Halogen spotlights

I am thinking of installing 6 halogen spots (recessed). How do I work out what sort of transformer I need? How does each spot link to the transformer - series or parallel? Furthermore, what sort of dimmer switch can I use? I'd like to be swanky and go for the remote controlled/touch dimmers you can get these days.

Any advice?

Regards,

Ian

Reply to
Ian
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If the halogens are 240V, you need no transformer. If 12V, add up the wattages of all the bulbs and get a transformer that big, or slightly bigger. E.g. 6*20W bulbs = 120W so you need a 120W transformer. Screwfix don't do one (for example), but their 150W electronic transformer should do the trick (but check that its minimum loading is 100W or less so it doesn't worry when a bulb blows).

It is still possible to get "real" transformers (bits of wire wound on a ferrite core). If you get one of these, the best sort is the "toroidal" (looks like a doughnut), but beware that they have a *very* large inrush (switch-on) current and may need to be used with special dimmers. You may even need to change the lighting circuit breaker in your consumer unit for a "C" type if it is a "B" type at the moment. The output voltage of a real transformer will vary with load; the less load, the higher the voltage. It is therefore very very important to get one matched to the number of bulbs you are using, and to replace blown bulbs as soon as possible.

Give consideration to two or more transformers instead of one for the whole lot. This has certain advantages if one of them dies. In my example you could go for 2*60W transformers. You can run them both from the same light switch / dimmer. This advice is even more relevant if you are using 35W or 50W bulbs - 6*50W is 300W, which is rather larger than you will normally find, though 2*150W is easy enough.

The only thing you're likely to find connected in series these days is a set of Christmas tree lights. Do you know the difference, or are you really asking (as others have done before you) whether you need to connect the lights in a chain or a star? If the latter, it doesn't matter. It depends on the layout, whether the terminals on each light fitting are big enough for two cables, and whether this makes the run to the last lamp excessively long, in which case it may, due to Voltage-drop be noticeably dimmer than the bulbs electrically closer to the transformer.

Here are some ASCII diagrams - use a monospaced font such as Courier to view them:

(o = transformer terminals, B=bulb)

SERIES CONNECTION:

o------B------B------B------B-----+ | o---------------------------------+

PARALLEL CONNECTION (chain / ladder)

o------+------+------+------+ B B B B o------+------+------+------+

PARALLEL CONNECTION (star) (wires only join at the "o"s, otherwise they cross)

+B+ | | +--o----+ B | | B +----o--+ | | +B+

First make sure that your transformer says "fully dimmable" (if the electronic sort). Then check that your dimmer (however swanky) says "suitable for dimming low voltage lighting". All but the cheapest are likely to be these days, though you may need to derate them: a dimmer suitable for 200W of ordinary lighting may only be rated at 140W with a transformer, especially if it isn't an electronic sort.

Surprised no-one jumped in any quicker with this, perhaps they've got bored with answering the same question time and again :-)

If what I have written has completely confused you, search uk.d-i-y on google groups for other questions on the same lines.

Hwyl!

M.

Reply to
Martin Angove

Have a look here on TLCs site:

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'Premium Electronic Transformer 0-150w' is £10.99 and the '0-250w' one is £11.99

Either of those should to the job but I have no knowledge on quality/life span of them.

Seri

| | First make sure that your transformer says "fully dimmable" (if the | electronic sort). Then check that your dimmer (however swanky) says | "suitable for dimming low voltage lighting". All but the cheapest are | likely to be these days, though you may need to derate them: a dimmer | suitable for 200W of ordinary lighting may only be rated at 140W with a | transformer, especially if it isn't an electronic sort. | | Surprised no-one jumped in any quicker with this, perhaps they've got | bored with answering the same question time and again :-) | | If what I have written has completely confused you, search uk.d-i-y on | google groups for other questions on the same lines. | | Hwyl! | | M. | | -- | Martin Angove:

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| Two free issues:
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Living With Technology | ... What are you doing?!? The message is over,GO AWAY!

Reply to
Seri

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