Laboratory power supply from a computer power supply DIY
In the article you will learn how to make a laboratory power supply yourself from what is at hand. To date, there are quite a few devices that need different power - and 5, and 3, and 12 volts. And some even feed on high frequency current (these devices will be discussed separately). But it is worth starting with the classical scheme - on the transformer. Of course, the design will be cumbersome, and the scheme is outdated, but the reliability is high.
Power supply transformer
For a laboratory power supply, it is necessary to use transformers of the TC-270 type (two-core, from old lamp color TVs). But they will have to be slightly modernized. The primary windings remain in place, the secondary ones are completely removed. This is how the laboratory power supply is made, the circuit of which is given in the article. New windings are wound based on existing needs. The easiest option is to make stepwise voltage regulation at the output.To do this, you need to calculate how many turns needed to remove one Volt:
- Wind up 10 turns of wire instead of secondary winding.
- Turn on the transformer and measure the voltage on the secondary winding.
- Suppose it turned out 2 V. Consequently, 5 turns issue 1 V.
- To make the "steps" in 1 V, you need to make taps every five turns.
This design will be massive, and you will have to use either several sockets or a special toggle switch to switch modes of operation. It will be much easier to wind the secondary winding in such a way that the output is approximately 30 volts of alternating voltage.
Above was an example of step adjustment. But the laboratory power supply unit, the circuit of which is given in the article, has one big advantage - in it the secondary winding is integral, without branching. Adjustment is made using a special circuit on semiconductor elements. With a variable resistor, the semiconductor junction parameters are changed. As a result, the circuit parameters and the output voltage change.
The fact is that you have an adjustable laboratory power supply. And in order to monitor the voltage at the output, you need to connect a voltmeter to it. The easiest way to use the arrow, as long as the scale was properly calibrated. But you can spend a little money and buy a digital voltmeter (its price is about one hundred rubles), whose measurement range is between 0 ... 30 volts. It will be much easier to work with it, because you will always see the voltage value at the output of your power supply.
Computer power supply
To put it bluntly, this is the perfect device. From it you can make any source of constant voltage. True, not everyone knows how to run it without a motherboard. It's very easy to do this - in the wiring harness you are looking for one green and connect it to any black. That's all, you can see how the fans spun. Now more about how to make a laboratory power supply from a computer power supply with your own hands.
Voltages in a computer power supply unit
The fact is that it is possible to find several types of voltages in a computer power supply unit:
- 3.3 V.
- 5 V.
- 12 V.
As you understand, these are the most "popular" values of stress. They are enough to power the chips, controllers, actuators. Please note that even a complex electronic mechanism can be powered from a computer power supply alone. If only there was a decent margin of power.
High frequency currents
Most importantly, you can make a laboratory power supply from a computer power supply unit with the presence of high-frequency current at the output. For some devices, such as monitor lamp backlight inverters, it is the RF current that is needed. As you know, a computer power supply unit is built according to an inverter circuit. Consequently, somewhere in it you can find a voltage of 12 volts with a high frequency. To do this, do the following:
- Disassemble the power supply case (disconnect it from the network beforehand).
- Find the largest transformer. This is a high-frequency transformer, and that is where the high-frequency current will be located.
- Solder two wires to the primary winding and pull out of the case.
Now it remains only to arrange everything beautifully - to make the front panel, install the required number of sockets and sign them, so as not to get confused.In the manufacture of a laboratory power source from a computer power supply unit, you get one big advantage - the output voltage is always stable. Additional stabilization schemes are not required. And the 0-30V laboratory power supply unit considered at the very beginning turns out to be much worse in terms of parameters than from a computer power supply unit.
You can argue about the advantages and disadvantages of various schemes, but the most high-quality product will be the power supply from a computer power supply unit. But it has a drawback - a short circuit at the output causes the power supply to go into protection mode. In fact, it is a complete stop to work. Only restarting the device will return the output voltage. But if the laboratory power supply is made according to the classical transformer circuit, you can avoid such problems - but you have to think about short circuit protection (at least a 16 or 25 amp fuse at the device output).