Introduction: Make a Bench Power Supply Mostly From Recycled Parts

Picture of Make a Bench Power Supply Mostly From Recycled Parts

This instructable will show you how to make a very good bench power supply using mainly recycled parts. This is the really the "mark II",  you can see "mark I" here. 

  When I finished my first bench power supply I was really happy, and used it very often, almost every day, until one day it decided not to work anymore, :(  so... I realized I had to do it all over again, including the not that easy drilling on the metal of the ATX, etc. So this time I'm making a bench power supply that you can replace the ATX in no more than 2min.

  Last time I did not take any pictures of the process, so  I could only do a slideshow of the finished product, but this time I took lots of pictures, so I did this Instructable, which I hope you'll like.

  May you decide to go ahead and build your own?... I would like to take the opportunity to say that I will be more than happy to help you with any questions you have, and also I will love suggestions so I can improve either this instructable or the bench power supply itself.

  As the title shows, with this instructable I want to encourage people to recycle. There are lots of things around the house or even in the streets, that you can take components off, and use them later to make so many interesting things. I used as many recycled parts as I could for this project, and if you do the same, you could have a very powerful and COOL! bench power supply for almost nothing.

OK.. lets start with a view of what we will be making....

Step 1: Materials and Tools

Picture of Materials and Tools

Here is a list of the materials and tools I used for this project. Some of them are optional, like the analogue panel meters, as you could use any multitester to check ether the voltage or amps.

  The same with tools, you may want to use a different tool, just go ahead, and also make any suggestions so we all can learn.

  Don't be scared of the quantity of materials, this project is not really difficult to make, trust me, if I've done it, anybody can.


1).- (1)Bread box.( Recycled, you could use any other enclosure that you can fit the ATX in with enough space)

2).-(3) Switches (2 single way switches recycled from old heaters, and a 2 double way switch recycled from an OHP)

3).-Cable connectors (Recycled from old amplifier, and from old TV)

4).-(1) ATX (Recycled from old computer)

5).-(3) PC Drive Molex to SATA Power Adapter (ebay £1.50, view)

6).-(1)  20-24 Pin ATX power adapter for Computer PSU (ebay £2.77, view)

7).-(1) USB connector (Optional, Recycled from old computer)

8).-(2) LED's (red, green) , (Recycled from old computer)

9).-(2) 5K Potentiometer (One Recycled, and the other one bought for £1.35, view)

10).-(2) Potentiometer knobs ( Recycled from old amplifier)

11).-(1) empty can of coke (Recycled)

12).-(1) 8cm computer fan (Recycled from bench power supply mark I)

13).-(1) Magnetic Catch (Bought  £1, view)

14).-(1) IEC cable (The cable that connects the computer to the power socket, Recycled)

15).-(1) IEC connectorRecycled from bench power supply mark I)

16).-Piece of trunking (Optional)

17).-Some cable ties.

18).-(1)Fridge magnet ("Stolen" from the fridge)

19).-Some wires. (Recycled from extension lead)

20).-(2) 8cm Fan grills (Recycled from old ATX)

21).-(2)  Screw eyes


1).-(1) LM350 Adjustable Voltage Regulator (ebay £0.50)

2).-(1) 560 Ohm Resistor (Recycled from old radio)

3).-(2) 1N4001 Diodes (Recycled from old radio)

4).-(1) 0.1 uf Capacitor (Recycled from old radio)

5).-(1)  10 uf Capacitor (Recycled from old radio)

6).-(1) Heat sink (Recycled from old radio)

7).-(1) 10W 10 Ohm Wirewound resistor (Maplin £0.48)

TOTAL COST = £7.60

If you want to use analogue meters like me, and you also want to make the continuity tester,  you will also need in addition to the previous list:

1).-(1) Voltage panel meter (Optional £6 ebay, view)

2).-(1) Amp panel meter (Optional,  £6 ebay, view)

3).-(1) 6V Mini Relay (Optional, £1.31, view)

4).- (2) 9v PP3 Battery box (£1.29 each, view)

5).-(1)  9v Buzzer (Optional, £1.99, view)

6).- (2) 9V PP3 Batteries 

7).-(1) 1N4001 Diodes (Recycled from old radio)

TOTAL COST = £16.59

GRAND TOTAL= £ 24.19



2)-Hot glue gun.

3)-Dremel (With a cutting disc and round sander)

4)-Hole saw ( about 7cm)


6)-Sand paper


8)-A Dymo (Optional, I don't have one, my wife did the labels for me at work, but you could print them and tape them)

note: In this list of materials I specified where I found some of the parts I've used. I'm not saying that you need to buy an OHP or a home heater to get the parts, but maybe you already have some of these things at home and they don't work any more, or you can find then on the street, or in garage sales or in markets like the one you see in the picture below. 

Step 2: The Enclosure

Picture of The Enclosure

  For my bench power supply I'll be using a bread box. This one had a glass door,  so the first thing I did was replace the glass with a wood panel. I added this step in case you face the same problem, but if your enclose is ready to go, skip to next step.

  One thing to take into consideration when choosing an enclosure is that if it is made of metal, not only will be difficult to make the cuts and holes, but you'll face the problem of the conductivity of metal, so if your connectors are not isolated that'll become a problem. Also make sure the ATX will fit inside.

1).- Take the glass door out, and place it on top of the wood panel so you can draw the lines with a pencil and cut an exact size wood door.

  If you want to make sure you don't do wrong cuts, you could always place the glass door on top of the wood panel and hold it with a clamp (see pics).

2).-I used the same handle for the door so I had to use some sticky stuff remover and a knife to get it out of the glass.

Step 3: Making the Front Panel

Picture of Making the Front Panel

1).- With the door outside the bread box, mark everything that is going in there, like the cable connectors, switches, potentiometer (when marking where the potentiometer is going to be, pay attention to the size of the knob), LED's, etc...

2).- Once you're happy with the distribution of everything, start cutting with the dremel, using the cutting disc.

  Make sure everything fits through the holes (you could use the circular sander with the dremel or sand paper if it needs to be a bit bigger)

3).- Then something I forgot to do is erase all the pen marks and writing. If you do it now, it would be a lot easier than once all the connectors are fitted.

4).-Now hot glue everything from the back of the door.(see pics)

Step 4: Placing the ATX

Picture of Placing the ATX

  When deciding where to put the ATX, take into consideration not to block any of the vents or the fan. In this case I decided to place it upright as you can see in the picture.

  The goal of this project is to be able to change the ATX really quickly and without having to take out any screws, so I cut 4 pieces of wood and then hot glued them to the sides of my enclosure after marking with a pen where they'll go, that way I can slide the ATX in or out really easily.

I also fit a self adhesive trunking to protect the power cable.

Step 5: Power Connector (IEC Connector)

Picture of Power Connector (IEC Connector)

 Mark where you want to put the IEC connector. I placed it at the back as this will help me not to put the unit to close to the wall which will stop the air flow.

1).- Mark the side of the connector with a pen, drill some holes near the line you drew and finish the job moving the drill one side to another until all the holes merge together.

2).- Make sure it fits in, and fit it with two screws (Later we'll take it out again to solder the cables)

Step 6: Ventilation

Picture of Ventilation

  Ventilation is very important in this project as you are fitting an ATX inside an almost sealed enclosure. If you don't do anything about ventilation, the ATX will get really hot and eventually will stop working.

1).- In this case as the ATX is upright, I fitted one fan at the bottom of the enclosure and made a hole on the top of the enclosure, as the ATX is always taking air out of the PC. So the fan at the bottom will blow air inside which will get through the ATX and then will get out at the top vent.

2).- To make sure the air that is blown from the ATX finds its way out, I decided to help it a bit by cutting a coke can and fitting it on top of the enclosure. (see pics).

3).- And then I glued  a fridge magnet to the can with some epoxy (this will stop unwanted noise from the vibrations)

Step 7: Making the Voltage Regulator.

Picture of Making the Voltage Regulator.

  The voltage regulator I made is based on a really good instructable you can see here. The only thing I changed was the voltage regulator itself, for a more powerful one:  the LM350  3A.

  The schematic is in that instructable but I did a graphic schematic to make it a bit easier. You can see also my circuit on its heatsink.

Step 8: Soldering the Cables, Schematic

Picture of Soldering the Cables, Schematic

1).-  Now is the moment to solder all the cables on the front panel, and here is a PDF file and a JPG file of the full schematic.

  In this schematic there are two 5k potentiometers, that's because my voltage panel meter goes just until 20V but in case I need a bit more, I can use the other potentiometer of 5k on series as a booster. (you could place a switch in series with the potentiometer and open the circuit to give the boost, but it will go straight to the maximum voltage, with this second potentiometer you will be able to control that voltage)

2).- Once you have finished soldering the cables, use some cable ties to make sure nothing will come loose when opening or closing the door.

3).- Glue the door with epoxy, I used wood epoxy.

In the schematic you'll see how I used the double two way switch to swap the negative cable that goes into the voltage regulator. I can use ether -12v or 0v (ground), the reason I've done this is because the -12v is not as powerful as the 0v output. So with setting 1) I can go from 1.2V to 23V but is limited to 2A, and with setting 2) I can go from 1.2v to 11V up to 3A (the voltage regulator is 3A)  Here is a video were you can see the difference:

  To connect the USB output  you just need to use the ground for the negative and the +5v for the positive. ( if you're not sure witch cables to use see here )

Step 9: AC Power Cables

Picture of AC Power Cables

1).- Solder the AC power cables. Be really careful not to leave any of these cables exposed as they could be really dangerous. I used some heat shrink to cover the wires.

2).-You could also fit the voltage regulator near the fan so it cools down as the air flow inside.

Step 10: Fitting Cables From the Door to the Inside.

Picture of Fitting Cables From the Door to the Inside.

  Using a couple of screw eyes, fit the cables with some cable ties, leaving enough cable to be able to open the door freely.

Step 11: The Quick Release Connectors.

Picture of The Quick Release Connectors.

1).- Take the molex to sata power adapter and cut them, we don't need the sata bit for this project, but save it for future projects.

2).- Join all the cables together like you can see in the picture. (Some ATX have more than 3 molex connectors, but with 3 you've got more than enough for this project.)

  Using a connection block join all the cables. ( this is done so if the ATX blows you don't need to cut or solder any cable, just disconnect the broken unit and connect the new one)

3).- Do the same with the 20-24 Pin ATX power adapter. you need to keep the side with 24 pins.

Step 12: Fitting the Wirewound Resistor

Picture of Fitting the Wirewound Resistor

Even when I've noticed no difference with the resistor or without it, I read everywhere that there is a need of a 10 Ohm wirewound resistor, so I fitted one.

These resistors get really hot when in use, so I found a heat sink for it, and placed it near the fan.

Then, I connected it to ground and +5V.

Step 13: Fitting a Magnet Catch to the Door

Picture of Fitting a Magnet Catch to the Door

  There are lots of cables so the door will tend to open. The way I solved this is with a magnet catch. I screwed the magnet bit to the enclosure and glued the metal bit to the door with some epoxy.

Step 14: Cutting Unwanted Cables From ATX

Picture of Cutting Unwanted Cables From ATX

  Before fitting the ATX inside we can cut unwanted cables and connectors. As you can see in the picture, I did cut the secondary cable and connector and left those that go straight to the ATX. Make sure you cut them really close to the connector so there is not danger of short circuit.

You could also use some cable ties to make the cable as less bulky as possible.

Step 15: Labeling

Picture of Labeling

  Use a Dymo to make the labels. If you don't have a Dymo ( like me), get somebody to do it for you. At the office my wife has one, so she did it for me. When doing the labels, just do as you would understand them. 

You can see in this picture lots of labels, I thought there were too many, so I took some out  later on.

Step 16: Fitting the Voltmeter and Ammeter

Picture of Fitting the Voltmeter and Ammeter

After a long wait, I finally received the digital meters form HK.

1).- Before fitting them in place, make sure they work.

2).- Place them in the hole you made for them. It may require some sanding, we want it to be tight in the hole.

-If you are using digital metes like mine, you need to power them with a battery, DO NOT TRY TO POWER THEM WITH THE ATX.  This not only won't work, but  could also damage the meters ( I broke one trying it )

3).- Use a relay to activate the power to the voltage meter and a switch to power the ammeter. The reason I've done this is so I can use the ammeter with other power supplies.

4).-To fix the batteries use a couple of battery boxes. I glued the lid, so I can slide the batteries in and out.

Step 17: The Continuity Tester

Picture of The Continuity Tester

I decided to install a continuity tester on my bench power supply. 

1).- Find a good place to fit the banana connectors. Mark where they'll go

2).- Drill the holes, I did not have a 12.4mm drill bit, so I used my step drill bit.

3).- Fix the connectors with the nuts and solder the cables (see schematic on step 8

4).- Hot glue the buzzer.

Step 18: You're Done!

Picture of You're Done!

  Well... you're done! I hope this Instructable helped you make a bench power supply. 

  Remember there are lots of components that can be recycled from old stuff that you have at home or even found on the street.

  I have to apologize for lots of mistake I'm sure I've done in this Instructable as English is not my first language. 

Step 19: Replacing the PSU

Replacing the PSU couldn't be easier. It only takes a couple of minutes. 


1).- Disconnect the molex connectors and the 24pin connector.

2).- Disconnect the main power connector on the PSU.

.- Lift the aluminium that helps the vent flow.

4.)- Slide the PSU out of its place. (this is in my case, maybe you've done it differently)


1).-Slide the PSU in its place.

2).-Connect the main power connector on the PSU (If it has a switch make sure is in the on position) 

3).-Pull down the aluminium until the magnet sticks to the metal of the PSU.

4).-Connect the molex connectors and the 24pin connector.


kasiriko005 (author)2017-02-24

can i connectthis circuit between photovoltaic and battery?

khturnings (author)2016-09-23

Very useful and detailed - I was just scratching my head as to why on my setup, were the digital meters where connected to the ATX PSU the meters stayed on even if I disabled it using a switch in the 'power on' signal wire. I will be adding a battery pack.

FerriteGiant (author)2016-07-12


rewalston (author)2015-06-12

I'm interested in building this but the link for the relay comes up blank. What are the specs for the relay? I'm in Canada, not the UK so the Maplin website wouldn't work. If I follow your link to the part, it's not listed. Any help would be great thanks.

HarryO3 (author)rewalston2015-11-05

The relay just needs to be able to stand the mains supply voltage. Most can, but its best to check before you but it

JoeI2 (author)2015-09-07

Your English is fine. Will this work for my Amateur radio that draws 22amps 12 volts?

Lee Wilkerson (author)JoeI22015-10-12

22A? No. I suggest you harvest an old microwave oven transformer, cut off the secondary winding, and rewind a new secondary from 10Ga. enameled wire. I did this once myself and, using 4 windings of 16 turns each, built a dual regulated+unregulated power supply. (I could recharge car batteries on the unregulated side.) I used a 25A. bridge rectifier on each side, but if you need 22A., you should use rectifiers capable of at least 40A. which most likely means stud-mount. Bear in mind that the voltage drop across the rectifiers is around 0.7V. so .7 x 40=24W. of heat dissipation for each rectifier. That's a pretty good size pair of heatsinks. I also suggest computer-grade electrolytic capacitors. I would be more than happy to assist you with tech and hands-on experience at my disposal. Email me at if you wish.

Pojsta (author)2015-06-26

Great Instructable, Just curious if you have to use the molex connections? don't they all run through the ATX plug? or is there something inside the PSU that I am missing?


jerry.ericsson2 (author)2015-05-24

Oh by the way, your English was much better than many English speaking people who attempt to show their ignorance when trying to make a point.

redman88 (author)2013-04-04

looking at a few other instructables and i found why you need the 10ohm resistor,

jerry.ericsson2 (author)redman882015-05-24

I read in one instructable that you can use a 1157 tail light bulb instead, I am planning one of these and I think I will go that route as the light will make a nice way to light up the control panel and use that electricity wasted in heat from the resistor.

kalliber (author)2015-05-08

Hi Newton,

I tried the VR before I go on to make my own labPSU but have some issues. when I put all the components on a breadboard and hooked it up with 12V, my output voltage starts with 1.25V and immediately when I turn the 500K pot it will increase to the max 12V. what am I doing wrong? please help me out. I tried with the diodes and without them. also tried with a 200K pot, same issue. appriciate what you've done here and want to learn from you.

many thanks!


andy.gaffney.5 (author)2015-04-01

I wish I'd read this before I blew my voltmeter !

newtonn2 (author)andy.gaffney.52015-04-11

Oh no! This is a very old instructable, see my other instructables if you want to use another type of voltmeter that allow to be power from the same source.

michaelhays (author)2015-03-21

Great Instructable, thanks! Is there any reason that all of these ATX bench power supplies use linear voltage regulators like the LM317/LM350 instead of a switching voltage regulator like the LM2596?

russ_hensel (author)2015-01-09

Just a note to let you know I have added this instructable to the collection:
Encyclopedia of ATX to Bench Power Supply Conversion
Take a look at about 70 different approaches to this project.

Additional note: if there were a prize for the collections entries, yours would get it, nice.

tytower (author)2014-12-21

Normally when making a power supply you state whether it is fixed or variable in relation to output voltage and output current . There is probably something in here that tells me this but I'm not going to waste a half a day looking for it . It should be in the HEADING !

DraakUSA (author)2014-11-04

You can [probably] power the meters from the 12v line you use a couple of 12v-to-9v isolated output converters. Such as

vimajks (author)2014-04-22

Hi Newton,

on your wiring diagam is it only two legs from the potentionmeters that be attached to pcb.

plus i am using 15v per side ie negative and positive so do i need to up the potentionmeter values??

my 5k potentionmetrs keep burning out and i see a light in it!!!

do i need to use 10k ones so it can control the voltage an using.

please let me know.



newtonn2 (author)vimajks2014-04-23

Hi Vim,
You need to connect the middle connector and any of the other to. Other ways you are making a shortcircuit.

Let me know if that fix your problem


Homepwner (author)2014-04-22

I made an AT based supply that didn't work for me. I have an enermax ATX high end PSU and figured I'd go all out on a fancy bench supply unit. I'm getting really frustrated. I thought that someone could enlighten me as to the weird results I get.

1.The PSU came with 2 fans and when connected they both spin slowly, Normal?

2. Connecting the green and Ground wire through a switch makes no difference in how it operates.

3. Not a real problem, but, connecting the Orange wire (3.3v) to the Brown sense wire through a power resistor only seems to stabilize voltage slightly.

4. The voltage readings I expected are not at all what I get.

GND - orange= 818mv , -5v-+12v= 20v, -12v-+12v=19.03v

GND-red= 3.5v, GND-+12 = 19.00v.

I built a variable LM317 based voltage regulator connected to ground and +12v (yellow).... It provides 1.2v-17.86v. It works great but most other terminals don't supply anything near what should be expected.

Any insight would be greatly appreciated!

bswt (author)2014-01-31

can i use the M9052 LM350K STEELP+ in this voltage regulator

junior_08 (author)2013-10-29

can u help to do the same box like urs i like tht one

cheegi (author)2013-08-19

I think you can use step down regulator with L200 with external transistor. huge power supply need if you load high current

zacker (author)2013-05-29

lol.. I like that you put "English is not my first language" because... Electricity is not mine! lol,lol,lol... +12v, -12v, +12 VB DC, +12 VA DC / SE what the heck?
Yes these are listed in the pin out diagram for my Dell PSU!

zacker (author)2013-05-29

wow...came out very nice!

newtonn2 (author)zacker2013-05-29

Thank you very much!

zacker (author)newtonn22013-05-29

lol no problem... Now Im getting all sorts of Ideas about making a box for the one im going to be making, once I figure out all the wiring. I especially liked the Amp and Volt meters you have in yours, the blue lights look great. Now those measure what's coming out of the PSU correct? So if you hook it to something, and you want to see how many Amps or volts its pulling, boom! you just look at the meters instead of getting out the Multimeter. Nice!

KylerKraus (author)2013-03-22

nice instructable and good results.

I need a power supply that will vary volts and amps. could i put a pot on one side of the output and vary the amps that way?

newtonn2 (author)KylerKraus2013-03-22

Hi there! Unfortunately you wont be able to adjust the current with just a potentiometer. Adjusting the current is more dificult than the voltage.

PREngineer (author)2012-11-12

Hello Newtonn2,

This is a great Instructable. I'm a Computer/Electrical Engineering student and I need a Bench PSU and this looks great.

So far, I'm doing small circuits with LEDs and it seems to me, the amount of current the ATX provides is ridiculously high for this type of circuit.

Question #1:
Does the ATX PSU regulate the amount of current it gives out according to the LOAD or is it the fix amount it states it gives out?
I've noticed that with the regulator you put, whenever you change the Voltage, the Amps also change... Does the amount of AMPs for 12V it gives you is safe for LEDs?

I was thinking if there was a way to regulate the amount of current that it outputs so that I won't be burning every LED I put in and I found this schematic for a current regulator:

However, I see the Resistance that controls the amount of current is very small (<1Ohm)... so there is no way for it to be substituted by a Potentiometer which will give me control... Also, I think it affects the voltage.

Is there any way I can fix the Voltage, let's say at 12V and regulate the current?


mobilohm (author)2012-08-26

rj_schad pointed some error but I don't see any answer to his comment... so what should one think today?

Bio961 (author)2012-08-25

i don't understand . Before conecting anything all the wires of the same color that come out of atx have to be soldered together ?

rj_schad (author)2012-08-12

I believe you have a small error in this schematic: the 10uf cap coming off the output from the LM350 has the ground connected BEFORE the 5k pots causing it to become in parallel with 560 ohm resistor and share the same voltage. Im using a LM317 that puts a voltage of 1.25v across my first resistor (560 ohm) on the voltage divider, which matches the datasheet from The negative end of the 10uf capacitor should be connected AFTER the second 5k pot.

Also when plugging in any iphone or ipod the 5 volt on the usb connector isnt enough. At least for these two products, the two middle data pins need to pulled to logic high (using the 5v source and large enough resistor).

Otherwise great tutorial.

paradise97402 (author)2012-07-09

Newton, This year I am taking your design and putting it into a clear acrylic case, so I will send you some photos when I get it finished..I ordered some new panel meters like yours..the ones I had were not back lit, and I liked the ones you used.
Thanks again for sharing your project..and after a year the only thing I had go wrong was I blew the fuse on the PSU, But I put a re set type of breaker on now I can just reset..and go.

Got most of the front panel done, a few more things to add..but here is what it looks like so far

Added tags

newtonn2 (author)paradise974022012-07-31

Wow! It looks very cool on fiiberglass! I like it.

paradise97402 (author)newtonn22012-07-31

Ok, I taped the case together to check it for space (Great..lots left) so I am going to add some spare cold cathode lights I have in a box of parts. Still have the relay, a cpl fuse boards, another power supply (smaller one) and the buzzer for the continuity tester, the USB outlets and some other stuff I have yet to think up.

paradise97402 (author)newtonn22012-07-31

No I am using all clear acrylic. I have updated a few of the components and went with the same style meters you did( I like those alot better).
Plastic is alittle tough to work with, get some cracks and chips..but after I get it all assembled, I am going to go ahead and re make the front cover. But I made a holder for the multimeter and a few other everything is clear.
I am going to use a power supply from an old DVD player to power the meters and a cpl other parts to seperate them from the other supply, and am going to use external fuses instead of the soldered on fuse on the power supply.
Now just to make it all look clean?
But I am still working off your design of re use parts where I can. even though its a new look..its still a Newton Bench top power supply!

lancellot07 (author)2012-07-05

additional question: when i used +12v and -12v using lm350 as regulator, why do i get 12v as an output, following your schematic..

lancellot07 (author)2012-07-05

how much is the max amperage of your power supply?

yoyology (author)2012-04-26

I'm thinking of making something like this using a big cigar box I have in my shop.

I want to make one set of outputs dedicated to 12V, one to 5V, one switchable (using a multi-position rotary switch I've salvaged) and then one more variable.

What I'd like to do is put a switch after the multi-position switch that will toggle between a straight line to one set of outputs, and a line with an in-line potentiometer to the other. That way I can adjust the output precisely. (See the block diagram below).

I'm just using the pot to dial down the voltage, instead of your voltage regulator circuit. I've tested the pot already from a 15V 1A wall wart, and it seemed to do fine. Will there be problems doing this over time?

newtonn2 (author)yoyology2012-04-28

You can't use a potentiometer to drop down the voltage, it will burn with load. A Wirewound potentiometer will do a bit better but not good enuf. The best way to do it is with the power regulator.

Sorry I took some time to answer.

yoyology (author)newtonn22012-04-28

That's okay. I suspected as much, but wanted to be sure before I proceed. I'll need to dig through my parts bins now to make the regulator circuit. :-)

I'll post pics once I have the whole thing together.

amarquez (author)2009-12-29

OH NOOOO!  Another PC Power supply conversion article using power resistors...   :(

 we go again...

In any PC power supply you MUST have some load to make it function properly...  say, the 12 V output usually stays below full 12 V unless there is SOME load.  That is the reason people converting ATX style power supplies put a load on the 5V branch. (Mine puts out only 11.85 V when there is no load on the 5 V output...)

NOW; using a power resistor IS NOT THE BEST WAY. period.

The 10 Ohm resistor draws a lot of current from the 5 V circuit, and PRODUCES A LOT OF HEAT !...

NOW, if you use an automotive taillight and turn signal bulb, and place it in a socket, you can place a nice three level load.  Using two small switches, you can wire each of the two filaments to the 5 V output, so that you can power one, the other, or both filaments together; so that you can put just enough load on the 5 V circuit, so as to make the 12 V output produce something more than 12 Volts, so that your battery charger, car stereo. HAM Radio (or anything that you decide to be fed by your ATX power supply) will work perfectly.  My Triton2 battery charger can now put out a full 6.5 amperes when recharging a common 12V car battery, a task  it wasn't designed to do, but it does easily!  It can work for hours and more hours at full load without a complaint.

The automotive bulb has MANY advantages, it doubles as an easily seen pilot light, it produces much less heat to the inside of the enclosure, since it is now fed by 5 V, it will last many many hours.  The glass bulb is gas filled at a low pressure, which becomes an excellent heat insulator that keeps the glowing lamp filament from overheating the inside of the ATX enclosure.  There is NO need to use any kind of heat sink.  I have converted several PC power supplies for my friends, and have put the socket and bulb inside the original ATX power supply enclosure, locating it between the inside heatsinks directly on the airstream of the fan, so that it never heats the power supply components.  When it is working, the bulb in my PC power supply stays hot to the touch, but WAY MUCH LESS HOT than a 10 Ohm resistor!

Forget about using 10 Ohm wire wound resistors, they overheat too much and can melt some wire insulation or the nylon ties used to hold them in place.  The automotive socket and a two bulb package costs less than two dollars or less!

Been there, done that!

Happy new year everybody.
amclaussen, Mexico City.

hemmikarl (author)amarquez2010-01-03

Exactly what i was thinking about.
why have a 10W power resistor at 10 ohms that will just be producing heat and using alot more power than needed

techxpert (author)hemmikarl2012-02-01

yes now i dont need to buy a power resistor from another shop thanks :) :) :) :)

techxpert (author)2012-01-30

so all the connectors are only needed if you want the psu back :)

kasatka6991 (author)2011-11-06

hello newtonn2 im kasatka6991
been building cheapo's psu out of old atx for some time and ran across your design
in a word marvelous
my only need is that i want the amp output to run as high as my psu will put out
antec true 430 watt psu
dc output +5v @ 36Amps +12volts @20 amps +3.3 volts @ 28amps
this is the big deal for me as i test and rebuild car power amps
some of which draw 15 to 20 or more amps at peak levels
the old unit we had at the old shop i worked at had a variac adjustable voltage and amps outputs
so to my question how can i create the same function usin you design if possible but get more amps instead of the 3 amps or so from the lm350 controler
any advice is desperatly need as i cant afford 700 buck for a comercial unit
thanks kasa

About This Instructable



Bio: Always loved electronics. I like to reuse parts or componets and I Love to be part of the Instructable community.
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