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Mild Electrostatic Discharge Felt - Page 2

post #21 of 25
1/24/03 at 2:29pm

Fact

As a matter of fact - DC is more dangerous than AC - this is because for the same resistance offerec by the body - a 100 V DC will discharge two times the current that will be dicharged by a 100V AC.

But I dont think 'your safety' was the motivation for Electric companies to send you AC to your home - this has something to do with minimizing losses in transmission.

Man....If I count the number of times i've been 'Shocked' hee! I was thrown out of the lab (even though I nearly died - nobody is sympathetic these days) for shorting the two terminals with a piece of naked wire and turning the switch on hee hee

How was I to know - I wasn in 8th grade then...

But come to think of it - i'll probably do the same thing today if I had the nerve - it felt sorta cool getting all electrocuted

Disclaimer : If you connect the ground wire to the bathtub or faucet - at least let your friendly roommate know Might save you the cost of buying a casket or even worse - a bottle to mail him back home hee hee
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post #22 of 25
1/24/03 at 2:36pm
Maybe the electrical god will correct me, but I thought the primary reason for not using DC current in homes was the resistance that would build up on the lines? (I'm sure safety *might* have come up later, but really, how many times in America has safety been the driving force behind any big business decisions
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post #23 of 25
1/25/03 at 5:00am

ac vs dc

AC voltage is considered to be discussed in terms of Volts RMS (Root mean squared).. This is the same amount of energy that a DC voltage of the same value would have.

The most DC voltage a normal person will ever come into contact with is 28V from an outboard motor battery.. 12 volts from a car battery..

DC voltage does not hurt as bad as AC voltage.. also 400 Hz AC hurts worse than 60Hz at least it feels worse to me.. I've not played with 50Hz but I bet it feels about the same as 60Hz


The reason AC voltage is used by power companies is the ease of which the voltage can be changed.. They use higher voltages to prevent losses due to resistance. So you were partially right.. It is harder to change one DC voltage to another than it is to change one AC voltage to another.

I wont bore you with the equations and all.. theres been enough of those in this thread..

but it all boils down to V = IR and P = VI

BTW I hated my power classes..

Digital > Analog >>>>>>>>>>>>>>>>> Power..
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post #24 of 25
1/25/03 at 1:43pm
Hehe, yeah, Thomas Edison wanted to use DC power in the U.S. and someone else who wasn't so famous was like "You're a crackhead, we have to use AC so we can use transformers..." and there was a big battle and eventually the AC guy won (obviously).
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post #25 of 25
9/2/05 at 11:30pm
Quote:
Originally Posted by gezs
As for a short inside the computer yes that could cause a tingle BUT unless the short was in the power supply you probably wouldn't feel it. The skins natural resistance is too high in most places to feel anything less than 50V DC.. Now if you stuck your tounge onto the metal then yes you are going to feel it.

In anything digital you typically have two GNDs. You have a chasis ground and a digital return. The digital return is connected through the transformer to the AC return. The chasis ground is connected to the GND wire that is in your home. Some designs combine the Chasis GND to the digital return lines or through short ect this happens.. This is where bad things can start to happen.

If the chasis GND is connected to the digital RTN lines then any voltage present on the GND will be forced through anything connected to the RTN. Most digital components can't handle anything more than a few volts more than their required voltage. If you push 12 volts thru a 5volt device it will probably survive for a few hours.. if you push 12 volts thru a 1.7V device well it may last a few seconds. What happens is the ciruitry melts due to the heat that builds up due to the resistance.................................
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Anything over 10k becomes unpleasent atleast to me.. Typically getting out of the car the charge will exceed 25kV.. I really hate touching the car door.. though I hate finger prints on the glass.. and the ruber molding around the glass isn't wide enough to keep from being shocked..

Hi,
I found this thread while trying to find a reason for my compaq evo n410c giving me shocks from the edge of the keyboard. My powersupply is standard compaq 3 prong 240v ac input and either 16 or 18.5dc output. Words too tiny for me to be exact. I had the same problem with my evo n200 as well.
It doesn't seem to happen if the computer isn't doing much but if it gets busy it gives me shocks. Could it be something heats up, expands and causes a short? if so what is most likely to do it. I know this is a huge ask, but I am hopeful you can give me some ideas. I remember the first time it happened I nearly threw it on the floor. But I was too interested in what I was doing and carried on, with occasional swear words.
cheers
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