Guide Bench PSU Build

Bench Power Supply or What to do with an old PSU

There are several reasons for doing this project, the main one being that I needed to power my Audigy 2 NX. The reason for this is that the Audigy displayed a common fault; at about the 2 year mark the power supply failed. So naturally, I looked through my PSU draw for a plug bug (wall adapter), and found several that supplied 5V, but none that supplied the required current of 1.5A. So I decided to build a power supply for it. Not content with building an Audigy only PSU (what a waste that would be), I decided that all my devices could be powered off it.

To that extent, I found that most devices are 5V, 12V or 7.5V.

Also I reckon this may save power, as well as plug sockets. I reason that 5 Plug Bugs run 5 transformers, all generating heat that needs to be dissipated, and thus is quite energy inefficient, whereas 5+ devices running of a PSU would only have one transformer and thus wouldn’t use up as much power.

Even if that isn’t true, I am still saving on plug sockets!

Building the PSU Breakout Box

I started off with a second PSU; I took the base and cut the sides and half of the length off:


Next I dealt with the top part, I deliberately made the length of the base just right, so that when the top was folded down, it reached the base perfectly:


I then used some L section to hold the front to the sides:


Held together pre drilling:



For power, I decided that phono plugs would be ideal, and so I bought 20 of each colour:


One PUS box, pre drilling:


The Cutting template, drawn in Adobe Illustrator:


I then centre punched all of the holes:


And then drilled them out, using the pillar drill, and mid sanding off of the template:


The box is now screwed together using 10mm M3 Hex Head Bolts:


The first layer of car body filler:


And the second layer:


Sanded and a single clear coat:


Painting it black (this is what council Green Recycling Box Lids are for)



I am sorry, but I don’t have any photos of the internal wiring, but I do have a circuit diagram:

The reason for the wiring is to split the power being used into as many cables as possible, to avoid overloading of a single cable.

The negative connections are the external part of the connector, with the positive connection on the inside

I installed a single temperature sensor into the PSU which needed about 2V to run on, so I have wired it between the 3.3V rail and the 5V rail, giving it 1.7V to run on, which it seems happy with.

I also under volted the fan, I have it running on 5V, as opposed to 12V, I have run the PSU with no extra devices for 4 days straight to see if the fan needs to be any faster.

It is now running for a few days with all those devices plugged in, so see what temps it reaches.


Working Shots

The setup nicely laid out on the dining room table:


The installed temperature sensor:


One ton of connectors:


The Right Corner of the unit:


The grill on the right, allowing somewhere for the air to come from for the fan!


Another two devices used with the PSU, a Molex adapter, and a variable regulator:


I hope you enjoyed/were interested reading that. Any questions, comments or suggestions are appreciated

Edit:


Circuit for Variable Voltage Regulator

 

Looks good, but have you loaded the 5V and 12V lines with power resistors? The PSU won't regulate properly without a proper load on the lines.

 

car light bulbs can be good loads too

 

Whats this about resistors on the 5 and 12 volt lines? I never put those on my bench PSU! I'm pretty sure my voltages are right on 12 and 5 too, but I left it nearly intact, just cut off the motherboard connector.

Nice mod by the way, I think it needs a few of those screw-down terminals for connecting loose wires.

 

Yeah, I thought about that afterwards, but decided most of the things I'm powering (PIC dev boards, etc) can have their own cables made up, or they run off the variable regulator circuit I pictured. I also have the molex adapter, and maybe i could make a small board with a phono connector on one side and screw down terminals on the other?

no, there is no load on it, unless it is powering something (like it is at the moment ) so until i put loads on it, i was testing for heat because of under volted fans, and to check all my connections were correct.

 

Wouldn't it have been better to make a completely new case for the PSU? Would've meant the casing was nice and clean. However, you still did an awesome job!

 

It would have been cleaner, but can you say you're bench PSU is better?

Looks awesome to me, but could you possibly reopen it and take a quick inside shot or is that not possible/easy?

 

Yes, this is not the cleanest of builds. On the next iteration (after this uni term) I will sand down both of the cases, and then re body fill and spray silver (I only had black at the time). I go back to uni this weekend, so there hasn’t been a great deal of time to make this completely perfect.

Thanks
Here are some photos of the inside for you all then


^ This one is the back of the temperature sensor. All I have done to it was open it and solder two leads to the batteries + and _ terminals, enlarge the sensor exit hole, and feed the wires through there too.


^ This mess of cables is the main part.

On the left you can see all the red yellow and black cables exiting the PSU and going into the Breakout box.
Towards the top is the temperature sensor cable, which is just folded up and zip tied.
To the base of the photo is the power for the temperature sensor (black wire to 3.3V, red wire to 5V). The temperature probe is just attached to the heat sink of the PSU.
The blue zip tie is holding the extra cables (The fan volt mod, and the green wire to a 0V wire).


^ The breakout box. The plug blocks are used to allow easy disconnection, and rewiring if necessary.

 

I like the use of phono sockets - simple and you can colour-code 12V and 5V lines. They do come in yellow too for 12V (though usually in the more expensive gold-plate ranges).

 

yeah, i tried to get yellow, but they were out of stock on them when i bought the rest of the stuff. i will get some yellow ones for this holiday when i upgrade the PSU though

 

You should make a guide how to do this, I would be interested(and scared) about making one.

 

Il do one aswell if you really want, but this guy has already done a guide: Here

 

ahh thnx a bunch. All i did while reading this was think about how i was going to beg you to explain all of the circuitry.

 

I definitly admire this mod. Good way to not only use an older Power Supply that might have otherwise gone neglected but an easy way to free up some of those electrical outlets. Not only that but it seems like to me that this method would be much more energy effiecient as its a switching mode powersuppply and not a coil style.

I have one question which probably could be answered with some googling but... Where did you get those colored RCA female bolt on jacks? I used some from radioshack but they only had them in black and I am looking for white and red as my first choice, but could settle with red and black. (Planning on adding RCA audio jacks to my computer)

I also wonder what all devices you currently have your PSU powering and how stable it seems to be. Also does the fan run constantly like most PSU's do. Also if you had to do it all over again would you? AKA at the end of the project are you completely satisfied. (Hint: I am thinking of doing a project similar to this one, I am so sick of having 3 power strips worth just to power basic things like switches and routers, cell phone and other things)

 

Black
The Red one has been discontinued.

the ones im going to use nwith the upgrade of it:
These ones That Cpemma gave me the link to.

Deviced being run:
Linksys Wireless switch
Generic 100Mb switch
Belkin USB2 hub
Safecom USB2 hub
Audigy 2NX << Most important to me
Fake Icybox external HD enclosure
Sony Ericsson Phone Charger
Samsung Phone Charger
PIC Dev board

i think thats about it

Stability wise its very good, no devices have crashed or restarted yet.

Yes, the fan runs constantly, but i cant hear it when my ear is next to it; its only running at 5V. It has never been higher than 38.3 Celsius.

If i was had to build it again: defiantly, saved plug space, seems to have put the electricity bill down slightly I will be 'upgrading' it in the next uni holidays, at which point i will build a new case, and do everything in a less rushed fashion.

Good luck with your version

 

Thanks for the info, I just realized I kinda had you under the spotlight there with all those questions.

 

haha, no worries

 

You do have skills in designing things! Do you have the same talent in designing furniture? You can be of great value to my home decor furniture.

 

haha, thanks i think wrong country though

 

hmmmmm pimping me thinks post reported!