Re: X10 dimming

[Nigel Orr <nigel.orr@xxxxxxx>]

At 11:00 26/03/99 -0000, you wrote:
>I've now got my Comfort alarm/automation system running quite nicely,
>barring a couple of incidents where it dialled out unexpectedly to my
>wifes mobile (at midnight I might add).

Bet that was well received ;-)

>My question is, what is the effect on (a) ordinary tungsten lamps, (b)
>mains voltage halogens, (c) the dimmer itself, if I run the dimmer
>continously at minimum brightness.

a) I would expect no change, but it _might_ decrease bulb life (they're not
expensive, so you can safely 'suck it and see')
b) I would expect nothing at all, but if minimum brightness means they glow
dimly, then their life will be shortened.  You say that no light is
produced, so it should be OK

>dimming down). I'm concerned because I don't properly know how the
>dimmer works, and I do know that the cold resistance of lights is very
>low, and hence am I pumping loads of current through the bulb when I
>think it is off? If current is flowing, is it likely to reduce the life
>of the bulb and will it kill the dimmer?

The dimmer works by switching on the mains at a variable time after each
half-cycle starts, and switching it off at the end of the half-cycle.  0%
means the dimmer switches on at the end of the half-cycle, and 100% means
it switches on at the beginning of the half-cycle.  50% means it switches
on at the peak of the supplied voltage, the sudden switching action is what
makes dimmers electrically and acoustically noisiest at 50%.

I would guess that at minimum brightness the lamp is not receiving any
current, but it's not something I've investigated deeply... you are correct
that cold resistance is very low, but do remember that if you were pumping
loads of current through them, it would heat them up, so it wouldn't be
cold resistance any more ;-).  I would guess that they will either be not
receiving any voltage (so they're effectively off), but you could check
with an AC voltmeter to get an idea for what is really happening.

As for the dimmer, it depends how well it is designed... there are 3
scenarios:
1) It is fully dimmed down, so it will not supply current to the light.
If that is the case, the dimmer will still be dissipating a small amount of
heat, so its lifetime may be reduced slightly, but if it doesn't feel warm
after 24 hours, it's probably not going to have much effect.
2) It is supplying about 10% of power
If that is the case, it probably will get 'tired' more quickly
3) It is 'intelligent' and goes into some sort of standby mode when dimmed
to minimum.
If that is the case, it's 'designed' to run at minimum power, and so should
have no problems...

>If it does work then it will be superb since not only do get the
ability
>to dim up from the off state, but you can implement soft start
>lighting...

Which _is_ a good thing for tungsten and tungsten/halogen lights.

Nigel

------------------------------------------------------------------------
Why are most stock sites so slow and annoying to use?  StockMaster.com
is fast, easy, powerful, and free!   Use company names, not ticker
symbols.  Track your portfolio.  Visit:   http://stockmaster.com/?a=f6

eGroup home: http://www.eGroups.com/list/ukha_d
Free Web-based e-mail groups by eGroups.com