leaving conductors exposed

S

s

Guest
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
 
Can you have the double-insulated symbol on
a product with exposed 20V AC conductors?
Click to expand...
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
<2a2eb7c7-a29d-4939-a1cc-982ff46cee9a@g26g2000vbi.googlegroups.com>,
s <ymailus@yahoo.com> 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?
Click to expand...
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 dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
In article <ie02jm$8h2$1@news.eternal-september.org>,
William Sommerwerck <grizzledgeezer@comcast.net> 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.
Click to expand...
Depends on transformer design - assuming it does use one.

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

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
Dave Plowman (News) wrote:
In article
2a2eb7c7-a29d-4939-a1cc-982ff46cee9a@g26g2000vbi.googlegroups.com>,
s <ymailus@yahoo.com> 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.
Click to expand...
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 <ie0lc2$qml$1@news.eternal-september.org>,
mike <spamme0@go.com> 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.
Click to expand...
A fuse somewhere?

Methinks the inspector was either asleep or out cruising in the Beemer
he bought with the payoffs.
Click to expand...
Think you're worrying too much.

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

Dave Plowman dave@davenoise.co.uk 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.
Click to expand...

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 <ymailus@yahoo.com> 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?
Click to expand...
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 <lsudnfyFHa-p35nQnZ2dnUVZ_ridnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> 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.
Click to expand...
Indeed. Often called 'medical quality'.

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

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
"mike"
Ok, but how did it make it past the "fire hazard" category.
Click to expand...
** 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.
Click to expand...
** 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.
Click to expand...

** 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
Click to expand...
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!!
Click to expand...

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!!
Click to expand...

** 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.
Click to expand...
 
On Sun, 12 Dec 2010 09:34:29 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:

In article <lsudnfyFHa-p35nQnZ2dnUVZ_ridnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> 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'.
Click to expand...
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 <aj0hg65q8716asl7teltu2vlg1jrahfcgq@4ax.com>,
mm <NOPSAMmm2005@bigfoot.com> 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.
Click to expand...
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 dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
On 12 dic, 23:51, mike <spam...@go.com> 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!!
Click to expand...
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)" <d...@davenoise.co.uk> wrote:
In article <aj0hg65q8716asl7teltu2vlg1jrahf...@4ax.com>,
   mm <NOPSAMmm2...@bigfoot.com> 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        d...@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Click to expand...
Certainly you can be killed with a few milliamps, but only if the
voltage is 60V or higher.
 
In article
<c0aabc33-2c52-4ca9-b83c-2a5d19ab5577@k22g2000yqh.googlegroups.com>,
lsmartino <luismartino76@gmail.com> 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.
Click to expand...
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 dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
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