bobsbeer
Well-Known Member
This is a How To make a versatile power supply to use with pumps, solenoid or motorised valves and other accessories from an ATX computer PSU.
It is easy to do, and as long as you are proficient at following instructions will take an hour or so, to put it all together once you have all your bits. Total cost is about £10 or less, not including the PSU. But for that you get a very powerful 12 or 24 v PSU. Good enough to run a mag pump, or with a bit of extra modding to run a solar pump with speed control. All this can be made with a little work from a redundant ATX power supply stripped from an old desktop computer.
They usually supply a range of voltages from the spaghetti bundle of wires that come out of the back of it. We don't need all of them, so don't get too worried. The good bit is that with a combination of the wires we can get 24 v, 12 v and for anyone who fancies running an Arduino or Raspberry Pi, it also chucks out 5v. It also does 3.3v, but that's not much use for our purposes, but it's there if you need it.
Typical outputs max amperage would be: 12v: 15 amp, 5v 30 amp, so plenty of power to rock that solar or mag pump. But before we get going the usual small print blurb.
ELECTRICITY CAN KILL. :electric: IF YOU DO NOT FEEL COMPETENT IN DEALING WITH 240vAC POWER APPLIANCES, DO NOT ATTEMPT TO USE THIS HOW TO. We may be talking about 12/5/3.3v DC which in themselves are fairly harmless, but this is a 240v AC power supply plugged into mains voltage. SO BEWARE. I do not pretend to be an electrician so take these instructions as a guide rather than a definitive text. If you are unsure ASK.
The next MUST READ. Inside the cover of this power supply are a bunch of very powerful capacitors designed to kill you. If you go poking around inside with a bare finger, or metal instrument you may be in for a big surprise. So, do NOT open or attempt to touch the insides if it has been recently switched on. The capacitors are designed to discharge VERY quickly when required, so you have been warned. They will discharge on their own over time, or you can plug a load into one of the outlets. But leave it alone for a couple of days before opening the cover. Either way be careful. Anyway this will give you time to gather the bits and pieces needed for the project.
So assuming the above hasn't put you off, lets get going. First off, read the whole How To thoroughly to the end. As you read you will notice that you need to make a few decisions along the way depending on how you plan to use the power supply. These decisions will determine what bits you need.
This is the list of bits I used.
Maplins are a good source for all the bits, but if you don't mind waiting you can get them cheaper online. I have put links to the various bits, but check around.
Bits
ATX power supply - I had one laying around but they can be purchased quite cheaply on the internet. Or look in the dump/freecycle. Loads get thrown away inside pc's and have years of use left in them.
10w 10ohm load resistor - We will come to this later, but suffice to say you need one. About 85p or less
LED of your choice - Not necessary but it looks good. About 75p or less
330 k resistor - Only needed if you are using an led
A set of banana socket connection posts plus plugs - You will use these to connect the various appliances £3.79 set of six
143mm x 83mm x 38mm project box - To mount the banana posts £3.42
A few small cable ties - To fix the load resistor
Some 5mm heat shrink tube - To cover joints
A set of 4 rubber feet 99p 0r less
Tools
Phillips screwdriver
Soldering iron
Snips
Drill
So lets get going
First off take off the cover. Most have four screws on the top. Two may be covered over by stickers just to fool you, so check under any stickers. See the photo below. There may also be another screw on the side. Mine had a transformer coil screwed to the top cover in the middle, so watch out as you may unscrew the wrong thing. Take the screws out and put to one side. You will need them later to put it all back together.
This is what you will be faced with:
Note the big capacitors on the left, but there are others. :grin: But you will be relieved to know we don't need to go anywhere near them. The bunch of wires coming out of the back is our interest, but we don't need all of them.
This is a list of the different colours you will find.
The wires
The first task is to snip the cable ties holding the bundle together. Take them out of the box gland and cut off the molex connectors. I would cut them off about 2 inches before the molex connector, as you can then reuse the connectors in future.
Once you have cut all the wires, separate them into different colour bunches. You will now have a bunch of black, red, orange , and yellow ones. There are a few which there are only one of each colour. Gray, green, brown, blue and purple. I will come to each in turn.
Because there wasn't much space inside mine to mount the banana posts on the back wall, I decided to fit a small project box on the top and mount the outlets in that. You may find on your model that you do have space, so decide on where you are going to fit them and proceed. Drill the holes for the posts and the LED if you are using one. Be careful you don't get any metal bits on the circuit board. They may cause a short when you power up. Put cling film over the board if you are going to drill the metal enclosure.
The load resistor:
As these power supplies are not designed to be 'on' without a load, you need to place a small load into the circuit. Hence the 10 ohm 10 w resistor. There is some debate whether this is important or not, but the general consensus is that you do, so I recommend you fit one. It helps to smooth the power and ensure you get the full voltage. These get warm in use, so I recommend you fix this onto one of the vented sides with the cable ties. First off decide where you are going to put it. Then take a black wire and a red one. Look at where it is going to be fixed and trim the wires to fit. Don't make them tight, but you don't want too much excess wire floating around when you put the lid back on.
I put a small length of shrink tube on each end leaving about 10mm of the wire exposed on the resistor. Also put a length of shrink tube on the red and black wires. Push them along out of the way. Expose the ends and solder one wire to each side of the resistor. Once done slide the shrink tube over the join and shrink it to fit. Once done there should be no exposed wires. Now position the resistor on the chosen vent area and fix in place with 2 cable ties. ( I know I used one, but I did add another after taking the photo. :grin: )
You can get other shapes of resistors that have a suitable resistance but are more easily attached to the casing. Here is an example, but Maplins only had the type I used. But the type below would be easier to fit and have better heat dissipation. This one was about £2. Anyway look around before you decide.
The Green wire.
This is important and needs to be trimmed back and connected to a black wire. Just solder and cover with shrink tube. If you don't do this, the unit will not turn on. These power supplies are more properly called Switch Mode power supplies and strangely enough are designed to be connected into the motherboard and other peripherals of a PC. In other words they will only switch on if connected to what it thinks is a computer. So to fool it, we need to join the Green wire to ground.
The LED
This is not important, but looks cool when you switch the unit on, and makes it easy to see that it is on. But as the unit has a fan, you will know when it's on if the fan is running, so it's up to you. But if you do go with an led this is how to connect it up. For those not familiar with LED's they are polarized. You will notice that one wire is longer than the other, and on one side there is a flat spot. The longer wire is +v and the flat side is -v. The led also needs a 330 ohm resistor in series.
We are going to use the Gray (power okay, +5v) wire and connect to one of the black wires. Again sliding heat shrink tube onto the wires before you join. Trim the wires to suit your desired location. Solder the resistor to the black wire and the +v long wire on the LED to the Gray wire. Then solder the resistor to the -v leg. Cover the joins with the shrink tube.
If you have decided to forego the LED then just cut back the gray wire, and cover the bare end with shrink tube. It is an important wire if you were connecting up a pc, but it's of no value to us. Hence the use as the power source for the LED.
The Purple Wire
The purple wire is of no use to us, so cut it back and seal the end.
The Brown Wire
This wire needs to be joined in with the orange wires. On a pc it is a signal wire and needs to be connected in, so just bunch it with the orange wires. But if you are not using 3.3v then trim it off at the board.
The Power Wires
Our main interest are the Yellow, Red and Blue wires.
Yellow
These are + 12v. You will have about 6 wires coming off the back. To ensure you have enough capacity to run a pump you will need at least 2 wires on the post. You may also want to have 2 x 12 v outlets. So just divide the wires between the 2 posts. But this depends on whether you want a 24v outlet, so see the Blue Wire next.
Blue
You will have 1 of these. This is minus - 12 v and if combined with a + 12 v yellow wire will give you 24 v. This may be useful depending on your intended use. So before you chop it off decide if you need it. You may want to put it on the box just in case. I didn't use it, but I left it long in the top project box covered with shrink tube should I decide to change the design.
Red
This is + 5 v. You will have about 7 of these. One is being used for the load resistor. Again depending on your intended use you may want to have more than one +5v outlet. In which case split the number of wires between the outlet posts. If you only want one outlet then just use 2 red wires onto the outlet. 2 wires ensures you have a decent current. Do this for more outlets if you want them. There would be nothing to stop you having 6 outlets if that's what you wanted. Don't forget the amperage is divided between all the outlets. I just used 1 5v outlet. But the choice is yours.
White
This wire is -5v, but if combined with a Red will give you 10v. Probably not much use in our brewery setup, but consider if you will ever have a need for 10v before you chop it off.
Orange
This wire is +3.3v. You have about 4 of these. Unless you are planning on brewery automation down the line, it is of little use. But you may want to consider putting one outlet in just in case. You will only need about 2 of the wires. If you do put in a 3.3v outlet, remember to add the brown wire to the post.
The Black Wire
These are the ground wires. You will have about 15 of these. One is being used to connect to the load resistor, and another is to connect to the Green wire. Depending on the number of things being used at any one time you will need a Ground for each, so you should consider at least two, if not three Ground outlets. I used 2 wires on each post. This number is determined on the number of wires you have used on the preceding posts. So if you used 5 red wires on one post, join 5 black wires to the ground posts. It's not good to have less wires than what's going out as they may get warm depending on the current. But if the max was 2, then 2 ground wires is all you need. Use the same number on each ground outlet. I.e. 2 and 2.
Unused Wires
You will no doubt have a few unused wires. Trim these down close to the main pcb if you can, or trim to about 1" and seal the ends. A cable tie around the bunch is good near the end of the cut wires. If you have a hot glue gun. Put a dab of hot glue on the ends to seal them.
That's it. All that is left to do is screw the top cover back on. You now have a very useful power supply to power your pumps or other peripheries such as valves and or an Arduino.
As I said at the beginning, this psu didn't have room to fit the outlet posts inside the unit, so instead I mounted a small project box on the to top of the unit. You can see the internal wiring. I chose 3 x 12v and 1x 5v for my outlets, but see above on the available choices. I don't want to confuse you with my outlet colour choices, as the internal wires don't correspond with my posts. Choose colours you will recognise. I also marked them as you can see in the final finished photo.
Finally Speed Control
For those who have or plan to use 12 v solar type pumps, then to control the flow you will need some form of speed control. I have not included it into this project as I use Mag pumps, but it would be easy to add this in, especially if you use a project box as I have done. But as this is outside of the scope of the present How To I will point you in the right direction if you want to add it.
Here is a link to an easy speed control circuit, which could be added to the box. DC Motor Speed Control
There are no doubt others available on the internet if you google it.
One final VERY BIG word of warning. These PSU's are NOT waterproof, and the fan may be sucking air into the unit. So you need to locate this unit well away from any water, or possibility of getting wet. Failure to follow this basic warning could result in the end of your brewing career. You have been warned. :electric:
If you want to know more about the inner workings of the ATX PSU there are a number of internet resources. HERE is the Wikapedia entry.
There are also a few How To's on the internet to convert ATX power supplies, mainly to lab power supplies, but similar to our needs. This is a good one, and the one I originally followed. HERE. And another good one HERE.
It is easy to do, and as long as you are proficient at following instructions will take an hour or so, to put it all together once you have all your bits. Total cost is about £10 or less, not including the PSU. But for that you get a very powerful 12 or 24 v PSU. Good enough to run a mag pump, or with a bit of extra modding to run a solar pump with speed control. All this can be made with a little work from a redundant ATX power supply stripped from an old desktop computer.
They usually supply a range of voltages from the spaghetti bundle of wires that come out of the back of it. We don't need all of them, so don't get too worried. The good bit is that with a combination of the wires we can get 24 v, 12 v and for anyone who fancies running an Arduino or Raspberry Pi, it also chucks out 5v. It also does 3.3v, but that's not much use for our purposes, but it's there if you need it.
Typical outputs max amperage would be: 12v: 15 amp, 5v 30 amp, so plenty of power to rock that solar or mag pump. But before we get going the usual small print blurb.
ELECTRICITY CAN KILL. :electric: IF YOU DO NOT FEEL COMPETENT IN DEALING WITH 240vAC POWER APPLIANCES, DO NOT ATTEMPT TO USE THIS HOW TO. We may be talking about 12/5/3.3v DC which in themselves are fairly harmless, but this is a 240v AC power supply plugged into mains voltage. SO BEWARE. I do not pretend to be an electrician so take these instructions as a guide rather than a definitive text. If you are unsure ASK.
The next MUST READ. Inside the cover of this power supply are a bunch of very powerful capacitors designed to kill you. If you go poking around inside with a bare finger, or metal instrument you may be in for a big surprise. So, do NOT open or attempt to touch the insides if it has been recently switched on. The capacitors are designed to discharge VERY quickly when required, so you have been warned. They will discharge on their own over time, or you can plug a load into one of the outlets. But leave it alone for a couple of days before opening the cover. Either way be careful. Anyway this will give you time to gather the bits and pieces needed for the project.
So assuming the above hasn't put you off, lets get going. First off, read the whole How To thoroughly to the end. As you read you will notice that you need to make a few decisions along the way depending on how you plan to use the power supply. These decisions will determine what bits you need.
This is the list of bits I used.
Maplins are a good source for all the bits, but if you don't mind waiting you can get them cheaper online. I have put links to the various bits, but check around.
Bits
ATX power supply - I had one laying around but they can be purchased quite cheaply on the internet. Or look in the dump/freecycle. Loads get thrown away inside pc's and have years of use left in them.
10w 10ohm load resistor - We will come to this later, but suffice to say you need one. About 85p or less
LED of your choice - Not necessary but it looks good. About 75p or less
330 k resistor - Only needed if you are using an led
A set of banana socket connection posts plus plugs - You will use these to connect the various appliances £3.79 set of six
143mm x 83mm x 38mm project box - To mount the banana posts £3.42
A few small cable ties - To fix the load resistor
Some 5mm heat shrink tube - To cover joints
A set of 4 rubber feet 99p 0r less
Tools
Phillips screwdriver
Soldering iron
Snips
Drill
So lets get going
First off take off the cover. Most have four screws on the top. Two may be covered over by stickers just to fool you, so check under any stickers. See the photo below. There may also be another screw on the side. Mine had a transformer coil screwed to the top cover in the middle, so watch out as you may unscrew the wrong thing. Take the screws out and put to one side. You will need them later to put it all back together.
This is what you will be faced with:
Note the big capacitors on the left, but there are others. :grin: But you will be relieved to know we don't need to go anywhere near them. The bunch of wires coming out of the back is our interest, but we don't need all of them.
This is a list of the different colours you will find.
The wires
The first task is to snip the cable ties holding the bundle together. Take them out of the box gland and cut off the molex connectors. I would cut them off about 2 inches before the molex connector, as you can then reuse the connectors in future.
Once you have cut all the wires, separate them into different colour bunches. You will now have a bunch of black, red, orange , and yellow ones. There are a few which there are only one of each colour. Gray, green, brown, blue and purple. I will come to each in turn.
Because there wasn't much space inside mine to mount the banana posts on the back wall, I decided to fit a small project box on the top and mount the outlets in that. You may find on your model that you do have space, so decide on where you are going to fit them and proceed. Drill the holes for the posts and the LED if you are using one. Be careful you don't get any metal bits on the circuit board. They may cause a short when you power up. Put cling film over the board if you are going to drill the metal enclosure.
The load resistor:
As these power supplies are not designed to be 'on' without a load, you need to place a small load into the circuit. Hence the 10 ohm 10 w resistor. There is some debate whether this is important or not, but the general consensus is that you do, so I recommend you fit one. It helps to smooth the power and ensure you get the full voltage. These get warm in use, so I recommend you fix this onto one of the vented sides with the cable ties. First off decide where you are going to put it. Then take a black wire and a red one. Look at where it is going to be fixed and trim the wires to fit. Don't make them tight, but you don't want too much excess wire floating around when you put the lid back on.
I put a small length of shrink tube on each end leaving about 10mm of the wire exposed on the resistor. Also put a length of shrink tube on the red and black wires. Push them along out of the way. Expose the ends and solder one wire to each side of the resistor. Once done slide the shrink tube over the join and shrink it to fit. Once done there should be no exposed wires. Now position the resistor on the chosen vent area and fix in place with 2 cable ties. ( I know I used one, but I did add another after taking the photo. :grin: )
You can get other shapes of resistors that have a suitable resistance but are more easily attached to the casing. Here is an example, but Maplins only had the type I used. But the type below would be easier to fit and have better heat dissipation. This one was about £2. Anyway look around before you decide.
The Green wire.
This is important and needs to be trimmed back and connected to a black wire. Just solder and cover with shrink tube. If you don't do this, the unit will not turn on. These power supplies are more properly called Switch Mode power supplies and strangely enough are designed to be connected into the motherboard and other peripherals of a PC. In other words they will only switch on if connected to what it thinks is a computer. So to fool it, we need to join the Green wire to ground.
The LED
This is not important, but looks cool when you switch the unit on, and makes it easy to see that it is on. But as the unit has a fan, you will know when it's on if the fan is running, so it's up to you. But if you do go with an led this is how to connect it up. For those not familiar with LED's they are polarized. You will notice that one wire is longer than the other, and on one side there is a flat spot. The longer wire is +v and the flat side is -v. The led also needs a 330 ohm resistor in series.
We are going to use the Gray (power okay, +5v) wire and connect to one of the black wires. Again sliding heat shrink tube onto the wires before you join. Trim the wires to suit your desired location. Solder the resistor to the black wire and the +v long wire on the LED to the Gray wire. Then solder the resistor to the -v leg. Cover the joins with the shrink tube.
If you have decided to forego the LED then just cut back the gray wire, and cover the bare end with shrink tube. It is an important wire if you were connecting up a pc, but it's of no value to us. Hence the use as the power source for the LED.
The Purple Wire
The purple wire is of no use to us, so cut it back and seal the end.
The Brown Wire
This wire needs to be joined in with the orange wires. On a pc it is a signal wire and needs to be connected in, so just bunch it with the orange wires. But if you are not using 3.3v then trim it off at the board.
The Power Wires
Our main interest are the Yellow, Red and Blue wires.
Yellow
These are + 12v. You will have about 6 wires coming off the back. To ensure you have enough capacity to run a pump you will need at least 2 wires on the post. You may also want to have 2 x 12 v outlets. So just divide the wires between the 2 posts. But this depends on whether you want a 24v outlet, so see the Blue Wire next.
Blue
You will have 1 of these. This is minus - 12 v and if combined with a + 12 v yellow wire will give you 24 v. This may be useful depending on your intended use. So before you chop it off decide if you need it. You may want to put it on the box just in case. I didn't use it, but I left it long in the top project box covered with shrink tube should I decide to change the design.
Red
This is + 5 v. You will have about 7 of these. One is being used for the load resistor. Again depending on your intended use you may want to have more than one +5v outlet. In which case split the number of wires between the outlet posts. If you only want one outlet then just use 2 red wires onto the outlet. 2 wires ensures you have a decent current. Do this for more outlets if you want them. There would be nothing to stop you having 6 outlets if that's what you wanted. Don't forget the amperage is divided between all the outlets. I just used 1 5v outlet. But the choice is yours.
White
This wire is -5v, but if combined with a Red will give you 10v. Probably not much use in our brewery setup, but consider if you will ever have a need for 10v before you chop it off.
Orange
This wire is +3.3v. You have about 4 of these. Unless you are planning on brewery automation down the line, it is of little use. But you may want to consider putting one outlet in just in case. You will only need about 2 of the wires. If you do put in a 3.3v outlet, remember to add the brown wire to the post.
The Black Wire
These are the ground wires. You will have about 15 of these. One is being used to connect to the load resistor, and another is to connect to the Green wire. Depending on the number of things being used at any one time you will need a Ground for each, so you should consider at least two, if not three Ground outlets. I used 2 wires on each post. This number is determined on the number of wires you have used on the preceding posts. So if you used 5 red wires on one post, join 5 black wires to the ground posts. It's not good to have less wires than what's going out as they may get warm depending on the current. But if the max was 2, then 2 ground wires is all you need. Use the same number on each ground outlet. I.e. 2 and 2.
Unused Wires
You will no doubt have a few unused wires. Trim these down close to the main pcb if you can, or trim to about 1" and seal the ends. A cable tie around the bunch is good near the end of the cut wires. If you have a hot glue gun. Put a dab of hot glue on the ends to seal them.
That's it. All that is left to do is screw the top cover back on. You now have a very useful power supply to power your pumps or other peripheries such as valves and or an Arduino.
As I said at the beginning, this psu didn't have room to fit the outlet posts inside the unit, so instead I mounted a small project box on the to top of the unit. You can see the internal wiring. I chose 3 x 12v and 1x 5v for my outlets, but see above on the available choices. I don't want to confuse you with my outlet colour choices, as the internal wires don't correspond with my posts. Choose colours you will recognise. I also marked them as you can see in the final finished photo.
Finally Speed Control
For those who have or plan to use 12 v solar type pumps, then to control the flow you will need some form of speed control. I have not included it into this project as I use Mag pumps, but it would be easy to add this in, especially if you use a project box as I have done. But as this is outside of the scope of the present How To I will point you in the right direction if you want to add it.
Here is a link to an easy speed control circuit, which could be added to the box. DC Motor Speed Control
There are no doubt others available on the internet if you google it.
One final VERY BIG word of warning. These PSU's are NOT waterproof, and the fan may be sucking air into the unit. So you need to locate this unit well away from any water, or possibility of getting wet. Failure to follow this basic warning could result in the end of your brewing career. You have been warned. :electric:
If you want to know more about the inner workings of the ATX PSU there are a number of internet resources. HERE is the Wikapedia entry.
There are also a few How To's on the internet to convert ATX power supplies, mainly to lab power supplies, but similar to our needs. This is a good one, and the one I originally followed. HERE. And another good one HERE.
