In this Instructable, we will be learning how to convert a 350W Computer ATX Power Supply Unit into a Lab power supply that is built into a panel that can fit into a cubby hole / shelf in your work station / desk.
Step 1: The Old Power Supply Configuration
As you can see by the picture below, I wasn't happy with my current Power Supply. It was bulky, took up space, and was rather unappealing to the eye.
The power supply tester (Bottom Left) is how I booted the power supply, all I had to do was turn on the switch on the back of the power supply. Since I don't use this tester for anything else, it will be used in this project. If you don't have one, then there are Instructables on this website that can teach you how to Modify the power supply to turn on/off without one of these devices. For the sake of keeping things short as possible, I won't go into details on that process.
The Box with the binding posts on it is how I used the power from the power supply (via Molex conenector) It has nothing to do with this project.
Step 2: Gather Your Materials
Here are the materials and tools you'll need to start this project:
- Screwdriver (and matching screws) (for mounting the panel to your shelf)
- Dremel with drill bit kit (recommended) (drill can be uses as a substitute)
- Wire Cutters
- Wire Crimpers
- Soldering Iron and Solder
- Box cutter or other sharp blade
- Pencil and Eraser
- Molex pin remover (Can be found in some car stereo or computer shops)
- Panel Material (I used the original 'backboard' from my desk that I never bothered to install. The material was very easy to manage).
- Banana Jack Compatible Binding Posts (Rather than buying these separately, I bought them with 'wall mounts/panels' and then removed the panels; this was a lot more cost effective)
- The Power Supply (Ideally a 300-350 Watt ATX should work for this project)
- Power Supply Tester (for booting up the Power Supply)
- Fan (80mm is recommended - I used a 60mm with a 80mm funnel adapter; I'll explain why later in this tutorial)
- An LED (color is up to your preference; I personally used green)
- A 470 Ohm Resistor (Recommend 1/2 W)
- A Power Switch (SPST should work fine) (Cover is optional)
- Hookup Wire (I used some old wires I got out of a broken ATX Power Supply)
- Electrical Tape
- Labels (Either using Label Paper or you can use regular paper / scotch tape)
- Banana Jack Plugs
- D-Sub Pins (these pins are used in Parallel / Serial cables)
Step 3: Preparing the Panel (Part 1)
As mentioned in the previous step, I used the back board from my corner desk to make the panel. Because it is essentially firm cardboard, it was rather easy to manage. It can be cut with a box cutter or other sharp blade. However because this material is flimsy in nature, I actually cut two panels of the same size, used tape to hold them together and after putting all the components into place and mounting it, i was able to remove the tape and it held itself together on its own.
Once you've selected and cut your panel to the preferred size, begin to make your measurements of where you will place your components. (I'm not going to give the measurements that I used only because some people may have different sized workstations or desks)
Step 4: Preparing the Panel (Part 2)
When drilling your holes, I strongly recommend starting with a very small drill bit to drill 'Guide Holes'. Do this on the side you made your measurements (the back of the panel). After you have your guide holes drilled, flip over to the front size of the panel and drill the appropriately sized holes for each of your components. (Depending on what kind of switches / binding posts / etc / you use, you may want to drill some 'test' holes into a piece of spare panel material, that way you can test different drill bit sizes so your holes aren't to big / small.
Again, I need to stress: If you are using the same panel material as this Instructable, then I recommend starting with guide holes on the back and the actual sized holes on the front. You'll see why when we get to Step 6.
Step 5: Inserting the Binding Posts and Other Components
Now that you have your holes drilled, you should be able to begin inserting your Binding Posts. I recommend that your holes should be sized so that the binding posts fit in snug and tight. After you have your binding posts put in, fasten them in by tightening the nuts / washer included with the binding posts (Most binding posts are sold with nuts / washers).
Do the same with you power switch. Insert it in the hole you drilled and fasten it with a nut / washer.
For the power LED, just place it in the hole you drilled. I would then recommend using hot glue to keep it in place, or it might fall out easily.
Step 6: Installing the Fan
Remember when I recommended the guide holes and then drilling the actual holes back in Step 4? Well if you look at the picture below you'll see why.
The fuzz you see around the holes is virtually impossible to remove using this material, and when I tried to install a 80mm fan, the fuzz interfered with the fan blades.
My work-around for this was to use a smaller fan, combined with a Funnel Adapter.
Make sure that when you're installing your fan you install it so the airflow is pulling air from outside of the panel to cool the components inside the compartment / shelf you install the Panel into.
Install this into the back of your panel.
Step 7: Final Inspection of Panel Components.
By now you should have all of your components mounted to the panel. Just go over everything you've done quickly, make sure everything is fastened securely. Once you've done that we'll move to the next step.
Step 8: Preparing the Molex Connectors
On the power supply, you should find two sets of standard Molex connectors. We will also be using the power connectors used to power old Floppy Disk Drives. What's a Floppy Disk Drive you ask? Come to think about it, I can't remember either..... : P
See the pictures below for details on what I explained above.
You will need to wire sets as shown below (totals 4 molex connectors)
Step 9: Wiring the Molex Pins to the Binding Posts.
Now we will attach the Molex pins to the Binding posts. If you used the same type of binding post I used in this tutorial, then your life just got that much easier. The molex pins fit very snug over the binding post contacts, so solder is not required. If you didn't use the same type of binding post, then you may be required to solder your molex pins to the binding posts.
There are 16 binding posts all together. The first column should be 12V, the second should be Ground (GND), the third should be 5V, and the fourth should be Ground (GND) again.
Just remember, the red molex wires carry 5V; The yellow wires carries 12V, and the black wires carry Ground signal.
I've included the binding post diagram again for quick reference.
Step 10: Installing the Power Switch
After installing the binding post wires, things got a little messy. So Instead of putting you through the hassle of trying the decipher my low resolution, blurry images as reference. I've designed some diagrams to help you in wiring the Power switch, the LED, and the Fan.
You'll need to cut the green wire on the motherboard connector cable bundle (There's only one green wire in a power supply anyway, so it should be easy to find). After cutting the wire I would recommend increasing the length of the green wires so you can reach the switch on the panel. Do this by stripping about 1/4 inch off the green wires, and then soldering extra hookup wire to the ends of the green wire.
After your green wire is of desirable length, solder the ends of the green wire to the contacts of your power switch.
(Also, at this time, if you haven't actually connected the Power Supply Tester to the Large Connector, now would be a good time to do this, as we'll be installing the unit after the next couple steps.
Step 11: Wiring the Fan
To wire the fan, take the yellow loose wire and one of the two black loose wires from the now disconnected floppy connector. Strip about 1/2 inch off the ends of the yellow and black wires.
Now for the fan. If your fan has three wires, then you'll need to keep the red and black wires intact. The yellow wire on the fan (Third Wire) needs to go, so cut it off completely. Also the fan connector needs to be removed as well, so cut it off as close to the head so your Red/Black fan wires are of good size. Strip about 1/2 inch off the ends of the red and black fan wires. Be careful doing this as the fan wire are thinner and more delicate.
Once you've prepared the wires, solder the black floppy wire to the black fan wire; then solder the yellow floppy wire to the red fan wire. After soldering, make sure you wrap the wires in electrical tape or shrink wrap.
(I know the diagram below doesn't show the fan attached to the panel; it's supposed to be by this step. I designed the diagram like that to better illustrate the wiring more than anything. I'll be using the same illustration technique for the LED in the next step).
Step 12: Wiring the LED
To wire up the LED, take the red loose wire and the remaining black loose wire from the floppy connector. Strip about 1/2 off the ends of these wires.
On the LED, made sure no to confuse the anode and cathode. The Anode is the Positive leg (Longer) and the Cathode is the negative leg (Shorter).
Solder a 470 ohm resistor to the end of the Cathode.
Solder the red wire to the anode.
Solder the black wire to the other end of the resistor.
Make sure to wrap your exposed wires with electrical tape or shrink wrap.
Step 13: Installing the Panel in the Shelf
By now your panel probably looks something like the image below. Before installing the unit, make sure the power supply tester is connected to the motherboard cable. You may want to plug in the unit and test it out before installation, only because it's a painful process to install the panel, only to find an error and have to uninstall it.
Once everything is in good working order, put the power supply into the shelf and then cover the shelf with the panel itself. While holding the shelf in place, drill some guide holes through the panel/shelf and begin to fasten the panel into the shelf with some screws.
Step 14: Final Touch
Last but not least, you'll probably want to put some labels over the binding posts so you can tell which ones are which.
After that you're all done.
This unit is perfect for anyone who needs to test their breadboard wire-ups or any other circuit.
I'll be releasing some more instructables soon for add-on features to this project.