leaving electrical conductors exposed

[s]

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?

[dom]

[Tabby]

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember s saying something like:

Howly Shiet!

Hewly Shoeti!

By forgery, dear boy, exactly the same as the 'CE' mark on some Chinese goods - never been approved by anyone.

Do the rest of us a favour - if it was a UK seller, report him to Trading Standards and it might prevent some sucker being dead. This kind of utterly irresponsible 'design' should be stamped out with extreme prejudice.

[John]

20 V is not dangerous:

The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation. (Wikipedia)

[Graham.]

Are you being serious? I genuinely can't tell. If so, you should take a good hard look at your (grand)children's train set or Scalextric.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Graham." saying something like:

I most certainly was in the first instance as I'd misread the 20V as

240V for some reason. After that, I continued for effect in a post-ironic sort of way, to counterpoint the essential weakness of the human condition as opposed to the ... blah snore. Has my Art Grant arrived yet?

[damduck-egg]

If on the other hand it was an early Hornby that may have belonged to your Father or Grandfather then some caution would be advised. Their first forays into electric powered ones in 1925 used mains voltage*,appropriately it represented a Metropolitan Electric Loco. Safer lower voltage ones were introduced a year or so later. Back then I suppose such things were too expensive for ordinary folk and were expected to used under the supervision of Nannies etc.

• which of course varied a fair bit depending on the supplier back then.

G.Harman

[Frank Erskine]

The Nanny State?

[Matty F]

It looks like it would make an excellent holder for my metal-framed glasses. Would that be OK or would the frame melt with lots of sparks?

[Mike Harrison]

Having said that, exposed DC conductors on a desk lamp are not without hazard. Suppose you had a lump of wire wool on the desk which happened to come into contact... Even an errant paperclip could plausibly start a fire.

[Dave Plowman (News)]

Ever heard of fuses? The transformer (if it is a transformer) will include a thermal fuse which will blow long before a paperclip would get hot enough to start a fire.

[Camdor]

when she draped a gold chain over it whilst doing makeup in the mirror with the light. Didn't half spark.

[Matty F]

So the thermal fuse didn't work properly then, or wasn't there one?

[Andy Dingley]

The transformer core is small enough to limit the output current. It's so small it runs close that to saturation and the transformer gets warmer than a well-designed transformer for this low power ought to. Although there is (if it's like mine) a thermal fuse in the transformer, there's no over-current fuse on the output.

I've used one of these as the housing for a Jacob's Ladder. It looks best when the audience of punters isn't expecting it to start arcing across 8-) Unfortunately there's so little use for a Jacob's Ladder these days, as they're so hideously noisy for RF they clobber every PA system in the vicinity. Much worse that Teslas or Wimshursts.

[Matty F]

If I have a wire cage around my proposed Jacob's Ladder that should help shouldn't it?

[Andy Dingley]

Not much. This is why Teslas and even Wimshursts are easier. They're resonant circuits (at least Wimshursts with Leyden jars are), so they dump most of their energy into a narrow frequency band. Stop this and you stop their interference. Jacob's Ladders (and rotary spark gaps for Teslas) are brute force broadband devices. You have to stop their interference across a much broader band to stop them.

[Matty F]

Well, we've had Jacob's Ladders in the past, where people press a button to cause the sparks, i.e. not very often. The nearest people who could be affected by interference are 500 metres away. There might be a short PA announcement every few hours. I think a Jacob's Ladder should be OK. The Wimshurst machine seemed rather dangerous in the hands of a clueless demonstrator. The Van de Graaff generator was quite popular. It took me a while to work out that I was getting charged up simply by walking near the thing, and I would get a shock when I touched anything that was earthed, such as the switch to turn the thing off!