Re: X10 dimming

["Keith Doxey" <keith.doxey@xxxxxxx>]

Adding to Nigels comments about the dimmer passing little or no current at
its lowest setting.

Most good commercial dimmer packs used in the entertainment industry have a
feature called "Pre-Heat" which basically does what you are
describing. The
dimmer passes just enough current to keep the filaments warm to eliminate
the surge when the lamp is turned on. There is no detremental effect to the
dimmer as long as it has an adequate heatsink to disipate any heat
produced.
There is a positive effect on the lamps in that they last much longer due
to
being pre warmed.

You may notice a slight increase in power consumption as the circuit would
be consuming a few watts at all times.

A way around the constant consumption would be to actually turn the lamp
off
at times when it was not going to be used. For example, if you have a home
theatre but only ever use the room between 7pm and 1 am then control the
module like this
6:45pm Lamp On, dim down to zero
7 pm to 1 am use the module as you want with the simulated soft start
1:15am Lamp Off until 6:45 the following night when you set it up for soft
start again.

Hope that helps

Keith

Keith Doxey
http://www.btinternet.com/~krazy.keith
Krazy Keith's World of DIY HomeAutomation


> -----Original Message-----
> From: Nigel Orr [mailto:nigel.orr@xxxxxxx]
> Sent: 29 March 1999 09:42
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: X10 dimming
>
>
> At 11:00 26/03/99 -0000, you wrote:
>
<SNIP>
> >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%.
>
> 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...
>
>
> Which _is_ a good thing for tungsten and tungsten/halogen lights.
>
> Nigel
>
>


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