I wonder if anyone can help - I have a 15 inch lcd tv with digital
freeview receiver. They each have their own power supply adaptor, one
at 12v - 4.2amp and the other at 12v - 1.25amp output. Becauase of the
lack of space where the tv sits I wanted to run both tv and digibox
from the one power supply adaptor. Is this possible/safe to do and
which supply do I use - 1.25amp or 4.2amp?

Thanks

Tommaz

"tommaz" wrote in message
oups.com...
I wonder if anyone can help - I have a 15 inch lcd tv with digital
freeview receiver. They each have their own power supply adaptor, one
at 12v - 4.2amp and the other at 12v - 1.25amp output. Becauase of the
lack of space where the tv sits I wanted to run both tv and digibox
from the one power supply adaptor. Is this possible/safe to do and
which supply do I use - 1.25amp or 4.2amp?

Thanks

Tommaz


Absolutely not. The 4.2 Amp power supply is highly unlikely to have been
designed with a safe extra 1.25A capacity, and connecting both appliances to
it is sure to kill it. The smaller supply doesn't even have half the
capacity that the LCD requires, so it goes without saying that it won't run
both applainces!

Dave

Thanks for that Dave

Is there another way of reducing the clutter? If I can get hold of a
power supply of say 5.5A capacity would this allow me to run both
appliaces from it?

Tom

"tommaz" wrote in message
oups.com...
Thanks for that Dave

Is there another way of reducing the clutter? If I can get hold of a
power supply of say 5.5A capacity would this allow me to run both
appliaces from it?

Tom


Use an RV car battery + charger, that'll supply enough current and top up
the charge overnight when you're not using it.

"tommaz" wrote in message
oups.com...
Thanks for that Dave

Is there another way of reducing the clutter?



You could try hiding the supplies behing the LCD and using some cable
tidying accessories like that spiral flexi conduit stuff to shroud the
wires. How bad can a couple of small SMPSs be? There must surely be a way to
hide them somewhere.


If I can get hold of a
power supply of say 5.5A capacity would this allow me to run both
appliaces from it?

Yes, that would work, but the supply would likely be bigger than either of
your existing supplies, what would you gain?

Dave

Just so I'm clear - if I use the 12 volt leisure battery in my caravan
(hence the restricted space), then all I have to do is wire the TV and
digibox direct to the 12 volt supply?
Do I need to put any in-line fuses in place first or will the TV and
box just take as much current as they need?

Thanks

Tom

"tommaz" wrote in message
ups.com...
Just so I'm clear - if I use the 12 volt leisure battery in my caravan
(hence the restricted space), then all I have to do is wire the TV and
digibox direct to the 12 volt supply?

Your LCD and digibox will likely want a very stable 12V supply, and a
battery will not offer that. Unless the appliances are explicity designed
for battery use, forget it. They will simply malfunction when the battery
starts to deplete, or worse it may cause damage.

Do I need to put any in-line fuses in place first or will the TV and
box just take as much current as they need?


No offence, but by asking a question like that you demostrate that you
really should leave things as they are and forget about experimenting with
expensive electronic appliances!

Fuses are not current limiters the way you think, they are a failsafe device
to protect an appliance when either the power supply fails or the device
itself develops a fault. They prevent catastrophic damage in the event of a
short or fault condition and do not 'limit' current to a normally working
device.

Yes, you most certainly should use a fuse inline if you're going to
experimentvlike this! A 5 Amp fast blow fuse should be OK, but if you create
a situation where the fuse blows, it's unlikely either the LCD or the
digibox will survive anyway.

Dave

Thanks for the advice Dave

I'd rather keep thind as they are than blow a perfectly good TV.

Tom

Dave D spake thus:

No offence, but by asking a question like that you demostrate that you
really should leave things as they are and forget about experimenting with
expensive electronic appliances!

Fuses are not current limiters the way you think, they are a failsafe device
to protect an appliance when either the power supply fails or the device
itself develops a fault. They prevent catastrophic damage in the event of a
short or fault condition and do not 'limit' current to a normally working
device.

No offense, but technically speaking, fuses *are* current limiters; it's
just that they can only perform that function once when the current
exceeds their rating.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

Dave D spake thus:

"tommaz" wrote in message
ups.com...

Just so I'm clear - if I use the 12 volt leisure battery in my caravan
(hence the restricted space), then all I have to do is wire the TV and
digibox direct to the 12 volt supply?

Your LCD and digibox will likely want a very stable 12V supply, and a
battery will not offer that. Unless the appliances are explicity designed
for battery use, forget it. They will simply malfunction when the battery
starts to deplete, or worse it may cause damage.

Damage from *undervoltage*?

Please be so kind as to explain how this could possibly happen.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

"David Nebenzahl" wrote in message
.com...
Dave D spake thus:

"tommaz" wrote in message
ups.com...

Just so I'm clear - if I use the 12 volt leisure battery in my caravan
(hence the restricted space), then all I have to do is wire the TV and
digibox direct to the 12 volt supply?

Your LCD and digibox will likely want a very stable 12V supply, and a
battery will not offer that. Unless the appliances are explicity designed
for battery use, forget it. They will simply malfunction when the battery
starts to deplete, or worse it may cause damage.

Damage from *undervoltage*?

Please be so kind as to explain how this could possibly happen.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

It can sometimes happen with badly designed SMPSUs, I don't know why maybe
its something to do with excessive duty cycle. Many currently available
SMPSU controller chips have UVLO which is considered a vital safety feature!

"David Nebenzahl" wrote in message
.com...
Dave D spake thus:

No offence, but by asking a question like that you demostrate that you
really should leave things as they are and forget about experimenting
with expensive electronic appliances!

Fuses are not current limiters the way you think, they are a failsafe
device to protect an appliance when either the power supply fails or the
device itself develops a fault. They prevent catastrophic damage in the
event of a short or fault condition and do not 'limit' current to a
normally working device.

No offense, but technically speaking, fuses *are* current limiters; it's
just that they can only perform that function once when the current
exceeds their rating.


That's what I said, did you even bother to read the OP's post and my*full*
reply before putting your foot in your mouth?

Dave

"David Nebenzahl" wrote in message
.com...
Dave D spake thus:

"tommaz" wrote in message
ups.com...

Just so I'm clear - if I use the 12 volt leisure battery in my caravan
(hence the restricted space), then all I have to do is wire the TV and
digibox direct to the 12 volt supply?

Your LCD and digibox will likely want a very stable 12V supply, and a
battery will not offer that. Unless the appliances are explicity designed
for battery use, forget it. They will simply malfunction when the battery
starts to deplete, or worse it may cause damage.

Damage from *undervoltage*?

Please be so kind as to explain how this could possibly happen.



TFTs often have small onboard SMPSs to drop the 12V down to 5V and sometimes
other voltages as well. SMPSs can pulse/cycle when the input voltage drops
below a value at which they can maintain a stable output, which can damage
the SMPS itself or the rest of the panel's electronics.

HTH.

Dave

Each unit must run on its own supply. These supplies are current rated for
one unit only. If you can find a single supply that is of double the current
rating, then using 2 units on one supply should work. But, you will be back
to your space problem again, because the double rated supply will be
physically much larger.

There is the other senerio, where dedicated supplies can have particular
safety sensing for the one unit that it is supposed to work with. By using
another type of supply, this safety aspect will be defeated. This can lead
to another set of problems.

If you are using the monitors for commercial purposes, and need to have
space savings, get them changed to monitors that have built in supplies.
This may be the best alternative for you.

You can't get around the laws of physics!

--

JANA
_____


"tommaz" wrote in message
oups.com...
I wonder if anyone can help - I have a 15 inch lcd tv with digital
freeview receiver. They each have their own power supply adaptor, one
at 12v - 4.2amp and the other at 12v - 1.25amp output. Becauase of the
lack of space where the tv sits I wanted to run both tv and digibox
from the one power supply adaptor. Is this possible/safe to do and
which supply do I use - 1.25amp or 4.2amp?

Thanks

Tommaz