dc-dc atx power supply question

[the yeti]

I have two of these R100D1205-12TS
(http://www.aconinc.com/pdf/R.pdf)and I want to use it to run a
computer on a car battery. Its a 100 Watt, so I think I can do it.
I'll use the first one to power the motherboard and the second one to
power the hard drive.

My 2 questins are:

1) Can I just use a resistor to step down the voltage?

2) Do you think I could get away with just using one to power the hard
drive and the motherboard?

I realize I have some reading ahead of me to learn som of these basic
electronics. Thanks for any advice you can give me.

 

[Robert C Monsen]

I have two of these R100D1205-12TS
(http://www.aconinc.com/pdf/R.pdf)and I want to use it to run a
computer on a car battery. Its a 100 Watt, so I think I can do it.
I'll use the first one to power the motherboard and the second one
to
power the hard drive.

My 2 questins are:

1) Can I just use a resistor to step down the voltage?

Going from 5V to 3.3V using a resistor will waste about 35% of the
available power. At 5A, the resistor will dissipate something like
8.5W, so it'll get hot. A little SMPS would be better, although more
complex.

2) Do you think I could get away with just using one to power the
hard
drive and the motherboard?

This depends on the current draw of the mainboard and drive. If you
are using an EPIA nano-itx mainboard, you might be able to get away
with it.

I realize I have some reading ahead of me to learn som of these
basic
electronics. Thanks for any advice you can give me.

Why not use a laptop, and charge the battery directly?

Regards,
Bob Monsen

 

[andy]

I have two of these R100D1205-12TS
(http://www.aconinc.com/pdf/R.pdf)and I want to use it to run a
computer on a car battery. Its a 100 Watt, so I think I can do it.
I'll use the first one to power the motherboard and the second one to
power the hard drive.

My 2 questins are:

1) Can I just use a resistor to step down the voltage?

2) Do you think I could get away with just using one to power the hard
drive and the motherboard?

I realize I have some reading ahead of me to learn som of these basic
electronics. Thanks for any advice you can give me.

have a look on the via epia motherboard site - they have a mini-itx
motherboard that's specifically designed to run off a single 12V supply
only, with onboard DC-DC converters. Also see www.mini-itx.com for other
stuff like this.