But dont monitors also essentially operate on 12 VDC, which is then cranked
up for the EHT etc.?

----- Original Message -----
From: "M. Adam Davis" <adampic@UBASICS.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, January 03, 2002 12:19 PM
Subject: Re: [EE]: Small UPS


> 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" <pmcalpin@BIGPOND.NET.AU>
> >To: <PICLIST@MITVMA.MIT.EDU>
> >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
> >>
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