12V Power supply otions....

"Martin Brown" wrote in message
...
Colin Dawson wrote:
"JG" wrote in message
news:313030303331393042FA38AA83@crescentcomputing. co.uk...

"adm" said

In my quest to have the LX200 and DSI set up outside but controlled from
inside, I am looking for a decent 240V AC to 12V DC power supply. I
would
ideally like one with two or three 12V cigarette lighter style outlets

Lateral thinking here - if you are happy making up a breakout panel then
why not use a standard 400W Computer PSU? The +12V rail on that has at
least 4 outlets and is rated at 22A it also has +5V at 34A. The cost is
something like £10-12 retail. You would need to provide a method of
triggering the 'Power OK' signal though.

Some of them do not like having no load on the 5v rail though.

I ideally want to make up a single "umbilical" type ccable that will run
from the house to the scope itself - it would consist of power (240V
AC),
USB2.0 and the LX200 communications cable itself. This would probably be
buried in a conduit in my garden

As Martin has already said - not a good idea.

Rigging up a system to do this won't be difficult, there's plenty of
websites which show how to do this. Normally, electronics hobbiests do
this as a cheap bench power supply. So you'll get some pretty good and
safe ways to do this.

Though bear in mind that the new regulations require you to have an
electrician install all new mains wiring and for oudoors with ELCB.

I'd suggest that you place the power supply and scope as close as
possible to the scope. 12v DC doesn't tend to travel too well.
Something to do with resistance in power cables.

Although this is true, one option would be to have a nominal 13.8 5A
supply indoors and run the rough DC supply out to the scope and heater, if
necessary regulating down the scopes feed to a true 12v. A hundred feet of
cheapest solid copper core 20A house wiring cable will not drop too much
voltage (check this, but a back of the envelope gives 0.6 ohm/100'). Use
all the conductors in the cable 2 for + 1 for -.

(Negative DC cables always rot away electrolytically in the damp)

At 4A max load it should drop about 2.4v - perhaps a bit marginal so a
thicker grade of cable might be advisable. At least with low voltage DC
you don't have to worry about armoured cable and deep trench burial.

You would need to do the sums a bit more carefully and put a couple of
capacitors at the far end to decouple the supply but it should be workable
over short distances (and certainly over longer distances than USB2).

Regars,
Martin Brown