This instructable will show you how to make a very good bench power supply using mainly recycled parts. This is the really the "mark II", you can see "mark I" here.
When I finished my first bench power supply I was really happy, and used it very often, almost every day, until one day it decided not to work anymore, :( so... I realized I had to do it all over again, including the not that easy drilling on the metal of the ATX, etc. So this time I'm making a bench power supply that you can replace the ATX in no more than 2min.
Last time I did not take any pictures of the process, so I could only do a slideshow of the finished product, but this time I took lots of pictures, so I did this Instructable, which I hope you'll like.
May you decide to go ahead and build your own?... I would like to take the opportunity to say that I will be more than happy to help you with any questions you have, and also I will love suggestions so I can improve either this instructable or the bench power supply itself.
As the title shows, with this instructable I want to encourage people to recycle. There are lots of things around the house or even in the streets, that you can take components off, and use them later to make so many interesting things. I used as many recycled parts as I could for this project, and if you do the same, you could have a very powerful and COOL! bench power supply for almost nothing.
OK.. lets start with a view of what we will be making....
Step 1: Materials and tools
Here is a list of the materials and tools I used for this project. Some of them are optional, like the analogue panel meters, as you could use any multitester to check ether the voltage or amps.
The same with tools, you may want to use a different tool, just go ahead, and also make any suggestions so we all can learn.
Don't be scared of the quantity of materials, this project is not really difficult to make, trust me, if I've done it, anybody can.
1).- (1)Bread box.( Recycled, you could use any other enclosure that you can fit the ATX in with enough space)
2).-(3) Switches (2 single way switches recycled from old heaters, and a 2 double way switch recycled from an OHP)
3).-Cable connectors (Recycled from old amplifier, and from old TV)
4).-(1) ATX (Recycled from old computer)
5).-(3) PC Drive Molex to SATA Power Adapter (ebay £1.50, view)
6).-(1) 20-24 Pin ATX power adapter for Computer PSU (ebay £2.77, view)
7).-(1) USB connector (Optional, Recycled from old computer)
8).-(2) LED's (red, green) , (Recycled from old computer)
9).-(2) 5K Potentiometer (One Recycled, and the other one bought for £1.35, view)
10).-(2) Potentiometer knobs ( Recycled from old amplifier)
11).-(1) empty can of coke (Recycled)
12).-(1) 8cm computer fan (Recycled from bench power supply mark I)
13).-(1) Magnetic Catch (Bought £1, view)
14).-(1) IEC cable (The cable that connects the computer to the power socket, Recycled)
15).-(1) IEC connector( Recycled from bench power supply mark I)
16).-Piece of trunking (Optional)
17).-Some cable ties.
18).-(1)Fridge magnet ("Stolen" from the fridge)
19).-Some wires. (Recycled from extension lead)
20).-(2) 8cm Fan grills (Recycled from old ATX)
21).-(2) Screw eyes.
1).-(1) LM350 Adjustable Voltage Regulator (ebay £0.50)
2).-(1) 560 Ohm Resistor (Recycled from old radio)
3).-(2) 1N4001 Diodes (Recycled from old radio)
4).-(1) 0.1 uf Capacitor (Recycled from old radio)
5).-(1) 10 uf Capacitor (Recycled from old radio)
6).-(1) Heat sink (Recycled from old radio)
7).-(1) 10W 10 Ohm Wirewound resistor (Maplin £0.48)
TOTAL COST = £7.60
If you want to use analogue meters like me, and you also want to make the continuity tester, you will also need in addition to the previous list:
1).-(1) Voltage panel meter (Optional £6 ebay, view)
2).-(1) Amp panel meter (Optional, £6 ebay, view)
3).-(1) 6V Mini Relay (Optional, £1.31, view)
4).- (2) 9v PP3 Battery box (£1.29 each, view)
5).-(1) 9v Buzzer (Optional, £1.99, view)
6).- (2) 9V PP3 Batteries
7).-(1) 1N4001 Diodes (Recycled from old radio)
TOTAL COST = £16.59
GRAND TOTAL= £ 24.19
2)-Hot glue gun.
3)-Dremel (With a cutting disc and round sander)
4)-Hole saw ( about 7cm)
8)-A Dymo (Optional, I don't have one, my wife did the labels for me at work, but you could print them and tape them)
note: In this list of materials I specified where I found some of the parts I've used. I'm not saying that you need to buy an OHP or a home heater to get the parts, but maybe you already have some of these things at home and they don't work any more, or you can find then on the street, or in garage sales or in markets like the one you see in the picture below.
Step 2: The enclosure
For my bench power supply I'll be using a bread box. This one had a glass door, so the first thing I did was replace the glass with a wood panel. I added this step in case you face the same problem, but if your enclose is ready to go, skip to next step.
One thing to take into consideration when choosing an enclosure is that if it is made of metal, not only will be difficult to make the cuts and holes, but you'll face the problem of the conductivity of metal, so if your connectors are not isolated that'll become a problem. Also make sure the ATX will fit inside.
1).- Take the glass door out, and place it on top of the wood panel so you can draw the lines with a pencil and cut an exact size wood door.
If you want to make sure you don't do wrong cuts, you could always place the glass door on top of the wood panel and hold it with a clamp (see pics).
2).-I used the same handle for the door so I had to use some sticky stuff remover and a knife to get it out of the glass.
Step 3: Making the front panel
1).- With the door outside the bread box, mark everything that is going in there, like the cable connectors, switches, potentiometer (when marking where the potentiometer is going to be, pay attention to the size of the knob), LED's, etc...
2).- Once you're happy with the distribution of everything, start cutting with the dremel, using the cutting disc.
Make sure everything fits through the holes (you could use the circular sander with the dremel or sand paper if it needs to be a bit bigger)
3).- Then something I forgot to do is erase all the pen marks and writing. If you do it now, it would be a lot easier than once all the connectors are fitted.
4).-Now hot glue everything from the back of the door.(see pics)
Step 4: Placing the ATX
When deciding where to put the ATX, take into consideration not to block any of the vents or the fan. In this case I decided to place it upright as you can see in the picture.
The goal of this project is to be able to change the ATX really quickly and without having to take out any screws, so I cut 4 pieces of wood and then hot glued them to the sides of my enclosure after marking with a pen where they'll go, that way I can slide the ATX in or out really easily.
I also fit a self adhesive trunking to protect the power cable.
Step 5: Power connector (IEC connector)
Mark where you want to put the IEC connector. I placed it at the back as this will help me not to put the unit to close to the wall which will stop the air flow.
1).- Mark the side of the connector with a pen, drill some holes near the line you drew and finish the job moving the drill one side to another until all the holes merge together.
2).- Make sure it fits in, and fit it with two screws (Later we'll take it out again to solder the cables)
Step 6: Ventilation
Ventilation is very important in this project as you are fitting an ATX inside an almost sealed enclosure. If you don't do anything about ventilation, the ATX will get really hot and eventually will stop working.
1).- In this case as the ATX is upright, I fitted one fan at the bottom of the enclosure and made a hole on the top of the enclosure, as the ATX is always taking air out of the PC. So the fan at the bottom will blow air inside which will get through the ATX and then will get out at the top vent.
2).- To make sure the air that is blown from the ATX finds its way out, I decided to help it a bit by cutting a coke can and fitting it on top of the enclosure. (see pics).
3).- And then I glued a fridge magnet to the can with some epoxy (this will stop unwanted noise from the vibrations)
Step 7: Making the voltage regulator.
The voltage regulator I made is based on a really good instructable you can see here. The only thing I changed was the voltage regulator itself, for a more powerful one: the LM350 3A.
The schematic is in that instructable but I did a graphic schematic to make it a bit easier. You can see also my circuit on its heatsink.
Step 8: Soldering the cables, schematic
1).- Now is the moment to solder all the cables on the front panel, and here is a PDF file and a JPG file of the full schematic.
In this schematic there are two 5k potentiometers, that's because my voltage panel meter goes just until 20V but in case I need a bit more, I can use the other potentiometer of 5k on series as a booster. (you could place a switch in series with the potentiometer and open the circuit to give the boost, but it will go straight to the maximum voltage, with this second potentiometer you will be able to control that voltage)
2).- Once you have finished soldering the cables, use some cable ties to make sure nothing will come loose when opening or closing the door.
3).- Glue the door with epoxy, I used wood epoxy.
In the schematic you'll see how I used the double two way switch to swap the negative cable that goes into the voltage regulator. I can use ether -12v or 0v (ground), the reason I've done this is because the -12v is not as powerful as the 0v output. So with setting 1) I can go from 1.2V to 23V but is limited to 2A, and with setting 2) I can go from 1.2v to 11V up to 3A (the voltage regulator is 3A) Here is a video were you can see the difference:
To connect the USB output you just need to use the ground for the negative and the +5v for the positive. ( if you're not sure witch cables to use see here )
Step 9: AC Power cables
1).- Solder the AC power cables. Be really careful not to leave any of these cables exposed as they could be really dangerous. I used some heat shrink to cover the wires.
2).-You could also fit the voltage regulator near the fan so it cools down as the air flow inside.
Step 10: Fitting cables from the door to the inside.
Using a couple of screw eyes, fit the cables with some cable ties, leaving enough cable to be able to open the door freely.
Step 11: The quick release connectors.
1).- Take the molex to sata power adapter and cut them, we don't need the sata bit for this project, but save it for future projects.
2).- Join all the cables together like you can see in the picture. (Some ATX have more than 3 molex connectors, but with 3 you've got more than enough for this project.)
Using a connection block join all the cables. ( this is done so if the ATX blows you don't need to cut or solder any cable, just disconnect the broken unit and connect the new one)
3).- Do the same with the 20-24 Pin ATX power adapter. you need to keep the side with 24 pins.
Step 12: Fitting the wirewound resistor
Even when I've noticed no difference with the resistor or without it, I read everywhere that there is a need of a 10 Ohm wirewound resistor, so I fitted one.
These resistors get really hot when in use, so I found a heat sink for it, and placed it near the fan.
Then, I connected it to ground and +5V.
Step 13: Fitting a magnet catch to the door
There are lots of cables so the door will tend to open. The way I solved this is with a magnet catch. I screwed the magnet bit to the enclosure and glued the metal bit to the door with some epoxy.
Step 14: Cutting unwanted cables from ATX
Before fitting the ATX inside we can cut unwanted cables and connectors. As you can see in the picture, I did cut the secondary cable and connector and left those that go straight to the ATX. Make sure you cut them really close to the connector so there is not danger of short circuit.
You could also use some cable ties to make the cable as less bulky as possible.
Step 15: Labeling
Use a Dymo to make the labels. If you don't have a Dymo ( like me), get somebody to do it for you. At the office my wife has one, so she did it for me. When doing the labels, just do as you would understand them.
You can see in this picture lots of labels, I thought there were too many, so I took some out later on.
Step 16: Fitting the Voltmeter and Ammeter
After a long wait, I finally received the digital meters form HK.
1).- Before fitting them in place, make sure they work.
2).- Place them in the hole you made for them. It may require some sanding, we want it to be tight in the hole.
-If you are using digital metes like mine, you need to power them with a battery, DO NOT TRY TO POWER THEM WITH THE ATX. This not only won't work, but could also damage the meters ( I broke one trying it )
3).- Use a relay to activate the power to the voltage meter and a switch to power the ammeter. The reason I've done this is so I can use the ammeter with other power supplies.
4).-To fix the batteries use a couple of battery boxes. I glued the lid, so I can slide the batteries in and out.
Step 17: The continuity tester
I decided to install a continuity tester on my bench power supply.
1).- Find a good place to fit the banana connectors. Mark where they'll go
2).- Drill the holes, I did not have a 12.4mm drill bit, so I used my step drill bit.
3).- Fix the connectors with the nuts and solder the cables (see schematic on step 8)
4).- Hot glue the buzzer.
Step 18: You're done!
Well... you're done! I hope this Instructable helped you make a bench power supply.
Remember there are lots of components that can be recycled from old stuff that you have at home or even found on the street.
I have to apologize for lots of mistake I'm sure I've done in this Instructable as English is not my first language.
Step 19: Replacing the PSU
Replacing the PSU couldn't be easier. It only takes a couple of minutes.
REMOVE THE OLD PSU
1).- Disconnect the molex connectors and the 24pin connector.
2).- Disconnect the main power connector on the PSU.
3).- Lift the aluminium that helps the vent flow.
4.)- Slide the PSU out of its place. (this is in my case, maybe you've done it differently)
INSTALL THE NEW PSU
1).-Slide the PSU in its place.
2).-Connect the main power connector on the PSU (If it has a switch make sure is in the on position)
3).-Pull down the aluminium until the magnet sticks to the metal of the PSU.
4).-Connect the molex connectors and the 24pin connector.