We are all makers
[youtube https://www.youtube.com/watch?v=5TJaREOi1SY]
There are a lot of ways that you can repurpose and reuse old electronics. For instance, a computer power supply can make a great bench power supply for your workshop. There are already a lot of tutorials online that show how to convert an old computer power supply into a bench power supply, but most of these designs require you to permanently modify it.
This design for an external adapter lets you use the power supply without modifying it. Any ATX power supply can be plugged into the adapter. The result is a high capacity power supply that can output 3.3V, 5V, 12V and -12V.
Before we begin, here is some background information on computer power supplies.
A computer power supply converts the AC power from the wall outlet into smaller DC voltages that power the various components of the computer. It regulates the voltages by rapidly connecting and disconnecting the load circuit (switched-mode power supply). Most modern computer power supplies follow the ATX convention: They output +3.3V, +5V, +12V and -12V on a series of color coded wires.
Computer power supplies have a number of safety features that help to protect you and the power supply itself. Here are a couple that you need to know about:
- Turning on the Power Supply It is designed to not turn on unless it is connected to a computer motherboard. This is controlled by the green “power on” wire. Connecting this wire to ground (any black wire) will allow the power supply to turn on.
- Minimum Load Requirement Many power supplies require a minimum load current in order to stay on. Without this load, the output voltages may vary significantly from the specified voltages or the power supply might shut itself off. In a computer, the current used by the motherboard is sufficient to meet these requirements. If your power supply has a minimum output requirement, you can meet this by connecting a large power resistor across the output terminals. This is discussed in the steps below.
Very useful
This might be a stupid question, but how do you connect to this? I admit I don’t know much about these “banana jacks” but I was just wondering how you would connect something like an arduino or anything else to this? Thanks.
if you take a look at this: http://imgur.com/gmHlsi5 you can see that the binding post has holes that you can insert a wire into and screw tight. These wires could connect to an ardunio and many other things.
Tadaaa!!!
Great project! I’m definitely going to do this. I did have one question. Rather than using the 10W Resistor to Meet the Minimum Load Requirement, wouldn’t it also work and make more sense to put in a light bulb or LED to indicate the power is on? I mean, you get the resistance needed, and you get a visual indicator that the power is on, which might be good to know.
How many amps can you pull from the +12v rail? I was thinking of making this for a lipo charger
+12 13A ; -12 1A
That depends on your power supply. They have different wattages. You’ll have to look at the nameplate for the specs.
1) depends on the power supply.
2) depends on how many wires from the power supply that you are using.
..) You certainly would want to use several red ones together, several yellow ones together, several black ones together. That’s the only thing I see missing from this guide.
Just made one for charging lipos and it blew pulling 9amps even though it is rated for 18 on that rail. I guess try using multiple rails if you can. Sad I just wasted a good psu :(
I’ve been using my 300w psu for years no problem. Solder all the 12v wires together and call it good. It’s been working reliably for me
It is a good idea to always put a fuse in line with the load that is a little higher than the number of amps you need. It may not have saved your psu in this case since you pushed a single channel past its breaking point, unfortunately. The psu may have been weak in this case. Is best not to load any single channel that past 50% of its rated currant to stay on the safe side.
It depends on the power supply’s total current capability for that rail. Also, per the ATX spec due to the gauge of the wire and the properties of the connector in the plug you are limited to about 8amps per wire. so if you need 10amps combine two wires of the same color conductor. Also make sure you you have as many black wires connected to your load as you have for a common rail, so that the return current for the ground observes the same current limit per wire as the on the supply side.
a further example, if you have a project that needs 15 amps on the 5v rail and 23 amps on your 12 rail, assuming your power supply can deliver those currents, you should have 2 red wires connected together for the 5V rail (2x8A=16A, good enough for the 15 amp load) and 3 yellow wires for the 12v rail (3x8A=24A, good enough for the 23 amp load) then have five black wires connected for the return current to ground.
Great advice, Paul. But, you need to check the current rating for that power supply for each channel (wire). They are different for various power supplies and sometimes on the same power supply.
if you want to get al the watts available on the 12v rails you need to cut all the yellow wires available and solder them together to the positive 12v end.
I used an Old shoebox big enough to fit the power supply so now its portable
12 volt rail on my supply supplied 20 volts so I turned it into a variable supply for 13-20 volts. All the other rails are messed up as well 3volt=5 5volt =8.something
Hey Palmer, I’d be interested in seeing your variable circuit. Did you just put a panel-mount pot in series with the connectors? Did you put a meter on it? Thx.
I wound up trying my hand at this, with a few tweaks. I used a toolbox to put the psu in, and bored holes in the removable tool tray to hold the binding posts. Works ok so far. Only mistake I made was putting the posts too close to each other. Other than that, works great. Nice project that becomes a useful too.
I really like your take on using a motherboard connector to make this work with with any (atx) power supply. A little more work up front, but well worth it in the long run as it is super easy to swap supplies if one fails. Also can serve as a quick tester for all those old supplies I have taking up space. Now the question is….buy a atx connector or take the time to desolder one from an old motherboard…
I’ve tried to desolder connectors from motherboards and always end up ruining them. They require a lot of heat and I almost always melt the plastic before the solder :(
I for one, would prefer to buy it.
great
Hi, I am in the process of making this, but I have a question. Can I have more the one 12 volt outlet?
As long as the sum of all the 12V outputs’ currents don’t exceed the maximum current for the 12V supply, you can have as many as you can. If your supply has a +12V 10A output, you can have 5 outputs of 12V @ 2A each or 20 outputs of 12V @ 500mA each, for example.
Very nice! I’ve used PSU’s but not taken much time to “improve” them – like with a switch, binding posts, USB etc. I was looking to build a few with kids to power various projects we are working on… Arduino, and some automotive stuff, so was hopping for ideas on how to make them a little nicer… and safer. You win:o)) !
Thanks for this! BTW I designed a 3D printable custom enclosure for this project, here: http://www.thingiverse.com/thing:665797.
For power supplies with a minimum-load requirement, how about lights (LEDs or older low-voltage incandescent bulbs) in place of the power resistor(s)? Same heat dissipation/power usage, but you’d get something useful (light, and a visual indication of ON status) along with the waste heat. Of course, it would require a few more holes in the enclosure and sockets/mounts, but it might be worth it.
I was about to suggest the same. Maybe a pilot light might make a good load resistor. And look retro-cool. :)
An LED cannot be used as a minimum load requirement. A diode (an LED is a type of diode), doesn’t limit current. It will actually keep drawing current and dissipating it as head, or fail. Your best bet is a simple resistor, an incandesent bulb’s resistance changes with heat and voltage, so its not ideal.
wouldn’t be bad to put an LED in series with a current limiting resistor though, to get the best of both worlds?
No, LED’s require a current limiting resistor in series with them. See the current rating for that particular LED and voltage. Use the formula
Ohms(resistance)= Volts/I(amps).
Cheers for this it was helpful, I do have one suggestion though. In looking at the wires etc I would make a plug board or other such apparatus so you could easily connect and disconnect different voltages. At first glance and because I do not have the components on hand to make it proper I thought a simple board with finishing nails through it on the one side only sticking out enough to solder the wire to the end of the nail and on the other side enough to connect an alligator clip jumper wire too. say in two rows the top positive, the bottom negative 12v grouped together 5v together and so on (or vice versa) then label them presto you have a bench top power source no loose wires easy to connect and disconnect you can also set it up so the green trigger wire is connected properly too. when I thought of this I was having a flashback to grade 7 electronics class lol where we used a similar method to connect led lights to a board as some simple game. of course you could do it much cleaner with the right components adding switches even some sort of control dial to adjust the Voltage and even hard wire an old multi meter to it for that added macgyver feel lol
I have a power supply in which no green wire is exist. FOLLOWING colors of wires are Red, orange, black, purple, white, brown, gray nd sky blue. I want to make 12v charger
Sounds like you have an old supply. The pre ATX supplies didn’t have this feature.
Are your connectors like these?:
http://www.cosam.org/images/a1200t/at_mb_power.jpg
If so, your supply is a bit old and it needs to be turned on and off with a switch, not a pushbutton.
Plz tell me how to make
For our makerspace classroom I designed a laser cut case that slips over a standard ATX supply and hides all the wiring, etc. It has a ground terminal for a wrist strap that ties to chassis, three voltage taps, and a switch to connect a DC barrel jack to one of three voltages. We have had tons and tons of old computers donated most of which we just strip for parts. So we had a massive stack of ATX supplies looking for a purpose.
raaaaaagggghhh I need a freakin 3d printer I am jealous!!
That was made wtih a laser cutter!
I would also take a look at Anderson Power Poles instead/in addition to the 5-way binding posts. Very good connectors, common in ham radio.
Very common in a lot of 12VDC connections. US FIRST Robotics also standardizes on the 45A Anderson Power Poles. Same connector arrangement as the ham radio standard. Our makerspace happened to have a west mountain radio battery analyzer we were able to use with our US FIRST team’s battery packs without modification.
I like the idea of having a USB output to use some devices like mobiles, just remember some brands require pull-up and pull-down resistors at the data lines to operate correctly. Like the iPhoney.
Are all the different coloured wires at the same potential i.e. all yellow wires can be joined together, all orange …, etc.? This would allow me to get the full potential via each coloured connection.
not always, there actually often 2 12v rails, and if joined can fail, one set of yellow wires may have a black band
I’m trying to run my power supply with a 12-volt car stereo in my garage. When I turn on the power supply and connect it to the stereo, the power supply shuts off. The 12-volt pin produces good voltage and it will run a 12-volt PC fan, no problem. There does not appear to be a short in the stereo unit—it shows several thousand ohms between the power wire and ground, which is roughly the same resistance as the fan. Do you know why the power supply is shutting off? By the way, the same thing happened when I tried to connect a 12-volt, 1 amp wall adapter to the stereo. The adapter will no longer produce sufficient voltage.
The car stereo will work off of 12 volts if the suply supports the amps required for the speakers. If you are drawing too many amps then it could shut the supply off.
Ex. If I have a 100 watt stereo then I need a supply that can handle 100 watts (keep in mind that 100 watts is not 100 amps)
I don’t know the wattage of the car stereo. It is a factory unit, so I have been unable to find any specs. I even tried to Google the number printed on the amplifier IC inside the stereo, but came up empty-handed on info. Since it’s a 1997 factory stereo, I doubt the power is much higher than 20W per channel. It’s a 4-channel stereo, so I don’t know if the total power draw is Watts/channel times 4 or how that is figured. But assuming the total power draw is 80W, this should be well within the power supply’s capacity. It’s rated to produce 21A at 12V, which should yield 252W. Besides, the stereo should only be drawing its maximum power at its highest volume setting during the loudest portion of music. I didn’t even have any speakers connected to the stereo when I connected the power supply to it, yet the power supply shut off immediately.
This looks really cool and I’ll make it over the weekend. One question I have is why use JB Weld? Is that what you had on hand or is it because its stronger than a regular 2-part epoxy?
If you’re ever going to use molded dual banana plugs you should space your jack pairs 3/4 inch (19mm) apart. That spacing has been standard since the dawn of electrical engineering, so why not use it for this project?
https://en.wikipedia.org/wiki/Banana_connector#Derived_plugs
If you’re ever going to use molded dual banana plugs you should space your jack pairs 3/4 inch (19mm) apart. That spacing has been standard since the dawn of electrical engineering, so why not use it for this project?
https://en.wikipedia.org/wiki/Banana_connector#Derived_plugs
Hello everyone. I have this PSU that was intended for an HTPC, but that project has fallen by the wayside. I would now like to use it to power a couple of RGB LED strip controllers and their attached strips. Here is my power supply: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151027
PLEASE HELP ME!
I have done everything to convert my old VTX power supply into lab bench power supply and it works fine and give the accurate volts on all the rails, but the problem is as soon as I put some load on 5v or 12v it simply trips itself and not powering anything.
PLEASE GUIDE ME.
Your “old” ps is likely seen its day and unable to produce current when loaded. .
Buy a NOS ps on Amazon or Ebay…
Great guide, but I see something wrong here:
If you want to do this for any considerable power, you’ll want to use as many of the wires from the PSU as you can, even repeat the process for drive connectors as well as the 4-pin yellow/black plug . The more conductors you have going in, the less they will want to heat up. If you have a 450W power supply, and you’re trying to draw half of that through only one of those little wires you’ll surely let the smoke out. (The positive could be going through one or more wires in your build for different voltage loads, but it’s got only one ground to get back to the PSU.) That is why there are so many black, several yellow, several red going into the mainboard connector. And it’s why drive connectors have two ground wires. And it’s why the 4-pin ATX connector (black and yellow) is not a 2-pin connector.
So bundle as many red together as you can, common the connection securely. Repeat for yellow, black, (orange if you want 3.3v) and try to avoid a fire. :o)
Great project! I’m definitely going to do this. I did have one question. Rather than using the 10W Resistor to Meet the Minimum Load Requirement, couldn’t you put in a light bulb or LED to indicate the power is on? I mean, you get the resistance needed, and you get a visual indicator that the power is on, which might be good to know.
I got a question for you Jason. My cb raido has a 12 volt 600 watt kicker hooked to it. It pulls a lot of power. If I hold a four foot florescent light out pointing it at the antenna and key the mike it will light up the bulb. Is there a way to take a few of these power supplies and hook them together to run the amp? It will also open security gates, garage doors and make gas pumps go crazy along with some neighbors.
Late reply..
Is my understanding that parallel connections between atx psu’s isnt an option.
Only series connections with some minor modification but that is no help to your situation.
I believe the “600 watt” rating is an output for the amp, right? You need to check the current it uses at 12 volts. The output is a much lower voltage, and 600 watts is an instantaneous current for certain sounds, very low notes drew the most current and voltage.
There is a chance that it would give you enough current if it is a powerful enough psu.
Sorry to post on a older project but i am working on a college project using this as the base for my build and was running into trouble with my brand new 24pin computer power supply. I can’t find any information on which pins specifically need to be loaded on newer supplies. I am trying to get 24V out of 2 of my 12V pins and limiting them to 8A. I saw the part about the 5V being loaded and sometimes the 3.3V and 12V needing loads.
You cannot get 24 volts from two 12 volt pins. First, they are the same 12 volt supply, so they are not independent. Second, even if your supply had two separate circuits to supply the 12 volt pins, they would share the same ground, so if you “stacked” them, you would be shorting out one supply.
Could you use a 12 volt pin and then use the -12 as a ground to create 24 volts difference? Sorry if this is a silly idea.
You can absolutely do that, but you must pay attention to the current capacity. Many old PC power supplies have a significantly smaller current capacity on the -12 V output.
this depends on if the supplies are isolated or grounded. You can check this by checking for continuity between the black wires and the metal case of the power supply, only do this when the supply isn’t plugged in. I have switch mode power supplies for non-computer applications that can be stacked this way. But I believe that most computer power supplies are grounded and should not be run in series this way.
See this article to stack 2 ATX supplies. Be sure to read the comments at the bottom of the article. http://www.instructables.com/id/Two-ATX-PSU-One-juiced-24-V-DC-PSU/
I just want to verify, to meet the minimum load requirement, the resistor goes between the 5v and gnd, not the 12v and gnd
Well, it depends on which output is the primary output. Most PSUs work by regulating one of the outputs and keeping the other outputs as a proportion of that rail. Nowadays the 5V rail is less important since most parts of a PC use either 3.3V, or 12V for heavier power requirements. I’ve found that the 12V rail is the primary output on many PSUs, so that’s where the resistor should go: between +12V and ground.
Just finished one of these. The power is not steady though, it cycles between high and low. I see the fan on the PSU rocks back and forth at the same rate as the power cycle. Any thoughts on what might cause this? I’ve triple checked my wiring…thanks!
It sounds like the PSU isn’t regulating correctly, most likely because it doesn’t have its minimum load applied. Better power supplies will shut down as described when the minimum load isn’t set, but cheaper ones will simply drift all over the place, which is dangerous. Applying a minimum load to the primary supply should sort it out.
In stead of canabalising an old motherboard and soldering all these wires, look on Ebay for “atx extension cable”. That will give you a pre-fabricated cable with crimped terminals for less than 2 USD! Just cut off the other end.
that’s so boring though.