ATX Power Supply

Using a PC power supply as a lab power supply

To implement experiments on electronics, the first thing you need will be an electric supply. You may buy a laboratory supply, build your own supply or use an ATX power supply as a lab supply.

I suggest to use an ATX power supply which is easy to use, easy to get, safe and cheap.

atx-power-supply

In the picture above, you see a standart ATX PC power supply. It has a high voltage cable, mainboard and device cables and sometimes a power on/off switch.

These power supplies has a power out around 200-300W. This power is provided from multiple outputs such as +5V, +12V, +3.3V, -5V, -12V. Therefore, +5V,+3.3V outputs drive 12A, 12V output drives 9A current. Negative outputs cannot drive as high as positive ones (around 0.5A).

atx-specs

In the above picture, you can see the specs which are written on one side of the power supply.

Color codes of the outputs:

+3.3V Orange
+5V Red
+12V Yellow
-5V White
-12V Blue
0V(GND) Black

There are variety of connectors on an ATX power supply. The only important thing is the color code of the cables. If you see a black cable, it is the ground, doesn’t matter where it comes from.

You don’t have to cut the cables to connect them to your circuits. Just plug cables inside of them (just for experiments for sure!).

Power On/Off

In the old AT power supplies, there was a push button which has two position on and off. When you turned this button on, the power supply gave the energy to the mainboard.

In the ATX power supplies, there is no on/off switch. Instead, there is a cable which has to be connected to the ground to turn on the supply (This process is done by motherboard in PCs). This cable is called Power Supply On pin and it is color code is green (sometimes this color code can be changed but its place is always same).

atx-power-on

As long as you short circuit the Power On pin (green) to the ground (black), your power supply works. If you don’t have a power on/off switch on the back of your power supply, connect an on/off switch between these two cables.

Now, we have a working lab supply for our experiments. Have a look at this page : http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
It has a more professional looking lab supply. But, i prefer to work by using only one short circuit cable (i am a bit lazy).

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