Power Bodge

[Boli]

OK here is a question(s) that I have been mulling over for a bit:

I know the basics of what a PSU is. It takes the alternating current from the mains and converts it to DC current which is then split and converted (very vague I know and yes I know that some is +ve current and some is -ve) to the lines such as the 12v, and 5v lines you use to power your computer.

So given that what separates a 300W PSU from a 550W PSU?

I know that the various lines can take up to certain wattages before “variance” and the total wattage is the PSU wattage. But I have seen inside all my PSUs (by virtue of a fan mod, or it broke and I was curious) and they all looked pretty similar.

So what separates the 300W from the 400W/550W or whatever? Is it better quality components different circuitry more hardcore cooling (though I seriously doubt the last one)

The components look pretty much what I can find easily enough in my Dad’s garage (you’ll be surprised at what we actually have in there) is it a serious business of exactly measured traces or can any one “bodge” together one and get a high wattage PSU for a fairly cheap cost providing you are willing to put the work in.

And on a similar vein anyone know anything about UPS (uninterruptible power supply) is it just a “big ass” capacitor dealing with surges and a battery that deals with cuts or is it more complex than that?

~ Boli

[Yo-DUH_87]

Originally posted by Boli
The components look pretty much what I can find easily enough in my Dad’s garage (you’ll be surprised at what we actually have in there) is it a serious business of exactly measured traces or can any one “bodge” together one and get a high wattage PSU for a fairly cheap cost providing you are willing to put the work in.

Overclockers has an article on building your own tec supply that may be a bit enlightening. I am planning to build a fairly low quality PSU (about 11.5-13v) using much the same components that they did.

In order to get decent power regulation (the 5% tollerances expected of top-of-the-line PC PSUs) requires a great deal more circuitry than what I'm doing. I think the component count of my psu so far is 4: fuse, transformer, bridge rect, and a large cap.

So I guess the answer to your question would be: yes you can bodge one together fairly simply, but you wouldn't want to run your PC off it

As far as UPSs go, the one I have (el cheapo pos) is basicaly a large battery and some circuitry to convert whatever the battery voltage is (I forget offhand) into a stepped AC pulse. So insead of being a true wave forum, the waveforum is kinda boxey and makes CRT monitors squeal

I have thought about making a UPS out of a couple car batterys and one of those "traveling power inverters" that plugs into the 12v jack in your car, but I decided that I already have enough projects on my plate

[Boli]

I said you would be surprised at the stuff in my Dad's garage we have a couple of acid baths that are used to etch circuits somewhere.

But is it just the tolerance that is the difference between good and bad quality, so given the right componants and solid connections it is possible to make a good quality PSU. So what stops every PSU being high quality is the quality of the componants used. is that right?

Or is it something more complex like arrays of capasitors work better and give more stable rails than one large capasitor so the circuity get even more complex - and thus expense.

~ Boli

[Groth]

You picked a huge topic to dive into....

The power supply Yo-DUH mentions is unregulated, meaning there is no circuit actively controlling the output voltage. Unregulated supplies are okay for motors and such, but not acceptable for a computer - the ouputs are too unstable.

Your PSU uses a switching regulator. Lots of possibilities, lots of complications. For an overview, try this pdf: Introduction to Power Supplies. While it's possible to home build a computer power supply, it ain't something many can or will do.

As for the UPS, the three key compenents are a battery charger, a power inverter, and a circuit to switch betwixt line and battery. The cheap inverters sold at the auto parts store or wherever output a 'modified sine wave' - squared off and stepped like was said. These are bad for computers. UPS's use better inverters that output nearly perfect sine waves.

If you build yourself a PSU or a UPS, you should combine the two. That way you could leave out the inverter and the AC to DC stage of the PSU.

Surge protectors: most use either Metal Oxide Varistors (MOV) or SCRs/diacs/triacs/sidacs/thyristors. If your brain isn't fried from power supply goodness, try a search for 'crowbar circuit'.

[Tempus]

What about building a PSU for a pelt or a compressor.

[Boli]

What? This is meant to be a challenge - combining the two has allways been an idea of mine. What has ben bugging me for the past year is the power in the flat is terrible and even though a surge protector and 550W PSU I am still seeming large variances on my voltage lines that have caused the computer to crash many times.

These various power sriges have blown three PSUs and two monitors with one of the PSUs taking a motherboard with it. If I were to build a PSU that could delivery "rock solid" voltage lines to my computer though power cuts and surges then I would consider it a job well done.

I'm just trying to gather as much information on the subject to see if it indeed worth it, or if it is indeed possible for me TO make one.

~ Boli

[Groth]

The big problem with surge protectors is that they are only as good as their ground connection. The longer the wire run and the smaller the wire gauge, the less use they are. To be truly effective, a surge protector should be attached to the mains at the primary distribution panel. I'd be impressed if you could do that in a flat.

If Dad's garage is really well stocked, build a motor-generator. Simpy put, mains current drives a motor, motor spins a generator, generator powers the computer. The absense of an electrical path between computer and mains will keep the bad volts away.

Another possibility is to hack into a UPS. Modify it so that it always outputs from the power inverter and never pass mains straight through. Problem there is that most UPS don't have a battery charger powerful enough for that kind of continuous operation. You'd need a big UPS, or some supplemental DC source.

[Boli]

I was going to have a check around and look to see what I can use Maybe I'll find an old car battery and such but I'll be looking into it at Christmas for about 5min or so then leave project till next year.

~ Boli

[Since87]

Originally posted by Groth
Another possibility is to hack into a UPS. Modify it so that it always outputs from the power inverter and never pass mains straight through. Problem there is that most UPS don't have a battery charger powerful enough for that kind of continuous operation. You'd need a big UPS, or some supplemental DC source.

It used to be that "UPS" actually meant that the output was alway provided from the DC voltage at the battery. (Truly no interruption.) Of course PC's drew a lot less power at that time, so it was a lot more practical.

You might still be able to find such a device, but it would likely cost a small fortune.

The motor-generator is a good idea, but you might want to put it in a garage or something. Not sure how noisy it might be.

[Tempus]

Would there be any advantage to creating a seperate PSU / UPS integrated unit to power all the fans? If I remember correctly, those little motors aren't very nice to wave forms. And the integrated UPS should help in the event of a brown out.

[Boli]

Perhaps a separate "line" to deal with the oscillating voltage uses i.e. fans, and maybe even hard drives. Would this create a more stable powerflow?


POWER ---> UPS |----> Isolator circuits ----- Power output 1
...........................|----> Isolator circuits ----- Power output 2
...........................|----> Isolator circuits ----- Power output 3



Where power output 1 would be for the use in static “diode” current where the current demands are pretty much static

Power output 2 would be used for the fans where it may be preferable to keep the power demands separate

And a third isolated power output to deal with the hard drives.


I’m pretty sure things like “isolator circuits exist” in involving transformers and capacitors.

So the entire thing would be more like having sub PSUs that perform more specialised tasks in current demand – the power need at the start that draw from having to start the fans would then be kept separate from the Hard drives and more importantly the CPU.

My server for example won’t start properly unless all its fans are in motion because of the power drain is not now sufficient to start the computer as a whole anymore.

This will also allow for maybe the more expensive components to be reserved for the mobo lead and a more “solid” voltage lines reserved for that where even I know fans are pretty resilient to voltage changes.



I have a feeling that PSUs are actually built on similar lines with the 12v/5v rails running in a separate path to the rest but I plan to expand on it.

Size won’t be an issue but moving parts is. I don’t want any moving parts – movement creates noise and that is a bad thing.

~ Boli