[Elecraft] Local Noise Problem

[David Cutter]

I'm quite happy with my wish.  I've seen led clusters in a MR16 package 
deliver the equivalent light to a 43W incandescent for a consumption of 
3.6W: that's 300mA at 12V.  Our rooms over here are probably smaller than 
yours, Jim, but I might have 4 ceiling-mounted units to give me a nice light 
in most of my rooms (<150sq ft).  Our lighting wiring is mostly rated 5A, 
so, the 1.2A ac/dc I would need is well within spec if I just put a 12V 
transformer on the lighting circuit.  So, in my house (fairly typical in the 
UK) my wiring would not change, but in a new build it could be not only 
smaller, but not have an earth/ground wire with it and no outer sheath, ie 
just twin.   That's a lot less copper and a lot less pvc.  It's easy to 
incorporate thermal trips (ptc devices) which are cheap and last my 
lifetime.

All this adds up to taking a lot less current out of the mains and therefore 
a lot easier to suppress if switching supplies are used.

Sorry for the thread drift, but it's an interesting subject.

David
G3UNA


> On 4/3/2011 3:24 AM, David Cutter wrote:
>> I'm looking forward to a time when all domestic lighting can be run
>> from a 12V supply at the main switchboard.
>
> Be careful what you wish for. A major advantage of higher voltage
> distribution is that copper losses are much less, and much smaller
> copper conductors are required.  This makes the 240V system used in much
> of the world superior to the 100V and 120V systems used in Japan and
> North America. It gives 240V a 20:1 advantage over 12V.
>
> More important, try a quick calculation for the cost of converting every
> building in the world from the existing 120VAC or 240VAC to your 12VDC.
> Remember -- none of the old wiring is sufficient, so one must rip out
> the walls and start over. Please tell me when this is going to happen -- 
> I want to buy stock in the copper industry, because the price is going
> to multiply by a factor of at least 5X, because copper is going to
> become VERY scarce.
>
> In addition, distribution of power as an AC voltage means that it is
> easily transformed from one voltage to another by transformers that
> don't make electrical noise. The electrical noise produced by switching
> power supplies to do that would wipe out all radio communications!
>
> 73, Jim  K9YC
>