Halogen desk lamp wiring

Cleaning up 3 old halogen desk lamps and noticed no internal wiring after the transformer.

All 3 are made in Italy, different designs and brand names, and fairly expensive. They all have 120-12v transformers, either in weighted bases or along the supply cord. The outputs from the transformer are carefully hidden from sight, but must be simply soldered onto the inside of the frames, and it appears the frames carry the current to the socket. There is no internal wiring within the frames that I can find.

Here's a pic of a very similar lamp to one of mine: http://img0109.popscreencdn.com/160268712_ledu---concentrolite-halogen-desk-lamp-tiered-shade.jpg

The design has some obvious advantages, it allows the frames to be very thin and lightweight. My question is what is coming out of the transformer, and why is it safe to do this? If there is not an insulated wire running from the transformer to the bulb socket then we are handling the conductors when we move the lamp around. Is the current so low we don't get shocked?

It'll be 12Volts. Quite possibly being conducted up the two separate arms. We have a number of cheap halogen desk lamps that have, effectively, a pair of telescopic aerials as the supports. The 12V goes up them.

Sea Farmer said:

why is it safe to do this? If there is not an insulated wire running from the transformer to the bulb socket then we are handling the conductors when we move the lamp around. Is the current so low we don't get shocked?

Click to expand...

not current but voltage. 12v is low enough to not cause significant current thru you when you come in normal contact with it.

What happens if the transformer shorts and sends 120 ac to the output? Hope it has some kind of overvoltage protection built into the transformer.

Probably about the same thing as when the insulation on the cord in a flexible lamp wears away and it shorts to the lamp stand....

I don't think the frame conducts the power to the lamp...I think there is some small insulated conductor of some sort hidden in the guts of the frame. Anything else would be a breach of basic electrical safety in my pea brain. It's a small voltage and a miniscule amount of current but is juice none the less...you can't just run it through the frame. Knob and tube wiring was archaic but still managed to use wire insulation and insulated standoffs, and this was years ago.

I could be wrong on this though!

I found the manufacturer's website for one of the lamps--it says: "Berenice operates with a transformer that allows low tension current to reach the bulb through its rods without electric wiring. Its figure thus remains slim and elegant."

Here's the data sheet, which is carefully incomplete ) : http://www.luceplan.com/Prodotti/1/2/159/t/84/Berenice

The only info on the transformer label is 120V AC input, 12V AC, POT 35 V.A.

It uses a 35w bulb. so 35/12=approx 2.9 amps? And that's safe to handle?

jkruger made an interesting point. . . .

12V is perfectly safe to handle. The transformer should be 'double insulated' which means that it's physically impossible for a fault in the primary winding to put mains voltage on the secondary. Usually, the primary is on one half of a segregated bobbin in the transformer and the secondary is on a separate half, thus giving the two separate insulation systems that the name implies.

Wow...learn sumpin new everyday.

Stuart

Yes, the transformer has the double insulation icon on it.