Since cables from your multi-wart are going to drop a significant
amount of voltage anyway, I think it is not useful to attempt very
close regulation of the output voltage. In that case, it might be
quite feasible and cheap for each output of the multi-wart to be
floating with respect to all of the others, since all of outputs could
be derived from separate secondary windings on the SMPS transformer.
If it is a small flyback converter, each winding would need a diode
and a couple of capacitors, and the regulation could be based on just
one of the outputs. Each output would not have very good regulation
(but cable will ruin the regulation anyway), and the outputs would all
be isolated, permitting people to ground whatever parts they want
without the power supply causing any particular extra problem.

Rich Grise <rich@example.net> wrote in
news:pan.2007.02.20.02.10.45.169515@example.net:

Why not just buy one that has room for wall warts?

Makes sense, but I have a totally different take on it.
Why not settle for some kind of common standard that means manufactures
can't exploit the public with high-cost warts of unusual voltage,
polarity,
whatever they can do to make their wart vital and another wart useless?

Given the amount of warts, and the amount of waste that results when they
are not needed, isn't it time some standard was set? Governments are
breathing down the necks of business, urging restraint in consumption. If
a
standard were made, people would get used to a single outlet with maybe 5V
and 12V and a slightly different conenctor for each, like the DC jacks
with
2.1 mm or 2.5 mm plugs. Imstead of warts, there's by small cables and
plugs, cheap and standard, and a single strong PSU with a meter that let
the user know if they were taxing it too much. It would always outlast the
products it drove, and the product could always be plugged into a similar
PSU anywhere.

In short, co-operation is better than conflict if waste is to be avoided.
The electronics world is full of successful standardizations like mains
voltages, plug shapes, MIDI and other protocols based on specific
connectors and signals. Sure, there are also obvious incomptibilites, but
compared to those, the wall wart situation is a disgraceful rabble.

I usually avoid them by buying stuff that will take an IEC mains
connector.
When I can't avoid them, I look for 12V or 5V capability, DC, postive on
centre pin. If it won't take that, then the only way I'll buy it is if
there is no alternative, and sometimes I'll modify it so it CAN use a
standard PSU I have lying around, so I can avoid relying on something that
is usually tatty, feeble, and expensive to replace with exact type.

Most people would welcome a standard low-volt buss for home and office
wiring. It works for boats, cars, planes, trains, wtf does it not work for
houses? Obviously it can, so it should, and the waste dreck of plastic and
steel would visibly decline within months of establishing it.

/rant.
-----------

Lets see. 12V DC wiring over what distances? In a car it appears OK
but with the increasing electrical loads in cars, there is serious
consideration of higher voltages for cars. In a house, or in other
than small aircraft and definitely not in trains- something like 12V
is simply too expensive in terms of material costs and weight.

"Bud--" <remove.BudNews@isp.com> wrote in message
news:da2ea$45db3feb$4213eb86$2385@DIALUPUSA.NET...

When MOVs fail they can overheat.

Or shoot flames out of the top!

Makes sense, but I have a totally different take on it.
Why not settle for some kind of common standard that means manufactures
can't exploit the public with high-cost warts of unusual voltage, polarity,
whatever they can do to make their wart vital and another wart useless?

Looking under my desk, I see that we have a total of 12 X 240V 13A
sockets, all occupied with various PC-related devices, plug-top PSU's
taking half that number for the network router, modem, network switch,
scanner and so on.

Given that we have a decent sized PSU in the PC itself, why not have
an auxiliary output from there to power all these PC-related items?

A daisy-chained PSU lead could then run to all external devices.

It'll never happen, but it would save a lot of floor space.

Then there's the KVM leads.....

On Tue, 20 Feb 2007 20:05:56 GMT, "Homer J Simpson"
nobody@nowhere.com> wrote:


"Bud--" <remove.BudNews@isp.com> wrote in message
news:da2ea$45db3feb$4213eb86$2385@DIALUPUSA.NET...

When MOVs fail they can overheat.

Or shoot flames out of the top!

Or explode. We had some large block MOV's across some electrolytics in
a big 620V 150A power supply/charger. Occasionally we would get a
start-up spike from the thyristor bridge that popped one, huge flash
and bang and lots of smoke.

Power Strip Liberator

I believe this product has been mentioned before
in the newsgroups. It's good enough that it bears
repeating. It is a ~1' long extension cord, that
allows you to plug a wall wart in without covering
other outlets on your power strip. You can have your
DSL modem, router, amplified speaker and whatever
else all plugged in to a strip, with the other strip
receptacles still accessible. Cyberguys (link below)
sells them, as well as other places.

http://www.cyberguys.com/templates/searchdetail.asp?productID=1757

Ed
With that money, I can get 5 plugs and five females and 5' of cable and make

Re KVM, good point, I've been contemplating replacing a KVM with a network
software based control system, like VNC, PC Anywhere or Kaseya. Not exactly
'thought' as looked wishfully in their general direction. KVM allows real
mode DOS without complications, so I'm not likely to replace it.

"Don Kelly" <dhky@shaw.ca> wrote in
news:eZPCh.1066718$1T2.985600@pd7urf2no:

Lets see. 12V DC wiring over what distances? In a car it appears OK
but with the increasing electrical loads in cars, there is serious
consideration of higher voltages for cars. In a house, or in other
than small aircraft and definitely not in trains- something like 12V
is simply too expensive in terms of material costs and weight.

10 feet? One per room, on average. Considering the stupid proliferation of
warts that is why this thread even exists, that seems like a good scale to
work with. The total wiring thickness and length on that scale would be no
worse than the wiring currently bringing low-volt lines out of those
warts.
Most of them are in one location, concentrated near a hi-fi or a computer,
or a bed. People like to organise when things get out of hand, especially
when the disorder is always in close proximity.

The 'buss' need not be any bigger than a mains 4-way plug strip. You could
fit a 200W PSU and lots of connectors on that, with a cost below £25,
which
given the wart count reduction, is a good spend.

I agree with you about cars though, a lot of high currents there, it would
save a lot of metal in switches and wires to use 24V. More is NOT a good
idea. In a crash, there's enough deal with without adding electrocution.

This is my rant. There are others like it, but this one is mine. >

Thank you, I had the impression that you were talking about a whole
house system. I assume that the room unit will be regulated as load
could vary widely. If not you could have problems which don't occur
with equipment which comes with its own wall wart designed for that
particular apparatus.

Peter A Forbes <diesel@easynet.co.uk> wrote in
news:v4snt2dniv0h0tett1q96okmk6tvqmtspr@4ax.com:

On Tue, 20 Feb 2007 20:05:56 GMT, "Homer J Simpson"
nobody@nowhere.com> wrote:


"Bud--" <remove.BudNews@isp.com> wrote in message
news:da2ea$45db3feb$4213eb86$2385@DIALUPUSA.NET...

When MOVs fail they can overheat.

Or shoot flames out of the top!

Or explode. We had some large block MOV's across some electrolytics in
a big 620V 150A power supply/charger. Occasionally we would get a
start-up spike from the thyristor bridge that popped one, huge flash
and bang and lots of smoke.


MOV = Metal Oxide Varistor?
I thought those were supposed to be a really neat idea... Can they be
redeemed by adding a series resistance designed to take the full current if
the MOV goes shorted, or would that just allow what they're meant to
prevent?
Right now they seem to look more like a detonator than a part with any real
usefulness.

They are useful, up to a point. They don't exhibit a great tolerance to spikes
as we found out, and it is difficult to assess their performance in-circuit.

If the source impedance is very low then they are definitely the weakest part of
the protection chain.

Interesting that in each case (3 separate failures) the actual failure mode was
identical, the body blew open and red-hot parts went like shrapnel through the
equipment cabinet, that was the most worrying part.