ATX Bench Power Supply - Convert a Computer Power Supply

today in the workshop we'll be building a bench power supply using an old computer ATX power supply you'll learn how the different types of ATX power supplies are wired up and how we can hook one up to create a versatile and powerful work meant power supply of our own we'll even add in a power meter to measure voltage and current we're getting all used up today so welcome to the workshop [Music] hello and welcome to the workshop today we are going to build a simple but useful project the bench power supply now here in the drôme bought workshop I have a number of different power supplies that I use when I'm working with microcontrollers or with electronics you can see one of them here on my workbench this is a DC supply 0 to 30 volts it's got 4 different preset outputs that I can set so I can set for different voltages and it'll display the amount of current that's being drawn as well this works up to about 5 amperes I've also got a bench power supply permanently built into this workbench here you've probably seen this before a 5 volt and a 12 volt power supply that it mounted behind the workbench and I use that for a lot of my power needs as well I've got a whole box of these I'm sure you probably do these little wall warts but USB supplies 9 volt supplies 12 volt supplies and there are also USB supplies on my power bar this little thing that rests my tablet also has three USB supplies in it so I've got no lack of power supplies and yet I've got a project coming up a new an exciting project that's you're going to be seeing a lot of very soon and in order to build this project I need a power supply and I don't want to use my bench power supply even though it's quite capable of satisfying the requirements because hey I want to dedicate the power supply just to this project and B I might be moving the project into another room occasionally I can't take my bench power supply with me because it's built into my workbench so I decided to put together another power supply and I'm going to use this now a lot of you are already familiar with these I'm sure if you've ever opened up a desktop computer this is a computer power supplier to be more accurate an ATX type power supply and this is one of the most common type of power supplies you will find in a computer I got this power supply out of a very old computer out of an Windows XP computer that time has come and gone but whose power supply is still perfectly functional and let me use this to build a workbench power supply that I can use for my project and let me show you how to do that as well now it's a very simple project because obviously they have already constructed the power supply for you but I'm going to tell you that it's not just a matter of connecting up the 5 volt and 12 volt lines to a couple of binding posters a little bit of wiring involved I'm also going to get rid of a lot of the wires on this power supply so I'll be opening it up and showing you what's inside but if you might ask well why don't you just go out buy a power supply for your project well power supplies aren't the most inexpensive things in the world and you'll find that bench power supplies can get pretty expensive whereas these even if you have to buy them brand-new are about 40 50 dollars and you can often to salvage one out of an old computer like I did now what I want to fill you about this supply is what's unbelievable here and perhaps you'll see why I'm so interested in using it this let me focus this in for you there you go now take a look at some of those specs over there now that's pretty impressive current that has on the three point three five and twelve volt lines and it's for that reason that I want to use this power supply it's very powerful it's very well regulated and as long as you do this correctly it's very safe so what I'm going to show you is how these power supplies work when I show you the insides of this supply some of the other parts we're going to need to put this project together and then of course we're going to build it and test it out so let's get going now here are some of the parts I'm going to be using for a project of course I have the ATX power supply itself now I wasn't able to get a connector to mate with the 20 pin molex connector on the power supply so because of that I'm going to be using this terminal strip I'm going to be cutting the leads on my power supply and putting wires onto the terminal strip so I've got the terminal strip there I've also got a number of these lugs over here that I'm going to put on the wires I thought it would neaten it up a little bit to do it that way I've got of course the binding posts that you're going to need for the project I've got six of them three of them are black and then I've got three other colors I'm only going to concern myself with the positive voltages with the three point three the five volts and the 12 volt output I'm not going to worry myself about the two negative voltages on the supplied but of course you can wire those ones out as well now I've got a power resistor over here you're going to need a power resistor because you need to keep a load across the five volt line in order for the power supply the function correctly and this style of power resistor I like quite a bit because it's actually first of all a 50 watt resistor so it can handle a lot of current so it'll dissipate the power it's going to consume with no problem it's also mounted in this package which has a heatsink and can be bolted down and that's going to be kind of nice because it is gonna dissipate a little bit of heat this is an 8 ohm resistor it's actually meant to be a speaker load but it'll work for this you can also use this style of resistor if you wish and something around 10 ohms is usually what they suggest you use I've got a power switch down over here now this switch is going to be used actually as the power on/off switch I've got a couple of LEDs and dropping resistors here the LEDs are going to be a power on LED and a standby LED and I've also got and this is optional but I thought they'd be nice to include I've got 3 fuse holders and a number of fuses and I'm going to fuse the output lines as well just as an added measure protection although the power supply does have a shutdown mechanism if it does draw too much current now up at the back over here I've got a few extra parts that aren't really part of the project but I'll film to you anyway this is a volt ammeter and I'm going to use this along with these finding posts to mount onto the same panel as the power supply output and what I want to use that for is just to be able to patch one of these lines in and monitor how much current it's actually consuming so it's not a permanent connection onto any one of the lines but it's just a separate thing so you don't need to worry yourself too much about that if you don't want to add something but if you do want to add something like that I'll tell you how that works as well so now that we've seen the parts that we're going to be using let's take a closer look at the ATX power supply itself now here's my ATX power supply this is a series one version of the power supply so it has a 20 pin power connector on it as opposed to the series two which have 24 pin but they all look pretty much alike they're obviously metal boxes there's a output for a fan over here here's the actual power switch there's a selector switch on it over here to allow you to select your line voltage so I've got mine set to a hundred and fifteen volts but if I was in Europe I would flip that over to 230 volts here's the input for the power cord itself now on this side we've got the connectors for the supply and they're grouped into a couple of sets now this is the main connector as I said I've got the type one so mine is a twenty pin connector if you've got the type two you'll have a 24-pin connector and I'll tell you how both of those can be talked about now there's another connector over here that has this four pins on it and this is this 12 volts it was originally meant to power the fan and the computer power supply this is the fan that goes on the CPU heatsink itself and these are the connectors that are normally used to connect the peripherals up things like hard disks and you know DVD drives etc etc you can connect with these now I'm going to get rid of these cables entirely but I'm going to save them because they're useful for other projects when you're expanding in a computer these are useful to hook up extra power things I'm going to keep the lines over here but as I said earlier I'm going to cut them because I wasn't able to get a molex connector to mate with this so I'm gonna have to wire to a terminal strip I do want the extra 12 volt lines over here you're going to find a lot of these lines are duplicates and the reason is they just want to be able to carry all of that current so rather than putting the current into one wire they put it into multiple wires I'm going to keep that arrangement myself so there you go a typical ATX power supply so let's take a closer look at the ATX power supply ATX is an abbreviation for advanced technology extended this was a standard created by Intel in the mid-1990s for motherboards but it also applies to the cases and power supplies that contain those motherboards since 1995 the ATX standard has become very common in fact it's likely the most common type of power supply that you'll find for desktop computers over the years there have been several variations on the ATX power supply the ATX power supply is a high current switching power supply it supplies both logic voltages at three point three and five volts and motor voltages at 12 volts for a standard desktop computer the ATX power supply is a sealed unit with an internal cooling fan there are two versions of the ATX power supply version one can be identified with its twenty pin motherboard connector version 2 has a 24 pin motherboard connector here are the pin outs through the 20 pin and 24-pin power connectors on the version 1 and version 2 ATX power supplies you'll notice that a lot of the wires are repeated in several different connections the function of the wire can be identified by its color the black wires are ground the orange wires are positive 3.3 volts the red wires are positive 5 volts the yellow wires are positive 12 volts on the version 1 supply the white wire supplied negative 5 volts this is not included on the version 2 supply the blue wire is for negative 12 volts the green wire is the PS on signal when this signal is sent the ground it will turn the power supply on the gray wire is the power good signal it will go to 5 volts from the power supply is working correctly the purple wire is a standby wire the standby is at 5 volts as soon as the power supply is turned on using its master switch the standby wire can supply up to two and a half amperes of current there are other power connections from the ATX power supply as well for all the different peripherals in the computer some manufacturers use specialized connectors here as well the ATX power supply has an AC input voltage selector to allow you to use it anywhere in the world the rear switch from the ATX power supply does not turn the device completely on it puts it into standby mode to turn on the power supply you need to use the PS on or a green wire on the motherboard connection and bring it to ground many ATX power supplies require a load on the 5 volt output to function this can be simulated with the resistor not all ATX power supplies have this requirement now I've opened up my ATX apply both the give you will look at what's inside and also to show you a couple of things that I'm going to be doing I'm going to be taking some of these wires out now before we get started I want to point something out there's a couple capacitors on this side over here these capacitors can retain a charge for several hours or even several days after the supply has been unplugged and they're on the high voltage side of the switching supply so be very careful around those they could still have a charge on them now my power supply has of course a lot of connectors on it for peripherals and I don't really want these wires anymore what I'm gonna do is I'm going to remove them down here you can see the wires are grouped and these are basically the output connections the grounds and the voltage outputs and a couple of control outputs and I don't want all of these wires so I'm going to snip them down over here and kind of neat and everything up and then just put everything back together this all just fastens in with four screws it's quite easy to get apart and get back into now I will tell you something there are a lot of people who have built these supplies and what they've done is they've drilled some holes on the side here and they've mounted their binding posts on there and it's made a quite nice little arrangement the little box that you don't have anything external to and while that does look nice if you're gonna do it be very very careful you don't want to get anywhere near any of the high-voltage stuff over here you don't want to interfere with any of the cooling that's so important to this power supply so personally I wouldn't recommend building it that way unless you really know what you're doing if you are going to be soldering in here make doubly sure that you don't have any soldered pieces that have fallen onto the circuit board give it a good shake afterwards if anything else you're probably gonna want to open this box up just to blow out the dust and everything that's probably accumulated this was pretty dusty when I first opened it up but be very careful again around the high-voltage area and the only modifications I'm suggesting you do are removing a couple of these wires none of the modifications of drilling into the side of the chassis or anything are going to be entertained here today so with that said let's get on with our project so I thought that it would be a good idea to test out my power supply after all it came from an old computer that's been sitting unused for many years now I've got it hooked up right now just sort of loosely on the workbench what I've done is I've put my dropping resistor across a couple of the 5 volt lines of 5 volt and the ground and I've put a jumper on over here this is from the power-on signal the green wire to the ground and that has turned on the power supply and as you can see on my meters I've got one meter monitoring the 5 volts and one monitoring a 12 volt and as you can see they're very very good now the one that's monitoring the 12 volt can actually be moved and can be used to probe further voltages so I'll go to an orange wire and that could be the 3.3 I'm getting three point four six three point four seven so that's pretty good there's a couple of wires down over here this gray y're over here is the power good wire it's at five volts and the purple wire over here is a standby it's also at five volts now what I want you to observe is I'm going to remove the link I have from the power on to ground temporarily so take it off my link and I don't know you can hear the fan has gone down now you'll see in my meters I've got zero volts on the one that's monitoring five volts and indeed if I go back to the 12 volts there's nothing over here but if I got to this purple one the standby line I still have five volts and what that shows is that you've always got five volts on the standby as long as the power supply has been turned on using the switch on the back of the power supply now let's ground the power on signal again and you probably hear my fan come back on and now again standby still has voltage but now the power good signal which is the gray line also has voltage and these are the two lines we're going to use for the two LEDs in the front panel by the way now my resistor doesn't seem to be getting very warm it builds up a little bit of heat but not very much and I like the package that it's in it's gonna dissipate the heat quite nicely you may not need the resistor but many of these ATX power supplies required the resistor in order to startup correctly if you find you don't need it by all means just omit it from your design but as you can see my ATX power supply seems to be working properly and so now that I've determined that I can go ahead and build my project so let's take a look at how we're going to hook up our ATX power supply to use as a bench supply now as you'll recall the motherboard connectors for both version 1 and version 2 have all the signals we need for the power supply and that those signals are grouped in the color-coded wires I'm just going to show those color-coded wires on the hookup diagram and I'm not going to fill the wires to the two negative supply voltages because I'm not using them so I've got the black which is the ground the orange was 3.3 volts the red which is 5 volts the yellow with his 12 volts the green wire with his the power supply online this needs to be grounded to turn the power supply on the gray line what does the power good signal this will come to five volts when the power supply is operating correctly and the Purple Line which is the standby line this will go to five volts as soon as the power supply has been switched on I'm also going to need some additional components an SP ST switch this is going to meet my power on/off switch a power resistor to use as a load across the five volts I'm using an 8 ohm 50 watt resistor but you could also use a 10 ohm 10 watt resistor or something similar to LEDs any color you like one of them will be the standby light the other one will be the power good LED you'll also need some dropping resistors for those LEDs I use 330 ohms but any value from 220 to 470 would work just fine I used three fuse holders now these are actually optional but I decided they were a good safety option you'll also need binding posts for your voltage output so I'm using three for the 3.3 5 volt and 12 volt output as well you'll need at least one binding poster ground I'm actually using three ground posts one for each output voltage now we'll begin by connecting our down to the ground connection make sure to leave a lot of space with the ground connection because you're going to be making several connections to ground here next we'll connect our supply voltages to the fuses the 3.3 volt the five volt and the twelve volt we'll connect the other side of those fuses to their respective binding posts next we connect the PSO signal to one side of our spst switch the other side of our switch will be connected to ground next we'll take the gray power good signal and connect it to the a node of the power LED we'll take the purple standby signal and connect it to the a node of the standby LED will connect the cathodes of both leds to one side of the dropping resistor and the other side of that resistor to ground finally we'll connect their load across the five volt line between five volts and ground and this completes the wiring of our bags power supply so here we have my modified power supply as you can see there are substantially fewer wires coming out of it than we have before what I did was I eliminated a lot of the excess wires I just wasn't going to use and I just clipped them right at the circuit board for all the major supply voltages I took three wires these are 18 gauge wires so by putting 3 together it can handle substantially more current and for each one of them I put a lug on the end I crimped it then I soldered it and then I put some heat shrink tubing on it so it's pretty secure now this is the yellow one so this will be the positive 12 volts and we've got an orange one down here again I took three of them that's for the positive 3.3 volts now I've got three of the red ones over here for my positive five and I also took an additional red and a black and I soldered my resistor across them so this is the power resistor I'm using for a load now if your supply doesn't require a load you of course won't need to do that but it just took an additional red and black wire to do it then on top of that the ground wires there are a lot of ground connections so I actually took six of them and again soldered them up in groups of three to a lug and then put some heat shrink tubing over them so I've got two ground connections here then I've got the three individual connections that I'm going to need this is the power on the signal that when you send to ground we'll send power off to it this is the standby signal this has 5 volts on it as soon as the power is on and this is the power good signal it goes to 5 volts when the supplies operating correctly so I've got everything prepared to mount on a base and then hook up to my front panel and I'll show you those bits next now here's the base I'm going to be using from my power supply project it's a very simple wooden base I'm sure you can come up with something fancier than this but it does the purpose now I've got my terminal strip down over here so this of course is where I'm going to be connecting all of the wires from the power supply and all of the wires from the front panel in the front panel I will show you in a moment and that of course will have all my fuses and my binding posts for the voltage outputs now the front panel itself is going to mount with these three angle brackets and I don't know if you can see that but I've actually bent the brackets back a little bit just so I could sort of tilt the front panel back a little bit now these brackets here are all to mount the power supply one of them with the power supply if you take a look at the ATX supply there are two screws over here two taps for it then another tap over here and one down here so in order to mount it what I decided to do was I built a bracket at the back over here and I put a couple of brackets on over here and the supply just sits down in here and these holes line up with the screws at the back so I can just put a couple of screws in there to hold it this just clamps it at the side and on this side over here I used a taller bracket I've got this little self tapping heat metal screw now I was very careful to look in the supply and found there was nothing directly behind here and so by putting the screw in over here I can actually secure the supply down to the base over here so I'll put that in right now and then between that the screws have holded at the back it's pretty secure at least for the purposes I'm going to give it and then I've got my power resistor if you'll notice on the base here there's a couple of holes down here that have been drilled and so I'm going to mount the power resistor on there and connect all the wire to the terminal strips and then that part of the project is complete then all I really need to show you next is the front panel and how I'm going to mount it over here and wire it to the terminal strip so let's take a look at that now now this is the front panel that I've come up with for my power supply now again I've made it out of a piece of wood I know it's rather crude looking but it does serve the purposes as you can see I've got the outputs for the three point three the five volt and a twelve volt I've got the fuses mounted right above them and I've got three ground connections one for each voltage these are all of course disconnected together I've also got my slipped over here which can put it in the standby or power on mode and I've got the two LEDs I used the blue LED for my standby LED and a red LED for my power good now you'll also see that I added a power meter a volt amp meter that I put into the case and I've got an input to it over here that's the positive input and then the output that you'll be measuring the load from and I'll talk about that in a little while but of course this is an optional thing it's not part of the actual project and you don't need to include a meter if you don't want to now if you look on the back over here one thing I did I don't know if you can see this very well is for the ground I actually used a piece of 14 gauge solid wire and I use that as my ground I put it across all three ground connections and then ran it out to the terminal strips it's very solid so it actually does serve to support the base to a small degree as well and that way all of the ground connections I needed from everything I could to solder to as you'll see again I used three wires for the 3.3 v and 12 volts and in order to go to the fuses because those wire go to one side of the fuse holder the other side of the fuse holder goes to the terminal strips I just used the third piece of 16 gauge wire I didn't think I'd drop too much voltage or suffer too much current loss with a half-inch piece of 16 gauge wire over here otherwise these are the connections to my LEDs I probably can drop some epoxy or hot glue in the back here but they seemed to fit pretty nicely you'll note that I used heat shrink tubing over everything the dropping resistors that are associated with each led are actually underneath the heat shrink tubing and then it goes to a common ground which is on the back of this switch over here and this is the power-on slipped so it's got one lead going to the green wire and the other side of the switch going to ground and I've got the gray and the purple wires now the purple wire is the the standby wire so that gives you five volts as soon as the power supply is on I'm actually using that to power my little meter over here so that's what the other connection to the meter is and the rest of these connections are for the meter and again I'll explain that at the end of the video but as you can see it's basically a very simple panel and it'll go on the front over here I've got my angle brackets and so this will slip down just on the front and I'll wire the connections up to the terminal strip over here and then that will pretty well complete the power supply project and we can test it so I'm going to wire that up right now and then we'll give this a test all right now here's my supply I've placed the front panel on and I've fastened it down and I've connected all the wires so it's actually just ready to test now I've got the switch on the back off when I turn it on the supply will go into standby mode and you can see the standby LED you can also see the power came on to my power meter and that's because I'm powering it from the standby power supply and again the power meter is just an optional thing but it seems to be working right now now if I go and measure voltage however I won't have any voltage right now on any of my outputs and that's of course because the supply is in standby mode so it's placed it in the power mode and the power good light comes on over here you may be able to hear a little bit of fan noise ELISA pretty quiet power supply and now here's my 3.3 volt it's I've been measuring a little hot at about 3.5 volts and my five volts is just about bang on and my 12 volts the twelve point one seven volts is pretty good as well and so there you have it a bench power supply constructed from a ATX type power supply and this actually will be a very handy unit not only for the project I'm planning to use it for but for my workbench in general now of course I'm going to tell you a little bit about this power meter in case you want to add one of those on to your project so let's discuss that right now now there's actually a story behind the meter I'm adding to my power supply and didn't actually turn out to be the way I'd originally intended but in the long run that was a good thing and I'll explain what I mean by that I went over to my electronics store with the idea that I was going to buy three of these little meters and put one onto each supply voltage and that way I could measure the current draw of all three of my output voltages however when I got to the store they only had one in stock so I bought it and took it home in retrospect I'd wished I'd also bought a 3-way switch so I could just switch between the three voltages instead of the arrangement I have over here with the input connector but it is what it is however when I got the meter home I started looking online to figure out how to hook it up and found out that the shunt the thing that you use to measure the current is actually on the negative side of the meter and not the positive side and that creates a bit of a problem that would have created a real problem if I'd had three of them because then I would have had three output voltages whose grounds were at slightly different potentials it's still a valuable unit but in a way I'm glad I only got one of them now as you can see I've mounted it here in the panel and a committee voltage and it can measure current and this is my input connector and what I do is I connect the output voltage one of these three to the input connector and then I connect my load across here and I can measure the voltage as well as the current that the load is drawing now another thing about this meter when I went over to the store it was advertised as being one that could measure 0 to 100 volts at up to 50 amperes well looking at the spec sheets I've seen online yes it can do 0 to 100 volts but the maximum may be as low as 10 amperes so again it may not be the perfect meter for the project nonetheless let me show you how I wired it up and then we'll take a look at a quick test of the meter it is to watch it in action now the power meter module that I'm using is a model DSN VC 2 8 8 and on the back of it you will find two sets of connectors one set has two very thick wires a black wire and a red wire this goes across the current shunt it does not go across the power supply if you do this you'll literally short out your power supply there's also another connector with three wires a black wire a red wire and a yellow wire now here is how we hook this up the current shunt is hooked on the ground side so you take the black wire and connect it to the input ground you then take the thick red wire and connect it to the output ground the input voltage and output voltage are connected together next you'll take the yellow wire from the other connector and connect it to the input voltage this is the sensing wire and it measures that voltage the other two wires on the connector are a small black and red wire these are the power supply for the module there is two ways that you can wire this if you wish you can connect the red wire to your input voltage and use this to power the module however your input voltage needs to be between four and a half and thirty volts for this to work in my case I'm also measuring 3.3 volts so this won't work for me so I'm taking my red wire and connecting it to a five volt input which in my case is the standby voltage that comes from the power supply the black wire is then connected to ground and this completes the wiring of the DSN vc 288 module now let's take a look at it in action so let's give this power meter a test now I've got the supply on and standby mode and of course the meter is already powered up because it's using the standby voltage so what I've got over here is a power resistor and I've attached it this to a couple of cave this so I can plug it in I'm going to plug this in as my output load I'm going to turn on the power now of course I've got nothing connected to the meter right now so there's nothing for it to read so what you need to do is take a lead and connect it to the input and then go to whatever voltage it is you want to pass through the meter so we'll start with our 3.3 volts and it's reading three point four eight volts and you can see the current that we're pulling right now zero point one seven amperes is what this is reading and that's because of the load over here if I take off my load you'll notice that my voltage goes up a bit because there's no load on there and of course I've got no current that I'm pulling so let's pull it back in seems to sample every second or so so I noticed a slight delay when I make changes over here now let's go over to the 5 volts side and there we are we're reading 5 volts 0.25 amps is what we're drawing and we can now go over to our 12 volts side and it's measuring 12 volts at 0.6 3 amps so as you can see it's a relatively useful little meter it could be good for monitoring one specific output voltage just remember that this ground is not anymore at the same potential as these grounds because you've got the little shunt in here that it's using to measure the current and so that could be an issue you if you want to connect this ground to the common ground of another power supply but if you're just measuring something on its own this is a pretty cool little meter to use and so there you have it our power supply and it's meter all right I want to make one additional note to those of you who might be concerned about opening up an ATX power supply you might be concerned about the high voltages that are in there and it's a very valid concern or you might have purchased a new ATX power supply to use as a workbench supply and you don't want to violate its warranty by cutting a bunch of wires there's a number of solutions for that one of the solutions is that you can buy a kit or a premade board that is already set up to convert an ATX type power supply into a workbench supply and you can get these things they have a connector on them it's usually for the type 2 ATX apply with a 24-pin connector you simply plug the connector onto the board the board has the binding posts and the switches and the LEDs essentially the same stuff that we've wired up over here it's already on the circuit board for you you can get these circuit boards pre-made you can also get them as kits Sparkfun for example as one as a kit and it will allow you to do exactly what we've done today convert an ATX power supply into a useful workbench supply without even needing to open up the box so you might want to look into that if you're not willing to jump into your supply and start snipping things around at any rate that brings us to the end of this video I hope that you enjoyed it and as always you will find an article that accompanies this with the schematic diagram that we've used on the drone bot workshop comm website so you'll find a link below the video to that while you're on the website if you haven't already could you please subscribe to my newsletter it's my way of keeping in touch with you and letting you know what's going on in the workshop and there are a lot of changes happening in the workshop in the next couple of weeks and I'll be keeping in touch with you by the newsletter to let you know about those the newsletter is free there's no advertising in it to send me your email address and you're on the list and speaking about being on the list if you're not a subscriber to the YouTube channel please do me a favor and click the subscribe button I would really appreciate it and that way you would know when I create new videos here in the workshop so until next time please take care of yourselves I hope to see you very soon again here in the workshop good bye for now [Music] Oh

Channel: DroneBot Workshop

Views: 1,325,865

Keywords: build a power supply, convert a power supply, ATX Power Supply, workbench power supply, computer power supply, atx power supply hack, how to build a 12 volt power supply

Id: n_A-jkpjpcM

Length: 40min 51sec (2451 seconds)

Published: Sat Feb 02 2019