Post by Bob MannixPost by George (dicegeorge)When i was a boy i'd lick the end of a 9volt battery with my tongue and
get a tingle!
I started a fire once running 12volts DC through a too thin wire,
the plastic round the wire melted and burnt poisonously,
it could probably be done with a 6 volt motorbike battery..
But i doubt if you could light a bicycle light bulb with the 5volt AC
which the original poster measured on his mains when turned off...
A friend when I was young put the two wires from the poorly regulated 12V
train track transformer on his tongue. Granted he (nor I, having seen it)
would ever do it again but he suffered no permanent damage!
As another poster said, 50V is (give or take) where it starts getting dodgy.
The same friend (as it happens, must be something about him!) did get stuck
on a 110V DC supply, through his hands and down to his feet which were bare,
on steel boat deck plates. Now we are actually in the realms of "it's the
mills that kills" rather than in the fantasy world of the 5V'ers. Yes he was
on the way out, he couldn't let go and knew he was blacking out and a goner.
One of the crew found him and threw the breaker in time (fortunately).
Know your enemy. A 110V DC supply on a boat is effing dangerous. 5V anywhere
isn't to humans as electricity.
I deal with large power supplies in my work - a 50V, 10000A power supply
(which we have) isn't particularly dangerous (unless you drop something
metal across the output and get flash burns). You could put your hand on the
conductors (unless stood in a metal bucket of water) and it's immaterial
whether it's a 10000A supply or a 1A supply, you would get a bit of a
tingle. Another supply up the way is about 130V /500A. This is a dangerous
beast to work on as the voltage is too high.
And that is one of the reasons why (archaic term coming) telephone
exchanges use equipment powered by 48V DC. It is less dangerous than
using higher voltages. Note that I did not say it was safe - as
pointed out by other people, shorting out a 48V DC supply that can
deliver high currents is a bad thing - so dropping conductive metal
tools onto bare bus-bars or terminals of opposite polarity is
seriously bad news.
However, telephony does have surprises up its sleeve - ringing
currents in the UK are nominally 75V AC at 25Hz, which is enough to
give you a nasty jangle. Thankfully, in normal working they are not
continuous, so giving you time to let go between rings if necessary.
For serious shocks, the old telephone magnetos could give a severe
belt. If you are familiar with really old phones that don't have a
keypad or dial, what they had was a small handle to crank that rang a
bell at the exchange. This was achieved by using a small magneto to
generate the power. Some American ones could generate up to 110V AC at
5 amps (at least according to this website: <URL:http://
www.oldphoneman.com/FSMagnetos.htm> !
Sid