Desktop Power Supply From Recycled Computer Power Supply


Introduction: Desktop Power Supply From Recycled Computer Power Supply

In this inscrutable I will walk you through building a desktop power supply from a recycled computer power supply. First off if you are wondering what a desktop power supply is and what it is used for , well it is a electronic device that takes the 120v or 220v from your wall outlet and reduces the voltage so that it can be used to power electronic inventions and things like electric motors and leds. For this inscrutable you will need only two components
* Computer power supply
* electrical tape
*******warning I am not responsible for any harm brought on by improperly handling high voltage or voiding of warranty on your computer or power supply*******

Step 1: Build It

The building process for the power supply is simple. First cut all of the connectors free of the wires coming out of the unit. Second find the light blue and green wires then cross them and cover the end of the wire with electrical tape. Then strip the ends of the other wires and plug the unit in. When you plug it in if the fan turns on it is working and is now a power supply for any of your electronic inventions. For the color coding
*red =5v
*yellow = 12v
*Orange= 3.3v
* black= ground
* purple= -12v
*Gray = -5v
with all of these voltages you can combine them to form many different voltages.

Other uses: power supply for 3dprinter, power your maker projects, and power anything that needs power
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    10 Discussions

    Please be very careful when handling computer (or any powerful) power supplies. The power supply in my very strong workstation is capable of a sustained 80A on the 12 volt rail. This much current is capable of starting a small car, welding light sheet steel together and starting a serious fire.

    While better made computer power supplies have very good protection against short circuits, some of the cheaper ones do not. In 25 years of building and repairing computers I have seen at least 10 power supplies that literally burst into flames upon an internal short.

    Also, as already pointed out, there are some very capable capacitors in computer power supplies and great respect should be shown to them. Cutting a number of wires at the same time risks a short (even unplugged) that could hurt you and/or the power supply. I NEVER cut more than one wire at a time.

    While the 3.3 Volt rail is only accessible from the 24 pin connector, 5 and 12 volts can be obtained from the 4 pin molex connectors. Female molex connectors are not hard to obtain and then you can wire up your project to the connector and just plug it in when you are ready to power it up.

    Lastly, the rated voltages can be out significantly on old and especially cheap computer power supplies; enough to fry your pi so to speak, so I always put a volt meter on it before I power up something delicate.

    As far as combining rails to get different voltages again care should be taken as not all computer power supplies can actually do this properly. Again, better quality ones almost always do and some cheaper/older ones don't.

    My rule of thumb is this: If it is a no-name cheap power power supply then I don't try to draw more than half of the rated current per rail on the label. Also remember that the wattage rating of computer power supplies is for the combined total of all rails. ie: a 500 Watt supply cannot safely provide 500 Watts on the 12 Volt rail. Usually it would be more like 375-400W. Others have two 12 Volt rails and are only capable of half of this power rating on each rail. As froKo pointed out, the -12 Volt rail is capable of only a fraction of the current the +12 rail can provide, so it is of limited use for 24 Volts. My platinum 1200 Watt supply only provides 1A on the -12 rail.

    Doom and gloom aside ;) they do make very good and inexpensive
    prototyping power supplies. You can frequently find them at the local
    recycle/reuse areas for free. If you want to use one, you do not really
    need to chop and short wires as you can use a paper clip to short the 24
    pin ATX plug and turn it on. This is what I usually do for temporary
    use. See

    instructions and pictures on how to find the correct pins. Using a paper clip lets
    me put enough "spring" on the contacts that they will stay there until I
    want them removed. I find copper wire too flexible to be reliable.
    There are pre-wired shorted connectors available for under $10
    available to buy if you are uncomfortable sticking a paper clip in a
    plug, but why would you be afraid of that if you are a regular of this

    Froko is right. You cannot have 24V by simply bringing together two separate 12V sources. To get 24V you have to bring together one +12V and one -12V (normally blue) and, as stated, the total output amperage will be limited to the lowest common denominator. If you are bringing together two +12V, you are doing something terribly wrong. Try to bring two 220V cables and see what happens. You will not get 440V. And don't even try this...

    Thanks for sharing, will you please, explain How do you do with all of these voltages then you can combine them to form many different voltages?

    best regards

    7 replies

    Sure , to make different voltages you simply cross two colored wires (there voltage is added together to form the total voltage) to form positive wire and then take any black wire which will be your negative wire. For example if you wanted to have 24volts you would cross two yellow wires and there combined voltage would be 24volts which you would put to the positive terminal and then a black one on the negative terminal.

    absolutely NOT... if you combine 2 yellow wires of the same power supply, you always get 12V, not 24... all of them come from the same source, and instead it is a good thing to do to link of same color cable together, to sum their global diameter and manage the higher ampere that the PSU can spit out... have you even tried what you say?

    and you completely missed the security: leave the PSU alone for even half an hour after you disconnect it from mains, to discharge the capacitors, or you can get a SERIOUS shock...

    and in many modern PSU you need a load between 5v and gnd, or even between 12v and gnd, or the psu will shut down after a few seconds...

    I have tried it and at this vary moment it is supplying 24v to a 3d printer

    it is a dlp printer with only one 24v .85amp motor

    Really? Here I'm a little skeptical. 3D printers are very power hungry and PC PSU are not designed to feed 24V for high amperages. Regards.

    I'm sorry I see my error now I forgot to say you need two black ground wires not just one

    You can in fact use the -12V line with the +12V line to get 24V, BUT BEWARE, the +12V lines are up to 20A, while the -12V is a couple amps MAX, so if you use the -12 and +12 to get 24V, you need to keep the amperage as low as possible, you cannot even get closer to the 20 amps of the positive rails.