LABORATORY POWER SUPPLY FROM AN ATX COMPUTER UNIT

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If you have an old computer power supply (ATX) at home, then do not throw it away. After all, from it you can make an excellent power supply for home or laboratory purposes. Modification will be minimal and in the end you will get an almost universal power source with a number of fixed voltages.

Computer power supplies have a high load capacity, high stabilization and short circuit protection.

I took this block. Everyone has such a plate with a number of output voltages and a maximum load current. Basic voltages for continuous operation 3.3 V; 5 V; 12 V. There are also outputs that can be used for a small current, this is minus 5 V and minus 12 V. You can also get the voltage difference: for example, if you connect to “+5” and “+12”, then you get a voltage of 7 V. If you connect to "+3.3" and "+5", you get 1.7 V. And so on ... So the line of voltages is much more than it might seem once.

Pinout of computer power supply outputs

The color standard, in principle, is one. And this 99 percent color scheme is right for you. Something may be added or removed, but of course everything is not critical.

Alteration has begun

What do we need?

- Screw terminals.
- Resistors with a power of 10 W and a resistance of 10 Ohms (you can try 20 Ohms). We will use the composite of two five-watt resistors.
- Heat shrink tube.
- A pair of LEDs with quenching resistors of 330 ohms.
- Switches. One for network, one for management

The scheme for finalizing the computer power supply

Everything is simple here, so do not be afraid. The first thing to do is to disassemble each other and connect the wires by color. Then, according to the circuit, connect the LEDs. The first on the left will indicate the presence of power at the output after switching on. And the second on the right will always light up while the mains voltage is present on the unit.
Connect the switch. He will start the main circuit by shorting the green wire to a common one. And turn off the unit when opening.
Also, depending on the brand of the unit, you will need to hang a 5-20 Ohm load resistor between the common output and the plus of five volts, otherwise the unit may not start due to the built-in protection. Also, if it does not work, be prepared to hang such resistors on all voltages: "+3.3", "+12". But usually one resistor is enough for an output of 5 volts.

Let's start

Remove the top cover of the casing.
We bite off the power connectors that go to the computer motherboard and other devices.
Unravel the wires by color.
We drill holes in the back wall under the terminals. For accuracy, we first go through a thin drill, and then thick to fit the size of the terminal.
Be careful not to spill metal shavings onto the power supply board.

We insert the terminals and tighten.

We add the black wires, it will be common, and we clean it. Then tin with a soldering iron, put on a heat shrink tube. We solder to the terminal and put the tube on the solder - blow it around with a hot air gun.

So do with all the wires. Which do not plan to use - bite off under the root of the board.
We also drill holes on the toggle switch and LEDs.

We install and fix the LEDs with hot glue. We solder according to the scheme.

We put the load resistors on the circuit board and screw the screws.
Close the lid. Turn on and test your new laboratory power supply.

It will not be superfluous to measure the output voltage at the output of each terminal. To be sure that your old power supply is fully functional and the output voltage is not out of range.

As you can see, I used two switches - one is in the circuit, and it starts the block. And the second, which is larger, bipolar - commutes the input voltage of 220 V to the input of the unit. You can not put it.
So friends, collect your block and use your health.