Charlie said:
I live off the power grid and am itching to build a 12 volt mini-itx
desktop system that is energy efficient.
The catch is that 12v LCD monitors, designed for automotive applications,
are VERY expensive ($300 for a 15" unit).
Don't the standard desktop LCD monitors convert AC grid power to 12v DC
anyway? How hard would it be to hack one of these units to run directly
from a 12v power source?
All advice and comments welcome. Thanks.
Charlie
My LCD monitor has a separate wall wart, and it converts 115VAC to
12VDC at 4 amps max. The monitor uses 3 amps max, and probably
a bit less than that. So my LCD would be a good candidate
for your project. There are also LCDs that integrate the
power into the base of the monitor, and those would not be
a good candidate for your project. So you're looking for a
monitor that uses a wall wart, as the most likely solution.
You can see in this picture, for example, that an external
power supply is used. This is just the first one I found in
the Newegg collection.
http://images10.newegg.com/NeweggImage/productimage/24-005-035-07.jpg
http://www.newegg.com/Product/Product.aspx?Item=N82E16824005035
The tough part, will be converting from your unregulated battery
voltage (13.2V perhaps) to the 12V the monitor is expecting.
Here is an example of a module to convert from your battery,
to drive the LCD. Some connector surgery will be
required, plus the addition of a switch, to disconnect the
battery when you are not using the monitor.
DC-DC Regulator Module : 10-17VDC to 12VDC 4 Amp $14.95 (not in stock)
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2494
Note that the above regulator module, is probably not an "isolating"
type. The wall wart that comes with the LCD is isolating, meaning the
AC power rails and the DC outputs are not connected in any way. When
you use the above 10-17VDC to 12VDC converter, that is probably
a buck converter, with a common ground. That means the ground of
your battery system, also is the ground of the monitor, the monitor
VGA shell will also be at the battery ground potential. This is fine
if the computer is also grounded the same way. There are also regulator
modules that will fully isolate the output (the same way that an
ATX power supply does), but they will likely be a few dollars more.
Paul
