i got a desk lamp from ebay like the one in the image link below. the
bulb is held up by two adjustable telescopic rods, exactly the same
type as you would find on the aerial of a FM radio. they are metal.

i saw the double insulated symbol on the bottom, which go me thinking.
how did they get the wiring through these rods double insulated, they
are pretty thin. then i examined the rods. they had joints in them.
they werent even hollow! there was no wiring. they were the
conductors.

a quick check with the meter gave 20V AC. thats how it was designed
to light the bulb .

my question is can you have the double insulated symbol on a product
with exposed 20V AC conductors?



http://www.flickr.com/photos/31506127@N03/3033028166


if interested this is a description of a similar product , which shows
the conductors are exposed by design:
http://www.freepatentsonline.com/5265000.html

In article
,
s wrote:
i got a desk lamp from ebay like the one in the image link below. the
bulb is held up by two adjustable telescopic rods, exactly the same
type as you would find on the aerial of a FM radio. they are metal.

i saw the double insulated symbol on the bottom, which go me thinking.
how did they get the wiring through these rods double insulated, they
are pretty thin. then i examined the rods. they had joints in them.
they werent even hollow! there was no wiring. they were the
conductors.

a quick check with the meter gave 20V AC. thats how it was designed
to light the bulb .

my question is can you have the double insulated symbol on a product
with exposed 20V AC conductors?

I'd guess because 20 volt AC is considered safe. A 20 volt AC power supply
could also have output terminals etc which wouldn't conform to mains etc
voltages. The 'double insulation' is to help prevent mains appearing on
parts you can touch easily.

BTW, it's more likely to be approx 12v under load.

--
*I believe five out of four people have trouble with fractions. *

Dave Plowman London SW
To e-mail, change noise into sound.

Can you have the double-insulated symbol on
a product with exposed 20V AC conductors?

Because humans aren't likely to be electrocuted by 20V, AC or DC.

But this does raise a question... What about insulation between the primary
and secondary windings? Its failure could put line voltage on the secondary.

In article ,
William Sommerwerck wrote:
Can you have the double-insulated symbol on
a product with exposed 20V AC conductors?

Because humans aren't likely to be electrocuted by 20V, AC or DC.

But this does raise a question... What about insulation between the
primary and secondary windings? Its failure could put line voltage on
the secondary.

Depends on transformer design - assuming it does use one.

--
*For every action, there is an equal and opposite criticism *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article
,
s wrote:
i got a desk lamp from ebay like the one in the image link below. the
bulb is held up by two adjustable telescopic rods, exactly the same
type as you would find on the aerial of a FM radio. they are metal.

i saw the double insulated symbol on the bottom, which go me thinking.
how did they get the wiring through these rods double insulated, they
are pretty thin. then i examined the rods. they had joints in them.
they werent even hollow! there was no wiring. they were the
conductors.

a quick check with the meter gave 20V AC. thats how it was designed
to light the bulb .

my question is can you have the double insulated symbol on a product
with exposed 20V AC conductors?

I'd guess because 20 volt AC is considered safe. A 20 volt AC power supply
could also have output terminals etc which wouldn't conform to mains etc
voltages. The 'double insulation' is to help prevent mains appearing on
parts you can touch easily.

BTW, it's more likely to be approx 12v under load.


Ok, but how did it make it past the "fire hazard" category.
It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

Methinks the inspector was either asleep or out cruising in the Beemer
he bought with the payoffs.

In article ,
mike wrote:
I'd guess because 20 volt AC is considered safe. A 20 volt AC power
supply could also have output terminals etc which wouldn't conform to
mains etc voltages. The 'double insulation' is to help prevent mains
appearing on parts you can touch easily.

BTW, it's more likely to be approx 12v under load.


Ok, but how did it make it past the "fire hazard" category.
It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

A fuse somewhere?

Methinks the inspector was either asleep or out cruising in the Beemer
he bought with the payoffs.

Think you're worrying too much.

--
*Constipated People Don't Give A Crap*

Dave Plowman London SW
To e-mail, change noise into sound.

William Sommerwerck wrote:

Can you have the double-insulated symbol on
a product with exposed 20V AC conductors?

Because humans aren't likely to be electrocuted by 20V, AC or DC.

But this does raise a question... What about insulation between the primary
and secondary windings? Its failure could put line voltage on the secondary.


There are high isolation transformers with the windings on separate
bobbins. The efficiency is lower than traditional overlaid winding, but
the two windings aren't close enough for anything less than a lightning
strike from reaching the secondary and there isn't any design that is
safe from a direct strike.


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

s wrote:
i got a desk lamp from ebay like the one in the image link below. the
bulb is held up by two adjustable telescopic rods, exactly the same
type as you would find on the aerial of a FM radio. they are metal.

i saw the double insulated symbol on the bottom, which go me thinking.
how did they get the wiring through these rods double insulated, they
are pretty thin. then i examined the rods. they had joints in them.
they werent even hollow! there was no wiring. they were the
conductors.

a quick check with the meter gave 20V AC. thats how it was designed
to light the bulb .

my question is can you have the double insulated symbol on a product
with exposed 20V AC conductors?

that's if you believe the markings on the product in the first place.

Can you measure the leakage from either of the antennae to ground?

In article ,
Michael A. Terrell wrote:

There are high isolation transformers with the windings on separate
bobbins. The efficiency is lower than traditional overlaid winding, but
the two windings aren't close enough for anything less than a lightning
strike from reaching the secondary and there isn't any design that is
safe from a direct strike.

Indeed. Often called 'medical quality'.

--
*I don't work here. I'm a consultant

Dave Plowman London SW
To e-mail, change noise into sound.

"mike"

Ok, but how did it make it past the "fire hazard" category.

** The design of the transformer prevents any fire or electrocution hazard.


It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

** Shorting the secondary winding is one of the tests carried out when
certifying a transformer as "class 2" or double insulated. The unit must not
overheat or burn to the extent that primary and secondary circuits can
become fused.

Most often this is achieved by adding a thermal fuse to the primary circuit
that will open if the winding temp reaches a point that could damage the
insulation used to make the tranny - about 120C in most examples.

Some older designs used fireproof insulation between the primary and
secondary and the winding were contained on separate halves of a plastic
bobbin. Such a tranny could smoke and burn but still not present an
electrocution hazard.


..... Phil

"Cydrome Leader"

my question is can you have the double insulated symbol on a product
with exposed 20V AC conductors?

that's if you believe the markings on the product in the first place.


** The double square symbol is one that any maker can simply apply
themselves - in most places no lab testing would be involved. It is on the
maker's head if the product does not comply with all class 2 safety rules
and is unsafe.

In this case however, the presence of a "one shot " thermal fuse in the
primary winding of the AC tranny will do the job ALONG with split bobbin
construction.


..... Phil

Phil Allison wrote:
"mike"
Ok, but how did it make it past the "fire hazard" category.

** The design of the transformer prevents any fire or electrocution hazard.


It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

** Shorting the secondary winding is one of the tests carried out when
certifying a transformer as "class 2" or double insulated. The unit must not
overheat or burn to the extent that primary and secondary circuits can
become fused.

Most often this is achieved by adding a thermal fuse to the primary circuit
that will open if the winding temp reaches a point that could damage the
insulation used to make the tranny - about 120C in most examples.

Some older designs used fireproof insulation between the primary and
secondary and the winding were contained on separate halves of a plastic
bobbin. Such a tranny could smoke and burn but still not present an
electrocution hazard.


.... Phil


Ok, but what about the spark that happens when you knock it over
while refilling your butane torch? Or when you just cleaned a part
with alcohol. Dumb design!!!
Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!

mike wrote:

Phil Allison wrote:
"mike"
Ok, but how did it make it past the "fire hazard" category.

** The design of the transformer prevents any fire or electrocution hazard.


It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

** Shorting the secondary winding is one of the tests carried out when
certifying a transformer as "class 2" or double insulated. The unit must not
overheat or burn to the extent that primary and secondary circuits can
become fused.

Most often this is achieved by adding a thermal fuse to the primary circuit
that will open if the winding temp reaches a point that could damage the
insulation used to make the tranny - about 120C in most examples.

Some older designs used fireproof insulation between the primary and
secondary and the winding were contained on separate halves of a plastic
bobbin. Such a tranny could smoke and burn but still not present an
electrocution hazard.


.... Phil


Ok, but what about the spark that happens when you knock it over
while refilling your butane torch? Or when you just cleaned a part
with alcohol. Dumb design!!!
Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!


I nominate you for a Darwin Award. The timing is up to you.


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

"mike"

Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!


** Never put a 9 volt alkaline battery in the same pocket as your keys.....



..... Phil

Phil Allison wrote:
"mike"

Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!


** Never put a 9 volt alkaline battery in the same pocket as your keys.....



.... Phil


At least don't fart if you do.

On Sun, 12 Dec 2010 09:34:29 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Michael A. Terrell wrote:

There are high isolation transformers with the windings on separate
bobbins. The efficiency is lower than traditional overlaid winding, but
the two windings aren't close enough for anything less than a lightning
strike from reaching the secondary and there isn't any design that is
safe from a direct strike.

Indeed. Often called 'medical quality'.

There was a guy in the steel mill I worked at (in the office) who was
killed by his table radio, iirc, It's a little rough in the mills,
the computer monitors and keyboards got very dirty, but I'm still
surprised the radio killed him.. After that, they wouldn't let us use
any radio or fan unless it had a 3-prong plug (and presumably 3 wires,
one of them grounding the chassis. I was a contractor and wan't going
to play games by pretending to have a grounded appliance when I
didn't, so I gave up on the fan and brought in a transistor radio.)

As to the risk here, I routinely touch both clips of the 1-amp 12 votl
battery charger I have. I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't and
tomorrow I will, I'll even find some alcohol to spark in. If I don't
post back, it means my house burned down and took my computer and me
with it.

In article ,
mm wrote:
As to the risk here, I routinely touch both clips of the 1-amp 12 votl
battery charger I have. I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't and
tomorrow I will, I'll even find some alcohol to spark in. If I don't
post back, it means my house burned down and took my computer and me
with it.

It only takes a few milliamps to kill you. Assuming the current has a path
to a vital organ, like the heart.

Of course many modern car battery chargers have a relay on their output
with the coil operated by the battery - via a diode - to prevent damage to
the charger if it's connected with the wrong polarity. Which also means
it's less likely you'll touch the connectors when they're live.

A powered up but disconnected battery charger of a basic design might well
present a greater 'hazard' than when connected to the battery as the open
circuit voltage could be much higher than the nominal 12 volts.

--
*Marathon runners with bad footwear suffer the agony of defeat*

Dave Plowman London SW
To e-mail, change noise into sound.

On 12 dic, 23:51, mike wrote:
Phil Allison wrote:
"mike"
Ok, but how did it make it past the "fire hazard" category.

** The design of the transformer prevents any fire or electrocution hazard.

It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.

** *Shorting the secondary winding is one of the tests carried out when
certifying a transformer as "class 2" or double insulated. The unit must not
overheat or burn to the extent that primary and secondary circuits can
become fused.

Most often this is achieved by adding a thermal fuse to the primary circuit
that will open if the winding temp reaches a point that could damage the
insulation used to make the tranny - * about 120C in most examples.

Some older designs used fireproof insulation between the primary and
secondary and the winding were contained on separate halves of a plastic
bobbin. Such a tranny could smoke and burn but still not present an
electrocution hazard.

.... *Phil

Ok, but what about the spark that happens when you knock it over
while refilling your butane torch? *Or when you just cleaned a part
with alcohol. *Dumb design!!!
Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!



But you bought a chinese no name "design" lamp, with chinese
construction "quality" and chinese design "aspect" and you pretend
that this lamp should be properly designed??? I bet you that the
creator of that "jewel" isn´t even an engineer.

If you don´t fell comfortable with the lamp, and I wouldn´t BTW, just
trash it.

On 15 dic, 05:21, "Dave Plowman (News)" wrote:
In article ,
* *mm wrote:

As to the risk here, I routinely touch both clips of the 1-amp 12 votl
battery charger I have. * I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't and
tomorrow I will, *I'll even find some alcohol to spark in. *If I don't
post back, it means my house burned down and took my computer and me
with it.

It only takes a few milliamps to kill you. Assuming the current has a path
to a vital organ, like the heart.

Of course many modern car battery chargers have a relay on their output
with the coil operated by the battery - via a diode - to prevent damage to
the charger if it's connected with the wrong polarity. Which also means
it's less likely you'll touch the connectors when they're live.

A powered up but disconnected battery charger of a basic design might well
present a greater 'hazard' than when connected to the battery as the open
circuit voltage could be much higher than the nominal 12 volts.

--
*Marathon runners with bad footwear suffer the agony of defeat*

* * Dave Plowman * * * * * * * * London SW
* * * * * * * * * To e-mail, change noise into sound.

Certainly you can be killed with a few milliamps, but only if the
voltage is 60V or higher.

In article
,
lsmartino wrote:
It only takes a few milliamps to kill you. Assuming the current has a
path to a vital organ, like the heart.

Certainly you can be killed with a few milliamps, but only if the
voltage is 60V or higher.

Current flow depends on resistance as well as voltage. And when talking
about the human body that resistance will vary by a huge amount depending
on many factors.

60 volts isn't considered 'safe' anywhere I know of. About half that is
the accepted norm.

--
*Give me ambiguity or give me something else.

Dave Plowman London SW
To e-mail, change noise into sound.

As to the risk here, I routinely touch both clips of the 1-amp 12 volt
battery charger I have. I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't
and tomorrow I will, I'll even find some alcohol to spark in. If I
don't
post back, it means my house burned down and took my computer
and me with it.

It only takes a few milliamps to kill you. Assuming the current
has a path to a vital organ, like the heart.

It takes about 100mA through the heart to kill you.

Guys, a battery charger is not a constant-current device! It provides only
the current determined by its charging voltage (which I assume starts at
around 14V) and your skin resistance, which even when your hands are wet, is
no lower than a few thousand ohms.

YOU CANNOT BE ELCTROCUTED BY THE OUTPUT OF A CAR-BATTERY CHARGER.

Certainly you can be killed with a few milliamps,
but only if the voltage is 60V or higher.

Wrong, wrong, wrong, wrong, wrong. The voltage has nothing whatever to do
with electrocution (other than affecting how much current flows). ONLY THE
CURRENT MATTERS.

You cannot be killed "with a few milliamps". The thresholds are known, and
the lethal level is at about 100mA through the heart.

I can't believe the participants in /this/ group aren't more familiar with
electrical safety.

60 volts isn't considered 'safe' anywhere I know of.
About half that is the accepted norm.

60V is not lethal (unless, perhaps, the electrodes were under the skin). It
can, however, deliver a nasty shock, which can provoke a fall, or bumping
into something that really is dangerous.

In article ,
William Sommerwerck wrote:
Certainly you can be killed with a few milliamps,
but only if the voltage is 60V or higher.

Wrong, wrong, wrong, wrong, wrong. The voltage has nothing whatever to
do with electrocution (other than affecting how much current flows).
ONLY THE CURRENT MATTERS.

That bit is correct.

You cannot be killed "with a few milliamps". The thresholds are known,
and the lethal level is at about 100mA through the heart.

The actual amount will vary from person to person. That may well be an
average. How many 'milliamps' on average does 'your' electric chair seek
to achieve to be fairly certain of killing someone without blowing them
apart?

I can't believe the participants in /this/ group aren't more familiar
with electrical safety.

Electrical safety standards vary between countries. And over the years.
The only truly safe advice is not to touch anything live.

--
*Why is it considered necessary to screw down the lid of a coffin?

Dave Plowman London SW
To e-mail, change noise into sound.

How many 'milliamps' on average does 'your' electric chair
seek to achieve to be fairly certain of killing someone
without blowing them apart?

That's one of the problems with electric chairs -- they don't work the way
they're supposed to. They do a better job of slowly frying the criminal,
rather than quickly stopping his heart.

I'll have to write a new version of Gilbert... "The criminal fried..."


I can't believe the participants in /this/ group aren't
more familiar with electrical safety.

Electrical safety standards vary between countries.

I was talking about safety, not safety standards or regulations.

On 15 dic, 09:55, "William Sommerwerck"
wrote:
Certainly you can be killed with a few milliamps,
but only if the voltage is 60V or higher.

Wrong, wrong, wrong, wrong, wrong. The voltage has nothing whatever to do
with electrocution (other than affecting how much current flows). ONLY THE
CURRENT MATTERS.

You cannot be killed "with a few milliamps". The thresholds are known, and
the lethal level is at about 100mA through the heart.

I can't believe the participants in /this/ group aren't more familiar with
electrical safety.

Human skin has a resistance between 1K and 6K, and that resistante
varies with the voltage aplied to skin. This table supplied by the IEC
indicates that human skin electrical resistance varies as follows:


Voltage 5% 50% 95%
25 V 1,750 Ω 3,250 Ω 6,100 Ω
100 V 1,200 Ω 1,875 Ω 3,200 Ω
220 V 1,000 Ω 1,350 Ω 2,125 Ω
1000 V 700 Ω 1,050 Ω 1,500 Ω

The 5%, 50%, and 95% columns represents the distribution of the
population percentile per measurement.

Now lets assume that you have a voltage source of 24V. According to
the above table your body impedance can be anywhere between 1,750 and
6,100 ohms at that voltage level. Using omhs law, and aplying the
lowest impedance, your body will draw only 13 mA. That´s why a 24V
battery WILL NOT kill anyone, no matter what is the aH capacity of the
battery, nor the maximum current available from the battery at a given
time. You body will only draw 0,013 mA from it. And also that´s the
reason no one gets killed when the touch the posts of a 12V car
battery.

Now lets repeat the calculations supossing that we have a voltage
source of 60V. Using again the table, and taking the lowest impedance
possible (1200 ohms), the amount of current that will be drawn by the
human skin would be 50 mA. OK, for sure that will be a painful
experience but no one will get killed from a 60V source... except if
the person is wet. In that case, the impedance will be lower.

The point I am trying to make here is that while is true that a 100 mA
current is lethal, you have to provide a voltage level high enough to
your body in order to make draw 100 mA. Voltage levels under 60V will
not kill anybody unless the person decides to put electrodes under the
skin, or the skin is wet.

Human skin has a resistance between 1K and 6K, and
that resistance varies with the voltage aplied to skin.

That's a way-low value. Try grabbing the probes of a DVM.

The actual resistance varies with the skin's wetness, the area covered, and
whether the skin has been penetrated.

On 15 dic, 12:07, "William Sommerwerck"
wrote:
Human skin has a resistance between 1K and 6K, and
that resistance varies with the voltage aplied to skin.

That's a way-low value. Try grabbing the probes of a DVM.

The actual resistance varies with the skin's wetness, the area covered, and
whether the skin has been penetrated.

Certainly a DVM will show a body impedance of 20K or more, but please
take into account that a DVM will, at most cases, apply 1.5V or 3V to
the test probes, and skin impedance is inversely proportional to the
voltage applied to it.

See this article:

http://en.wikipedia.org/wiki/Electric_shock

"The voltage necessary for electrocution depends on the current
through the body and the duration of the current. Ohm's law states
that the current drawn depends on the resistance of the body. The
resistance of human skin varies from person to person and fluctuates
between different times of day. The NIOSH states "Under dry
conditions, the resistance offered by the human body may be as high as
100,000 Ohms. Wet or broken skin may drop the body's resistance to
1,000 Ohms," adding that "high-voltage electrical energy quickly
breaks down human skin, reducing the human body's resistance to 500
Ohms."[9]

The International Electrotechnical Commission gives the following
values for the total body impedance of a hand to hand circuit for dry
skin, large contact areas, 50 Hz AC currents (the columns contain the
distribution of the impedance in the population percentile; for
example at 100 V 50% of the population had an impedance of 1875Ω or
less):[10]

Voltage 5% 50% 95%
25 V 1,750 Ω 3,250 Ω 6,100 Ω
100 V 1,200 Ω 1,875 Ω 3,200 Ω
220 V 1,000 Ω 1,350 Ω 2,125 Ω
1000 V 700 Ω 1,050 Ω 1,500 Ω "

Notice that depending on the amount of voltage applied to the skin, it
resistance decreases. That´s why a DVM will show a higher impedance
than the one that is published in the table.

Summarizing: we agree that current is what kills, but in order to make
your body draw that amount of current, you need a high enough voltage.
Voltages under 60V are unlikely to kill anyone, unless the person is
applying electricity directly through an open wound. Just do the math.

lsmartino wrote:

Summarizing: we agree that current is what kills, but in order to make
your body draw that amount of current, you need a high enough voltage.
Voltages under 60V are unlikely to kill anyone, unless the person is
applying electricity directly through an open wound. Just do the math.


A humman body doesn't 'draw current'. It 'passes current' if you are
in a circuit.


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

In article ,
William Sommerwerck wrote:
How many 'milliamps' on average does 'your' electric chair
seek to achieve to be fairly certain of killing someone
without blowing them apart?

That's one of the problems with electric chairs -- they don't work the
way they're supposed to. They do a better job of slowly frying the
criminal, rather than quickly stopping his heart.

I'll have to write a new version of Gilbert... "The criminal fried..."

;-)


I can't believe the participants in /this/ group aren't
more familiar with electrical safety.

Electrical safety standards vary between countries.

I was talking about safety, not safety standards or regulations.

Indeed. To you or me it seems so simple.

--
*Lottery: A tax on people who are bad at math.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
William Sommerwerck wrote:
Human skin has a resistance between 1K and 6K, and
that resistance varies with the voltage aplied to skin.

That's a way-low value. Try grabbing the probes of a DVM.

The actual resistance varies with the skin's wetness, the area covered,
and whether the skin has been penetrated.

Then there's me. Thick skinned. As you have to be to post to a US group
from the UK.

I'd guess they are measuring through the skin - from front to back as it
were. But of course it varies in thickness according to where it is in on
the body.

--
*Confession is good for the soul, but bad for your career.

Dave Plowman London SW
To e-mail, change noise into sound.

On 15 dic, 13:18, "Michael A. Terrell"
wrote:
lsmartino wrote:

Summarizing: we agree that current is what kills, but in order to make
your body draw that amount of current, you need a high enough voltage.
Voltages under 60V are unlikely to kill anyone, unless the person is
applying electricity directly through an open wound. Just do the math.

* *A humman body doesn't 'draw current'. *It 'passes current' if you are
in a circuit.

--
For the last time: *I am not a mad scientist, I'm just a very ticked off
scientist!!!

Certainly. My mistake.

In message
,
lsmartino writes
On 15 dic, 13:18, "Michael A. Terrell"
wrote:
lsmartino wrote:

Summarizing: we agree that current is what kills, but in order to make
your body draw that amount of current, you need a high enough voltage.
Voltages under 60V are unlikely to kill anyone, unless the person is
applying electricity directly through an open wound. Just do the math.

* *A humman body doesn't 'draw current'. *It 'passes current' if you are
in a circuit.

--
For the last time: *I am not a mad scientist, I'm just a very ticked off
scientist!!!

Certainly. My mistake.

It's not a mistake at all. To 'draw current' is a common figure of
speech. A resistor, connected across a battery, by passing current, will
'draw current' from the battery.
--
Ian

On Wed, 15 Dec 2010 09:21:30 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
mm wrote:
As to the risk here, I routinely touch both clips of the 1-amp 12 votl
battery charger I have. I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't and

BTW, I know that an 8 amp charger won't put any more current through
me than a one amp charger. Maybe I don't hold both claimps at once
because they are big and ugly and and "zinc"-coated and seem dirty
even when they're not, and much harrder to hold in one hand than the
other little ones, and they are on separate wires instead of
two-conductor wire that splits only a few inches from the clamps, like
he little charger.

tomorrow I will, I'll even find some alcohol to spark in. If I don't
post back, it means my house burned down and took my computer and me
with it.

It only takes a few milliamps to kill you. Assuming the current has a path
to a vital organ, like the heart.

The body gives thousands of ohms resistance, even when one's fingers
are wet.

Has anyone every been killed by 12-volts, DC or AC? I doubt it.

Of course many modern car battery chargers have a relay on their output
with the coil operated by the battery - via a diode - to prevent damage to
the charger if it's connected with the wrong polarity. Which also means
it's less likely you'll touch the connectors when they're live.

A powered up but disconnected battery charger of a basic design might well
present a greater 'hazard' than when connected to the battery as the open
circuit voltage could be much higher than the nominal 12 volts.

20 volts.

Thanks for recommending the Powermid pyramid remote extender. I got
one and it works great. I'm going to get more for other rooms.

I knew about it, but hadn't had a personal recommendation before.

Sort of ironic, since my Leapfrog IR-45 was finally working pretty
well on all 3 floors, but the Powermid is even quite a bit better.

On Wed, 15 Dec 2010 05:55:52 -0800, "William Sommerwerck"
wrote:

Certainly you can be killed with a few milliamps,
but only if the voltage is 60V or higher.

Wrong, wrong, wrong, wrong, wrong. The voltage has nothing whatever to do
with electrocution (other than affecting how much current flows). ONLY THE
CURRENT MATTERS.

Except that the current is directly proportional to the voltage, so I
don't think it's fair to say the votage ahs nothing whatever to do it
with it.

And you can only apply voltage. You don't know how much current will
go through most things until there is a voltage across it either from
an ohmmeter or some power supply.

No offense meant, but I'm reminded of a JHS science teacher who said
that water had nothing to do with rust, because the formula for rust
production is Fe + 02 = Fe02 (or something like that) and water isn't
in it. Even though everyone can tell that wet things rust much more
than dry things.

Other than this, I agree with your posts.

You cannot be killed "with a few milliamps". The thresholds are known, and
the lethal level is at about 100mA through the heart.

I can't believe the participants in /this/ group aren't more familiar with
electrical safety.

lsmartino wrote:
On 12 dic, 23:51, mike wrote:
Phil Allison wrote:
"mike"
Ok, but how did it make it past the "fire hazard" category.
** The design of the transformer prevents any fire or electrocution hazard.
It's surely a source of ignition when you knock it over onto
a pair of scissors on the desk.
** Shorting the secondary winding is one of the tests carried out when
certifying a transformer as "class 2" or double insulated. The unit must not
overheat or burn to the extent that primary and secondary circuits can
become fused.
Most often this is achieved by adding a thermal fuse to the primary circuit
that will open if the winding temp reaches a point that could damage the
insulation used to make the tranny - about 120C in most examples.
Some older designs used fireproof insulation between the primary and
secondary and the winding were contained on separate halves of a plastic
bobbin. Such a tranny could smoke and burn but still not present an
electrocution hazard.
.... Phil
Ok, but what about the spark that happens when you knock it over
while refilling your butane torch? Or when you just cleaned a part
with alcohol. Dumb design!!!
Safety design is a LOT more than just the obvious.
There'd be a lot fewer houses burned to the ground if only engineers
thought more about how their products are used and the hazards
caused by confluence of circumstance.
Did I mention...DUMB DESIGN!!



But you bought a chinese no name "design" lamp, with chinese
construction "quality" and chinese design "aspect" and you pretend
that this lamp should be properly designed??? I bet you that the
creator of that "jewel" isn´t even an engineer.

If you don´t fell comfortable with the lamp, and I wouldn´t BTW, just
trash it.

Well...
I didn't buy it.
The issue is not about the buyer's ability to determine the safety
of a Chinese lamp.
The issue is about the certification agencies who have the device in their
lab for qualification.
Their JOB is to protect me from harm.
They should not have qualified such a device.
You may feel otherwise, that's your right.

Michael A. Terrell wrote:
lsmartino wrote:
Summarizing: we agree that current is what kills, but in order to make
your body draw that amount of current, you need a high enough voltage.
Voltages under 60V are unlikely to kill anyone, unless the person is
applying electricity directly through an open wound. Just do the math.


A humman body doesn't 'draw current'. It 'passes current' if you are
in a circuit.



That's a "creative" interpretation.

To get current, you must have volts.
Power = volts x amps.
So, where does that power end up?
And how do you rationalize a useful distinction between
"drawing" and "passing"?

William Sommerwerck wrote:
As to the risk here, I routinely touch both clips of the 1-amp 12 volt
battery charger I have. I havent' done that with the 8 amp charger,
probably because the phrase "8 amp" scares me, but it shoudln't
and tomorrow I will, I'll even find some alcohol to spark in. If I
don't
post back, it means my house burned down and took my computer
and me with it.

It only takes a few milliamps to kill you. Assuming the current
has a path to a vital organ, like the heart.

It takes about 100mA through the heart to kill you.

Guys, a battery charger is not a constant-current device! It provides only
the current determined by its charging voltage (which I assume starts at
around 14V) and your skin resistance, which even when your hands are wet, is
no lower than a few thousand ohms.

YOU CANNOT BE ELCTROCUTED BY THE OUTPUT OF A CAR-BATTERY CHARGER.


That statement suggests a misguided interpretation of "certainty".
I doubt you've considered ALL possibilities.
"unlikely" might be a better word than "cannot" for use in that
sentence.

In article ,
mike wrote:
But you bought a chinese no name "design" lamp, with chinese
construction "quality" and chinese design "aspect" and you pretend
that this lamp should be properly designed??? I bet you that the
creator of that "jewel" isn´t even an engineer.

If you don´t fell comfortable with the lamp, and I wouldn´t BTW, just
trash it.

Well... I didn't buy it. The issue is not about the buyer's ability to
determine the safety of a Chinese lamp. The issue is about the
certification agencies who have the device in their lab for
qualification. Their JOB is to protect me from harm. They should not
have qualified such a device. You may feel otherwise, that's your right.

I've got three of those design lamps here. Bought many years ago. Didn't
know they'd come back into fashion. I'm no more worried about using them
than I worry about having a PP3 battery with the terminals exposed...

--
*Is it true that cannibals don't eat clowns because they taste funny?

Dave Plowman London SW
To e-mail, change noise into sound.

YOU CANNOT BE ELCTROCUTED BY THE
OUTPUT OF A CAR-BATTERY CHARGER.

That statement suggests a misguided interpretation of
"certainty". I doubt you've considered ALL possibilities.
"unlikely" might be a better word than "cannot" for use
in that sentence.

You're right in principle, but it's difficult to think of /any/ situation in
which 14 volts could pump enough current through a human body to kill its
owner. You'd need a net resistance (across the heart) of 140 ohms. Not
likely.