There are a lot of ways that you can re-purpose and reuse old electronics. For instance, a computer power supply can make a great bench power supply for your workshop.
There are already a lot of tutorials online that show how to convert an old computer power supply into a bench power supply. But most of these designs require you to permanently modify the power supply itself.
Another option is to make an external adapter for your power supply. Any ATXpower supply can be plugged into the adapter. The adapter then connects the appropriate wires to a series of output jacks that can be easily accessed to provide power for your projects. This design lets you utilize the power supply without having to modify it.
Step 1: Materials
ATX Computer Power Supply
20 Pin (or 24 Pin) Female ATX Connector (these can be purchased online or salvaged from an old motherboard)
Plastic Project Housing
8 Female Banana connectors/ Bind Posts
Heat Shrink Tubing
Crimp-On Spade Terminals
12V DC Power Outlet (optional)
USB Extension Cord (optional)
Drill and Bit Set
Soldering Iron and Solder
Step 2: Background: Computer Power Supplies
Computer power supplies have a number of safety features that help to protect you and the power supply itself. Here are a couple that you need to know about.
Turning on the Power Supply
A power supply is designed to not turn on unless it is connected to a computer motherboard. This is controlled by the green "Power On" wire. Connecting this wire to ground (any black wire) will allow the power supply to tun on.
Minimum Load Requirement
Many power supplies require a minimum load current in order to stay on. Without this load the output voltages may vary significantly from the specified voltages or the power supply might shut itself off. In a computer the current that is used by the motherboard is sufficient to meet these requirements. If your power supply has a minimum output requirement, you can meet this by connecting a large power resistor across the output terminals. This is discussed in a later step.
Step 3: Identify the Wires on the 20 Pin (or 24 Pin) Connector
The green wire is the power on sensor. This wire is internally connected to 5V with a pull-up resistor. If you connect this wire to ground (any black wire) the power supply will turn on.
The purple wire is the +5 "stand by" power. This outputs a 5V signal even if the rest of the power supply has not yet turned on. This allows you to power any circuit that might control the ON/OFF signal.
The gray "Power Good" indicator. This wire is at 5V if each of the output wires is operating at the correct voltages.
To make the connections easier to identify, I used colored markers to color code each slot on the 20 pin connector.
Step 4: Solder Wires to the Female ATX Connector
Step 5: Cut a Slot in the Housing for Then Female ATX Connector
Step 6: Drill Holes in the Top of the Housing for the Banana Jack Terminals and the Power Switc
Once all the holes were drilled I inserted the switch and the power terminals and fastened them in place.
Step 7: Glue the Female ATX Connector to the Side of the Housing
Step 8: Connect the Green Wire to the Power Switch
Step 9: Attach the Banana Jack Terminals to the Top of the Housing
I inserted the post of each terminal into holes and tightened them in place with their screws.
Step 10: Connect Spade Terminals to the End of Each Wire
Step 11: Connect the Wires to the Appropriate Terminals
I connected the rest of the wires in ascending order according to their voltages. On the far left, I connected the 3.3V wire (orange). Then I connected the 5V wire (red), the +12V wire yellow, and the -12V wire (blue).
Step 12: If Necessary Add a 10W Resistor to Meet the Minimum Load Requirement
To take care of this, you can add a power resistor between the 5V terminal and ground. In most cases a 10 watt 10 ohm resistor will work. In very rare cases you may also have minimum output requirements on the 12V pin and the 3.3V pin. This will require additional power resistors.
These power resistors create a lot of heat. So if you add a power resistor, make sure that your project housing has adequate ventilation. In some cases you may even need to add a small PC fan to help dissipate the heat.
Step 13: Add a 12V DC Power Outlet (optional)
Step 14: Add a USB Power Outlet (optional)
Once the wires are connected, you need to mount it to the side of the housing. Trace the outline of the USB connector onto the side of the housing. Then use a sharp knife or a rotary tool to cut it out. You can then glue the USB connector to the side of the housing. I recommend using J-B Weld just like you used for the 20 pin power supply connector.
Step 15: Add Labels for Each Pair of Terminals
Now your power supply converter is complete.