MetkuMods

ModLab

I've dreamt for quite some time now to get a decent laboratory power source. Now that I've made a few of these mods, my needs have been mainly two voltages: +5 and +12 volts. Once you get these out of the power supply, you're going strong. Just add the most frequently used connectors that are used in PCs and the constructing and testing of new mods is eased quite a bit. One of the greatest benefits is that you don't have to use your PC's for testing, but you can test them with this device. This way, the poorly made connections etc. don't danger the health of your beloved computer. So, let's see what kind of a gadget I threw together.

I couldn't find a suitable plastic box to which build the device in, so I decided to build my own out of plexiglass. Put measurements in their places and get out that saw.
The plexiglass is the same old 5 mm thick one that I used to create the first glowpad. I guess one euro is enough to buy these parts.

Now to the circuit itself..

To stabilize the voltage, I used 7805 and 7812 regulators. These are easily connected and used. They also allow the external transformers to be approximately +12 - +30 volts.

It's good to sufficiently cool these circuits. I used an old Pentium heatsink for this. The 7805 (5 volt) regulator is the only one that actually needs a cooling profile. Cooling was applied for the other components mainly as a precaution.

The condensators must be placed as close as possible to the regulators. This prevents possible oscillation of the circuit.

The adjustable side (the red section) was made as a emitter follower. This leads to a very simple, yet powerful, structure. The potentiometer is linear by its type. The transistors in use can easily be switched to corresponding ones. The BC547 transistor (ie. NPN transistor) can be replaced by almost any cheap NPN transistor. The BD442 PNP transistor should be replaced only by a transistor that has enough current endurance.

As the fuse, I used a normal 500 mA glass fuse.

So, the connectors are drawn the way they are when you look at the back panel of the computer. The keyboard and mouse have an identical pin order, so the gadget doesn't require two separate ps/2 connectors.

Note that the intention of all of this is to use the connectors as sources of voltage. The datalines of the connectors aren't plugged or connected anywhere.

With the potentiometer in place. Same with the ps/2 connector, the switch, the connector to the external transformer and the casing for the fuse.

The first tests. The picture shows the fan (on top) with which I tested the warming of the 7805 regulator. The cooling profile warmed up enough within 15 minutes of use to notice it with one's hand. But it didn't heat up burning hot, so everything's going just fine thus far.

This is a good picture showing the condensators that are soldered directly to the legs of the regulators. Between the regulators themselves and the cooling profile a drop of silver paste was added to enhance heat conductivity.

More tests. This time we're checking that the ps/2 connector is in shape. As a tool, I used the MouseFan.

I took the USB connector from my old bx6-motherboard. Of course, you can buy these connectors separately from your local computer store. Sometimes you just have to get by with what you've got.

The transformer that gives the required voltage and current to our gadget. The transformer in question gives +12 volts of direct current, up to one ampere.

A shot of the completed gadget. The cooling profiles are attatched to the plexiglass with superglue, as are the molex and USB connectors.

From low behind. As you can see, the box is quite open. If possible, you should try to get a roomy and sturdy plastic box in which to build this device. I thought I could manage with this 'convertible' model.

A profile from both sides.

 

This was it. Hopefully someone gets at least a bit of use from this article. Not that many have great usage for this kind of a gadget, but these regulator connections are quite commonly in use and are easily applicable in other electronic constructing.

I tried to include all possible connectors that are commonly used in modding of the PC as a source of power. The only thing that was left out was the three-pinned fan connector from motherboard. Nevertheless, it is rarely used as you should strive to avoid straining the motherboard with too many added circuits.

 

PART INDEX:

Part Quantity
7805-regulator 1
7812-regulator 1
BD442 PNP-transistor 1
BC547 NPN-transistor 1
10 microfarad electrolyte condensator 4
1 kilo-ohm potentiometer, linear 1
Banana connectors 6
USB-connector, male 1
PS/2-connector, female 1
Molex-connector, female 1
Fuse casing 1
500 mA glass fuse 1
Switch 1
Some cooling profile  
Power connector for the transformer 1

And some cable and miscellaneous smaller parts..

Questions, comments?
Back to the frontpage.

20.02.2002 - ©Japala    21.02.2002 translated to English by Henrik Paul


 
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Disclaimer! I will not take any responsibility for any destroyed or damaged hardware.




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