Power supply from your CPU

How'd you like a high-quality regulated 5V and 12V bench supply for less than Rs 30?
It’s pretty easy, and you won't even need a soldering iron.

Inside every PC is good quality switching power supply. The exact details depends on the PC, but you can expect to find regulated 5V and 12V often at 200W or more of power. Modern PCs rarely consume that much power, so there is plenty of spare juice for your projects. The problem is how to get to it.

In this article I'll show you a quick and easy way to gain access to your PCs power supply. Of course, you need to be careful not to exceed the maximum current capacity of the supply--don't run your 100W stereo amp from the PC supply! For many projects, however, you can use the +5 and +12 supplies with no ill effects. This is pretty good for any digital device that needs highly regulated +5v and +12v. Logic uP microcontrollers (using parallel port to send RF signals and CMOS cams work great on this rigged up power supply.

Construction is very simple. Just remove an unused drive plate. These plastic plates cover the holes where you would install a floppy disk or a disk drive. I used a 5.25 inch cover, but if you only have a 3.5 inch cover open, that should work just as well. Be sure there isn't a disk drive behind the plate -- sometimes there is a hard drive hiding behind one of these plates.

Using a center punch/compass/long nail, mark 4 holes in the plate equally spaced Then drill out the holes to fit 4 binding posts; if u don’t have drilling equipment, use a cheap 20-30 w soldering iron to melt the hole thru and file the rough edges. . Mount the binding posts on the drive plate. You should use two black posts in the center 2 holes. It is nice if you can find a red post for the 5V supply and another color post (I used yellow) for the 12V supply.

The next piece of hardware you need is a Y splitter .This is a wiring harness that plugs in to the connectors that the power supply provides and ends in two similar connectors. You usually use these when you have run out of connectors and you want to add something else to your PC.

Locate one of the female connectors on the Y splitter and cut it off close to the connector body. Strip the wires back about a half inch. If you are meticulous, you could crimp on some spade lugs or ring terminals to the wires. However, you can also just work with the bare wire. The splitter has two black wires (ground), a red wire (5V) and a yellow wire (12V). Connect these to the appropriate binding posts.

Feed the wiring harness back into the PCs body and reinstall the drive plate. If you can locate a free connector from the power supply, just plug the mating connector on the harness into it and you are set. If you don't have a free connector, don't worry. Find the closest disk drive and gently remove the power connector from it. Replace it with the connector from the wiring harness. Then plug the newly freed connector into the harness. Now the drive has power, and so do the binding posts.

Here's what it looks like ready to install:





Before your button up the PC, take a look at the power supply's label and see if you can get idea of how many amps the supply can handle. Of course, the PC is taking some of this power, but the trend has been towards lower-powered cards and drives, making most PC supplies quite large for their typical load. Turn on your PC and measure the voltage at the binding posts.

There are many things you could do spruce this project up. For example, you could mount a cheap digital panel meter in another drive plate to monitor the voltage or current. You could also mount an inline fuse holder in the wires leading to the binding posts. In particular, if you short something accidentally, you run the risk of damaging your PC. Every time I've done this, the power supply just shut down until I cycled the input power (with the short removed) and there was no other harm done.

Whatever you do, you'll get a useful addition to your bench and one other benefit. Everyone who sees those posts sticking out of your PC will want to know what they are for!

By the way, another good way to get a 5V supply is to cut the end off of a USB cable, find the red and black wires (make sure with a voltmeter) and connect them to some sort of connector or binding posts. This has the advantage of being highly portable. Powered USB hubs can provide 500mA at 5V and many are current limited!

Imp; Keep these in mind- Take care that u do not short the supply, especially if you haven rigged in a fuse. & do NOT load it more than 3-4 Amps. That’s about it. I rigged them in a hurry cause I had to power 4 CMOS X10 cams, and the power adapters were rated 110v/60htz(for USA)Hence, I am using these to power them.. They work like a charm :)

The next project I am doing is a full version of power supply (+5v, +3.3v, +12 v,-5v,-12v) using a scrapped CPU SMPS power supply which works independently and after finishing that I am converting a regular surveillance cam infrared spy cam.
Have fun :)
My upcoming projects (already in progress) pic below-




Any problems, contact me at csingh@gmail.com.