Small tutorial on Computer ATX Power Supplies. How to use them, how to connect them in series, in parallel. What is 12V rails? Is it possible to connect 12V rails together? ATX connector wiring explained. What is difference between old computer power supplies and new ones?
And finally how to make Lab Bench Power Supply from Computer ATX Power Supply.
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Additional info on ATX specification: http://en.wikipedia.org/wiki/Atx
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All Photos Are Clicable
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158 comments
18 pings
Vinicius Abreu says:
June 19, 2011 at 3:18 pm (UTC -7)
Beautifully done, both the PSU and the video!
I’ve been wanting to make one of these for some time, but settled with a little 2A 120v-12v converter, to which I later added a LM317 based variable output. One problem is that i have no idea how bad is the ripple from this thing, and I have no osciloscope at hand. Also i have to use my multimeter to set the voltage before using it, since there’s no V-meter or A-meter. Other thing that always bugged me about the PSU power supply is the constant small load on the +5 volt rail… something about this energy waste annoys me, but whatever.
I have the power supply from an old Xerox photocopier, but have no idea if it needs this kind of load for it to work properly. What do you think?
Thanks for the great video! Cheers!
admin says:
June 19, 2011 at 4:09 pm (UTC -7)
Thanks!
Usually ripple on the output of LM317 should be pretty low. About 3-5 millivolts peak-to-peak. But it largely depends on a few things, like how much ripple and noise input voltage has, what type and capacity of output caps you use (pretty good choice is ceramic caps or low-ESR electrolytic ones).
For example you can put ordinary 10uF electrolytic cap on the output and get 10mVp-p ripple or put 1uF ceramic or 1uF low-ESR electrolytic cap and get 2mVp-p.
If you use transformer-rectifier-cap on the input – you will get much less noise, than if you will use switch-mode PS.
I’m actually planning on making tutorial on building simple LM317-based power supply with metering panel in couple of weeks. (with metering panel, i’ll probably tell about them too)
About Xerox PS. Most likely that it’s SMPS and it can have dummy load resistor already inside. If not – you would need to put a small load. You can take it apart and look for comparatively big resistor near the output connector/wires.
I’m not fan of pointless power waste either, but IMO for lab PS it’s ok. For example linear power supplies – they could be really wasteful, but they have very low output ripple & noise.
p.s. I have TV satellite receiver that consumes about 13W!!! in standby. – it killing me..))
Jewlz says:
February 29, 2012 at 6:39 pm (UTC -7)
Hey excellent video, everything is looking nice and neat…i just have one question…where did u connect the power good cable(grey wire) too?
alfa says:
August 21, 2012 at 8:21 am (UTC -7)
Actually the 5 volts constant load is necessary because most ATX power supplies are switched-mode power supplies. This refers to the technique used to convert line power from 120V AC to the DC power required in the output lines. It is recommended to place a high load (which is a low resistance, ~10 ohms or so) between the +5V rail and ground. This high load (>2,5watts) allows the power supply to stay On, because switched-mode PS require a permanent load.
This permanent load might seem a waste of energy, but in fact it is more energy efficient than regular power supplies with no permanent load. Regular power supplies running during the same period of time would waste more energy in the regulation part of the circuit. So, the main advantage of this power supplies is power efficiency. They’re also lighter because they don’t require transformers, but use a switched controlled by a PWM.
Energy waste in switched-mode permanent resistor < energy waste in regulation circuit heat
jet says:
April 21, 2013 at 4:13 am (UTC -7)
what is the use of gray wire
Olesya says:
June 20, 2011 at 12:50 pm (UTC -7)
Good to be smart!))
Mathew says:
June 20, 2011 at 10:05 pm (UTC -7)
Nice job on this, great video and it has plenty of information to help beginners to do this.
Vladimir says:
June 20, 2011 at 10:15 pm (UTC -7)
cool
i had make it 2 years ago
rhon says:
June 21, 2011 at 6:59 am (UTC -7)
how did you make the nice label?
admin says:
June 21, 2011 at 7:07 am (UTC -7)
Just printed it out on a glossy paper (laser printer) and glued it to the case.
And for drawing labels you can use InkScape (http://inkscape.org/download/)
it’s free and cool vector graphics software.
Iuri~ says:
June 21, 2011 at 4:29 pm (UTC -7)
awesome work!!! i’ll try this later.
nice blog btw!
Drew says:
June 22, 2011 at 5:12 am (UTC -7)
Great video, I’m going to have to do this with one of the old PSUs I have lying around from old PCs.
Don B says:
June 22, 2011 at 3:25 pm (UTC -7)
Really great job, I am ready to make one of these for myself, and have two power supplies coming to me tomorrow from a friend.
Thanks!
Brett says:
June 22, 2011 at 4:31 pm (UTC -7)
Hiyya guys (and lasy guys),
This has been done before, and successfully because even a low-end PSU can supply at high efficiency, the most useful voltages.
Your +5V and +12V are essential, and with a fir current. A tick for both here.
Your -5V and -12V are of finite value, and the -12V use that comes to mind is for working with op-amp circuits. Anyone using these knows little current is needed.
The -5V is almost worthless except to give a +/-5V around oV for whatever reason.
Now, if a newer supply you will get 3.3V and while there are many CPU’s or micro-processors using this, just as may run on 5V. But hell, it is there and who knows what use you may find.
But what I think I found was absense of a warning about short circuiting even low voltages. It is current that does the damage and can do it spectacularly. I have seen a 14mm spanner dropped across a high current rail (about 70A and more under SC loads) and it glowed, brightened, sagged and melted – taking out the supply obviously. High currents are dangerous. High currents, moreso than voltage, cause electrical fires. If you don’t believe me, put some 8A fuse-wire across the 3.3V terminals (this will be a one-way trip for the PSU – be warned) and you will see the lowest voltage melt wire.
I see nowhere any BIG warnings about fuses or circuit breakers. I would also suggest on the +5V and +12V you simply gave 2 terminals for outyputs as this PSU will deliver a lot to multiple loads potentially.
LM317 and types of regulator similar? Yes, these serve many purposes, one of which is ready adjustability. But the whole point here is to resurrect an old, thoroughly decent PSU with useful outputs ready-set for stable voltages in equipment that depends on them.
But guys, all except the earth pin MUST have a fuse or circuit breaker. 1A fuses for the 2 negative voltages are probably OK, and if you have 2 5V output lugs and 2 12V ones, fues each with a 7.5-10A fuse. Even 10 Amps is a lot of current – you will have fire and snap-crackle-pop from it if a short happens (and they do). For test beds, maybe use circuit breakers as although they cost more, you save in the long term.
Brett says:
June 22, 2011 at 5:01 pm (UTC -7)
Not a reply, a re-wording and spellcheck – sorry about that!
Hiyya guys (and lady guys),
This has been done before, and successfully because even a low-end computer PSU can supply, at decent efficiency, the most useful voltages in a home lab.
Your +5V and +12V are essentials, and will output a fair current. A tick for both here.
Your -5V and -12V are of less value to many people, and the -12V use that comes to mind is for working with op-amp circuits. Anyone using these knows little current is needed in mmost cases.
The -5V is even less valuable except to give a +/-5V around 0V for whatever reason. But hell, it is there; better to have it and not need it, than need it and not have it!
Now, if from a newer supply (even years agol) you will get 3.3V and while there are many CPU’s or micro-processors chips using this, just as may run on 5V. Even serial-chip-programmers like me will chose 5V over 3.3V as it is likely other devices will demand it. You can argue the chip has a cleaner supply. Yeah, OK, you win. And who knows what other use you may find.
But what I think I found was absense of a warning about short circuiting even low voltages. It is current that does the damage and can do it spectacularly. These supplies are great because they give you current ig great dollops and could probably start a small car in place of the battery ((maybe-maybe noty).
I have seen a 14mm spanner dropped across a high current rail (about 70A and more under short-circuit loads) and it glowed, brightened, sagged and melted – all in the time it took you to read those 4 main words. It happened too fast to hit an off switch – and those currents can cause massive expense if the short is within a wiring harness – a car one or even bigger. Fire is a definite possibility, and the car harness? A friend had one burn out because a new car from the factory had an over-rated fuse (no names, it doesn’t matter and bound by secrecy) and burned the whole loom so badly it would need total replacement. That is so expensive the car was a write-off – from new! TAKE CURRENT SERIOUSLY.
High currents are dangerous. High currents, moreso than voltage, cause electrical fires. If you don’t believe me, put some 8A fuse-wire across the 3.3V terminals (this may be a one-way trip for the PSU but they are common as mud – be warned) and you will see the lowest voltage melt wire.
I see nowhere any BIG warnings about fuses or circuit breakers. I would also suggest on the +5V and +12V you simply have 2 or even 3 terminals for outputs as this PSU will deliver a lot to multiple loads potentially. Switches maybe? Watch current ratings. I have a PSU in my newer machine with 750W PSU and the 5V and 12V rails are enormus. 5V at 68A for instance. 68A? Yep, not a typo. The 12V rail from memory is far less at about 40-something amps. (Don’t point out these numbers don’t add up – I know why and it also is not a typo – ask any Overclocker).
LM317 and types of regulator similar? Yes, these serve many purposes, one of which is ready adjustability – turn a knob and get anything you want. A desktop supply like this is essential in any lab, but so too are guys like this which are simple suppliers of bulk power, regulated, very clean, and if cared for will look after you (do NOT turn them an/off, on/off, etc – they hate this being done repetitively).
But the whole point here is to resurrect an old, thoroughly decent PSU with useful outputs ready-set for stable voltages in equipment that depends on them.
Please people, all except the earth pin MUST have a fuse or circuit breaker. 1A fuses for the 2 negative voltages are probably OK – look at the rated output and put in a fuse 75% of this is a rough idea (ensuring there is enough current to blow it if a short occurs). And if you have 2 x 5V output terminals and 2 or 3 x 12V ones, fuse each with a 7.5-10A fuse. Even 10 Amps is a lot of current – if you have switched them it is very likely your switch is rated at 10A – it is common enough. If not, be prepared for fire and snap-crackle-pop from it if a short happens (and they do).
For test beds, maybe use circuit breakers as although they cost more, you save in the long term. This isn’t merely a safety issue but a very critical one that you can, with a small omission, burn down a building containing occupants – this is serious design omission unless I missed it. YOU COULD KILL PEOPLE. Please, use something to protect the outputs on what is a totally decent project which I will now probably build myself despite having several supplies.
admin says:
June 23, 2011 at 7:21 am (UTC -7)
That’s a long comment.. )
Yes, big currents could be dangerous, but in every computer power supply each output must have an overcurrent protection!
And I shorted out few of my supplies many times and they just shut down. Click the switch and they work again.
If people want they can include fuses. Or, for example, make 2, 3 binding posts for 12V rails. It’s not a rocket science.
You could burn house even with half an amp 12V. or even less.
Ed says:
January 6, 2013 at 8:40 am (UTC -7)
I would recommend using breakers after the output to protect the circuit that is being powered up
Steve Miller says:
June 22, 2011 at 9:35 pm (UTC -7)
Good day to you sir.
That was a very professional looking job and a very good use for a junk power supply that we all have laying around.
The fellow above does have a good point about current limiting devices, these switching power supplies have a lot of current available and can let the “magic smoke” out in a big hurry.
I would love to see you take the power supply and use it as a basis for a current voltage regulated supply. There must be a way to hack the regulator circuitry of the power supply so it could be made adjustable.
Thank you for a very professional looking video and a very good looking build.
As an aside, where are you from sir?
Cheers,
Steve
admin says:
June 23, 2011 at 7:58 am (UTC -7)
Howdy!
There is many ways to hack this power supplies to output adjustable voltage/current. But none of them is easy enough for beginners. Because of vast variety of atx power supply schematics there is no way to do step-by-step howto on that.
In a few weeks I will make tutorial on making simple linear power supply with adjustable voltage based on LM317 from scratch. Then howto on constant current electronic load. – Two essential tools for electronic workbench. Combine two together – and you’ll get power supply with adjustable voltage and current.
Later there would be more complicated projects (including programmable PS and electronic load) – but for now I will start from simple projects.
About “magic smoke” see my reply to Brett above.
And I’m from Ukraine (and currently live there). I speak russian and occasionally ukrainian.
Cheers,
Phil
peter says:
June 23, 2011 at 5:39 pm (UTC -7)
Beautiful workmanship on the power supply!
First class video! Informative, concise — I learned a few new things.
I look forward to reading your future blog entries. Keep up the good work!
Woodsmoke says:
June 23, 2011 at 7:04 pm (UTC -7)
Hi Phil,
Fantastic tutorial and video. Just what a beginner to electronics like me really needs, thanks a lot. Here’s a typical beginner’s question for you – Does it matter what resistance the two resistors protecting the LED’s are? I can’t be certain of the colours on the resistors in the video. Perhaps you could give me a range of acceptable resistances so I don’t fry my salvaged LEDs.
I’m also really looking forward to your tutorial on the metered power supply. This is very helpful stuff.
Woodsmoke says:
June 23, 2011 at 7:14 pm (UTC -7)
Ah I see 5W each.
Woodsmoke says:
June 23, 2011 at 7:17 pm (UTC -7)
5W for the dummy load, but how about the resistors beside the LEDs? Thanks.
admin says:
June 24, 2011 at 1:22 am (UTC -7)
Hey!
Most of the 3mm and 5mm (118mils and 196mils) LEDs have a forward voltage drop about 2V (some of them 3V+) and forward current about 10mA to 30mA.
And If you have a datasheet for your LED, you can easily calculate current limiting resistor using this formula:
R = (Vs – Vf)/If
where,
Vs – Voltage of your power source (in case of atx psu it could be ether 3.3, 5 or 12v),
Vf – Forward voltage drop of your LED,
If – Forward current of your LED.
So, if you have small LED that consumes 10mA with forward voltage drop 2V and you need to power it from 5V source you would get this:
R = (5V – 2V)/0.01A = 300 Ohms resistor. (and if you want led to be a little bit dimmer you could take higher value resistor or put smaller current in the formua)
If you have a salvaged LEDs you can start from small values, like Vf = 2V and If = 10mA. Try it on your LED and if it’s too dim or it doesn’t lights up – just gradually decrease the resistor value.
Woodsmoke says:
June 24, 2011 at 6:30 am (UTC -7)
The salvageable resistor hunt begins; no electronic convenience is safe! Thank you very much indeed.
Matt says:
February 10, 2012 at 5:24 pm (UTC -7)
Hi Phil,
I just recently found your video and I also had a related question about the power supply. I’ve noticed in other tutorials about how to covert ATX to bench power supply they also use higher power wirewound/ceramic resistors but I was hoping you could explain why you need high power and why 22 Ohms for 12v new PSU?
In my case I’ll be working on a newer ATX supply so I’ll need to add the resistors to the 12V line. I only have the 1/4 Watt resistors that I use for bread boarding so I thought I could use the following math:
P = IV = ( 1/4 W ) / ( 12 V ) = 1/48 A = 0.0208 A
So I need a resistor that will limit the current down to 0.0208 A and still be under the 1/4 W max power dissipation rating limit of the resistor.
Then to find the resistor: R = V / I = ( 12 V ) / ( 0.021 A ) = 571.42 Ohm
So couldn’t I use a smaller carbon compositions or metal film resistor at about 660 Ohms to connect the 12V to the Ground in order to make the power supply stable?
The only other reason I could think of not being able to use those lower power resistors is that maybe there is also a current requirement to make the PSU work?
Ok, and as always, thanks for making these high quality videos. I hope to make my own web site one day and help the community as you do.
Craig Williams says:
June 24, 2011 at 8:07 am (UTC -7)
Beautiful projects! I would only suggest you wrap the wires around the binding posts before you solder them. Those of us who started in the vacuum tube days cringe when we see wires laid on a terminal and soldered. You really need that mechanical connection.
admin says:
June 24, 2011 at 1:43 pm (UTC -7)
Yeah, you totally right about that. I should’ve done that, but all started with that thick 5v wire which I couldn’t wrap around binding post and I just decided to keep everything that way. My psu will not be subjected to any vibrations, so while connecting wires I just put lots of solder there and heatshrink tube is wrapping around providing additional support “just in case”.
Fred says:
June 24, 2011 at 3:04 pm (UTC -7)
If I have a 300w ATX PSU and modify it in a similar way, across +12v rail and 0v, what is the maximum current the modified PSU can safely deliver?
Great Video by the way…. Thanks.
admin says:
June 24, 2011 at 3:38 pm (UTC -7)
It depends on what kind of PSU you’ve got. Info about maximum current for each rail should be written somewhere on the unit, if it’s not – you can google for your PSU’s name.
And just a small heads up on cross regulation. (you can google for it) in case if you’re going to put very high current on one of the rails. (maybe you’ll gonna need to put dummy load also on 5v rail)
DC Regulated Power Supply says:
June 24, 2011 at 8:06 pm (UTC -7)
Hi,
Thank you very much for posting this!!!!
Computer repairs Perth says:
June 25, 2011 at 10:39 pm (UTC -7)
this is the first knowledgable article I have seen on this subject. Excelllent job.
Markos Fragoulopoulos says:
June 26, 2011 at 8:34 am (UTC -7)
Excellent work!
I look forward to the LM317-based power supply tutorial.
I am interested in making one that accepts 24V from batteries and provides 19V, 12V, 9V, 5V and 3V
I will use it in a robot to provide power for all parts: motors, on-board laptop PC, arduino etc.
Thanks.
admin says:
June 26, 2011 at 11:27 am (UTC -7)
Hey Markos,
LM317 is great for powering stuff when you have a small difference between input voltage and output voltage.
If difference is big – you’ll have huge power losses in form of a heat.
Or for using it as a bench power supply where you don’t really care about low efficiency and heat dissipation.
For example:
you have 24V input and 12V 0.5A output for motors.
(24V-12V)*0.5A = 6W – which is a lot. and you will need pretty big heatsink to dissipate all that heat. And that’s only just for motors.
What is not wasteful – is a dc-dc switchmode converters which stores energy in inductors. They a bit harder to design, but there’s a lots of info out there.
I recommend you to watch Dave’s tutorial on dc-dc converters:
http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/
Cheers,
Phil
gigasquid says:
July 6, 2011 at 2:08 am (UTC -7)
Superb ATX video and tutorial. Thanks for making these tuts available Phil.
Imrahil says:
July 6, 2011 at 5:30 am (UTC -7)
Hi. Stunning video and realization!
Can I add more binding posts for +5V and +12V (instead of -5V and -12V – they are useless for me) ? I thought about splitting +12V cables into two groups and connect them to two different binding posts… Or it doesn’t make sense?
admin says:
July 6, 2011 at 7:50 am (UTC -7)
Sure you can, but you might need -12V someday, because you can get 24V between +12 and -12 (at about 0.5-1A) – could be useful for powering some relays, solenoids, etc.
And It’s a good idea to connect 12V rails (if you got more than one) to separate binding posts – to have safer overcurrent protection.
Jeremy says:
July 13, 2011 at 7:14 pm (UTC -7)
Great tutorial! I wish every power supply looked the same in the inside.
What heat gun are you using? It looks like it works really well.
admin says:
July 14, 2011 at 1:02 am (UTC -7)
It’s a cheap chinese Lukey 852D+ soldering station
Wiko says:
July 14, 2011 at 4:17 pm (UTC -7)
Im converting my power supply, and I don’t exactly understand why the 5W resistors are needed or if I need them. I have measured the voltages with the dummy load (in 5V and 12V) and without it, and the resistor doesn’t appear to affect the voltages. Also I have searched without luck for a dummy load in the power supply.
Can you give me a clue?
P.S. nice and clean conversion you made.
admin says:
July 15, 2011 at 1:06 am (UTC -7)
In all power supplies that I’ve seen dummy resistors have an influence on output voltage. In some PSUs more in some less. If dummy resistors in your case doesn’t affect the voltages, then you’ve got a nice designed PSU with good load regulation. And every power supply should have at least small output dummy load. It could be 2W or even 1W resistor – which is much smaller than 5W ones.
Wiko says:
July 15, 2011 at 5:30 pm (UTC -7)
Oh i see, thank you for the answer
Jamila Duke says:
August 15, 2011 at 8:53 am (UTC -7)
Excellent post. I was checking constantly this blog and I am impressed! Extremely helpful info specifically the last part
I care for such info much. I was looking for this particular info for a long time. Thank you and good luck.
James Becwar says:
August 15, 2011 at 1:39 pm (UTC -7)
Great video! The results look really good. The products you make are beautiful.
In my option the way you drill in this video and in the pcb video doesn’t look very safe. I would either get some clamps and a small drill press or a backer board so you don’t have to hold the work piece with your hands. Also you might want to wear some eye protection in case the bit breaks.
Hope to see lots more videos, I really enjoy them.
admin says:
August 16, 2011 at 3:55 pm (UTC -7)
You’re completely right about that. I’m actually drilled a few holes barehanded just for the video, and drilled everything else wearing gloves. It’s because I forgot to buy a new pair of gloves and gloves I had were really dirty.
But IMHO eye protection is a bit overkill in this case.
Kincy says:
September 15, 2011 at 3:11 pm (UTC -7)
I would be more concerned with getting metal bits flung into the electronics and causing a short. A trick that I use is to take some wide masking tape and stick one edge to the wall under where I am drilling and let the rest stick out over the electronics to catch the bits. You can stick some paper or more tape to make it wider. When you go to remove the tape let the bits all slide down towards the V where the tape is stuck to the wall then peel downwards to remove the tape. Any bits that are not stuck to the tape can be made to stick to the tape by pressing-resticking the tape back against the wall and re-peeling it. Repeat as necessary as you remove the tape. You can also vacuum the unstuck/loose bits off the paper/tape as you go if you have a small vacuum.
Kincy says:
September 15, 2011 at 3:23 pm (UTC -7)
Another trick, if you have enough room, is to use the end of your vacuum centered behind the hole as a way to both back the piece and catch the metal bits.
Thanks for the intelligible videos.
Dave H says:
August 15, 2011 at 1:42 pm (UTC -7)
Thank you Phil, a very useful and interesting tutorial. I even have an old IBM XT power supply I wanted to convert, but ATX ones are so cheap and easy. Thanks for your hard work and very clear style of instruction.
FL180 says:
August 15, 2011 at 3:16 pm (UTC -7)
I am very impressed with your videos. Great job on a very useful tutorial!
Paulo G. says:
August 20, 2011 at 12:17 pm (UTC -7)
Great post, great video, great info! Thanks for sharing this information in such clever way. Much appreciated!
Daniel L says:
September 7, 2011 at 3:59 am (UTC -7)
Awesome tutorial! I’m planing on modding my PSU soon.
I was also considering adding some usb ports to charge multiple devices with this as well. Would this be difficult to do? Could I simply just add ports to some of the 5v rails or is there anything im forgetting?
Thanks.
admin says:
September 7, 2011 at 4:53 am (UTC -7)
Yeah, just connect usb ports to 5V rail. But also you can add 150 ohms resistor between D+ and D- of usb port to tell devices, which you would charge that they can draw more than 500mA current from this port.
You can read more about this in Power section here:
http://en.wikipedia.org/wiki/USB#Power
Freddy says:
September 11, 2011 at 1:26 pm (UTC -7)
Nicely done, I’m actually following the Video tutorial and making 1.
I have some questions about the old ATX and New ATX thingy, adding 2 x 11 ohms 5w resistors in pararell, for old atx you wire +5v to the resistors and for new atx you add 12v to the resistors, correct? My atx does not have -5V, so I guess mine is a new atx.
@ 11:53 of the video, is it correct that LED goes before the resistor or after?
thanks,
admin says:
September 11, 2011 at 5:27 pm (UTC -7)
To determine whether you have an old or new atx psu revision look at your power supply manufacturing year and go to:
http://en.wikipedia.org/wiki/Atx#ATX_power_supply_revisions
To check exact revision.
For 12V revision you need to put one 27 or 33 ohms 10W resistor or two 15 ohms 5W resistors in parallel.
And about LED and resistor. If you mean current limiting resistor that is connected in series with LED, than it doesn’t matter. If you don’t know how to determine that resistor value – you can look in comments above, I answered to this question.
Dmitri says:
November 19, 2011 at 6:37 am (UTC -7)
you should use 15ohms 5W resistors in series!
admin says:
November 19, 2011 at 6:42 am (UTC -7)
Yeah! You right. Sorry about that! My bad.
Kincy says:
September 15, 2011 at 3:27 pm (UTC -7)
Earlier in the video you mentioned connecting the 3.3v sense to the 3.3v power to monitor the 3.3v, but I did not see you do this during the build. Why?
Thanks again for the videos.
Reginald lorenzo says:
October 1, 2011 at 8:27 pm (UTC -7)
man i cant find a dummy load power resistors here in the Philippines are there any substitute……………….. i’ll be waiting for ur reply
……….. thanks a lot for ur tutorials i made useless things o usefull ones!!
admin says:
October 2, 2011 at 3:19 am (UTC -7)
If you can’t find power resistors (5W, 10W ones) you can surely find some 2W or maybe 1W resistors. And then you can connect those 2W(1W) resistors in series or in parallel to dissipate more power. Or maybe your power supply doesn’t even need too much dummy load. This dummy load needed for better load regulation with small loads, and your power supply can have a pretty good load regulation from the start without big dummy load resistors.
Just google for “Load Regulation”.
Reginald lorenzo says:
October 3, 2011 at 10:38 pm (UTC -7)
how can i install fuses/ how to control voltage rates??? i need a 9 volts example how can i lower a 12 volt to 9 or 3v to 1v??
admin says:
October 4, 2011 at 5:17 am (UTC -7)
There’s a few ways exists:
1. Linear voltage regulator, like LM317 or something from 78xx series (for 9 volts – it’s 7809)
http://jumperone.com/2011/08/lm317-adjustable-psu/
http://www.youtube.com/watch?v=IjJWWGPjc-w
http://www.youtube.com/watch?v=GSzVs7_aW-Y
2. Put a few diodes in series. Since each diode has about 0.7V voltage drop (which also depends on load) you can put 4 diodes in series to get 9.2V from 12V or 3 diodes to get 1.2V from 3.3V.
3. You asked if you can use a potentiometer to adjust voltage of your PSU. Yes, you can! It is possible to embed potentiometer in voltage feedback circuit of your power supply PWM controller.
But it is pretty hard to do, because you need to know how SMPS power supply works.
There is no step-by-step guide for doing that.
Reginald lorenzo says:
October 3, 2011 at 10:49 pm (UTC -7)
if u don’t mind i’m just 15 y old im pretty interested in all your videos……and can i want also to control a computer fan through using fuse controler………..i dont know the term for these ones….
Reginald lorenzo says:
October 3, 2011 at 11:26 pm (UTC -7)
oh yah can i use potetiometer???to control out put voltage???
Reginald lorenzo says:
October 3, 2011 at 11:28 pm (UTC -7)
can i also have ur FACEBOOK account if u have one??
admin says:
October 4, 2011 at 12:36 am (UTC -7)
There’s link on my FB account in the top right corner.
reginald lorenzo says:
October 4, 2011 at 2:23 am (UTC -7)
i found a power resistor 5watts 12ohms is that alright??
admin says:
October 4, 2011 at 5:26 am (UTC -7)
For 5V rail – yes. For 12V – no, it will dissipate much more than 5W of power.
For 5V:
5V/12Ohms = 0.42A
0.42A x 5V = 2.1W < 5W - perfectly fine!
For 12V:
12V/12Ohms = 1A
1A x 12V = 12W > 5W – more than two times more power would be dissipated. resistor will probably burn with time. Plus it will be very very hot – which is bad.
But in this case you can put two resistors in series, thus each one will dissipate only 3W.
Malcolm Hartlep says:
October 4, 2011 at 9:42 am (UTC -7)
It’s really a great and helpful piece of info. I’m glad that you shared this helpful information with us. Please keep us up to date like this. Thank you for sharing.
Reginald Lorenzo says:
October 5, 2011 at 1:19 am (UTC -7)
power supply————-5 volts—fuse—switch—–potentiometer——binding posts..
\\——LED
————-Ground——–120 ohm——-\\
……….. i’ve done this also to 3.3v,12v and -12 volts ………also connected a load resistor between 5volts a ground……..i connected led between the voltages and ground and added 120 ohm resistor to the negative side of the LED…. except for -12 volt connected to positive side……………………. please check for any problems?……..
admin says:
October 5, 2011 at 1:46 am (UTC -7)
You don’t need to put dummy load resistors to every rail on your PSU. If your PSU was manufactured after 2003, then just put resistor between ground and +12V rail.
David says:
October 8, 2011 at 10:19 am (UTC -7)
Excellent video and very clear explanations! I am thinking about building a 24V power supply using two ATX power supplies in series, as you outlined at the beginning of the video, and was wondering if you could provide a more detailed explanation (pictures really help) of how to wire this setup for a beginner.
- How do you safely disconnect mains earth on PSU#1? Do you simply cut the green wire coming from the power plug to the board? Also, how do you ensure that the power supply is completely isolated from earth, do you need to remove it from its metal case and place it into a wooden/plastic case?
- Next, to connect the +12V from PSU#2 to ground on PSU#1, do you simply directly connect all the yellow 12v wires from PSU #2 to all the black ground wires on PSU#1?
- What will be the effect on the max current that can be drawn (I’m guessing its unchanged from the max current that one PSU can supply on the 12V rail).
- Do the two PSUs need to be identical (what problems arise if they are not?), and what would be the max current draw if they are different? (once again I’m guessing it would be limited to the max current of the less powerful PSU).
- Finally, how dangerous is the setup, and what could I do to reduce the danger of electrical shock?
Thanks again!
admin says:
October 9, 2011 at 10:21 am (UTC -7)
Can I ask, where you planning to use this 24V psu? How much current you need at 24V?
Because it is much easier to buy dedicated 24V power supply, for example like this one:
http://www.allelectronics.com/make-a-store/item/PS-24150/24-VDC-6.5A-150W-POWER-SUPPLY/1.html
- Yeah, just cut the green wire. No need to put it in wooden/plastic case, cuz PSU’s metalic case acts like a RF shield. Just make sure that two PSUs do not touch each other.
- Yep. Just all the yellow to all the black (you can mach number of black wires to number of yellow ones, by removing excess of black ones; of course if you don’t planning to put some load to the other rails.
- Not sure what you mean. You should check the REAL max current that each of the PSUs can give by testing them.
- I guess there should be no problems in connecting two non-identical PSUs. Yep, current from less powerful PSU would be the ceiling.
- It’s really better to buy a dedicated psu. But I didn’t really given a much thought to this problem. Theoretically everything should be ok. But don’t take my word for it.
David says:
October 10, 2011 at 1:54 pm (UTC -7)
Thanks so much for the info, that helps greatly. I was going to use the PSUs to power 2x wheelchair motors which each draw 10-15A at 24V, so I need a total of 30A power supply at 24V. Online, it seems that dedicated lab power supplies that can give that kind of amps at 24v are very expensive, while 2x ATX power supplies are much cheaper, so it seems like a good alternative (unless you know of a place to buy high-amp dedicated power supplies for cheap).
I’m aware that the ATX power supplies will probably not be able to deliver the max current they are rated for, but I’ll just have to work with what I get (the motors will hopefully not be under heavy load and thus shouldn’t be drawing their max current very often). I found some 680W power supplies that claim to be able to deliver 38A on the +12V rail, I’m sure that is an exaggeration, but if it can get close to that value it probably should be enough. What is your experience with ATX power supplies? Do they actually provide even close to the rated current?
Alternatively, I guess I could use 2x 12V car batteries, however, the apparatus is stationary and that seems like a waste to constantly be charging/discharging the batteries when there is an AC wall socket right there. Thanks again for your advice!
admin says:
October 11, 2011 at 2:07 pm (UTC -7)
I don’t have much experience with drawing high current from PC power supplies. Try to google for it.
jacobsen says:
October 10, 2011 at 9:29 pm (UTC -7)
Good writeup.
If I’m simply using the +12V rail, can I leave them out?
I am using it as an RC battery charger power supply.
Thank you,
jacobsen says:
October 10, 2011 at 9:41 pm (UTC -7)
Should proof read before I hit the “Submit” button.
Anyways, I’m using the +12V output only, is it safe to just use the +12V output soldered to a banana plug and leave the rest tied together by color and wrapped?
Thanks again!
admin says:
October 11, 2011 at 2:09 pm (UTC -7)
Yeah, of course! If you don’t need other power rails, you can just cut the wires from the board.
Brad Dangerfield says:
October 11, 2011 at 3:47 pm (UTC -7)
I built one of these, man its nice to have! My ATX power supply had built-in load resistors
so i didn’t even need to add anything, Sweet! also has short circuit protection built in as
well, works fantastic.
http://imageshack.us/photo/my-images/708/sany0140x.jpg/
Andy says:
October 12, 2011 at 2:53 am (UTC -7)
hi great little use of old psu .i have a little problem u may be able to help .i have bought some 1u atx psu from the states.i got them only to find they have no -12volt rail output .is their a easy way to install this in the psu or do u have to change the transformer for a centre tap type etc .i got them gore a good price so not worth returning them .i need the -12 rail to run a audio op amp . thanks in advance for any ideas .
Thanos says:
October 15, 2011 at 9:26 am (UTC -7)
Hello there,
Congrats for your work…
Let me ask you a question…
How do you wire the two switches?
Which wire, goes where?
Thank you in advance!
Keep up the hard work!!!
admin says:
October 15, 2011 at 9:42 am (UTC -7)
I’ve provided schematic in the video.
Thanos says:
October 17, 2011 at 2:58 am (UTC -7)
I ment sth else…
You have two switches…
The main (boat-type) one and the low current(toggle-type) one.
I’m not so experienced with electronics, apparently, however I think that the middle point in the toggle switch is connected to the ground while the green one to the upper or lower point…
You have wired the vice versa…
Your main switch has 4 ways…
As I can see from the images, you connect a blue and a brown wire…
These wires come from an other plug in the power supply…
Where do you connect the brown and the blue wire?
I mean, there are two wires and 4 connection points in the switch…
Thank you in advance!
Adrian says:
October 26, 2011 at 6:08 am (UTC -7)
hi great video. I was wondering if you can tell me how to connect 2 ATX PSU together. i have a car amplifier that i am using in my room and the psu i am using to power it, is not supplying enough amperage, but if i connect 2 ATX PSU then it can be supplied with enough power. and yes i know i can use inverters and other devices or buy a more powerful PSU, but i want to use the Computer PSUs that i have, any help will be appreciated.
admin says:
October 26, 2011 at 6:56 am (UTC -7)
In order to get more current, you need to connect PSUs in parallel, but since computer power supplies doesn’t have current sharing capability, you just can’t connect them like that.
So, probably you would need to buy a new more powerful PSU. Or maybe if you need only a little bit more current on the peaks, you can try to put capacitor close to your car stereo. But if cap would be too big – it will short out the psu. It will be simply turning off.
JayKay says:
November 6, 2011 at 8:11 pm (UTC -7)
Thanks for the great posting.
Would it be possible to get 8.3V by bridging 3.3V and 5V ?
Ciao, Jay
admin says:
November 7, 2011 at 2:12 pm (UTC -7)
Not, it’s not. However, you can get that voltage between -5V and +3.3V with only small current (about 1A).
JOHN says:
November 13, 2011 at 2:18 pm (UTC -7)
i must do this one . its the best i hav seen
admin says:
November 13, 2011 at 2:22 pm (UTC -7)
It’s one of the most useful bit of equipment I have. And I use it every day.
John says:
November 20, 2011 at 1:32 pm (UTC -7)
AWESOME video, I want to do the same thing but for my new hobby “RC electric planes and for my Turnigy charger which is 12 volts. I picked up two PC power supply’s from a computer supplier for $4 each. Here’s what I got;
http://s3.amazonaws.com/kpsurplus_images/7ab802bdfcf50dec70b1ca874e93bb79c3fd6769.JPG
For the time being I have the pins green and black jumped with a paper clip, and I use the switch that’s already on the back of the power supply to turn it on and off. I also have a DELL power supply P5-5201-1D which I took out of a P3 computer a year ago and quickly found out that the pin coloring is not the same as standard ATX power supply’s (gray and black) are the green and black and not even in the same pin layout location. With the DELL PSU I noticed you have to put load on it so I used a old hard drive to keep it going (for load) but the P4 power supply it does not need a load and the power on my multimeter from the 12v rail is showing a constant 11.79 volts, do I still need to put load resistors on the PSU?
On the dell with out the hard drive I would be in the middle of charging a battery and the PSU would shut off, on the Turbolink it doesn’t care.. keeps going.
Thanks again for the very educational video, and what was it you used on the shrink tubing? I just picked up a butane torch, my friend said use a lighter, but I find the butane torch will get the job done faster and with more control.. Lighters are clumsy IMHO.
admin says:
November 20, 2011 at 1:47 pm (UTC -7)
Thanks, John!
If power supply works without dummy load resistors – it means, that it already has one inside. You can leave it like that, or you can try to put some load on the output and measure voltage difference with and without additional load. If difference is pretty big then you might want to put additional load resistor.
But if you would only use that power supplies for RC stuff – just don’t bother, battery chargers don’t care about poor load regulation.
For DELL PSU you need to put dummy load resistor across GND and +5V rail.
That was SMD rework station hot air gun, I’ve used on shrink tubing. Be careful with butane torch or lighter. You can burn shrink tubing pretty easily. Better heat it up slower from higher distance.
- Phil
J says:
December 8, 2011 at 7:11 pm (UTC -7)
hey what did you use to heat the heatshrink thing?
admin says:
December 9, 2011 at 5:41 am (UTC -7)
Hot air gun from SMD rework station
John says:
December 12, 2011 at 7:59 am (UTC -7)
Hi Phil,
Thanks to you my power supply is almost done, I have two power supply’s that are exactly the same and only paid $4 each for them. I came across another question for you. Why would one need the -12 -5 or -3? I read somewhere you can get odd voltages like 16volt or 18, 22volts something like that.
I understand +12 but I dont understand -12. Thanks again bro, when I am finished with my project would you like to see my before, during and after pictures?
Many thanks, a quote for ya from one of my favorite movies.. “Your the dude! The man in the chair!”
BTW, you’re right.. I put a load on my power supply and the voltage only increases .4 or so from 11.59 volts it went to 11.79 or something.
John
admin says:
December 12, 2011 at 8:07 pm (UTC -7)
Hey John,
Negative voltage rails could be quite useful. For example, you can get 24V using +12V and -12V rails. Or, if you need bipolar power supply for some amplifier circuits -5V and -12V rails could be handy.
For +12V rail, GND is a negative terminal, and +12V is a positive.
For -12V rail, GND is a _positive_ terminal, and -12V is a negative.
It’s like you would connect two 12V batteries in series. “+” from one battery connected to “-” of the other one. And assume that point where two batteries is connected together is a GND. And so you’ll have +12V and -12V __in relation to GND__.
* ground (GND) is actually a _virtual_ point. For example – if you would connect -12V from your power supply to GND of your circuit, then GND of your PSU would be +12V for your circuit, and +12V from power supply would be +24V in relation to your circuit’s ground.
Sure, it would be nice to see the pictures
- Phil
Adni says:
December 13, 2011 at 1:38 am (UTC -7)
AWESOME VIDEO. This is THE best tutorial video. I am a beginner trying to learn how to do this and still do some basic reading. I have some electronic board that need +5V 1Amp (maximum 10Amp), and several panel that need +12V LED backlighting.
When I saw your video, you mentioned that in the older power supply we need to put 5 ohm 10 watt resistor, and for newer power supply we need to put 22 ohm 10 watt resistor. Does it mean that if I need to use both +5V and +12V from a newer power supply, I also have to put the 5 ohm 10 watt resistor to maintain the load?
Also, from other reading sources I find that some people use only one 10 ohm 10 watt resistor and put it in series for the +5V. If my understanding is correct, by using the formula I = W/V, the one with 10 ohm 10 Watt and put in series will produce 2 Amp ( 10 Watt / 5V). Is that correct? I don’t know how to calculate them when you put them in paralel like in your video, and to be honest, I don’t know the difference by placing them in series and paralel ( I understand when it come calculating resistor in series and paralel, is it the same?).
Sorry for this basic question.
Thanks so much.
- Adni
admin says:
January 8, 2012 at 3:03 am (UTC -7)
I = W/V is only applicable for case where your resistor already dissipates W watts of heat and you’ve got V volts across that resistor.
Power rating of resistor means that the resistor _can_ dissipate _up to_ [x]W of heat.
But an actual power dissipation depends on current going through that resistor.
I = U/R
About dummy load resistor: you just need to put that resistor across either 12V rail for newer PSUs or across 5V for older ones.
Stefano says:
January 5, 2012 at 1:36 am (UTC -7)
Hi! This is great! I’m trying to make my PSU from an ATX one but I have some doubts about the dummy loads. I have this PSU
http://www.sparklepower.com/pdf/FSP300-60THA.pdf
In the specification I find various minimum load requirements, 0.5A for the 3.3V rail, and 1.0A for the two 12V rails and for the 5V rail. What should I do? Do I need to put different dummy loads for every required minimum load?
Bye!
admin says:
January 8, 2012 at 2:56 am (UTC -7)
I guess those values is for 5% load regulation. ATX power supplies have single transformer with a couple of secondary outputs for 12, 5 and 3.3V.
And their main control loop is tied to 12V. So, first of all it is important to put some dummy load on 12V rail. And in most of the cases 3.3 and 5V rails is irrelevant.
Stefano says:
January 8, 2012 at 4:44 am (UTC -7)
Thank you for your reply. I’m just not able to understand WHY I need a minumum load ^^’ I’m not a guru in electronics and I know only a little about transformers. Could you please explain that? Thank you!
Daniel Abrantes says:
January 16, 2012 at 4:22 pm (UTC -7)
Hi!!I’m going to build one o that!!I have a 300W ATX power suply!!The outputs currents are
+5V-25A
+3,3V-15A
+12V-13A
+5VSB,-5V,-12V-1.5A
What power resistors i have to put in the circuit???
Best regards
Chris says:
January 21, 2012 at 2:09 pm (UTC -7)
Im doing this conversion with a newer 3 rail 650W PSU.
The darn thing has almost 30 ground wires that seem impossible to twist together and solder to the posts.
Are there any tricks to that?
Daniel says:
January 23, 2012 at 9:08 pm (UTC -7)
Hey man excellent project!
I have a doubt…where do you connect the gray cable POWER GOOD???
Thanks!
nicusor says:
January 24, 2012 at 8:33 am (UTC -7)
Hy!
I’ve already built one BenchLab Power Supply after seeing your video, and I must Thank You Verry verry much!!!
AND I need one advice,if you can help me with it: How much real Amp’s can I get from an Accopia dual Fan power supply 450watt ,wich has on the +12v branch 22 amp’s!
can I get at least 15-17 AMP’s on it? some ”experts” told me that I cannot get more than 10 Amp’s from this ATX!
What should I do ? (I need it to supply an amplifier who ”eats” a lot of current)
Thank you verry much for the lesons you give for free!
Jazly says:
January 31, 2012 at 10:19 am (UTC -7)
Thanxxxxxxxxx alot dude….
what is the value of the load resistor????
admin says:
January 31, 2012 at 2:48 pm (UTC -7)
You’re welcome!
Watch the video again. I gave info about different load resistors there.
Jimmy says:
February 4, 2012 at 11:40 pm (UTC -7)
what happen if i connect a LED to the +3.3v ? will it burns the LED since the +3.3v has high current at 20A.
EmilN says:
February 26, 2012 at 1:48 pm (UTC -7)
Study the very basics of electrics.
Think of your LED as a hard drive; the hd only draws the current it needs, so it’s irrelevant to even think of amperes here, as long as the minimum required is available.
However, an LED is designed for a max A draw, and that is related to the voltage. If you serve a 3V LED (i.e. white, green or blue) with 3,3V, the LED will draw too much current, get hot and burn out quickly. And 5V fries it instantly.
Google: led resistance calculator
Cheers
Damian says:
February 14, 2012 at 9:01 pm (UTC -7)
I am recently working on my new ATX CORSAIR GS 700 which has most of its power on 12v and what I did I separate everything and I only made yellow and black biding post because I would be only using 12v for most cases. I did make a switch where I put one black and one green on it. I also connect one black wire through the 330 ohm resistor to led and then to gray wire for power good. Then I connected the black wire also through 330 ohm resistor to LED and then to purple wire for stand by is this correct or I have to connect to 12v yellow wire?? Then I bought the wirewound resistor 10 ohm 10 watts and I connected to black and yellow wire. Everything was done and I turn it on after like a minute or so wirewound resistor became so hot and I could smell it. So what could be wrong with it is it the wiring or the wirewound resistor?? Please help me. Thank you!
Megamouse says:
March 3, 2012 at 4:47 pm (UTC -7)
Hi there I am currently working on a ATX PSU like the one in your video. I have a quick question. What determines where you place your dummy load? You mention briefly that this could be on the +5 line for old supplys and +12 on either. Excellent video!
Drewski says:
March 5, 2012 at 3:44 am (UTC -7)
Thank you for the excellent tutorial! I am a novice and have several questions regarding a conversion of a 500 watt Dynex PSU. First off it has two 12 volt rails, one at 16A and one at 18A. I know that i could split them, but should I? Also, My +5V rail puts out 40A which is…..a lot of juice! If i split this into, say, 3 terminals, would each provide ~13A? Or, alternately, is there a relatively simple circuit that can be built to control current via a control pot or some other mechanism?
A more complicated question as well: Can I draw from both the 12V and the 5V rails simultaneously with a voltage regulator on each ? i am just getting into robotics, and i would like to power some 5V logic circuits and some 9 volt motors at the same time.
sometimes i feel like i try to invent the CD before the laser, you know? Again, i’m new at this so i’d appreciate any help you can offer in addition to what you have already taught me!
and seriously: wear goggles!!! XP
Ray says:
March 12, 2012 at 6:25 pm (UTC -7)
This is really an excellent video and I’ve seen and read several articles on this subject. Why do you join all of the 12V leads together and connect them to the +12V binding post? Wouldn’t any of the 12V leads be sufficient? Same for the ground wires. Wouldn’t any of the ground wires be enough? Why are all of them joined together?
If you have a 2-rail PSU with a 12V connection at 15A and another 12V connection at 20A, wouldn’t joining all of the 12V wires together limit the maximum 12V output to 15A before the PSU becomes overloaded and shuts down? Wouldn’t it be better to identify the 20A 12V lead and just use that?
easybudget says:
March 20, 2012 at 1:27 pm (UTC -7)
Great tutorial and fantastic video!
Here I have a simple question asked above already but I could not find the answer.
I have a new 700W psu with two separate +12V rails (+12V1 & +12V2), each gives 20A current. After connecting green and black it starts itself without any extra load/resistor.
My questions are simple I think:
1. Do I need to put a dummy load if it starts itself? IF I need then do I need to put it on each rail or just on one of them?
2. I want to get as much as possible of the current so will it be OK if I screw all yellow wires +12V1 and +12V2 together to get upto 40A current. I understand there will be never 40 but approx 32A – Is that correct?
Thanks again for your great tutorial.
Arthur
Electroalek says:
March 30, 2012 at 4:27 am (UTC -7)
Hey, Phil
I heard someone said that ATX PSU’s are not great for electronics projects because they have a lot of amps.
I’ve combined the “ATX Power Supply” and the “Simple Adjustable Power Supply”. And it works perfect. Thank you. Please replay.
Electroalek
admin says:
April 2, 2012 at 1:09 pm (UTC -7)
No, it’s perfectly fine for any electronic projects. Just be careful and don’t short out for more than a second.
But it’s not so great for precision analog stuff like op-amps and such. It has some voltage ripple on the output.
Vladimir says:
March 31, 2012 at 4:00 pm (UTC -7)
Very good tutorial! Thank you!
However, I still have some questions.
First of all, what kind of LED should I use and which current-limiting resistor to go with it? There is quite a fiew tutorials all over the web on how to convert an ATX PSU into a bench PSU and in all of them the LED and the resistor are being used but nobody ever talks nabout the specifics of these two parts. I mean things loke Ohmmage and Voltage! Another question is regarding the wire cholor scheme. I’m trying to convert a Thermaltake W0119RU 400W Power supply but I cannot find the Brown wire in it! There is Black, Red, Orange, Yellow, Blue, Gray, Green, Purple, White,…. but no Brown!
What do I do?
Thank You!
admin says:
April 2, 2012 at 1:20 pm (UTC -7)
Hi,
About LED and current limiting resistor: well, there’s a lot of different types of LEDs out there and each has different required current and forward voltage drop (If and Vf parameters in datasheet), and that’s why it’s not included in any of the tutorials about power supplies.
If you need more info, just google for it. “How to use an LED”, or something like that.
Brown wire is optional.
Matt says:
April 13, 2012 at 2:00 am (UTC -7)
Hi,
I have an AT power supply, it was creating 11.43v from the yellow 12v wire. I wired a 12v globe to one of the black wires and one of the red (5v) wires. I put the multimeter on the 12v and ground wire while the globe was on. it read -12.21 I was wondering why it said negative? and also my lipo charger can handle 12v-17v, would it be ok if I put another globe on the 5v rail? or is one enough already?
cheers
Craig says:
April 27, 2012 at 4:41 am (UTC -7)
Hi,
I’ve connected a 10W 22Ohms resistor between my 12V and gnd, and its running VERY hot, quite quickly. Is this normal?
Thanks
Elad says:
May 8, 2012 at 6:34 am (UTC -7)
It’s a great tutorial. Thank you!
I’m trying to make one too, but I can’t figure out which version is the PSU I have.
The sticker says:
ATX 450W
+12V = 16A
+5V = 32A
+3.3V = 20A
-5 0V =0.5A
-12V = 0.5A
+5V/SB = 2.0A
How can I know which PSU I have?
Thank you for your time!
hermes says:
May 10, 2012 at 2:47 pm (UTC -7)
Собрал почти такой же. Inspired, так сказать, by this tutorial
Получил массу удовольствия от процесса, после завершения процесса захотелось ещё более православный источник собрать, с вольтметром, амперметром, регулятороми напряжения и тока, ну и так далее… Спасибо!
Dikran says:
May 20, 2012 at 4:42 pm (UTC -7)
Hi,
What is the name of the device you are using to heat the yellow and blue plastic cable shields or sleeves?
Thank you.
Dikran.
Dillon Percival says:
May 21, 2012 at 2:44 pm (UTC -7)
Its everything here what precisely I became in search of
Im so happy i part of right here.
hfufhvihfiusvg says:
May 27, 2012 at 6:41 am (UTC -7)
how do you call the red and black pins for power output?
Vince says:
June 4, 2012 at 5:55 am (UTC -7)
Thanks for the great video! I couldn’t wait to try it out. I had a leftover 300W PSU that has never been used.
But then, it did not work. I followed your video, but with one difference:
I hard-soldered the green to the blacks.
I am using the power switch on the back to switch it on. The LED blinks once very briefly, the fan twitches a moment, but no voltages on the binding posts at all. The purple carries 5 V. In other words: it doesn’t stay on. I tried dummy loads over 5V and 12V.
What can I try?
Thanks!
WAN ABU BAKAR says:
June 7, 2012 at 4:10 am (UTC -7)
Hey excellent video, everything is looking nice and neat…i just have one question…where did u connect the power good cable(grey wire) too?
Thanks!
..
Dikran says:
June 14, 2012 at 1:57 pm (UTC -7)
How about making a DC-DC converter like the one you did before, but to convert the 12 V present on this power supply into 13.8 V for ham radio equipment as a separate output? I think about 25 A or more is needed …
Polanskiman says:
June 18, 2012 at 6:27 pm (UTC -7)
Hello,
I am not an electric engineer to please be tolerant
Followed your tutorial. Great job! However I have several questions:
1. You are powering the green LED with a 5V Red wire. Why didn’t U use the Grey wire instead?
2. I want to use one of those Load Resistor which come with a golden heat-sink but I am unable to find it with the specs (11Ω/5W) that U specify. I can find load resistors of 11Ω/10W. Would that work?
3. The load resistor needs to be wired with a 12v supply on newer power supplies. Why is that?
4. Strangely, I am only pulling 4.75v on the 5v supply line. Any idea why this is happening?
5. Finally, is it possible to mix channels, lets say 12v and 5v to obtain 17v?
Thanks
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Michael says:
June 22, 2012 at 12:06 am (UTC -7)
First off I would like to thank you for your website.
My first question is, I have the same power supply in the video. I am trying to use a single on off switch with a built in led. How do I get the led in the switch to come on when the power supply turns on? The switch is labeled Power, ACC, and Ground. For temporary use I have wired the green wire to power and black ground to acc so that the machine will come on.
Again thank you for all of your help and support.
PeterEdin says:
July 9, 2012 at 8:47 am (UTC -7)
3 times, people have asked what the grey wire is use for, but no one has replied re the grey wire. Searching on other PSU related sites the grey wire is quote: …”Since the signal is generated by the PS for use by the MPU, the PWR_OK (gray) wire should not be grounded, attached to any of the other output lines or tied to a resistor. It is not required for the PS to function — its sole purpose is to allow the motherboard to initiate the boot process and to continue to function in the absence of unstable or improper power levels”.
admin says:
July 9, 2012 at 8:49 am (UTC -7)
I guess more than 3 times. As long as I remember I explained that grey wire is PWR_OK, and that it goes high when power is stabilized.
martinhemm says:
July 10, 2012 at 10:36 am (UTC -7)
ive tried this on a cooler-master silent pro gold 600w psu but when i put it on a meter it reads 15v and slowly creeps up and up and doesn’t really stop……have i done something wrong? i have a 4.7ohm 10watt ceramic on the +5v ………its a new supply
3.3v +3.3vs are together and the +5v and +5vs are together
admin says:
July 10, 2012 at 12:29 pm (UTC -7)
Strange. I don’t think that you could done something, so that voltages would rise like that.
I guess it is one of two: either you have a faulty power supply or you have a broken multimeter.
martinhemm says:
July 10, 2012 at 1:47 pm (UTC -7)
the supply is new and ive only used it once in a computer, i was testing voltage before the resistor was on, could this of buggered the supply?
i had 2 other supplys which done the same on me , i guessed they was knackered so i binned them
admin says:
July 10, 2012 at 1:51 pm (UTC -7)
Take a different multimeter, check if you measuring DC(not AC) voltage, check everything again.
Very often these kind of problems have the easiest solution. Maybe something has been overlooked
dc says:
July 23, 2012 at 8:59 pm (UTC -7)
Some help. Power Supply modified as per video, tested successfully. But after putting components in ATX case accidentally touched Blue (-12V) line with Yellow (+12V) line for millisecond and power supply stopped. Now when I turn on, ATX fan spins for a second, +12V,+5V, lines spike up and all shuts down. Purple line is always +5V regardless of grounding green. Board and components do not look damaged. Any suggestions on how to reset or what component was damaged. Model: DPS-450DP
Thanks for any help.
Mau says:
September 1, 2012 at 5:28 pm (UTC -7)
I bought a Diablotek 250 W for $11 to convert it into a Lab Bench like you did here. It comes with a main switch for the wall outlet. I put a small switch like you did. The only problem is, when I turn the switch on it the PS stays on, even if I switch it back to the off position. The only way to switch it of is by switching off the main switch (I know I used the “switch”word a lot, my apologies). Any ideas why I can’t switch the PS off using the small switch?
Thanks!
admin says:
September 2, 2012 at 1:09 am (UTC -7)
Maybe your PSU needs a pull-down resistor. Try to put 1k-10k resistor between GND and POWER_ON (green wire).
Mau says:
September 2, 2012 at 10:01 am (UTC -7)
It worked!
Thanks a lot!
Joshfinley says:
September 8, 2012 at 4:45 pm (UTC -7)
Thanks for the most excellent tutorial. I have done two of these, the first one I did all the different +&- voltages available on the second one I just did 3.3, 5 & 12 volts.
Is there a way I could adjust the output current (amps) and keep the voltage constant? Maybe using some type of potentiometer so current could be adjusted with a knob.
I am using it for various RC applications and need adjustable current for a hot wire foam cutter. Cutting quality has a direct relation with constant watts/inch of wire. To little and it won’t cut, to much creates meltdown of foam or worse, melting and breaking the wire.
Thanks again for the tutorial, I have learned a lot from this project and I was able to use the power supply from my old broken computer, which I was going to throw away.
Zahari says:
September 14, 2012 at 8:11 am (UTC -7)
Hi sir..Can i use the +5V supply form ATX PSU to supply the microcontroller and +12V to drive the wiper motor?
admin says:
September 14, 2012 at 9:23 am (UTC -7)
Yes, you can! Just don’t forget to put 0.1uF ceramic decoupling cap near your microcontroller’s VCC and GND pins. And a diode between motor terminals to suppress back EMF.
Lee hodgson says:
September 24, 2012 at 4:10 pm (UTC -7)
Thanks for a great video, I do have a couple of questions though, The connections to the two LEDs one appears to be the purple wire and the other is connected from +5v through the dummy load resistors which I believe were wired in series. Is this correct?
Also where do you connect the current limiting resistors?
The green wire to the toggle switch and a ground to the other side of the switch?
Once I understand this I can start my pus project too.
Thanks a lot!
Tuned says:
September 25, 2012 at 5:59 am (UTC -7)
Very nice video and informative. Neatly made power supply. Any ideas on how to lift the +12v to 13.8v so I can use it for Ham Radio equipment?
Mike Doughty says:
October 7, 2012 at 5:15 pm (UTC -7)
Thank you for the quality tutorial. I am not sure if it is newer or older power supply. Id does have +12v1 and +12v2 which makes me think it is a newer power supply. But the amps on the 3.3v and 5v rails are more than the 12v rails which makes me think it is an older power supply. I have a Coolmax 400 watt V-400 ATX power supply (from TigerDirect). 18 amps on 5v, 20 amps on 3.3v, 18 amps on 12v1 and 16 amps on 12v2. Do the power resistors have to be 10w 5 ohms on the red wire or 10w 22 ohms on the yellow wire? Any help would be appreciated.
Jeff says:
October 25, 2012 at 7:55 pm (UTC -7)
Hi, I love the project. Thanks! Very easy to understand.
My problem is just as the poster above me asked. I need to understand an absolute check to know wether the 12V should have the dummy load or the 5V. I do not understand how to determine old and new. My particular supply has a 20 pin connector instead of 24. The currents on 3.3V and 5V are higher than 12V. 5V rail is over double the current capacity of 12V. Leads me to believe it is the old ATX? The site you listed gives ATX Revs but even that is not real clear in determining which one should use 5v load resistor or 12v load. Any help would be appreciated. Again… nice work!
Steven says:
November 3, 2012 at 6:59 pm (UTC -7)
I have a novice question about the current output of the converted ATX bench PS.
I Don’t quite understand how to determine how much current will come out of the +-5v and +-12v, I understand the maximum and minimum Amperage ratings but I need to power OP-AMPs that can only handle 25mA with the ATX PS. How can I achieve this using the +-5V or +-12 output? I’ve heard that you just connect the output to your circuit and it will automatically give you the right current, but somehow I don’t trust that statement…
Paul says:
November 12, 2012 at 5:36 pm (UTC -7)
Hi,
Is it the purple and green wire that I need to connect together to allow the power supply to turn on? I just need to use my ATX power supply as is but only need it to turn on when I plug it as I will be using the original molex conector to provide the needed current.
Thank you very much for all your time, it is greatly appreciated and your video is awesome.
Paul
Galih Wr says:
November 13, 2012 at 6:43 am (UTC -7)
Exciting movie, actually if You give the extra tools for finish Converting ATX Power Supply, You can give next example with using some tools in You Converting. Perhaps using recharge mobile, Lamp, etc. Than we’ll understand for next Creation of You.
I have not used Power Supply in my home to touch it, because it will be electrocuted You can paint Power Supply and than not be electrocuted.
Thank you.
Randy says:
November 24, 2012 at 9:00 pm (UTC -7)
first this is a great video. but I was wondering if you might have some insite as to why my power supply still wont turn on unless I hook up a old floppy drive.
I wired up 2 10w 10ohm resistors and the fans in it will run but it shuts down if I hook my battery charger up to it. but if I leave the resistors out and use a old floppy drive hooked up it stays on and I can use the battery charger.
what am I doing wrong?
Micah says:
November 27, 2012 at 4:42 pm (UTC -7)
First of all, thank you for sharing your knowledge with the rest of us. This power supply is a huge upgrade to my work space.
I took apart the unit and found that I don’t really have the space to put the binding posts and for rerouting the wiring. I picked up a high-density polyethylene (HDPE) container that will fit everything and make it all nice and enclosed (which is my main goal). One question (well it might turn into more than one by the time I write all this out):
Do you see an issue with using HDPE plastic as a container if I were to abandon the metal case and reattach all the hardware to the inside of the new case, including drilling air holes and such for the fan? I was kind of concerned that the HDPE could have a capacitance and charge itself.
Do any parts of the unit (even when properly cooled by the fan) get hot enough to soften or melt the HDPE?
If there is an issue with either of these, I suppose I could place the whole unit in the HDPE case and connect all the wiring such that the all the externals protrude from the case (LEDs, plug, posts, etc.)
What do you think?
Thanks again. You’re the best.
Christos Akris says:
December 28, 2012 at 12:34 pm (UTC -7)
I have a Computer ATX 450W PSU to power a Led Panell at 330W, various power Leds, 90pcs 3W + 30 pcs 1W in paralel circuit into two equal parts 5 Led x 9 arrays of 3w each party and, 5 Leds x 6 arrays of 1w on each party with The resistors per array as the wizart says. The whole thing is 330W, 13.500mA (3w Led) + 4200mA (1w Led). Right or wrong ???
My question is: Since the yellows cables are +12 V, can I split and solder Them (Connect) in different places on each paralell circuit to minimize the risk of uneven flow into each party without losing the over-current etc etc protection???
I am very thank the team for the answer. I received a lot of info of all your lay-ups.
Greetings from Greece
Christos
Evenpeven says:
February 7, 2013 at 4:42 am (UTC -7)
I converted my 300w Seasonic ATX psu, the same way, but I get a really unstable (pulsing) output voltage on the 12v rail. I tried putting my 10ohm 10w resistor on the 3.3v, 5v and the 12v rail, but still not getting any stable output.
Could the load be too low?
I’ve converted 2 of the same type, and both are behaving the same way. It tested fine with at ATX powersupply tester before i modded it.
Any help would be good.
CFMetalcraft says:
February 8, 2013 at 1:49 pm (UTC -7)
One of the best tutorials I’ve seen. Clear, easy to follow, love the graphics and the hands-on stuff. Wonderful for the neophyte as well as experienced guys. I’m at the beginning of doing my first conversion, and you’ll be my guide. Again, thanks. I look forward to looking at everything else on your site.
Philip Morley says:
February 15, 2013 at 11:19 am (UTC -7)
great job
almost 2 years from original posting and the info is still helping people
thanks
Rwiens says:
February 19, 2013 at 7:47 am (UTC -7)
I have a REALLY old (<1995 when ATX was introduced) PSU and it doesn't have the green, brown, purple or grey wires. When I took it out I left the mains switch from the front of the computer attached and when I plug it in and turn it on, I seem to get +5V where I expect it (between red and black).
Is it safe to assume that this is a switched-mode power supply, and therefore I still need the dummy load resistors?
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Turn a Computer Power Supply Into a Desktop Power Supply | LED World says:
June 20, 2011 at 6:41 pm (UTC -7)
[...] Levchenko shot this tutorial showing how to turn an ATX power supply into a DPS. Small tutorial on Computer ATX Power Supplies. How to use them, how to connect them in series, in [...]
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June 24, 2011 at 3:37 am (UTC -7)
[...] have the basic components to build a desktop supply. Over at JumperOne they have put together a great tutorial on how to make this conversion. It does take a bit of knowledge to do, but thankfully they go [...]
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November 21, 2011 at 11:32 am (UTC -7)
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[...] http://jumperone.com/2011/06/atx-power-supply-tutorial/ [...]
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May 5, 2013 at 6:10 pm (UTC -7)
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