Almost a Power Supply




Introduction: Almost a Power Supply

About: For now see me at:

Every electronics project needs power. You can spend a lot of time building supplies or a lot of money on batteries. If you build projects to use in your lab you can use one supply with a lot of projects plugged into it. Then just cable up the project and plug it in. In this project I describe a way that I have done this that I thinks works out pretty well. You still need some sort of power supply ( there are lots on instructables, many base on old computer powere supplies ) I use mostly salvage parts, but you can adapt it to other parts, and buy them if you wish. When you are done you can use "free" cables to connect up to 6 projects at a time to power.

Step 1: Materials

Cable and Plug: I use one for each project they are the PS2 style Mouse and keyboard cables. People are throwing a lot of these out, fairly easy ( at least for me ) to find.

Jacks I use 6 per system I get them from old computer mother boards. The ones I used were dual plugs one on top of the other. So I can plug in up to 6 projects at once.

.1inch perforated board ( perfboard a pretty standard electronics item )

Case for the whole thing, I had one around.

Power supply, I wired up to one that I had, a computer power supply can be useful as they often supply +12, -12, and +5 volts. There are several power supply projects on instructables, some are very good.

The cable have n wires plus a ground the ground is a shield for the other wires, I did not use it. The other wires are colored.

Step 2: Tools

Tools are good. Man is the only animal that borrows tools. Go and get some now. Soldering iron, wire cutters, strippers..... are good ones to start with. Epoxy glue may help you put it together. Something to cut and shape the enclosure would be good.

Step 3: Building It.

The sockets I found had 3 large tabs on the bottom, the middle one made the part difficult to mount so i broke it off. The other 2 large tabs did not fit into the perfboard so I drilled out the holes until it did fit. Then I epoxied the sockets to the perf board. When the epoxy was hard I wired all the identical pins in parallel. To identify the needed pins ( not all pins are needed ) I inserted a keyboard plug and use a continuity tester ( or you can use an ohm meter ) on the colored wires. The common connection for each pin was brought to one place on the board where another cable was connected that in turn went to the power supply. When all the wiring was complete I mounted the perf board and sockets in a small plastic project box, a hole was cut in the box to access the sockets.

Step 4: Other Ideas

Add an LED to indicate that the power is on.
You can make a one socket version of the box to supply your project when it is out of the lab. This could be powered by a battery or wall wart ( especially if you do not need all three voltages.
You could add this as an output connection built into your power supply rather than as a separate project. Whatever works best for you.
You can also get the junk parts for USB connections ( computer mother boards and broken USB devices ). I would use 5 volts only for this so you do not blow out a USB device on the + and – 12 volt connections. If you supply has only + and – 12 volt connections then put a 5 volt regulator in the box to get all 3 voltages.
One instructable showed a proto board as the power distribution system. Could be useful check it out at:
Old connectors from the back of speakers have a level you press down and insert a wire, might be a nice connection for projects.

The wire in the cable is pretty thin, good for perhaps 100ma, would not use for high power devices.

Step 5: Using It

Connect it to a power supply, Connect one or more things to it. Turn it on. See photo.

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    14 years ago on Introduction

    I finally broke down and bought a benchtop adjustable power supply on EBay. The one I got has three channels - one fixed 5V@2A and two adjustable 0-15V@0-1A. The two adjustable outputs can be either voltage limited or current limited, and can be combined to provide one output at 0-30V@0-1A or 0-15V@0-2A. It's the most-used piece of equipment on my bench. An enormous improvement over batteries and wall-warts.

    Callum Snowden
    Callum Snowden

    Reply 10 years ago on Introduction

    I got one for my birthday a few years ago from maplin and it was only £60, 0-35V adjustable @ 0-2.5A, fixed 5V/12V outputs at 500mA. Still going strong apart from current limit doesn't like limiting low-current loads


    14 years ago on Introduction

    Great idea! Especially if your working on more than one project at a time.


    14 years ago on Introduction

    Nice! You might want to fix up the 2nd paragraph in step 1, there is a lot of those A symbol things.


    Reply 14 years ago on Introduction

    Yes, I took them out a couple of times, but they keep coming back, why? Got me.

    Keep in mind most computer power supplies have +12v, +5v, +3.3v, -3,3v, -5v, -12v, and that you can mix and match these. ie: +12v and +5v results in 7v. I have a power supply with 12v, 5v, and 3.3v taps and it really is invaluable. I prefer 4mm bullet connectors myself but thats personal preference.