ATX power supply conversion for bench usage

Description

I have a few old power supplies lying around, so I picked one to become a bench power supply. The choice was mainly based on the fact that I could find a manual that specifies the minimum load for each output of this thing.

The minimum load is just a power resistor that is not too small (that would be a waste of available current for actual work), and not too large (then it wouldn't be enough of a load). As the resistors would just dissipate heat, I'll see if they need any cooling and provide that with a small fan, or by just hanging them into the air that flows through the power supply.

A mainboard power adapter and a few old HD power adapters will be used to connect to the power supply, so I'm actually building a big adapter instead of modifying the power supply itself. This has a great advantage: The power supply can be replaced with an older/newer/really working/more powerful one.

Components

1 × Enermax EG465AX-VE(G) ATX Power Supply

1 × Piece of wood, 300 mm x 300 mm x 16 mm to hold the aluminum front and the power supply

1 × U-shaped Aluminum, 90 mm x 50 mm x 3 mm cross section, about 250 mm long (or something like that, I had that lying around) This holds all the connectors, switch, LEDs

1 × A few Connectors (4mm banana jacks) A pair for each voltage you want to have access to, plus one for protective ground

1 × Old ATX power supply adapters The power supply will be left untouched, it can even be swapped later.

Build Instructions

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1

Step 1

Create drilling templates for the front and base plates
Figure out how many 3.3V, 5V, 12V, -5V, and -12V banana jacks you want to have in your front plate. I used two each for the high-current voltages (3.3V, 5V, and 12V) and one each for the low-current ones (-5V and -12V, prepared a hole for -3.3V just in case I need it later).
The front plate will also hold a switch and two 3 mm LEDs (red for standby and green for power good). I also added holes for two cable glands.
Mark the positions of each hole on a piece of paper (or print the whole thing, it doesn't matter).
Do the same thing for mounting the front plate on the base plate. I used 4 M8 screws for that.
Here's a picture of my front template:
It's missing the marks for the switch and the LEDs, I added them later.
2

Step 2

Drill front and base, mount front on base plate
Straight forward: My banana jacks needed 8 mm holes, the cable glands needed 12 mm-ish (12.5? I'm not sure what I used), then there's 5 mm for the switch and 3.2 mm for the LEDs, and finally 8.5 mm for the mounting screws:
I used additional spring washers for the M8 screws.
3

Step 3

Drill front and base, mount front on base plate
Straight forward: My banana jacks needed 8 mm holes, the cable glands needed 12 mm-ish (12.5? I'm not sure what I used), then there's 5 mm for the switch and 3.2 mm for the LEDs, and finally 8.5 mm for the mounting screws:
I used additional spring washers for the M8 screws.

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Discussions

Simon Whetham wrote 05/01/2020 at 14:33

hi christoph and thanks. i'm a total beginner with this, but have used atx psu's to power arduinos and motors in my sound installations for a couple of years now.

usually i only need to connect the green cable to a black ground and it works fine but i tried this on a new unit i just bought and it's runs for a fraction of a second then cuts out... is this where the minimum load comes in?

and do you need to add a minimum load on every output as in this project, or usually only on the 5vsb output?

also, if i am unable to get my hands on these power resistors (or even this doesn't work) do you have any other suggestions please?

Are you sure? yes | no

Hari Wiguna wrote 05/28/2014 at 19:43

Thanks Christoph!

Are you sure? yes | no

Hari Wiguna wrote 05/28/2014 at 05:04

This is the second time I read someone mentioning the use of a resistor to load the power supply. How much current did you end up running through your resistor? Could you add a resistor and an LED in series so you can use it as a power indicator AND dummy load at the same time?

Are you sure? yes | no

Christoph wrote 05/28/2014 at 06:51

The power resistors (resistance, resulting current and rating) are included in the parts list. The biggest load is on the 12 V line with about 1.6 A.
Of course, I could have added an LED with current limiting resistor to each output, but I used the power supply's "power good" output instead. Another option would have been to monitor the current drawn by the "real" load (ie. what I actually want to supply with power) and switch off the dummy load with a transistor when it is not needed.

Are you sure? yes | no

ATX power supply conversion for bench usage

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