PC Power Supply Project Box

Introduction

Are you looking for a solid project box for small electronics projects?  Does your electronics project require 120v and a cooling fan?  Do you have an old PC power supply sitting around?  If yes, consider turning that old PC Power Supply Unit (PSU) into a project box.  This instructable will tell you exactly how to do that.

**WARNING!!!! BEFORE CUTTING WIRES, USE A MULTIMETER TO CHECK THE CAPACITORS TO ENSURE THEY ARE NOT STORING ANY ENERGY. IT WOULD ALSO BE A GOOD IDEA TO LET THE SUPPLY SIT FOR SEVERAL DAYS FOR ANY CHARGE TO DISSIPATE.

Materials Needed

• PC Power Supply Unit (PSU)
• 1/8" thick 200mm x 150mm wood
• Four (4) #4-40 1/4" long screws

Tools Needed

• Phillips head screwdriver
• Wire cutter
• CNC router or wood saw
• 1/8 inch bit for router or drill for holes

Here is a link to my project where I am going to use this project box: Home Environmental Sensor Array

Step 1: Take out the unneeded electronics.

Remove the cover

First, take the cover off of the box.  There are four screws on the top of the PSU -- one on each corner. One screw is under the warranty label.  Just push through the label with the philips screwdriver.  The top lifts off and has three sides.

Cut all the Wires

Next, cut all of the wires coming off of the Printed Circuit Board (PCB).  Actually, you only need to cut the white and black power wires that connect to the power switch and the red and black wires that connect to the fan.  I like to cut all of the wires off and recycle the copper.  I know its not a lot but it all adds up.  Don't forget to remove the black collar from the wire bundle that comes out of the PSU.  You might want to use it in future projects.

Remove the PCB

After cutting off the wires, remove the PCB from the PSU.  There are four screws that hold the PCB on the PSU.  Remove those screws and the PCB just lifts out.  The PCB is probably not worth recycling.  

Remove the Power Switch

The last thing to do in this step is to remove the power setting switch since it is not needed.  The power setting switch would allow the PSU to work with either 120 or 240 volts.  I was able to just plug in a 120 volt power cord to the PSU after gutting it.  I'm not sure what would happen if you plug in a 240 volt power source.  

Step 2: Cut a wood base

Attaching a wood surface to the bottom of the PSU makes it more usable as a project box.  Circuit boards and other electronic parts can be attached to the wood easily and without shorting anything out.

I wanted to use the CNC router at the Milwaukee Makerspace to cut the wood mainly because I was looking for another project to do on it.

Design the cut

I'm not going to go into a lengthy explanation of how to use a CNC router but there are some basic steps.  Normally, one would start out by designing the cuts in the wood in a CAD program that produces STL files.  I used a free program called LibreCAD.  It runs on Linux.  

The wood piece itself is 145mm by 120mm.  There are four holes near the corners for the screws.

Fortunately, the STL file is included in this instructable.  Download it and load it into your favorite CAM tool.

Make the cut

Converting the STL drawing to a cut piece of wood is pretty straightforward.  First, load the STL drawing into a program that will create the g-code for the CNC machine.  Then load the g-code into the computer program that controls the router.  Setup the router and position the wood.  Start the cycle and sit back.

The Milwaukee Makerspace has a custom built CNC router.  The PC has software called CAMBAM that will convert the STL file to g-code.  There is also software called Mach3 that is used to control the CNC router.  The software used for your CNC machine will vary.

Step 3: Install the wood and close up the case.

The final step is to attach the wood inside the PSU.  This is probably the easiest part.  However, there is a slight trick.  the holes are drilled differently based on what side they are closest to.  The holes near the fan and power supply are a bit closer to the edge than the holes opposite them.  Put the wood in the bottom of the PSU and use the 4-40 screws to attach the wood to the PSU.

The project box is ready to accept components.

Here are some tips.

• Make sure that the ground wire stays connected to the frame.  Connect other ground wires to this connection.
• The fan probably says it needs 12 volts DC but it will run with as little as 3.  The more volts, the faster the fan will spin.