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Step 9: Updates


Originality

This project is not necessarily original and has been done by many people.

The most "together" project is that of this guy: http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

There are a multitude of other projects, but I feel mine and his are the best I've seen so far.

Issue of the Resistor

Power supplies need a certain minimum load to work properly. The min. load for mine is around 0.8 amps. Thus if you plan on powering LED's or other such low-power device exclusively, you'll need a resistor to provide a load. Otherwise you will damage the PSU.

A meaty 10-Ohm, 10 watt resistor from Radio Shack is a good choice. Wire it across 12 volt and ground.

-12V and -5V lines

It has been brought to my attention that the -12V and -5 lines are pretty handy for diversifying the voltages this thing can produce. These are the white and blue wires I told you to cut earlier.

Of course, adding them is simple, it's just a matter of getting two extra binding posts and connecting the wires to them. It's just a question of "Do I need these?"

I didn't, all I really needed was the 12V line. But as I said, if you need them, they're easy to install.

UPDATE 12-1-11

Still going strong! This little PSU has been super handy. 
<p>Could we used this PSU for car battery charging? If not, what does we need to enable that?</p>
<p>Hello</p><p>I have an old power supply from a LinotronicRIP50 that is not working.</p><p>The power outputs are 12V (6 amp) and 5.1v (20 amp) would I be able to use a modern psu?</p>
<p>If you hook the +12v too the +3.3v would that give me +15.3v ? And would it make it 41amps ?</p>
No, by connecting those wires in series you will get 17+ volts, but the amperage that can be drawn safely is the lowest of the two outputs. 23 amps, in this case.
<p>why it will give 17+ V instead of 15.3V?</p>
<p>ok, thanks for the help :)</p>
<p>Can it kill me if I touch it? Because I heard that 30 mAmps can kill you, so ...</p>
Yes. Amps kill, not voltage. So long as you don't have it plugged in while working on it you're fine. Once work is done and cover back on, these are well grounded and safe.
<p>nope not enough voltage .....i wouldnt stand and pee on it holding a cold water pipe tho either ....gettiing ur hands across a 12 v car battery makes a burning sensation at 12 v ....if u have alot of cuts on ur hands then u could have a problem ...a guy in a junk yard carrying a half dead car battery fell down both hand on the terminals they determined 6v and half an amp stopped his heart ...thats blood contact ...</p><p>but if ur at the work bench dont worry much about it ..just watch the sparks when u mess up</p>
Last one working so well I made another from a unit that came bundled with a case I bought. Lack of pci'e connectors made it useless for my pc.
<p>I made mine some time ago, using an old PC cd-rom and car amplifier and added two usb from an old motherboard, looks ugly but it does the job</p>
Made mine fron a 500W Dynex unit.
<p>I built my power supply with the similar instructions as yours using only the 12Volt output to power my Car Airpump (12V 14Amp max).I joined all 5 12V wires (Yellow) together and same for the ground connections to get the max current on the 12V rail which is rated for 17A on this supply.</p><p>With no load connected, the SMPS turns on and works fine but as soon as i connect the Car Airpump it trips (shuts itself down) not sure why ?</p><p>Now if i connect the same Power supply with a Digital Ampere meter connected in series, the Air Pump works perfectly. Could you help me understand the possible cause for this behaviour and how could i go about fixing or diagnosing it.</p>
<p>Hay I'm having the same problem with my power supply that you where. Mine just shuts off if I connect much of anything to it! Did you ever figure out what the problem is?</p>
<p>i solve my problem by connecting sensing voltage wire(brown) to 3.3v rail. </p>
<p>i got same problem ,i did't use resistor is that cosing shutdown?</p>
I think the issue some folk may be experiencing with power lines not powering up is down to lack pf the power resistors on the lines. More modern power supplies need a load resistance on the 12v, 5v and 3.3v lines. If they aren't given that load, the power supply can't stabilise the outputs. Worth a try if you're struggling to get your supply up and running.
<p>Correct, a switch-mode power supply will need a load to operate properly.</p><p>I use a 10ohm, 25watt power resistor from the 5v rail to ground. </p>
<p>I have a little problem here I keep getting double voltages on each group of cables . For example in 3.3 v i get 6.6 v on 12.v i get 24.v etc.. What is happening ?</p>
<p>Make sure you're meter is set to measure Volts DC, not Volts AC. </p>
<p>Mine doesn't have a green wire!</p>
<p>Hi ! I've done this to plug a lipo charger but i have a problem. When i plug the lipo charger, the screen light for a second and the atx cut off. On the voltmeter i have 12v showed, so no problem, but it seems that when i apply some little load (just the charger without charging anything) it goes away.</p><p>Any idea ? :/</p>
I am new at this ...... i didn't understand why we can not use atx directly in our circuit when our cpu's mother board and all things work with it.....what is diffrence b/w atx and regulated power supply? <br>please someone help me....
<p>Great article and great idea. I've used these PSUs in the past for various purposes, but the idea of adding the banana plugs, etc. is so much better!</p>
Hi there i tried a lot but there is no power in orange red and yellow. Only live wire is purple. Can u help me
<p>You need to short the green wire with any black wire to make the PSU power up. The purple is a constant +5v supply no matter if the PSU is on or off. Once you have shorted the green and any black wire, the PSU fan will spin up and you'll receive power on all rails.</p>
<p>I made it! Thanks for providing such an easy-to-follow Instructable -- this is something I've wanted to make for a while and was finally able to take the plunge. Thanks!</p>
<p>Great tutorial, it does a lot of help esp to the newbie like me.</p><p>I'll just ask what if I have multiple devices that required 12V DC supply and different ampere supply? </p><p>My 12V DC-requierd devices are the ff:</p><p>12V DC Arduino</p><p>12V DC DC-geared motor</p><p>12V DC Relay (2 relays)</p><p>12V DC LED Strips</p><p>I also have 5V devices like Microswitch, Honeywell water Level sensor and LCD.</p><p>Guys, please help me how to connect these devices to the 500 Watts PSU.</p><p>Thank you and you may all have a great day :)</p><p>Any response will be appreciated.</p>
<p>Can anyone tell me if one of these resistor will work ? i want to add just to be sure ? it wont blow op :D</p><p>http://www.ebay.com/itm/2x-5-10w-10-ohm-10-J-Ceramic-Cement-Power-Resistors-Flame-Resistance-Brand-New-/401045504802?hash=item5d602cc322:g:NrIAAOSwT5tWGjvK</p><p>http://www.ebay.com/itm/Chassis-Mounted-10-Watt-10-Ohm-5-Aluminum-Case-Wirewound-Resistor-/191680189623?hash=item2ca10794b7:g:WycAAOSwHnFV5mMN</p><p>Thanks :D</p>
<p>A follow-up question.. how can I use this power supply for a circuit requiring 12v and 6 amps?</p>
<p>I have a question on volts, amps and watts... Is 400w variable depending on whether 12v or 5v used? When you are using 12v, the total wattage will be 276 and with 5v, 200W. Am I understanding this correctly? What if I use both 12v and 5v at the same time?</p>
I had a little project which required 12v dc current to power it... But couldn't find a power supply/adapter powerful enough for the job.. So I decided to use my old computer PSU... This guide has been very useful.. Thank you!
I have a 12v psu how can i make that into a 14v so then i can power a 14v car head unit
12v is enough to power a car head unit... <br>Usually... Car head units can work on a voltage range from 11.2 to 14.4v..
It works so good. I had no problems during modifications. I don't know if i was lucky or good building it.
<p>I made it using an old power supply. The rails are 12 V, 5 V and 3.3 V. It can provide 15 A from each rail.</p>
<p>I have a more basic question concerning how a power supply would be used to power a device.</p><p>If I have a device that requires 12 volts@3.33 amps (40 watts) and I have a power supply that produces 12 volts@15 amps (180 watts) is it safe to use the larger power supply?</p><p>Also is there any way to figure out how a power supply with a larger voltage would impact a device that requires a smaller one?</p><p>As an example, I have a device that requires 5 volts at 1 amp, I have an 18 volt power supply rated at 0.5 amp. Is there any way to make the 18 volt power supply fit the requirements of the 5 volt device.</p><p>Thanks.</p>
<p>The power supply is actually a &quot;voltage supply&quot;. Each voltage rail will provide it's rated voltage, and the load will draw as much current as it needs (up to the voltage rail maximum). It is safe to use a device that requires 12v@3.3A with a power supply that provides 12v@15A. The device will only draw the needed 3.3A which is well-within the capabilities of the PSU.</p><p>It's not straightforward to directly use an 18v@0.5A power supply with a device that requires 5v@1A. You can use a voltage converter that will reduce the 18v down to 5v, but there are some different considerations you need to think about. Especially if your input current rating is less than the output current you need. The simplest way to reduce a voltage like this is a simple-but-inefficient linear voltage regulator chip like the 7805, which will waste ( (input_voltage - output_voltage) * current) watts worth of electricity as heat. It is also limited to the input PSU's current limit. There are other converters like switch mode converters (a buck converter) but these are usually more complex. I'd honestly suggest finding a different power supply.</p>
<p>You can buy a basic 5V buck converter on Ebay or Amazon for just a few dollars; spend a little more ($10 or so) and you get one that's adjustable with an LED voltage display. Then you can run the power from your power supply into the buck converter and it will output 5V. </p><p>However the easiest way is just to buy a 5V, 1A power supply, also available on Ebay or Amazon for a few dollars. Or scavenge a charger from an old piece of electronics.</p>
Works like a charm!
<p>What is the difference between 12v and -12v? Also can i connect more Voltages together eg 3.3v and 5v for 8.3v?</p>
<p>Hey! So, in DC we have positive and negative tension, so, -12 would represent negative 12, and 12 is positive 12V, meaning, if you connect 12 to -12 you'd get 24! The voltage is the difference between the two pins you connect, thus, for 8.3V you'd need -5V and 3.3V or 5V and -3.3V. </p>
<p>&quot;if you connect 12 to -12 you'd get 24&quot; </p><p>To get 12 can I connect +12 to ground?</p>
<p>Keep in mind that the negative voltage rails (-12v and -5v) usually provide only very little current (a few hundred milliamps max in most I've seen).</p>
<p>How can we use this power supply in laser engraving where the current requirement s about 1-1.8 amps at 12 volt dc.. ? </p>
<p>Im not sure I understood your question, But most ATX power supplies can give ~15-20 amps...</p>
Just a small warning: Most ATX supplies have a minimum current on one (or two) rails below which regulation is not guaranteed. I've done this many times and I have not yet had problems, but just in case I started adding a minimum load resistor to the rails in question. It's a bit wasteful though, so for non-critical use, leave it out. I also add an LED on the POWER OK and a switch on the PSU ON, but that's not really needed.
<p>How much of a resistor would I need? I've got an old power supply which seems to put out only half the rated voltage for each unless it is plugged into the motherboard. Obviously it needs some load to kick on, but how much and where?</p>
<p>It isn't always the same - different supplies have different minimum current ratings, so you may have to experiment a bit. For an old supply, start by drawing 1/2 an amp (10 ohm) on 5V. Remember it will be dissipating a bit of power - 2.5W for my example above. Also, use a resistor with at least double the power rating that you intend to dissipate and be careful - it gets hot.</p>

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