ive scearched the net, and the guides section of bit tech, and i cant find a guide on how to make an uninterruptible power supply. I know i need an inverter for AC-DC, a battery, then another inverter for DC/AC. but i dont know what kind of inverters or where to get them. ill probably use a car battery, that will last for a while, enough time to shut down and will cover me for those 2 second power outtages. can anyone help me out with this project?
Depending upon what kind of wattage you need, one of those car inverters might work for the DC-AC, as it's already prewired for voltage etc if I have it right. AC-DC is just a normal transformer, but I'd be thinking you'd use a battery charger. For me I'd have the battery charger wired to the battery which is wired to the inverter and a junction with the wall AC current. The problem I guess is unless your charger supports it, you're just running tons of current through the battery, but otherwise that seems basic enough. There was a hackaday entry for this, lemme find it real quick... http://www.dansdata.com/diyups.htm That's a pretty in depth article about it, should get you started. Hope that helps!
i probably only need about <250 watts of power, some of those car inverters are like 300 for about 40 bucks canadian, so ill look at them. and then a modified psu for the ac to dc, and a car battery. this is coming together quite nicely.
This PS skips the inverter so your battery lasts 40% to 60% longer http://www.voxtechnologies.com/power_supplies/vtc0144.htm . The hookup would be Charger-Battery-PSU. The input range of the PSU is 9V (discharge end) to 18V (charging over-voltage + some safety) for just this purpose. Be careful when you select the charger and battery. At 250W output and 60% efficiency (see datasheet) the PS has 420W input. At 12V that's 35A that your charger has to deliver. If the computer is off a simple charger will dump those 35A into the battery. A lead acid battery likes to be charged at a current of Ah-rating/10h at most, otherwise it dies fast. That means the battery has to have at least 350Ah, or you need a computerized charger that can detect the charging level to turn down the current.
