I have seen SMPS for PC with built in batteries, its charging circuit & 12VDC-330VDC inverter circuit. Good for 2-3 mins for PC. But that maynot feed your monitor. So in case power fails, your monitor will turn-off but PC will be alive. then you can initiate shuttdown. Probably you have a PC with such power supply but external batteries. OR may be its SMPS with 12VDC output for poweing external devices for same SMPS! Hitesh Mahant VITAL -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Mark Newland Sent: Thursday, January 03, 2002 10:03 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Small UPS I actually have a fullsized desktop PC that has a 12Vdc plug in the back. Can hook it up directly to a 12V car battery. 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: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu