Dimmers For Low Voltahe Halogens

[The Question Asker]

Hi, Was wondering if its possible to fit a dimmer to low voltage lights with a transformer. Was looking for a remote control one, but keep reading that its not possible to use one but have read a few post about them being used what's the correct procedure. Cheers Oli

[Bob Minchin]

AFAIK, Halogens with an electronic transformer (much lighter than iron cored one) can be used with a dimmer designed for use with such things. Those with ordinary iron cored heavy transformers cannot be used with dimmers due to their inductance upseting the triac control and possibly overheating the transformer arising from a DC component fed to the transformer.

Bob

[Roger Mills]

overheating the

My experience with these was that, although they dim ok, the use of a dimmer makes the transformer buzz unacceptably - even when the dimmer control is set to full power.

It may depend on how much you pay - and these were relatively cheap ones from Screwfix - but they were claimed to be dimmable and compatible with the dimmers used.

In the end, I did away with the dimmers and resorted to switching the lamps in banks. [I have 12 lamps in 3 groups of 4, with each each group having its own switch and transformer].

Roger

[Robin Prater]

overheating the

My experience has been the reverse of Bobs - I have been using low voltage Halogen lamps via standard transformers and a dimmer for the last ten years without any problems. I started with electronic transformers but they did not like dimming lights less than 50% before they cut out. They also didn't last long and I replaced them with standard transformers. Because the switch on current is higher with inductive loads, I took the precaution of halving the power rating of the dimmer. Read the manufactures spec carefully before you buy.

Robin

[The Question Asker]

So OK, how am I meant to know if I have a electronic transformer, or an iron corded one. The light set came with 3 halogens with a transformer, will it say on the transformer if it is electronic or not, and where do u recommend I buy a inductance dimmer? Thanks Oli

[Lawrence]

An electronic transformer weighs a few ounces and is generally an oblong shape, about 4cm by 4cm by 15cm.

iron cored one will weigh a few pounds and be a lot larger, e.g

150W toroidal approx 18cm diameter and 10cm high or laminated iron 10cm by 10cm by 15cm.

This is a 50VA toroidal weight 750g (approx 2lb)

a list of bare transformers: this helps.

Lawrence

usenet at lklyne dt co dt uk

[Dave Plowman]

A dimmer suitable for a transformer will work ok with a resistive load - although it's more expensive. Any electrical wholesaler should have them - as do some of the sheds.

The lighting set should say what dimmer is needed and whether it is suitable for dimming.

LV transformers are usually round and heavy. Electronic, or SMPS types, are usually rectangular and light.

[The Natural Philosopher]

Yews its possible, and I have done it.

I used stansdard dimmers and electrionic transformers that were sold as 'dimmer capable' and indeed they are. I believe its also possible to get dinmers that will handle the load f a toroidla transformer as well. But no one seemd to give me a definite YES when I asked, so I didn't use toroids - which I prefer cos they buzz less, and are probably more simple and roubust creatures.