The newer motherboards (ATX) generally start out on 250W power supplies which provide up to: +5v at 27A -5v at 0.5A +5v at 1A (Always on) +12v at 9A -12v at 0.5A +3.3v at 14A The thing you're missing is that to supply 27 and 14 amps requires a good bit of design in a switching power supply. Of course, your particular setup may require less, but the cost in time and money to design it is much more than the cost of a decent external 120V UPS - which can also power your monitor. Given that you probably aren't about to create a new PS for your monitor, and the computer is useless without the monitor, you may just think twice about making an internal system, instead of external. -Adam Anand Dhuru wrote: >This is something I've always thought about. Essentially what the PC >requires are +/-12Volts, and +/- 5V. Why dont they come out with a standard >for a 'power supply port'? Since the current requirement for the -ve >voltages is minimal, wouldnt it make a lot of sense to just connect the >motherboard to a battery thru proper rectifiers to block current when the >power is present? The most expensive electronic stage in a conventional UPS, >the inverter, could be completely eliminated. The battery could have an >external charger, or the 'port' could have a source trickling back from the >SMPS to charge it. The negative voltages could be derived from the battery >as well. > >I do have a feeling i am missing something here, but what is it? > >Anand > >----- Original Message ----- >From: "Peter Mcalpine" >To: >Sent: Wednesday, January 02, 2002 5:55 AM >Subject: [EE]: Small UPS > > >>Hi All and happy new year :) >> >>I want to make a small UPS, one that would be able to run my >>PC for a little while if the power failed (enough so it can >>shutdown it self down properly). >> >>2 ways I have thought of doing it. >>1st would be a 240V to 12Vbattery back to 240V that can be run >>in series with the incoming supply. >>2nd would be to modify the existing switch mode computer power >>supply to include the battery. >> >>I would like to do the second method as that sounds easier :) >> >>Any suggestions or pointers to websites that may help me out? >> >>Thanks! >>Peter Mcalpine >> >>-- >>http://www.piclist.com hint: To leave the PICList >>mailto:piclist-unsubscribe-request@mitvma.mit.edu >> >> >> > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics