BP from the computer. The simplest power supply. How to make an adjustable power supply from a computer. Soldering the diode assembly

A good laboratory power supply is quite expensive and not all radio amateurs can afford it.
Nevertheless, at home you can assemble a power supply with good characteristics, which can cope well with providing power to various amateur radio designs, and can also serve as a charger for various batteries.
Such power supplies are assembled by radio amateurs, usually from , which are available and cheap everywhere.

In this article, little attention is paid to the conversion of the ATX itself, since converting a computer power supply for a radio amateur of average qualification into a laboratory one, or for some other purpose, is usually not difficult, but beginning radio amateurs have many questions about this. Basically, what parts in the power supply need to be removed, what parts should be left, what should be added in order to turn such a power supply into an adjustable one, and so on.

Especially for such radio amateurs, in this article I want to talk in detail about converting ATX computer power supplies into regulated power supplies, which can be used both as a laboratory power supply and as a charger.

For the modification, we will need a working ATX power supply, which is made on a TL494 PWM controller or its analogues.
The power supply circuits on such controllers, in principle, do not differ much from each other and are all basically similar. The power of the power supply should not be less than that which you plan to remove from the converted unit in the future.

Let's look at a typical ATX power supply circuit with a power of 250 W. For Codegen power supplies, the circuit is almost no different from this one.

The circuits of all such power supplies consist of a high-voltage and low-voltage part. In the picture of the power supply printed circuit board (below) from the track side, the high-voltage part is separated from the low-voltage part by a wide empty strip (without tracks), and is located on the right (it is smaller in size). We will not touch it, but will work only with the low-voltage part.
This is my board and using its example I will show you an option for converting an ATX power supply.

The low-voltage part of the circuit we are considering consists of a TL494 PWM controller, an operational amplifier circuit that controls the output voltages of the power supply, and if they do not match, it gives a signal to the 4th leg of the PWM controller to turn off the power supply.
Instead of an operational amplifier, transistors can be installed on the power supply board, which in principle perform the same function.
Next comes the rectifier part, which consists of various output voltages, 12 volts, +5 volts, -5 volts, +3.3 volts, of which for our purposes only a +12 volt rectifier will be needed (yellow output wires).
The remaining rectifiers and accompanying parts will need to be removed, except for the “duty” rectifier, which we will need to power the PWM controller and cooler.
The duty rectifier provides two voltages. Typically this is 5 volts and the second voltage can be around 10-20 volts (usually around 12).
We will use a second rectifier to power the PWM. A fan (cooler) is also connected to it.
If this output voltage is significantly higher than 12 volts, then the fan will need to be connected to this source through an additional resistor, as will be later in the circuits under consideration.
In the diagram below, I marked the high-voltage part with a green line, the “standby” rectifiers with a blue line, and everything else that needs to be removed with red.

So, we unsolder everything that is marked in red, and in our 12 volt rectifier we change the standard electrolytes (16 volts) to higher voltage ones, which will correspond to the future output voltage of our power supply. It will also be necessary to unsolder the 12th leg of the PWM controller and the middle part of the winding of the matching transformer - resistor R25 and diode D73 (if they are in the circuit) in the circuit, and instead of them solder a jumper into the board, which is drawn with a blue line in the diagram (you can simply close diode and resistor without soldering them). In some circuits this circuit may not exist.

Next, in the PWM harness on its first leg, we leave only one resistor, which goes to the +12 volt rectifier.
On the second and third legs of the PWM, we leave only the Master RC chain (in the diagram R48 C28).
On the fourth leg of the PWM we leave only one resistor (in the diagram it is designated as R49. Yes, in many other circuits between the 4th leg and the 13-14 legs of the PWM there is usually an electrolytic capacitor, we don’t touch it (if any) either, since it is designed for a soft start of the power supply. My board simply didn’t have it, so I installed it.
Its capacity in standard circuits is 1-10 μF.
Then we free the 13-14 legs from all connections, except for the connection with the capacitor, and also free the 15th and 16th legs of the PWM.

After all the operations performed, we should get the following.

This is what it looks like on my board (in the picture below).
Here I rewound the group stabilization choke with a 1.3-1.6 mm wire in one layer on the original core. It fit somewhere around 20 turns, but you don’t have to do this and leave the one that was there. Everything works well with him too.
I also installed another load resistor on the board, which consists of two 1.2 kOhm 3W resistors connected in parallel, the total resistance was 560 Ohms.
The native load resistor is designed for 12 volts of output voltage and has a resistance of 270 Ohms. My output voltage will be about 40 volts, so I installed such a resistor.
It must be calculated (at the maximum output voltage of the power supply at idle) for a load current of 50-60 mA. Since operating the power supply completely without load is not desirable, that’s why it is placed in the circuit.

View of the board from the parts side.

Now what will we need to add to the prepared board of our power supply in order to turn it into an regulated power supply;

First of all, in order not to burn the power transistors, we will need to solve the problem of load current stabilization and short circuit protection.
On forums for remaking similar units, I came across such an interesting thing - when experimenting with the current stabilization mode, on the forum pro-radio, forum member DWD I cited the following quote, I will quote it in full:

“I once told you that I couldn’t get the UPS to operate normally in current source mode with a low reference voltage at one of the inputs of the error amplifier of the PWM controller.
More than 50mV is normal, but less is not. In principle, 50mV is a guaranteed result, but in principle, you can get 25mV if you try. Anything less didn’t work. It does not work stably and is excited or confused by interference. This is when the signal voltage from the current sensor is positive.
But in the datasheet on the TL494 there is an option when negative voltage is removed from the current sensor.
I converted the circuit to this option and got an excellent result.
Here is a fragment of the diagram.

Actually, everything is standard, except for two points.
Firstly, is the best stability when stabilizing the load current with a negative signal from the current sensor an accident or a pattern?
The circuit works great with a reference voltage of 5mV!
With a positive signal from the current sensor, stable operation is obtained only at higher reference voltages (at least 25 mV).
With resistor values ​​of 10 Ohm and 10 KOhm, the current stabilized at 1.5 A up to the output short circuit.
I need more current, so I installed a 30 Ohm resistor. Stabilization was achieved at a level of 12...13A at a reference voltage of 15mV.
Secondly (and most interestingly), I don’t have a current sensor as such...
Its role is played by a fragment of a track on the board 3 cm long and 1 cm wide. The track is covered with a thin layer of solder.
If you use this track at a length of 2cm as a sensor, then the current will stabilize at the level of 12-13A, and if at a length of 2.5cm, then at the level of 10A."

Since this result turned out to be better than the standard one, we will go the same way.

First, you will need to unsolder the middle terminal of the secondary winding of the transformer (flexible braid) from the negative wire, or better without soldering it (if the signet allows) - cut the printed track on the board that connects it to the negative wire.
Next, you will need to solder a current sensor (shunt) between the track cut, which will connect the middle terminal of the winding to the negative wire.

It is best to take shunts from faulty (if you find them) pointer ampere-voltmeters (tseshek), or from Chinese pointer or digital instruments. They look something like this. A piece 1.5-2.0 cm long will be sufficient.

You can, of course, try to do as I wrote above. DWD, that is, if the path from the braid to the common wire is long enough, then try to use it as a current sensor, but I didn’t do this, I came across a board of a different design, like this one, where the two wire jumpers that connected the output are indicated by a red arrow braids with a common wire, and printed tracks ran between them.

Therefore, after removing unnecessary parts from the board, I removed these jumpers and in their place soldered a current sensor from a faulty Chinese "tseshka".
Then I soldered the rewound inductor in place, installed the electrolyte and load resistor.
This is what my piece of board looks like, where I marked with a red arrow the installed current sensor (shunt) in place of the jumper wire.

Then you need to connect this shunt to the PWM using a separate wire. From the side of the braid - with the 15th PWM leg through a 10 Ohm resistor, and connect the 16th PWM leg to the common wire.
Using a 10 Ohm resistor, you can select the maximum output current of our power supply. On the diagram DWD The resistor is 30 ohms, but start with 10 ohms for now. Increasing the value of this resistor increases the maximum output current of the power supply.

As I said earlier, the output voltage of my power supply is about 40 volts. To do this, I rewound the transformer, but in principle you can not rewind it, but increase the output voltage in another way, but for me this method turned out to be more convenient.
I’ll tell you about all this a little later, but for now let’s continue and start installing the necessary additional parts on the board so that we have a working power supply or charger.

Let me remind you once again that if you did not have a capacitor on the board between the 4th and 13-14 legs of the PWM (as in my case), then it is advisable to add it to the circuit.
You will also need to install two variable resistors (3.3-47 kOhm) to adjust the output voltage (V) and current (I) and connect them to the circuit below. It is advisable to make the connection wires as short as possible.
Below I have given only part of the diagram that we need - such a diagram will be easier to understand.
In the diagram, newly installed parts are indicated in green.

Diagram of newly installed parts.

Let me give you a little explanation of the diagram;
- The topmost rectifier is the duty room.
- The values ​​of the variable resistors are shown as 3.3 and 10 kOhm - the values ​​are as found.
- The value of resistor R1 is indicated as 270 Ohms - it is selected according to the required current limitation. Start small and you may end up with a completely different value, for example 27 Ohms;
- I did not mark capacitor C3 as a newly installed part in the expectation that it might be present on the board;
- The orange line indicates elements that may have to be selected or added to the circuit during the process of setting up the power supply.

Next we deal with the remaining 12-volt rectifier.
Let's check what maximum voltage our power supply can produce.
To do this, we temporarily unsolder from the first leg of the PWM - a resistor that goes to the output of the rectifier (according to the diagram above at 24 kOhm), then you need to turn on the unit to the network, first connect it to the break of any network wire, and use a regular 75-95 incandescent lamp as a fuse Tue In this case, the power supply will give us the maximum voltage it is capable of.

Before connecting the power supply to the network, make sure that the electrolytic capacitors in the output rectifier are replaced with higher voltage ones!

All further switching on of the power supply should be carried out only with an incandescent lamp; it will protect the power supply from emergency situations in case of any errors. In this case, the lamp will simply light up, and the power transistors will remain intact.

Next we need to fix (limit) the maximum output voltage of our power supply.
To do this, we temporarily change the 24 kOhm resistor (according to the diagram above) from the first leg of the PWM to a tuning resistor, for example 100 kOhm, and set it to the maximum voltage we need. It is advisable to set it so that it is 10-15 percent less than the maximum voltage that our power supply is capable of delivering. Then solder a permanent resistor in place of the tuning resistor.

If you plan to use this power supply as a charger, then the standard diode assembly used in this rectifier can be left, since its reverse voltage is 40 volts and it is quite suitable for a charger.
Then the maximum output voltage of the future charger will need to be limited in the manner described above, around 15-16 volts. For a 12-volt battery charger, this is quite enough and there is no need to increase this threshold.
If you plan to use your converted power supply as an regulated power supply, where the output voltage will be more than 20 volts, then this assembly will no longer be suitable. It will need to be replaced with a higher voltage one with the appropriate load current.
I installed two assemblies on my board in parallel, 16 amperes and 200 volts each.
When designing a rectifier using such assemblies, the maximum output voltage of the future power supply can be from 16 to 30-32 volts. It all depends on the model of the power supply.
If, when checking the power supply for the maximum output voltage, the power supply produces a voltage less than planned, and someone needs more output voltage (40-50 volts for example), then instead of the diode assembly, you will need to assemble a diode bridge, unsolder the braid from its place and leave it hanging in the air, and connect the negative terminal of the diode bridge in place of the soldered braid.

Rectifier circuit with diode bridge.

With a diode bridge, the output voltage of the power supply will be twice as high.
Diodes KD213 (with any letter) are very suitable for a diode bridge, the output current with which can reach up to 10 amperes, KD2999A,B (up to 20 amperes) and KD2997A,B (up to 30 amperes). The last ones are best, of course.
They all look like this;

In this case, it will be necessary to think about attaching the diodes to the radiator and isolating them from each other.
But I took a different route - I simply rewound the transformer and did it as I said above. two diode assemblies in parallel, since there was space for this on the board. For me this path turned out to be easier.

Rewinding a transformer is not particularly difficult, and we’ll look at how to do it below.

First, we unsolder the transformer from the board and look at the board to see which pins the 12-volt windings are soldered to.

There are mainly two types. Just like in the photo.
Next you will need to disassemble the transformer. Of course, it will be easier to deal with smaller ones, but larger ones can also be dealt with.
To do this, you need to clean the core from visible varnish (glue) residues, take a small container, pour water into it, put the transformer there, put it on the stove, bring to a boil and “cook” our transformer for 20-30 minutes.

For smaller transformers this is quite enough (less is possible) and such a procedure will not harm the core and windings of the transformer at all.
Then, holding the transformer core with tweezers (you can do it right in the container), using a sharp knife we ​​try to disconnect the ferrite jumper from the W-shaped core.

This is done quite easily, since the varnish softens from this procedure.
Then, just as carefully, we try to free the frame from the W-shaped core. This is also quite easy to do.

Then we wind up the windings. First comes half of the primary winding, mostly about 20 turns. We wind it up and remember the direction of winding. The second end of this winding does not need to be unsoldered from the point of its connection with the other half of the primary, if this does not interfere with further work with the transformer.

Then we wind up all the secondary ones. Usually there are 4 turns of both halves of 12-volt windings at once, then 3+3 turns of 5-volt windings. We wind everything up, unsolder it from the terminals and wind a new winding.
The new winding will contain 10+10 turns. We wind it with a wire with a diameter of 1.2 - 1.5 mm, or a set of thinner wires (easier to wind) of the appropriate cross-section.
We solder the beginning of the winding to one of the terminals to which the 12-volt winding was soldered, we wind 10 turns, the direction of winding does not matter, we bring the tap to the “braid” and in the same direction as we started - we wind another 10 turns and the end solder to the remaining pin.
Next, we isolate the secondary and wind the second half of the primary onto it, which we wound earlier, in the same direction as it was wound earlier.
We assemble the transformer, solder it into the board and check the operation of the power supply.

If during the process of adjusting the voltage any extraneous noise, squeaks, or crackles occur, then to get rid of them, you will need to select the RC chain circled in the orange ellipse below in the figure.

In some cases, you can completely remove the resistor and select a capacitor, but in others you can’t do it without a resistor. You can try adding a capacitor, or the same RC circuit, between 3 and 15 PWM legs.
If this does not help, then you need to install additional capacitors (circled in orange), their ratings are approximately 0.01 uF. If this doesn’t help much, then install an additional 4.7 kOhm resistor from the second leg of the PWM to the middle terminal of the voltage regulator (not shown in the diagram).

Then you will need to load the power supply output, for example, with a 60-watt car lamp, and try to regulate the current with resistor “I”.
If the current adjustment limit is small, then you need to increase the value of the resistor that comes from the shunt (10 Ohms) and try to regulate the current again.
You should not install a tuning resistor instead of this one; change its value only by installing another resistor with a higher or lower value.

It may happen that when the current increases, the incandescent lamp in the network wire circuit will light up. Then you need to reduce the current, turn off the power supply and return the resistor value to the previous value.

Also, for voltage and current regulators, it is best to try to purchase SP5-35 regulators, which come with wire and rigid leads.

This is an analogue of multi-turn resistors (only one and a half turns), the axis of which is combined with a smooth and coarse regulator. At first it is regulated “Smoothly”, then when it reaches the limit, it begins to be regulated “Roughly”.
Adjustment with such resistors is very convenient, fast and accurate, much better than with a multi-turn. But if you can’t get them, then buy ordinary multi-turn ones, such as;

Well, it seems like I told you everything that I planned to complete on remaking the computer power supply, and I hope that everything is clear and intelligible.

If anyone has any questions about the design of the power supply, ask them on the forum.

Good luck with your design!

Not only radio amateurs, but also just in everyday life, may need a powerful power supply. So that there is up to 10A output current at a maximum voltage of up to 20 volts or more. Of course, the thought immediately goes to unnecessary ATX computer power supplies. Before you start remaking, find a diagram for your specific power supply.

Sequence of actions for converting an ATX power supply into a regulated laboratory one.

1. Remove jumper J13 (you can use wire cutters)

2. Remove diode D29 (you can just lift one leg)

3. The PS-ON jumper to ground is already installed.

4. Turn on the PB only for a short time, since the input voltage will be maximum (approximately 20-24V). This is actually what we want to see. Don't forget about the output electrolytes, designed for 16V. They might get a little warm. Considering your “bloatiness”, they will still have to be sent to the swamp, it’s not a pity. I repeat: remove all the wires, they are in the way, and only ground wires will be used and +12V will then be soldered back.

5. Remove the 3.3-volt part: R32, Q5, R35, R34, IC2, C22, C21.

6. Removing 5V: Schottky assembly HS2, C17, C18, R28, or “choke type” L5.

7. Remove -12V -5V: D13-D16, D17, C20, R30, C19, R29.

8. We change the bad ones: replace C11, C12 (preferably with a larger capacity C11 - 1000uF, C12 - 470uF).

9. We change the inappropriate components: C16 (preferably 3300uF x 35V like mine, well, at least 2200uF x 35V is a must!) and resistor R27 - you no longer have it, and that’s great. I advise you to replace it with a more powerful one, for example 2W and take the resistance to 360-560 Ohms. We look at my board and repeat:

10. We remove everything from the legs TL494 1,2,3 for this we remove the resistors: R49-51 (free the 1st leg), R52-54 (...2nd leg), C26, J11 (...3- my leg)

11. I don’t know why, but my R38 was cut by someone :) I recommend that you cut it too. It participates in voltage feedback and is parallel to R37.

12. We separate the 15th and 16th legs of the microcircuit from “all the rest”, to do this we make 3 cuts in the existing tracks and restore the connection to the 14th leg with a jumper, as shown in the photo.

13. Now we solder the cable from the regulator board to the points according to the diagram, I used the holes from the soldered resistors, but by the 14th and 15th I had to peel off the varnish and drill holes, in the photo.

14. The core of cable No. 7 (the regulator’s power supply) can be taken from the +17V power supply of the TL, in the area of ​​the jumper, more precisely from it J10/ Drill a hole into the track, clear the varnish and there. It is better to drill from the print side.
for a good laboratory power supply.

Many already know that I have a weakness for all kinds of power supplies, but here is a two-in-one review. This time there will be a review of a radio constructor that allows you to assemble the basis for a laboratory power supply and a variant of its real implementation.
I warn you, there will be a lot of photos and text, so stock up on coffee :)

First, I’ll explain a little what it is and why.
Almost all radio amateurs use such a thing as a laboratory power supply in their work. Whether it's complex with software control or completely simple on the LM317, it still does almost the same thing, powers different loads while working with them.
Laboratory power supplies are divided into three main types.
With pulse stabilization.
With linear stabilization
Hybrid.

The first ones include a switching controlled power supply, or simply a switching power supply with a step-down PWM converter. I have already reviewed several options for these power supplies. , .
Advantages - high power with small dimensions, excellent efficiency.
Disadvantages - RF ripple, presence of capacious capacitors at the output

The latter do not have any PWM converters on board; all regulation is carried out in a linear manner, where excess energy is simply dissipated on the control element.
Pros - Almost complete absence of ripple, no need for output capacitors (almost).
Cons - efficiency, weight, size.

The third is a combination of either the first type with the second, then the linear stabilizer is powered by a slave buck PWM converter (the voltage at the output of the PWM converter is always maintained at a level slightly higher than the output, the rest is regulated by a transistor operating in linear mode.
Or it is a linear power supply, but the transformer has several windings that switch as needed, thereby reducing losses on the control element.
This scheme has only one drawback, complexity, which is higher than that of the first two options.

Today we will talk about the second type of power supply, with a regulating element operating in linear mode. But let's look at this power supply using the example of a designer, it seems to me that this should be even more interesting. After all, in my opinion, this is a good start for a novice radio amateur to assemble one of the main devices.
Well, or as they say, the right power supply must be heavy :)

This review is more aimed at beginners; experienced comrades are unlikely to find anything useful in it.

For review, I ordered a construction kit that allows you to assemble the main part of a laboratory power supply.
The main characteristics are as follows (from those declared by the store):
Input voltage - 24 Volts AC
Output voltage adjustable - 0-30 Volts DC.
Output current adjustable - 2mA - 3A
Output voltage ripple - 0.01%
The dimensions of the printed board are 80x80mm.

A little about packaging.
The designer arrived in a regular plastic bag, wrapped in soft material.
Inside, in an antistatic zip-lock bag, were all the necessary components, including the circuit board.

Everything inside was a mess, but nothing was damaged; the printed circuit board partially protected the radio components.

I won’t list everything that is included in the kit, it’s easier to do this later during the review, I’ll just say that I had enough of everything, even some left over.

A little about the printed circuit board.
The quality is excellent, the circuit is not included in the kit, but all the ratings are marked on the board.
The board is double-sided, covered with a protective mask.

The board coating, tinning, and the quality of the PCB itself is excellent.
I was only able to tear off a patch from the seal in one place, and that was after I tried to solder a non-original part (why, we will find out later).
In my opinion, this is the best thing for a beginner radio amateur; it will be difficult to spoil it.

Before installation, I drew a diagram of this power supply.

The scheme is quite thoughtful, although not without its shortcomings, but I’ll tell you about them in the process.
Several main nodes are visible in the diagram; I separated them by color.
Green - voltage regulation and stabilization unit
Red - current regulation and stabilization unit
Purple - indicating unit for switching to current stabilization mode
Blue - reference voltage source.
Separately there are:
1. Input diode bridge and filter capacitor
2. Power control unit on transistors VT1 and VT2.
3. Protection on transistor VT3, turning off the output until the power supply to the operational amplifiers is normal
4. Fan power stabilizer, built on a 7824 chip.
5. R16, R19, C6, C7, VD3, VD4, VD5, unit for forming the negative pole of the power supply of operational amplifiers. Due to the presence of this unit, the power supply will not operate simply on direct current; it is the alternating current input from the transformer that is required.
6. C9 output capacitor, VD9, output protective diode.

First, I will describe the advantages and disadvantages of the circuit solution.
Pros -
It's nice to have a stabilizer to power the fan, but the fan needs 24 Volts.
I am very pleased with the presence of a power source of negative polarity; this greatly improves the operation of the power supply at currents and voltages close to zero.
Due to the presence of a source of negative polarity, protection was introduced into the circuit; as long as there is no voltage, the power supply output will be turned off.
The power supply contains a reference voltage source of 5.1 Volts, this made it possible not only to correctly regulate the output voltage and current (with this circuit, voltage and current are regulated from zero to maximum linearly, without “humps” and “dips” at extreme values), but also makes it possible to control external power supply, I simply change the control voltage.
The output capacitor has a very small capacitance, which allows you to safely test the LEDs; there will be no current surge until the output capacitor is discharged and the PSU enters current stabilization mode.
The output diode is necessary to protect the power supply from supplying reverse polarity voltage to its output. True, the diode is too weak, it is better to replace it with another one.

Minuses.
The current-measuring shunt has too high a resistance, because of this, when operating with a load current of 3 Amps, about 4.5 Watts of heat are generated on it. The resistor is designed for 5 Watts, but the heating is very high.
The input diode bridge is made up of 3 Ampere diodes. It is good to have diodes with a capacity of at least 5 Amperes, since the current through the diodes in such a circuit is equal to 1.4 of the output, so in operation the current through them can be 4.2 Amperes, and the diodes themselves are designed for 3 Amperes. The only thing that makes the situation easier is that the pairs of diodes in the bridge work alternately, but this is still not entirely correct.
The big minus is that the Chinese engineers, when selecting operational amplifiers, chose an op-amp with a maximum voltage of 36 Volts, but did not think that the circuit had a negative voltage source and the input voltage in this version was limited to 31 Volts (36-5 = 31 ). With an input of 24 Volts AC, DC will be about 32-33 Volts.
Those. The op amps will operate in extreme mode (36 is the maximum, standard 30).

I'll talk more about the pros and cons, as well as about modernization later, but now I'll move on to the actual assembly.

First, let's lay out everything that is included in the kit. This will make assembly easier, and it will simply be clearer to see what has already been installed and what remains.

I recommend starting the assembly with the lowest elements, since if you install the high ones first, then it will be inconvenient to install the low ones later.
It is also better to start by installing those components that are more of the same.
I'll start with resistors, and these will be 10 kOhm resistors.
The resistors are high quality and have an accuracy of 1%.
A few words about resistors. Resistors are color coded. Many may find this inconvenient. In fact, this is better than alphanumeric markings, since the markings are visible in any position of the resistor.
Don’t be afraid of color coding; at the initial stage you can use it, and over time you will be able to identify it without it.
To understand and conveniently work with such components, you just need to remember two things that will be useful to a novice radio amateur in life.
1. Ten basic marking colors
2. Series values, they are not very useful when working with precision resistors of the E48 and E96 series, but such resistors are much less common.
Any radio amateur with experience will list them simply from memory.
1, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.7, 3, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1.
All other denominations are multiplied by 10, 100, etc. For example 22k, 360k, 39Ohm.
What does this information provide?
And it gives that if the resistor is of the E24 series, then, for example, a combination of colors -
Blue + green + yellow is impossible in it.
Blue - 6
Green - 5
Yellow - x10000
those. According to calculations, it comes out to 650k, but there is no such value in the E24 series, there is either 620 or 680, which means either the color was recognized incorrectly, or the color has been changed, or the resistor is not in the E24 series, but the latter is rare.

Okay, enough theory, let's move on.
Before installation, I shape the resistor leads, usually using tweezers, but some people use a small homemade device for this.
We are not in a hurry to throw away the cuttings of the leads; sometimes they can be useful for jumpers.

Having established the main quantity, I reached single resistors.
It may be more difficult here; you will have to deal with denominations more often.

I don’t solder the components right away, but simply bite them and bend the leads, and I bite them first and then bend them.
This is done very easily, the board is held in your left hand (if you are right-handed), and the component being installed is pressed at the same time.
We have side cutters in our right hand, we bite off the leads (sometimes even several components at once), and immediately bend the leads with the side edge of the side cutters.
This is all done very quickly, after a while it is already automatic.

Now we’ve reached the last small resistor, the value of the required one and what’s left are the same, which is not bad :)

Having installed the resistors, we move on to diodes and zener diodes.
There are four small diodes here, these are the popular 4148, two zener diodes of 5.1 Volts each, so it’s very difficult to get confused.
We also use it to form conclusions.

On the board, the cathode is indicated by a stripe, just like on diodes and zener diodes.

Although the board has a protective mask, I still recommend bending the leads so that they do not fall on adjacent tracks; in the photo, the diode lead is bent away from the track.

The zener diodes on the board are also marked as 5V1.

There are not very many ceramic capacitors in the circuit, but their markings can confuse a novice radio amateur. By the way, it also obeys the E24 series.
The first two digits are the nominal value in picofarads.
The third digit is the number of zeros that must be added to the denomination
Those. for example 331 = 330pF
101 - 100pF
104 - 100000pF or 100nF or 0.1uF
224 - 220000pF or 220nF or 0.22uF

The main number of passive elements has been installed.

After that, we move on to installing operational amplifiers.
I would probably recommend buying sockets for them, but I soldered them as is.
On the board, as well as on the chip itself, the first pin is marked.
The remaining conclusions are counted counterclockwise.
The photo shows the place for the operational amplifier and how it should be installed.

For microcircuits, I do not bend all the pins, but only a couple, usually these are the outer pins diagonally.
Well, it’s better to bite them so that they stick out about 1mm above the board.

That's it, now you can move on to soldering.
I use a very ordinary soldering iron with temperature control, but a regular soldering iron with a power of about 25-30 watts is quite sufficient.
Solder 1mm in diameter with flux. I specifically do not indicate the brand of solder, since the solder on the coil is not original (original coils weigh 1 kg), and few people will be familiar with its name.

As I wrote above, the board is of high quality, soldered very easily, I did not use any fluxes, only what is in the solder is enough, you just need to remember to sometimes shake off the excess flux from the tip.

Here I took a photo with an example of good soldering and not so good one.
A good solder should look like a small droplet enveloping the terminal.
But there are a couple of places in the photo where there is clearly not enough solder. This will happen on a double-sided board with metallization (where the solder also flows into the hole), but this cannot be done on a single-sided board; over time, such soldering may “fall off”.

The terminals of the transistors also need to be pre-formed; this must be done in such a way that the terminal does not become deformed near the base of the case (elders will remember the legendary KT315, whose terminals loved to break off).
I shape powerful components a little differently. Molding is done so that the component stands above the board, in which case less heat will transfer to the board and will not destroy it.

This is what molded powerful resistors look like on a board.
All components were soldered only from below, the solder that you see on the top of the board penetrated through the hole due to capillary effect. It is advisable to solder so that the solder penetrates a little to the top, this will increase the reliability of the soldering, and in the case of heavy components, their better stability.

If before this I molded the terminals of the components using tweezers, then for the diodes you will already need small pliers with narrow jaws.
The conclusions are formed in approximately the same way as for resistors.

But there are differences during installation.
If for components with thin leads installation occurs first, then biting occurs, then for diodes the opposite is true. You simply won’t bend such a lead after biting it, so first we bend the lead, then bite off the excess.

The power unit is assembled using two transistors connected according to a Darlington circuit.
One of the transistors is installed on a small radiator, preferably through thermal paste.
The kit included four M3 screws, one goes here.

A couple of photos of the nearly soldered board. I won’t describe the installation of the terminal blocks and other components; it’s intuitive and can be seen from the photograph.
By the way, about the terminal blocks, the board has terminal blocks for connecting the input, output, and fan power.

I haven't washed the board yet, although I often do it at this stage.
This is due to the fact that there will still be a small part to finalize.

After the main assembly stage we are left with the following components.
Powerful transistor
Two variable resistors
Two connectors for board installation
Two connectors with wires, by the way the wires are very soft, but of small cross-section.
Three screws.

Initially, the manufacturer intended to place variable resistors on the board itself, but they are placed so inconveniently that I didn’t even bother to solder them and showed them just as an example.
They are very close and it will be extremely inconvenient to adjust, although it is possible.

But thank you for not forgetting to include the wires with connectors, it’s much more convenient.
In this form, the resistors can be placed on the front panel of the device, and the board can be installed in a convenient place.
At the same time, I soldered a powerful transistor. This is an ordinary bipolar transistor, but it has a maximum power dissipation of up to 100 Watts (naturally, when installed on a radiator).
There are three screws left, I don’t even understand where to use them, if in the corners of the board, then four are needed, if you are attaching a powerful transistor, then they are short, in general it’s a mystery.

The board can be powered from any transformer with an output voltage of up to 22 Volts (the specifications state 24, but I explained above why such a voltage cannot be used).
I decided to use a transformer that had been lying around for a long time for the Romantic amplifier. Why for, and not from, and because it hasn’t stood anywhere yet :)
This transformer has two output power windings of 21 Volts, two auxiliary windings of 16 Volts and a shield winding.
The voltage is indicated for the input 220, but since we now already have a standard of 230, the output voltages will be slightly higher.
The calculated power of the transformer is about 100 watts.
I parallelized the output power windings to get more current. Of course, it was possible to use a rectification circuit with two diodes, but it would not work better, so I left it as is.

First trial run. I installed a small heatsink on the transistor, but even in this form there was quite a lot of heating, since the power supply is linear.
Adjustment of current and voltage occurs without problems, everything worked right away, so I can already fully recommend this designer.
The first photo is voltage stabilization, the second is current.

First, I checked what the transformer outputs after rectification, as this determines the maximum output voltage.
I got about 25 Volts, not a lot. The capacity of the filter capacitor is 3300 μF, I would advise increasing it, but even in this form the device is quite functional.

Since for further testing it was necessary to use a normal radiator, I moved on to assembling the entire future structure, since the installation of the radiator depended on the intended design.
I decided to use the Igloo7200 radiator I had lying around. According to the manufacturer, such a radiator is capable of dissipating up to 90 watts of heat.

The device will use a Z2A housing based on a Polish-made idea, the price will be about $3.

Initially, I wanted to move away from the case that my readers are tired of, in which I collect all sorts of electronic things.
To do this, I chose a slightly smaller case and bought a fan with a mesh for it, but I couldn’t fit all the stuffing into it, so I purchased a second case and, accordingly, a second fan.
In both cases I bought Sunon fans, I really like the products of this company, and in both cases I bought 24 Volt fans.

This is how I planned to install the radiator, board and transformer. There is even a little room left for the filling to expand.
There was no way to get the fan inside, so it was decided to place it outside.

We mark the mounting holes, cut the threads, and screw them for fitting.

Since the selected case has an internal height of 80mm, and the board also has this size, I secured the radiator so that the board is symmetrical with respect to the radiator.

The leads of the powerful transistor also need to be slightly molded so that they do not become deformed when the transistor is pressed against the radiator.

A small digression.
For some reason, the manufacturer thought of a place to install a rather small radiator, because of this, when installing a normal one, it turns out that the fan power stabilizer and the connector for connecting it get in the way.
I had to unsolder them, and seal the place where they were with tape so that there would be no connection to the radiator, since there is voltage on it.

I cut off the excess tape on the back side, otherwise it would turn out completely sloppy, we’ll do it according to Feng Shui :)

This is what a printed circuit board looks like with the heatsink finally installed, the transistor is installed using thermal paste, and it is better to use good thermal paste, since the transistor dissipates power comparable to a powerful processor, i.e. about 90 watts.
At the same time, I immediately made a hole for installing the fan speed controller board, which in the end still had to be re-drilled :)

To set zero, I unscrewed both knobs to the extreme left position, turned off the load and set the output to zero. Now the output voltage will be regulated from zero.

Next are some tests.
I checked the accuracy of maintaining the output voltage.
Idling, voltage 10.00 Volts
1. Load current 1 Ampere, voltage 10.00 Volts
2. Load current 2 Amps, voltage 9.99 Volts
3. Load current 3 Amperes, voltage 9.98 Volts.
4. Load current 3.97 Amperes, voltage 9.97 Volts.
The characteristics are quite good, if desired, they can be improved a little more by changing the connection point of the voltage feedback resistors, but as for me, it’s enough as is.

I also checked the ripple level, the test took place at a current of 3 Amps and an output voltage of 10 Volts

The ripple level was about 15 mV, which is very good, but I thought that in fact the ripples shown in the screenshot were more likely to come from the electronic load than from the power supply itself.

After that, I started assembling the device itself as a whole.
I started by installing the radiator with the power supply board.
To do this, I marked the installation location of the fan and the power connector.
The hole was marked not quite round, with small “cuts” at the top and bottom, they are needed to increase the strength of the back panel after cutting the hole.
The biggest difficulty is usually holes of complex shape, for example, for a power connector.

A big hole is cut out of a big pile of small ones :)
A drill + a 1mm drill bit sometimes works wonders.
We drill holes, lots of holes. It may seem long and tedious. No, on the contrary, it is very fast, completely drilling a panel takes about 3 minutes.

After that, I usually set the drill a little larger, for example 1.2-1.3mm, and go through it like a cutter, I get a cut like this:

After this, we take a small knife in our hands and clean out the resulting holes, at the same time we trim the plastic a little if the hole is a little smaller. The plastic is quite soft, making it comfortable to work with.

The last stage of preparation is to drill the mounting holes; we can say that the main work on the back panel is finished.

We install the radiator with the board and the fan, try on the resulting result, and if necessary, “finish it with a file.”

Almost at the very beginning I mentioned revision.
I'll work on it a little.
To begin with, I decided to replace the original diodes in the input diode bridge with Schottky diodes; for this I bought four 31DQ06 pieces. and then I repeated the mistake of the board developers, by inertia buying diodes for the same current, but it was necessary for a higher one. But still, the heating of the diodes will be less, since the drop on Schottky diodes is less than on conventional ones.
Secondly, I decided to replace the shunt. I was not satisfied not only with the fact that it heats up like an iron, but also with the fact that it drops about 1.5 Volts, which can be used (in the sense of a load). To do this, I took two domestic 0.27 Ohm 1% resistors (this will also improve stability). Why the developers didn’t do this is unclear; the price of the solution is absolutely the same as in the version with a native 0.47 Ohm resistor.
Well, rather as an addition, I decided to replace the original 3300 µF filter capacitor with a higher quality and capacitive Capxon 10000 µF...

This is what the resulting design looks like with replaced components and an installed fan thermal control board.
It turned out a little collective farm, and besides, I accidentally tore off one spot on the board when installing powerful resistors. In general, it was possible to safely use less powerful resistors, for example one 2-Watt resistor, I just didn’t have one in stock.

A few components were also added to the bottom.
A 3.9k resistor, parallel to the outermost contacts of the connector for connecting a current control resistor. It is needed to reduce the regulation voltage since the voltage on the shunt is now different.
A pair of 0.22 µF capacitors, one in parallel with the output from the current control resistor, to reduce interference, the second is simply at the output of the power supply, it is not particularly needed, I just accidentally took out a pair at once and decided to use both.

The entire power section is connected, and a board with a diode bridge and a capacitor for powering the voltage indicator is installed on the transformer.
By and large, this board is optional in the current version, but I couldn’t raise my hand to power the indicator from the maximum 30 Volts for it and I decided to use an additional 16 Volt winding.

The following components were used to organize the front panel:
Load connection terminals
Pair of metal handles
Power switch
Red filter, declared as a filter for KM35 housings
To indicate current and voltage, I decided to use the board I had left over after writing one of the reviews. But I was not satisfied with the small indicators and therefore larger ones with a digit height of 14mm were purchased, and a printed circuit board was made for them.

In general, this solution is temporary, but I wanted to do it carefully even temporarily.

Several stages of preparing the front panel.
1. Draw a full-size layout of the front panel (I use the usual Sprint Layout). The advantage of using identical housings is that preparing a new panel is very simple, since the required dimensions are already known.
We attach the printout to the front panel and drill marking holes with a diameter of 1 mm in the corners of the square/rectangular holes. Use the same drill to drill the centers of the remaining holes.
2. Using the resulting holes, we mark the cutting locations. We change the tool to a thin disk cutter.
3. We cut straight lines, clearly in size at the front, a little larger at the back, so that the cut is as complete as possible.
4. Break out the cut pieces of plastic. I usually don't throw them away because they can still be useful.

In the same way as preparing the back panel, we process the resulting holes using a knife.
I recommend drilling large-diameter holes; it does not “bite” the plastic.

We try on what we got and, if necessary, modify it using a needle file.
I had to slightly widen the hole for the switch.

As I wrote above, for the display I decided to use the board left over from one of the previous reviews. In general, this is a very bad solution, but for a temporary option it is more than suitable, I will explain why later.
We unsolder the indicators and connectors from the board, call the old indicators and the new ones.
I wrote out the pinout of both indicators so as not to get confused.
In the native version, four-digit indicators were used, I used three-digit ones. since it didn’t fit into my window anymore. But since the fourth digit is needed only to display the letter A or U, their loss is not critical.
I placed the LED indicating the current limit mode between the indicators.

I prepare everything necessary, solder a 50 mOhm resistor from the old board, which will be used as before, as a current-measuring shunt.
This is the problem with this shunt. The fact is that in this option I will have a voltage drop at the output of 50 mV for every 1 Ampere of load current.
There are two ways to get rid of this problem: use two separate meters, for current and voltage, while powering the voltmeter from a separate power source.
The second way is to install a shunt in the positive pole of the power supply. Both options did not suit me as a temporary solution, so I decided to step on the throat of my perfectionism and make a simplified version, but far from the best.

For the design, I used mounting posts left over from the DC-DC converter board.
With them I got a very convenient design: the indicator board is attached to the ampere-voltmeter board, which in turn is attached to the power terminal board.
It turned out even better than I expected :)
I also placed a current-measuring shunt on the power terminal board.

The resulting front panel design.

And then I remembered that I forgot to install a more powerful protective diode. I had to solder it later. I used a diode left over from replacing the diodes in the input bridge of the board.
Of course, it would be nice to add a fuse, but this is no longer in this version.

But I decided to install better current and voltage control resistors than those suggested by the manufacturer.
The original ones are quite high quality and run smoothly, but these are ordinary resistors and, in my opinion, a laboratory power supply should be able to more accurately adjust the output voltage and current.
Even when I was thinking about ordering a power supply board, I saw them in the store and ordered them for review, especially since they had the same rating.

In general, I usually use other resistors for such purposes; they combine two resistors inside themselves for rough and smooth adjustment, but lately I can’t find them on sale.
Does anyone know their imported analogues?

The resistors are of quite high quality, the rotation angle is 3600 degrees, or in simple terms - 10 full turns, which provides a change of 3 Volts or 0.3 Amperes per 1 turn.
With such resistors, the adjustment accuracy is approximately 11 times more accurate than with conventional ones.

New resistors compared to the original ones, the size is certainly impressive.
Along the way, I shortened the wires to the resistors a little, this should improve noise immunity.

I packed everything into the case, in principle there is even a little space left, there is room to grow :)

I connected the shielding winding to the grounding conductor of the connector, the additional power board is located directly on the terminals of the transformer, this is of course not very neat, but I have not yet come up with another option.

Check after assembly. Everything started almost the first time, I accidentally mixed up two digits on the indicator and for a long time I could not understand what was wrong with the adjustment, after switching everything became as it should.

The last stage is gluing the filter, installing the handles and assembling the body.
The filter has a thinner edge around its perimeter, the main part is recessed into the housing window, and the thinner part is glued with double-sided tape.
The handles were originally designed for a shaft diameter of 6.3mm (if I’m not confused), the new resistors have a thinner shaft, so I had to put a couple of layers of heat shrink on the shaft.
I decided not to design the front panel in any way for now, and there are two reasons for this:
1. The controls are so intuitive that there is no particular point in the inscriptions yet.
2. I plan to modify this power supply, so changes in the design of the front panel are possible.

A couple of photos of the resulting design.
Front view:

Back view.
Attentive readers have probably noticed that the fan is positioned in such a way that it blows hot air out of the case, rather than pumping cold air between the fins of the radiator.
I decided to do this because the radiator is slightly smaller in height than the case, and to prevent hot air from getting inside, I installed the fan in reverse. This, of course, significantly reduces the efficiency of heat removal, but allows for a little ventilation of the space inside the power supply.
Additionally, I would recommend making several holes at the bottom of the lower half of the body, but this is more of an addition.

After all the alterations, I ended up with a slightly less current than in the original version, and was about 3.35 Amperes.

So, I’ll try to describe the pros and cons of this board.
pros
Excellent workmanship.
Almost correct circuit design of the device.
A complete set of parts for assembling the power supply stabilizer board
Well suited for beginner radio amateurs.
In its minimal form, it additionally requires only a transformer and a radiator; in a more advanced form, it also requires an ampere-voltmeter.
Fully functional after assembly, although with some nuances.
No capacitive capacitors at the power supply output, safe when testing LEDs, etc.

Minuses
The type of operational amplifiers is incorrectly selected, because of this the input voltage range must be limited to 22 Volts.
Not a very suitable current measurement resistor value. It operates in its normal thermal mode, but it is better to replace it, since the heating is very high and can harm surrounding components.
The input diode bridge operates at maximum, it is better to replace the diodes with more powerful ones

My opinion. During the assembly process, I got the impression that the circuit was designed by two different people, one applied the correct regulation principle, reference voltage source, negative voltage source, protection. The second one incorrectly selected the shunt, operational amplifiers and diode bridge for this purpose.
I really liked the circuit design of the device, and in the modification section, I first wanted to replace the operational amplifiers, I even bought microcircuits with a maximum operating voltage of 40 Volts, but then I changed my mind about modifications. but otherwise the solution is quite correct, the adjustment is smooth and linear. Of course there is heating, you can’t live without it. In general, as for me, this is a very good and useful constructor for a beginning radio amateur.
Surely there will be people who will write that it is easier to buy a ready-made one, but I think that assembling it yourself is both more interesting (probably this is the most important thing) and more useful. In addition, many people quite easily have at home a transformer and a radiator from an old processor, and some kind of box.

Already in the process of writing the review, I had an even stronger feeling that this review will be the beginning in a series of reviews dedicated to the linear power supply; I have thoughts on improvement -
1. Conversion of the indication and control circuit into a digital version, possibly with connection to a computer
2. Replacing operational amplifiers with high-voltage ones (I don’t know which ones yet)
3. After replacing the op-amp, I want to make two automatically switching stages and expand the output voltage range.
4. Change the principle of current measurement in the display device so that there is no voltage drop under load.
5. Add the ability to turn off the output voltage with a button.

That's probably all. Perhaps I’ll remember something else and add something, but I’m more looking forward to comments with questions.
We also plan to devote several more reviews to designers for beginner radio amateurs; perhaps someone will have suggestions regarding certain designers.

Not for the faint of heart

At first I didn’t want to show it, but then I decided to take a photo anyway.
On the left is the power supply that I used for many years before.
This is a simple linear power supply with an output of 1-1.2 Amperes at a voltage of up to 25 Volts.
So I wanted to replace it with something more powerful and correct.

The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.

I'm planning to buy +207 Add to favorites I liked the review +160 +378

I recently assembled a very good laboratory regulated power supply according to this scheme, tested many times by different people:

• Adjustment from 0 to 40 V (at XX and 36 V when calculated with the load) + stabilization up to 50 V is possible, but I needed it exactly up to 36 V.
• Current adjustment from 0 to 6A (Imax is set by shunt).

It has 3 types of protection, if you can call it that:

1. Current stabilization (if the set current is exceeded, it limits it and any changes in voltage towards an increase do not make any changes)
2. Trigger current protection (if the set current is exceeded, turns off the power)
3. Temperature protection (if the set temperature is exceeded, it turns off the power at the output) I didn’t install it myself.

Here is a control board based on LM324D.

With the help of 4 op-amps, all stabilization control and all protection are implemented. On the Internet it is better known as PiDKD. This version is the 16th improved version, tested by many (v.16у2). Developed on the Soldering Iron. Easy to set up, literally assembled on your knee. My current adjustment is quite rough and I think it’s worth installing an additional current fine adjustment knob, in addition to the main one. The diagram on the right has an example of how to do this to regulate voltage, but it can also be applied to adjusting current. All this is powered by an SMPS from one of the neighboring topics, with croaking “protection”:

As always, I had to deploy according to my PP. I don’t think there’s much to be said about him here. To power up the stabilizer, 4 TIP142 transistors are installed:

Everything is on a common heat sink (heatsink from the CPU). Why are there so many of them? Firstly, to increase the output current. Secondly, to distribute the load across all 4 transistors, which subsequently eliminates overheating and failure at high currents and large potential differences. After all, the stabilizer is linear and plus to all this, the higher the input voltage and the lower the output voltage, the more energy is dissipated on the transistors. In addition, all transistors have certain tolerances for voltage and current, for those who did not know all this. Here is a diagram of connecting transistors in parallel:

Resistors in emitters can be set in the range from 0.1 to 1 Ohm; it is worth considering that as the current increases, the voltage drop across them will be significant and, naturally, heating is inevitable.

All files - brief information, circuits in .ms12 and .spl7, a signet from one of the people on a soldering iron (100% verified, everything is signed, for which many thanks to him!) in .lay6 format, I provide it in an archive. And finally, a video of the protection in action and some information about the power supply in general:

I will replace the digital VA meter in the future, since it is not accurate, the reading step is large. Current readings vary greatly when deviating from the configured value. For example, we set it to 3 A and it also shows 3 A, but when we reduce the current to 0.5 A, it will show 0.4 A, for example. But that is another topic. Author of the article and photo - BFG5000.

Discuss the article POWERFUL HOMEMADE POWER SUPPLY

From the article you will learn how to make an adjustable power supply with your own hands from available materials. It can be used to power household equipment, as well as for the needs of your own laboratory. A constant voltage source can be used to test devices such as a relay regulator for a car generator. After all, when diagnosing it, there is a need for two voltages - 12 Volts and over 16. Now consider the design features of the power supply.

Transformer

If the device is not planned to be used to charge acid batteries and power powerful equipment, then there is no need to use large transformers. It is enough to use models with a power of no more than 50 W. True, to make an adjustable power supply with your own hands, you will need to slightly change the design of the converter. The first step is to decide what voltage range will be at the output. The characteristics of the power supply transformer depend on this parameter.

Let's say you chose the range of 0-20 Volts, which means you need to build on these values. The secondary winding should have an output voltage of 20-22 Volts. Therefore, you leave the primary winding on the transformer and wind the secondary winding on top of it. To calculate the required number of turns, measure the voltage that is obtained from ten. A tenth of this value is the voltage obtained from one turn. After the secondary winding is made, you need to assemble and tie the core.

Rectifier

Both assemblies and individual diodes can be used as a rectifier. Before making an adjustable power supply, select all its components. If the output is high, then you will need to use high-power semiconductors. It is advisable to install them on aluminum radiators. As for the circuit, preference should be given only to the bridge circuit, since it has a much higher efficiency, less voltage loss during rectification. It is not recommended to use a half-wave circuit, since it is ineffective; there is a lot of ripple at the output, which distorts the signal and is a source of interference for radio equipment .

Stabilization and adjustment block

To make a stabilizer, it makes the most sense to use the LM317 microassembly. A cheap and accessible device for everyone, which will allow you to assemble a high-quality do-it-yourself power supply in a matter of minutes. But its application requires one important detail - effective cooling. And not only passive in the form of radiators. The fact is that voltage regulation and stabilization occurs according to a very interesting scheme. The device leaves exactly the voltage that is needed, but the excess coming to its input is converted into heat. Therefore, without cooling, the microassembly is unlikely to work for a long time.

Take a look at the diagram, there is nothing super complicated in it. There are only three pins on the assembly, voltage is supplied to the third, voltage is removed from the second, and the first is needed to connect to the minus of the power supply. But here a small peculiarity arises - if you include a resistance between the minus and the first terminal of the assembly, then it becomes possible to adjust the voltage at the output. Moreover, a self-adjustable power supply can change the output voltage both smoothly and stepwise. But the first type of adjustment is the most convenient, so it is used more often. For implementation, it is necessary to include a variable resistance of 5 kOhm. In addition, a constant resistor with a resistance of about 500 Ohms must be installed between the first and second terminals of the assembly.

Current and voltage control unit

Of course, in order for the operation of the device to be as convenient as possible, it is necessary to monitor the output characteristics - voltage and current. A circuit of an regulated power supply is constructed in such a way that the ammeter is connected to the gap in the positive wire, and the voltmeter is connected between the outputs of the device. But the question is different - what type of measuring instruments to use? The simplest option is to install two LED displays, to which connect a volt- and ammeter circuit assembled on one microcontroller.

But in an adjustable power supply that you make yourself, you can mount a couple of cheap Chinese multimeters. Fortunately, they can be powered directly from the device. You can, of course, use dial indicators, only in this case you need to calibrate the scale for

Device case

It is best to make the case from light but durable metal. Aluminum would be the ideal option. As already mentioned, the regulated power supply circuit contains elements that get very hot. Therefore, a radiator must be mounted inside the case, which can be connected to one of the walls for greater efficiency. It is desirable to have forced airflow. For this purpose, you can use a thermal switch paired with a fan. They must be installed directly on the cooling radiator.

Every radio amateur, in his home laboratory, must have adjustable power supply, allowing you to produce a constant voltage from 0 to 14 Volts at a load current of up to 500mA. Moreover, such a power supply must provide short circuit protection at the exit, so as not to “burn” the structure being tested or repaired, and not to fail yourself.

This article is primarily intended for beginner radio amateurs, and the idea of ​​writing this article was prompted by Kirill G. For which special thanks to him.

I present to your attention a diagram simple regulated power supply, which was assembled by me back in the 80s (at that time I was in the 8th grade), and the diagram was taken from the supplement to the magazine “Young Technician” No. 10 for 1985. The circuit differs slightly from the original by changing some germanium parts to silicon ones.

As you can see, the circuit is simple and does not contain expensive parts. Let's take a look at her work.

1. Schematic diagram of the power supply.

The power supply is plugged into the outlet using a two-pole plug XP1. When the switch is turned on SA1 voltage 220V is supplied to the primary winding ( I) step-down transformer T1.

Transformer T1 reduces the mains voltage to 14 –17 Volt. This is the voltage removed from the secondary winding ( II) transformer, rectified by diodes VD1 - VD4, connected via a bridge circuit, and is smoothed by a filter capacitor C1. If there is no capacitor, then when powering the receiver or amplifier, an AC hum will be heard in the speakers.

Diodes VD1 - VD4 and capacitor C1 form rectifier, from the output of which a constant voltage is supplied to the input voltage stabilizer, consisting of several chains:

1. R1, VD5, VT1;
2. R2, VD6, R3;
3. VT2, VT3, R4.

Resistor R2 and zener diode VD6 form parametric stabilizer and stabilize the voltage across the variable resistor R3, which is connected in parallel with the zener diode. Using this resistor, the voltage at the output of the power supply is set.

On a variable resistor R3 a constant voltage equal to the stabilization voltage is maintained Ust of this zener diode.

When the variable resistor slider is in its lowest (according to the diagram) position, the transistor VT2 closed, since the voltage at its base (relative to the emitter) is zero, respectively, and powerful transistor VT3 also closed.

With the transistor closed VT3 its transition resistance collector-emitter reaches several tens of megaohms, and almost the entire rectifier voltage falls at this crossing. Therefore, at the output of the power supply (terminals XT1 And XT2) there will be no voltage.

When will the transistor VT3 open, and the transition resistance collector-emitter is only a few ohms, then almost all of the rectifier voltage is supplied to the output of the power supply.

So here it is. As the variable resistor slider moves up to the base of the transistor VT2 will arrive unlocking negative voltage, and current will flow in its emitter circuit (EC). At the same time, the voltage from its load resistor R4 supplied directly to the base of a powerful transistor VT3, and voltage will appear at the output of the power supply.

How more negative gate voltage at the base of the transistor VT2, those more Both transistors open, so more voltage at the output of the power supply.

How to make a full-fledged power supply yourself with an adjustable voltage range of 2.5-24 volts is very simple; anyone can repeat it without any amateur radio experience.

We will make it from an old computer power supply, TX or ATX, it doesn’t matter, fortunately, over the years of the PC Era, every home has already accumulated a sufficient amount of old computer hardware and a power supply unit is probably also there, so the cost of homemade products will be insignificant, and for some masters it will be zero rubles .

I got this AT block for modification.

The more powerful you use the power supply, the better the result, my donor is only 250W with 10 amperes on the +12v bus, but in fact, with a load of only 4 A, it can no longer cope, the output voltage drops completely.

Look what is written on the case.

Therefore, see for yourself what kind of current you plan to receive from your regulated power supply, this potential of the donor and lay it in right away.

There are many options for modifying a standard computer power supply, but they are all based on a change in the wiring of the IC chip - TL494CN (its analogues DBL494, KA7500, IR3M02, A494, MV3759, M1114EU, MPC494C, etc.).

Fig No. 0 Pinout of the TL494CN microcircuit and analogues.

Let's look at several options execution of computer power supply circuits, perhaps one of them will be yours and dealing with the wiring will become much easier.

Scheme No. 1.

Let's get to work.
First you need to disassemble the power supply housing, unscrew the four bolts, remove the cover and look inside.

We are looking for a chip on the board from the list above, if there is none, then you can look for a modification option on the Internet for your IC.

In my case, a KA7500 chip was found on the board, which means we can begin to study the wiring and the location of unnecessary parts that need to be removed.

For ease of operation, first completely unscrew the entire board and remove it from the case.

In the photo the power connector is 220v.

Let's disconnect the power and fan, solder or cut out the output wires so that they don't interfere with our understanding of the circuit, leave only the necessary ones, one yellow (+12v), black (common) and green* (start ON) if there is one.

My AT unit does not have a green wire, so it starts immediately when plugged into the outlet. If the unit is ATX, then it must have a green wire, it must be soldered to the “common” one, and if you want to make a separate power button on the case, then just put a switch in the gap of this wire.

Now you need to look at how many volts the large output capacitors cost, if they say less than 30v, then you need to replace them with similar ones, only with an operating voltage of at least 30 volts.

In the photo there are black capacitors as a replacement option for the blue one.

This is done because our modified unit will produce not +12 volts, but up to +24 volts, and without replacement, the capacitors will simply explode during the first test at 24v, after a few minutes of operation. When selecting a new electrolyte, it is not advisable to reduce the capacity; increasing it is always recommended.

The most important part of the job.
We will remove all unnecessary parts in the IC494 harness and solder other nominal parts so that the result is a harness like this (Fig. No. 1).

Rice. No. 1 Change in the wiring of the IC 494 microcircuit (revision scheme).

We will only need these legs of the microcircuit No. 1, 2, 3, 4, 15 and 16, do not pay attention to the rest.

Rice. No. 2 Option for improvement based on the example of scheme No. 1

Explanation of symbols.

You should do something like this, we find leg No. 1 (where the dot is on the body) of the microcircuit and study what is connected to it, all circuits must be removed and disconnected. Depending on how the tracks will be located and the parts soldered in your specific modification of the board, the optimal modification option is selected; this may be desoldering and lifting one leg of the part (breaking the chain) or it will be easier to cut the track with a knife. Having decided on the action plan, we begin the remodeling process according to the revision scheme.

The photo shows replacing resistors with the required value.

In the photo - by lifting the legs of unnecessary parts, we break the chains.

Some resistors that are already soldered into the wiring diagram can be suitable without replacing them, for example, we need to put a resistor at R=2.7k connected to the “common”, but there is already R=3k connected to the “common”, this suits us quite well and we leave it there unchanged (example in Fig. No. 2, green resistors do not change).

On the picture- cut tracks and added new jumpers, write down the old values ​​​​with a marker, you may need to restore everything back.

Thus, we review and redo all the circuits on the six legs of the microcircuit.

This was the most difficult point in the rework.

We make voltage and current regulators.

We take variable resistors of 22k (voltage regulator) and 330Ohm (current regulator), solder two 15cm wires to them, solder the other ends to the board according to the diagram (Fig. No. 1). Install on the front panel.

Voltage and current control.
To control we need a voltmeter (0-30v) and an ammeter (0-6A).

These devices can be purchased in Chinese online stores at the best price; my voltmeter cost me only 60 rubles with delivery. (Voltmeter: )

I used my own ammeter, from old USSR stocks.

IMPORTANT- inside the device there is a Current resistor (Current sensor), which we need according to the diagram (Fig. No. 1), therefore, if you use an ammeter, then you do not need to install an additional Current resistor; you need to install it without an ammeter. Usually a homemade RC is made, a wire D = 0.5-0.6 mm is wound around a 2-watt MLT resistance, turn to turn for the entire length, solder the ends to the resistance terminals, that's all.

Everyone will make the body of the device for themselves.
You can leave it completely metal by cutting holes for regulators and control devices. I used laminate scraps, they are easier to drill and cut.

PROJECT No. 20: power supply with adjustable Uout from an ATX block

I have repeatedly paid attention to recommendations on the Internet for converting computer power supplies into laboratory ones with adjustable output voltage. And so I decided to try to upgrade the ATX unit with minimal intervention in the circuit. Because I've accumulated enough stuff RADIOshabara, then financial costs should be minimal.

1. I took the ATX block out of storage:

2. It says:


I am somewhat skeptical about these parameters. But God be with them, with the parameters. I will be quite satisfied if they are at least half correct.

3. Don’t forget to turn on the unit from the rear:


according to the color coding of the power connector


closed the green wire “PsON” and the black wire “Gnd” - the unit turned on:

4. I checked the voltages at the +12V and +5V outputs:

5. I begin the autopsy. I sweep away dust and other debris with a brush:

6.Disconnect the input ~ 220V, unscrew the screws securing the board and fan and remove them from the case:

7. I unsolder the extra wires and the fan (for now, so as not to interfere):

8. I’m trying to determine which PWM controller is in this block. The inscription is difficult to read: KA7500V



9. Bottom view of the controller wiring:

10. Remaking the power supply is quite simple - you need to find a resistor R34 (shown by an arrow) connecting the 1st leg of the microcircuit and the +12V bus, and unsolder it:


It is also highlighted in yellow in the diagram:


True, the nominal value on the diagram is 3.9 kOhm, and measurements show that not everything that is written on the diagram is true... In reality, the resistance of this resistor was about 39 kOhm.

11. In place R34 you need to solder a variable resistor. Without bothering myself with a long search, I took a 47 kOhm + 4.3 kOhm variable in series with it (I believe you can use slightly different values):

12. Turned on the power supply - no unnecessary sounds, smells, sparks, fires, etc. – it worked immediately:

13. Measured the ranges of voltage changes:



+12V: 4.96…12.05V

+5V: 2.62…5.62V

+3.3V: 1.33…3.14V
This suits me, since I did not set any GLOBAL goals for upgrading this power supply.

14. To indicate the output voltage, I will use a regular analog voltmeter:

His readings agree quite well with the digital ones:

15. The block must be given the appearance of a finished structure. I think that the PSU case is already good enough. Only the front panel will have to be decorated. To do this, I will connect terminals and a switch to it (I just want to say “TUMBLE SWITCH type” by analogy with the “SORTER type” toilet located strictly to the north, indicated on the plan by the letters “ME” and “JO” - see photo from my favorite comedy ),


voltmeter, ammeter and, of course, LED.

Like that:


However, as an estimate showed, I had gone too far. I don’t have enough miniature instruments, so there’s nowhere to put an ammeter! And if you install it, then there will be no place to place all the other elements, if you make the front panel no larger than the actual size of the front side of the block.

This is how it looks in FrontDesigner 3.0. You can download it from HERE, or you can search it on the Internet.

16. After thinking a little, I decided to replace the previous voltmeter with another one that I wouldn’t mind redoing. This voltmeter is also designed to work in a horizontal position, and if it is placed vertically, the scale angle will be negative - this is not very convenient for observations. This is the device I will modernize a little.

The device is open:

I measure the resistance of the additional resistor:


The new measurement limit will be 15V. Based on the fact that the voltage U is proportional to the resistance R (and vice versa), i.e. according to Ohm's law for the section of the circuit U=IR and R=U/I, a simple proportion follows Rd/x=6V/15V, from which x=Rd×15/6, where Rd=5.52 kOhm is the old additional resistor, x is the new one additional resistor, 6V – previous limit, 15V – new voltmeter limit.
So, x = 5.52x15/6 = 13.8 kOhm. This is elementary physics and mathematics.
I made up a new resistor from two:

The body of the device had to be “shortened” somewhat to match the height of the power supply:



I made a new scale in the same FrontDesigner 3.0 program. The voltmeter will have to work in extreme conditions: upside down and vertically, and the countdown will be “reverse” - from right to left!

17. This is approximately how everything will be located on the front panel:

I mark the panel:

And I make holes in it:

I install the elements:

The panel will be attached to the PSU case using U-shaped brackets:

Looking out the window, I discovered that, as always, the first snow had unexpectedly fallen - Oct 26, 2016:

18. I begin final assembly. Once again I estimate the placement:

I first install the voltmeter and the front panel on the PSU case:


I inserted the fan in reverse so that it would blow air inside the case, inserted the board, connected “GND”, the switch (“PsON” and “Gnd”), turned it on - the power supply started up. The output voltage is also adjusted in the opposite direction - counterclockwise. I checked the voltage change on the +12V bus:

I soldered all the wires, installed and connected the voltmeter, installed the front panel, turned it on - the LED blinked, the voltmeter needle jumped to the left (I have it installed “in reverse”) and that’s it! Turned it off, turned it on - the same thing! I checked if there were any short circuits on the back of the front panel - everything was fine. What's the matter? I turned the variable resistor down (it was at maximum), turned it on, and the power supply started working. I smoothly rotate the regulator - everything is fine again: the voltage at the outputs increases and decreases, the unit does not turn off. Turned it off. Turned it up to maximum, turned it on - it won’t turn on again! Turned it off. I set it to an intermediate position, turned it on - the power supply started up. That. The error is not in the installation, but somewhere deeper. But the power supply works!

I finally assemble the structure and turn it on again to check:

Here is the finished design:

I'll call it "BP-ATX v2.0".
Financial costs are ZERO. I only used parts and materials that I had.

If you have an old computer power supply (ATX) at home, you shouldn’t throw it away. After all, it can be used to make an excellent power supply for home or laboratory purposes. Minimal modification is required 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 maximum load current. The main voltage for constant operation is 3.3 V; 5 V; 12 V. There are also outputs that can be used for a small current, these are 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 voltage range is much larger than it might seem at first glance.

Pinout of computer power supply outputs

The color standard is, in principle, the same. And this color connection scheme is 99 percent suitable for you too. Something may be added or removed, but of course everything is not critical.

The rework 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 composites of two five-watt resistors.
• - Heat shrink tube.
• - A pair of LEDs with 330 Ohm quenching resistors.
• - Switches. One for networking, one for management

Computer power supply modification diagram

Everything is simple here, so don't be afraid. The first thing to do is to disassemble and connect the wires by color. Then, according to the diagram, connect the LEDs. The first one on the left will indicate the presence of power at the output after switching on. And the second one from the right will always be on as long as the mains voltage is present on the block.
Connect the switch. It will start the main circuit by shorting the green wire to common. And turn off the unit when opened.
Also, depending on the brand of the block, you will need to hang a 5-20 Ohm load resistor between the common output and plus five volts, otherwise the block may not start due to the built-in protection. Also, if it doesn’t work, be prepared to put the following resistors on all voltages: “+3.3”, “+12”. But usually one resistor per 5 Volt output is enough.

Let's get started

Remove the top cover of the casing.
We bite off the power connectors going to the computer motherboard and other devices.
We untangle the wires by color.
Drill holes in the back wall for the terminals. For accuracy, we first go through with a thin drill, and then with a thick one to match the size of the terminal.
Be careful not to get any metal shavings on the power supply board.

Insert the terminals and tighten.

We put together the black wires, this will be common, and strip them. Then we tin it with a soldering iron and put on a heat-shrinkable tube. We solder it to the terminal and put the tube on the solder and blow it with a hot air gun.

We do this with all the wires. Which you don’t plan to use, bite them off at the root of the board.
We also drill holes for the toggle switch and LEDs.

We install and fix the LEDs with hot glue. Solder according to the diagram.

We place the load resistors on the circuit boards and screw them in with screws.
Close the lid. We turn on and test your new laboratory power supply.

It would be a good idea 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 voltages are not outside the permissible limits.

As you may have noticed, I used two switches - one is in the circuit, and it starts the block. And the second, which is larger, bipolar, switches the input voltage of 220 V to the input of the unit. You don't have to install it.
So friends, collect your block and use it to your health.

Watch a video of making a laboratory block with your own hands