finding transformers in ceiling

[christopher]

I want to change the 12v downlighters in my kitchen for mains tracklighting using low energy bulbs.I want to use the existing switches.

Ive looked in the ceiling space near the lights and in a couple of speculative test holes in the ceiling and there is no sign.

Ive tried a radio to pick up the mains electomagnetic activity, nothing .

I can see the wires from the switches ( mains ) disapearing into a bunch of wires heading for the far end of the kitchen ( 20 ft).

Can anyone suggest a teqnique for locating the transformers without pulling half the ceiling down. If in fact they are in the ceiling.

Would an EMF meter help or are they just for ghosts

Chris

[dennis]

Do you need to? If you disconnect the switch end and the fitting then the transformers should be doing nothing.

[RobertL]

What about one of those cable detectors sold by the DIY sheds? Switch on the lights so the transformer is live of course!

Or, detect the magnetic field by using a small coil of wire connected to the input socket of an audio amplifier. move the coil around listening for the loudest 'hum'.

Or, see if you can hear the transformer humming. Switch the lights on and creep around on the floor above your ear to the ground. best to do this at night when it's quiet.

Robert

[christopher]

I want to use the existing switches and wiring and the power supply that must be in the ceiling already.

Chris

[Dave Liquorice]

12v wiring tends to be short or if not short very heavy due to not wanting to lose to many volts in the wiring. Be aware that the "transformer" these days might be a small SMPSU not a couple of coils around a gert lump of iron.

A radio tuned to a quiet part of the MW wave band might pick up switching noise from a SMPSU but it won't detect the stray field from a traditional transformer. The coil of wire and audio amp should detect the stray 50Hz field from a traditional transformer but 50Hz is quite low for a small low power speaker to reproduce.

[Dave Plowman (News)]

*If* you're lucky the transformers will have been inserted afterwards, so remove each fitting and see if you can pull them out of the hole. They could drive more than one lamp so you'd need to check them all. But an older installation could use transformers too large for this trick so has been wired from above.

[Chris J Dixon]

Do the downlights pull out of the ceiling? Each one should then provide a hole you can, with the aid of a mirror, peer through. If this is what you have already done, then you should at least be able to get an idea of the cable run, and rule out some potential locations. A compact digital camera is also very handy for seeing where you cannot get your eyes.

What is in the room above? Are these lights original, or a later addition? If the latter, have you looked at the floorboards in the room above? There may (indeed should if they cannot be reached from below) be an access point.

If the detector can tell the difference between ac and dc, you might be on a winner there. Otherwise how can you determine which bit of the circuit contains the "transformer".

The "transformer" could actually be an electronic device rather than a traditional core and windings, so neither the hum nor the external field may be detectable.

Chris

[christopher]

thanks so far.

Lights are from when house built 18 years ago have already taken out to look

Transformers in roof for upstairs room lights are traditional so assume these are same vintage

Access from above very difficult fitted carpet and large sheets of chipboard.

Small coil ? could do with more info .

Chris

[meow2222]

if you mean the heavy iron types then youre looking for 50Hz

100 turns of enamelled copper wire round a pencil should do it. Connect to the mic input of any pocket audio device and listen. The coil picks up the 50Hz field near it.

If you've got a scrap electronic item, many have a suitable coil in them. A plastic cased earphone or headphones may also work.

NT

[Dave Plowman (News)]

I'd still say it's easier to lift the carpet and cut some traps in the chipboard. Well it would be for me over making good holes in a ceiling.;-)

[BigWallop]

When the lights were fitted, did the electrician leave access from the floor above? Look for a hatch in the floor, probably with screws holding it down.

Pull one of the lights to see if it pulls the transformer toward you.

Pull all the lights out of the ceiling and tug them toward you. You should hear the larger transformer banging around in the ceiling.

Are the lights actually Low Voltage? Mains voltage version of these downlighters are also available. Make sure yours aren't mains voltage and that there is no transformer.

[meow2222]

Somehow I dont think a 100w 50Hz transformer is going to do any banging about.

NT

[BigWallop]

Didn't word that bit quite right. What I meant was the cables going to the transformer banging about. At least you'd get the right direction to hunt in.

Anywhoooo. :-) Can just imagine yanking a 250VA Iron Core out the loft space. That would bang about a bit. LOL

[Michael Chare]

No but you just might be able to hear it with a home made stethoscope (plastic tubing pressed to ceiling)

[Fred]

They also sometime give a kick when turned on which you might be able to hear.

[christopher]

More thanks - better particulars

I have plasterer coming in to do the walls so a few holes in the ceiling no problems New ceiling a NO NO

I can see inside the ceiling void between the joists and there are no transformers.

Definatley 12v Ive checked the bulbs. Switches are 240v

Chris

[Harry Bloomfield]

[e-mail] explained :

No good for this :-)

You could take out the lights and use a light and mirror to see if you can see where the cable goes, that should lead you back to the transformer.

A loop of several turns of small wire, connected to an old crystal earpiece would produce a 50Hz hum, when brought near a transformer (if it is a proper transformer and turned on.

A metal detector would also find the above, if its sat on the ceiling plaster.

A medium wave portable radio should pick up the hash from a more modern switch mode type 'transformer'.

[meow2222]

ah, good idea

Yanking the wire from each light fitting might help locate it further if need be, since they'll all point vaguely towards the transformer.

ha

NT

[christopher]

Thanks to all. I salvaged a coil from and old transformer and connected it to the mike socket of a Laptop. As i test i went to a place where a transformer lurked and bingo mains hum turned off the light and it disappeared. However a scan of the ceiling in question and no sight of transformers. I did pick up the route of some mains cables though.

thanks for all your help

Chris

[christopher]

On Tue, 25 Nov 2008 10:04:27 +0000, [e-mail]

YIPPEE

Modified the rig to put it on the end of a stick with a wheel to make scanning the ceiling easier and found both transformers side by side in the ceiling of the adjacent hall. Access was via a trapdoor in the hall floor above.

Result !!!!

wrote: