Hello

Ever thought about building a power supply load to properly test your ATX power supplies. Well I have finally finished mine and I thought I would just tell you briefly how I went about it.

I am using aluminium clad wirewound resistors as the loads. Pictures here:



These resistors come in a range of wattage (power handling) ratings from 10W to 200W. The circuit diagram of my load is here:



I have designed it to give me a choice of three loads for each of the 3V3, 5V0 and 12V0 DC lines. (I have initially repeated the 12V0 resistor bank 4 times so that I can load up 4 seperate 12V0 lines). I calculated all my resistors for various loadings and tried to keep it to 100W resistors and below. There is quite a price jump if you use 200W resistors.

Just as an example lets say you wanted to pull 5A (I) from the 12V0 (V) line.

Resistance R= V/I = 12/5 = 2.4R (ohm).

The power handling rating of this resistor in Watts W= V*I = 12*5 = 60W.

You would need to connect a 2.4R 60W resistor across the OV (Black) and 12V (Yellow) lines on your power supply.

You will not get a 2.4R as they come in standard prefared values, the nearest aluminium clad wirewound resistor you can get is 2.2R 100W. (This partly explains why my circuit diagram looks a bit complicated. It was a mix of trying to get certain values of resistors and keeping them below 100W to try and keep costs down). The wattage ratings of these resistors is somewhat misleading. If you buy an 100W resistor it is only safe at about 50W unless it is bolted to an heatsink to help dissipate the heat they generate. Hence:



This is two large heatsinks bolted together with the fins on the inside. (I have to say I was lucky enough to find these on ebay. New they would have cost a small fortune). This photograph shows the power resistors mounted with heatsink compound to the sides:



The final wired load is shown here:



..and wired up to a power supply here:



Note the addition of the 12V fans at either end to force air through the centre and help cool it down. When the power supply is loaded at 500W is does get rather warm!

This photograph shows the final design. I have changed the terminal block and used crimp connectors to try and reduce the resistance in the wiring.



Note the addition of a small 12V power supply. This powers my fans so that it doesn't affect the loading on the power supply (although it's only a few watts) and more importantly I can keep the cooling on after the power supply is switched off to cool the beast down.

So now I have a custom built ATX power supply load which gives me the following options:

A 3V3 load of 3.3A, 9.7A or 16.5A
A 5V0 load of 5.0A, 10.6A or 17.5A
A 12V0 load of 2.5A, 8.5A or 12A (x4)
A fixed -12V0 load of 0.4A
A fixed +5VSB load of 2.3A

Selecting my loads carefully I can now load up basically any power supply to a level of approximately 750W.

I think 750W will provide sufficient load to test power supplies upto and at a level used by 99% of PC users out there. I have measured the load on my system and I was surprised to find it at only 180W. In the future I can if necessary add two more 12V load banks (12V0[5] and 12V0[6]) which will take the load up to approximately 1kW.

Hope you found this slightly interesting.

Regards

Paul

That thing looks Badass!

What would be a ballpark figure of what one of these would cost?

Also, you should dump imagecrap and use a real image host like the Overclockers Image Database that likewhoa was kind enough to set up for us

Keep it up man, nice work!

and/or link them with the proper image tags so we don't have to click on each one individually.

nice Paul Glad to see you posted this up...it's a real DIY-Street project and something we really like to see...


EDIT: Paul...if you have large full res pictures we can host them...we can make thumbs of them for forum friendlyness and link them to the full res pictures if you like...just get with any of us...

or if you like you can get an account at the forum picture data base from Likewhoa and we can show you how to do the same thing if you dont know how...

Edited with thumbnails using The Overclockers Image Database. Larger pictures available as links. Is this more acceptable?

Regards

Paul

ElissD

It as cost me approximately £125.00 ($250.00) and several nights building so far and thats with me trying to keep the cost down!

I will now use it for my first power supply review for DIY Street and see what Praz thinks. My first test power supply will be a Atrix 500T. It is turning out exactly as I hoped it would, a fine example of what not to buy for an enthusiast/performance system!

Regards

Paul

It was acceptable before, its just a nice touch not to have to click on the links to view the pictures

I'd prefer if they were just image tags so that the full image appears in the thread

radodrill

I can do that no problem. Am I right in saying that 800x600 is the maximum allowable size or does it not matter as the image is being hosted elsewhere.

Regards

Paul

Correct. An 800x600 image is the largest you are allowed to use in img tags.

EDIT: Oh, and 600x800 is not the same even though the pixel count is the same. I saw someone get dinged for it, lol, so keep that in mind.

Still needs to be 800x600, it's set to that size so virtually any monitor anywhere will be able to show it without any issues. Which is why 600x800 isn't the same thing.

Depending on where you host it, they can resize it for you. Otherwise there are all kinds of batch image resizers out there. The one I use is simply called "image resizer".

http://www.thejackol.com/2004/10/27/image-resizer/

Yes 800x 600 is the biggest allowable when used with image tags BUT, the reason I suggested thumbs is if you have a much larger resolution picture and you dont want to shrink it to 800x600....you can simply host the full size pick and make a thumbnail of your choice in size I go 150x150 or so even 600x400 is a fine thumb for showing more in the thread...



for looks yes...people like to see the pic in the thread just looks nicer too...



see 1st quote...^^^

How's that?

Regards

Paul

Smexy :cool:

Also, you can see the whole pic in detail without having to open any new windows

awesome man just awesome....I love it..

I smell front page material...

I am very excited to see this review!!