Question about DC-DC vs ATX PSU Efficiency - First Post!
Ok, here goesÖ as this is my first post, I would like to first introduce myself and my project, and Ďgetting to the pointí has never been my forte, so bear with me.
First of all my name is Ashley, I'm a guy (if you have problems with a guy being named Ashley then... you have problems), Iím 22, I drive a 2000 Trans-Am WS6 6-speed (yay!) and Iíve wanted for the past 5 years to put a computer in my car, but Iím only now getting to the point of having the money, skill and parts.
I have a long history as a bit of a NERD, Iíve been programming since age 11 (C++ since 15) and built quite a few computers, networks, etc, so needless to say, I know a great deal about computers. I have a fair knowledge of electronics and limited experience with micro-controllers, but from what Iíve seen in the forum, nothing at all to brag about. If you really need to know anything more or just have some time to kill visit my car-club at http://www.nfspmotorsports.com sorry if it still has my recently totaled 94 Trans-Am listed as my car, Iíll fix that soon enough.
The parts Iíve scraped together for my car project are an Asus A7N micro ATX mobo from an old Dell, with an Athlon 2800, 1G ram, an old Albatron nVidia 5700 256Mb AGP video card, and a 10G 2.5Ē 4600RPM laptop HD. Parts I still have to get include the Panasonic slot-load dvd burner and the 8Ē widescreen Lilliput touchscreen from mp3car. I havenít picked out a sound card yet (onboard is broken and disabled and sucks anywayÖ) a 500G external HD that Iíll probably run off a separate power supply, and most important of allÖ a Power Supply.
SoÖ all that being said, hereís my question. What power supply do I get? Iíve considered the inverter idea, but that seems problematic, and on top of that, itís a pain to setup automatic turn on, turn off, battery monitoring, stay alive during crank, etc. So right now Iím leaning toward DC-DC. Iím thinking either an A2-MTX (or maybe 2 if need be?) or the DSATX or the OPUS 250 (though Iím trying not to break the bank here)
The testing Iíve done so far is this: I have the computer running right now off the OEM 250W AC PSU. The only difference from the way the system is listed above is that I donít have the parts under the Ďstill to getí list (duh) but Iím substituting a regular tray-load DVD burner. Iíve done some testing of how much wattage the computer actually pulls by checking the AC load from the wall with an AC ĎClampí style Ammeter, and checking the voltage at that outlet VxA=W . Under these test conditions I get a standard idle at about 1.2A @ 120V so 144W. At a full load I canít get it to go over 172W though it will hit 166 during games or other heavy CPU loads. So basically my question is will an A2-MTX be enough? I know itís only rated for 160W but I donít know if itís under rated. I also have to consider that Iím measuring how much the AC PSU is pulling from the wall, not how much the components are actually pulling from the PSU. Just as an inverter is not 100% efficient so to an AC PSU is not. Iím just not sure how much so. If itís 95% Iím still cutting it close to 160 at full load but if itís more like 80% then I never go over 135W peek. I donít want to spend more than I need to, but I donít want to have a PSU that wonít cut it. I would also really like to survive cranking, or at least only have to go to stand by.
So thatís my story, thanks for reading it, thanks for any help you can give, and sorry I took up 4 hours of your time while you read all this crap!