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1) Is it a linear or at switching PSU?
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mine is linear, switching are very difficult to make, I've had a thought about modding a standard comp psu to put out just 20V or similar though, no progress yet.
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2) Dimensions and weight?
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Well I built it to fit a space, you could make it smaller but at least 80mm tall for fans / transformer, then you need it about 6 to 8 inches long and maybe that much wide, or longer and thinner etc.
As for weight it's about 4 Kg which is about half the weight of a computer (air cooled).
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3) What about EMI, you figure it is safe to build it into the computer chassi?
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I used a torroidal transformer as they are cheaper and lighter for a given amount of power, and also have very good EMI characteristics, if building into a case you'd almost certainly need it in a metal case (which you should do anyway to cover the AC line connections), that should help cut EMI, if it;s still a problem you could probably do some shielding with nickel paint or similar.
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4) Blueprint/guide/shematics?!
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hehe, I have a schematic for the circuit but it's just drawn by hand in my notebook atm, I could dig it out and get it into electronic form if you think it'd be useful.
As for a guide, I drew the circuit from scratch then just assembled it according to the schematic, it's not a particularly conplex circuit.
Specs of the circuit are:
Voltage 20V nominal (can be adjustable if required).
Max current: 25A (could be increased/decreased with different components).
Heat output: approx 50W, fan-cooled (dual 80mm) Al heatsinks used.
Cost: transformer (20-100 depending on size, location, etc.) plus about 10 bucks of stuff, heatsinks would probably cost an extra 10 bucks or so, I had some lying about.
Extras I could throw in include sensors for the fans so they run slower when the psu is cool (couple of bucks for them), a sensor on the coldplate to drop the psu voltage when it gets cold enough (although I think that might blow my current design to bits
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