, did you in fact break the law?<br>

I think the best way of reducing the electrical shock would be to reduce the coupling between you and ground. Wear shoes/sandals of insolating materials. <br>

You could also just unplug the laptop from the AC power supply. That would very likely solve the problem. Aren't laptops meant to be used without an AC hook-up anyway... ;-)

<p>

Happy shootin'

<p>

Tom

[iztok_mrzljak]

well, i did not read all the answers, but i would blame the usb cable, like u did. usb connestions trasmit some electricity (2 or 3 volts, i dont remember right now), that's why they selling all that desk lamps and fans, which u can connect direct to usb port and they work.

but u sholdn't feel any currents from camera, i think, maybe the camera was wet or something and cable wasnt fit correctly, so the current went to surface of the camera and your nose get shocked, hehe.

i hope it's something like that (i also own 300d, and don't want to be suprised like you)..