Re: Halogen lights / Transformers (robots in disguise)

[Nigel Orr <Nigel.Orr@xxxxxxx>]

At 21:08 23/06/00 +0200, you wrote:
>Here goes - oh and by the way most of this means nothing to me but I
*can*
>turn off the mains and wire up modules!

As no-one else has replied, I'll try to help...

>Each Halogen light has a transformer 'attached'

That's a little unusual, but not a bad thing, usually one transformer does
a couple of lights, with each one being 20W.  I presume yours are 20W, as
11 x 50W ones would be _very_ bright (and hot!)

>The input voltage is 230-240v @50hz the output voltage is 11.5v [max
2m]
>(I'm assuming that the [max 2m] means a maximum distace from the
>transformer is 2meters(?))

Yup, they might mention a cable size too (something like 1.5, 2.5 or 4
mm^2)

>Electronic Transformer

Are they quite small/light, or about the size of a small coffee jar and
heavy?  I presume the former...

>20-70w

That means the output voltage should be in the right range for halogen
lights if you connect between 20W and 70W of bulbs to it (ie between 1 and
3 20W bulbs, or 1 50W bulb).  If the minimum power had been 40W, and you
only connected 1 20W bulb, then it would probably have too high a voltage,
and would burn out prematurely.

>Dimming by leading edge

That's an unusual way of putting it, but it _probably_ means that it will
work with a standard dimmer.  This is probably on howstuffworks too, but
briefly, and without the benefit of a safety net (or pictures!)...

A mains dimmer works by chopping out some of the AC waveform.  The voltage
coming in looks like a sine wave (stop me if I'm not making sense...), and
the dimmer decides how high the voltage gets before it is switched through
to the bulb (or transformer in your case).

So, if the dimmer is set to 0%, it will wait as the whole sine wave goes
past, and not allow any power through to the light.  At 100%, it will let
power through to the light the whole time.  At 50%, it will start letting
power through when the sine wave reaches it's peak.

There is another way of dimming, which is more complex, and is required for
fluorescent lights etc.  this 'spec' seems to be saying that these
transformers are happy with 'standard' dimming.  You could phone Osram and
ask them if the transformers just need a 'standard' dimmer, they will
probably be able to give a yes/no answer.

>Phase control for inductive loads

Probably means it's got a capacitor in it to make it 'look' like a normal
bulb.

> anyone got any ideas here?

No guarantee, as the spec on the transformer is suitably technical sounding
but not very meaningful, but if it was mine, I'd be happy trying one on an
X10 dimmer.  At absolute worst, the transformer might go up in smoke, but
the remaining 10 are over-rated, so you can just connect the bulb to one of
'em :-)

In this case, I wouldn't expect that damaging the X10 dimmer would be
likely.  But as ever, free advice is worth exactly what you pay for it :-)

Nigel


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