Somehow recently on the Internet I came across one scheme very simple block power supply with adjustable voltage. The voltage could be regulated from 1 Volt to 36 Volts, depending on the output voltage on the secondary winding of the transformer.

Take a close look at the LM317T in the circuit itself! The third leg (3) of the microcircuit clings to the capacitor C1, that is, the third leg is the INPUT, and the second leg (2) clings to the capacitor C2 and the 200 Ohm resistor and is the OUTPUT.

With the help of a transformer from a mains voltage of 220 Volts, we get 25 Volts, no more. Less is possible, no more. Then we straighten the whole thing with a diode bridge and smooth out the ripple using the capacitor C1. All this is described in detail in the article how to get a constant from an alternating voltage. And now our most important trump card in the power supply is the highly stable voltage regulator LM317T microcircuit. At the time of this writing, the price of this microcircuit was around 14 rubles. Even cheaper than a loaf of white bread.

Chip Description

LM317T is a voltage regulator. If the transformer produces up to 27-28 Volts on the secondary winding, then we can easily regulate the voltage from 1.2 to 37 Volts, but I would not raise the bar more than 25 volts at the output of the transformer.

The microcircuit can be executed in the TO-220 case:

or in a D2 Pack

It can pass a maximum current of 1.5 amperes through itself, which is enough to power your electronic knick-knacks without a voltage drop. That is, we can deliver a voltage of 36 Volts at a current strength of up to 1.5 Amperes to the load, and at the same time our microcircuit will still also produce 36 Volts - this is, of course, ideally. In fact, fractions of a volt will sink, which is not very critical. With a high current in the load, it is more expedient to put this microcircuit on a radiator.

In order to assemble the circuit, we also need variable resistor at 6.8 Kilo-ohms, it is even possible at 10 Kilo-ohms, as well as a fixed resistor of 200 Ohm, preferably from 1 Watt. Well, at the output we put a capacitor of 100 uF. Absolutely simple schematic!

Assembling in hardware

I used to have a very bad power supply with transistors. I thought, why not remake it? Here is the result ;-)

Here we see the imported GBU606 diode bridge. It is designed for a current of up to 6 Amperes, which is more than enough for our power supply, since it will deliver a maximum of 1.5 Amperes to the load. I put the LM-ku on the radiator using KPT-8 paste to improve heat transfer. Well, everything else, I think, is familiar to you.

And here is the antediluvian transformer, which gives me a voltage of 12 volts on the secondary winding.

We carefully pack all this into the case and bring out the wires.

So what do you think? ;-)

The minimum voltage I got was 1.25 Volts, and the maximum voltage was 15 Volts.

I put any voltage, in this case the most common 12 Volts and 5 Volts

Everything works with a bang!

This power supply is very convenient for adjusting the speed of a mini-drill, which is used for drilling circuit boards.

Analogs on Aliexpress

By the way, on Ali you can immediately find a ready-made set of this unit without a transformer.

Too lazy to collect? You can take a ready-made 5 Amp for less than $ 2:

You can see by this link.

If 5 Amperes is not enough, then you can look at 8 Amperes. It will be enough for even the most hard-core electronics engineer:

The master, whose device description in the first part, having set himself the goal of making a power supply with adjustment, did not complicate his business and simply used the boards that were idle. The second option involves the use of even more common material - adjustment was added to the usual block, perhaps this is a very promising solution in terms of simplicity, despite the fact that the necessary characteristics will not be lost and even an inexperienced radio amateur can implement the idea with his own hands. As a bonus, there are two more options for very simple schemes with all detailed explanations for beginners. So, there are 4 ways to choose from.

We will tell you how to make a regulated power supply from an unnecessary computer board. The master took the computer board and cut out the block that powers the RAM.
This is how it looks.

Let's decide which parts you need to take, which ones are not, in order to cut off what is needed so that all the components of the power supply are on the board. Usually, a pulse unit for supplying current to a computer consists of a microcircuit, a controller PWM, key transistors, an output inductor and an output capacitor, an input capacitor. The board also has an input choke for some reason. He left him too. Key transistors - maybe two, three. There is a seat for 3 transistors, but it is not used in the circuit.

The controller PWM microcircuit itself may look like this. Here it is under a magnifying glass.

It may look like a square with small pins on all sides. This is a typical PWM controller found on a laptop motherboard.

This is how the power supply unit looks like on a video card.

The power supply for the processor looks exactly the same. We see the controller and several processor power channels. 3 transistors in this case. Choke and capacitor. This is one channel.
Three transistors, a choke, a capacitor - the second channel. 3 channel. And two more channels for other purposes.
You know what a PWM controller looks like, look under a magnifying glass for its marking, look for a datasheet on the Internet, download a pdf file and look at the diagram so as not to confuse anything.
In the diagram we see a PWM controller, but at the edges the conclusions are marked, numbered.

Transistors are indicated. This is a choke. These are the output capacitor and the input capacitor. The input voltage ranges from 1.5 to 19 volts, but the PWM controller supply voltage must be between 5 volts and 12 volts. That is, it may turn out that a separate power supply is required to power the PWM controller. All piping, resistors and capacitors, do not be alarmed. You don't need to know. Everything is on the board, you do not assemble a PWM controller, but use a ready-made one. You only need to know 2 resistors - they set the output voltage.

Resistor divider. Its whole point is to reduce the signal from the output to about 1 volt and apply feedback to the input of the PWM controller. In short, by changing the value of the resistors, we can adjust the output voltage. In the case shown, instead of the feedback resistor, the master put a 10 kilo-ohm trimmer resistor. This proved to be sufficient to regulate the output voltage from 1 volt to about 12 volts. Unfortunately, this is not possible on all PWM controllers. For example, on PWM controllers of processors and video cards, in order to be able to adjust the voltage, the ability to overclock, the output voltage is supplied by software via a multi-channel bus. It is possible to change the output voltage of such a PWM controller only with jumpers.

So, knowing what the PWM controller looks like, the elements that are needed, we can already cut out the power supply. But this must be done carefully, since there are tracks around the PWM controller that you may need. For example, you can see - the track goes from the base of the transistor to the PWM controller. It was difficult to keep it, so the board had to be carefully cut out.

Using the tester in continuity mode and focusing on the circuit, I soldered the wires. Also using the tester, I found the 6th pin of the PWM controller and the feedback resistors rang from it. The resistor was rfb, it was evaporated and instead of it, a 10 kilo-ohm trimmer resistor was soldered from the output to regulate the output voltage, and also through the calls I found out that the power supply of the PWM controller is directly connected to the input power line. This means that it will not be possible to supply more than 12 volts to the input, so as not to burn the PWM controller.

Let's see how the power supply looks like in operation

Soldered the plug for input voltage, voltage indicator and output wires. We connect external power supply 12 volts. The indicator lights up. Has already been configured for a voltage of 9.2 volts. Let's try to adjust the power supply with a screwdriver.

It's time to check out what the power supply is capable of. I took a wooden block and a homemade wirewound resistor made of nichrome wire. Its resistance is low and, together with the tester's probes, is 1.7 ohms. We turn on the multimeter in ammeter mode, connect it in series to the resistor. Look what happens - the resistor is heating up to red, the output voltage is practically unchanged, and the current is about 4 amperes.

Previously, the master has already made similar power supplies. One is cut by hand from the laptop board.

This is the so-called duty stress. Two sources for 3.3 volts and 5 volts. I made a case for him on a 3d printer. You can also look at the article where I made a similar regulated power supply, I also cut it out of the laptop board (https://electro-repair.livejournal.com/3645.html). This is also a PWM power controller for RAM.

How to make a regulating power supply from a conventional one, from a printer

We will talk about the power supply of the canon printer, inkjet. They are left idle for many. This is essentially a separate device, held on a latch in the printer.
Its characteristics: 24 volts, 0.7 amperes.

I needed a power supply for a homemade drill. It just fits in power. But there is one caveat - if you connect it like that, we get only 7 volts at the output. Triple output, connector and we get only 7 volts. How do I get 24 volts?
How to get 24 volts without disassembling the unit?
Well, the simplest is to close the plus with an average output and get 24 volts.
Let's try to do it. We connect the power supply unit to the 220 network. We take the device and try to measure it. We connect and see the output of 7 volts.
Its central connector is not used. If we take and connect to two at the same time, the voltage is 24 volts. This is the easiest way to make this power supply 24 volts without disassembling.

A homemade regulator is needed so that the voltage can be regulated within certain limits. 10 volts to maximum. This is easy to do. What is needed for this? First, open the power supply itself. It is usually glued. How to open it so as not to damage the case. There is no need to poke or pry anything. We take a piece of wood more massively or there is a rubber mallet. We put it on a hard surface and peel it along the seam. The glue comes off. Then they knocked on all sides well. Miraculously, the glue comes off and everything opens up. Inside we see the power supply.

Let's get the board. Such power supply units can be easily converted to the desired voltage and can also be made adjustable. On the reverse side, if we turn it over, there is an adjustable tl431 zener diode. On the other hand, we will see the middle contact goes to the base of the q51 transistor.

If we apply voltage, then this transistor opens and 2.5 volts appear on the resistive divider, which are needed for the zener diode to work. And the output is 24 volts. This is the easiest option. How to start it, you can also throw out the q51 transistor and put a jumper instead of the r 57 resistor and that's it. When we turn it on, the output is always 24 volts continuously.

How do I make the adjustment?

You can change the voltage, make 12 volts from it. But in particular, the master does not need it. You need to make it adjustable. How to do it? We discard this transistor and instead of the resistor 57 by 38 kilo-ohms, we will put an adjustable one. There is an old Soviet one for 3.3 kilo-ohms. You can put from 4.7 to 10, which is. Only the minimum voltage to which it can lower it depends on this resistor. 3.3 is very low and unnecessary. The engines are planned to be delivered at 24 volts. And just from 10 volts to 24 is normal. Who needs a different voltage, you can have a large resistance trimmer.
Let's get started, we will solder. We take a soldering iron, hair dryer. I removed the transistor and resistor.

I soldered the variable resistor and try to turn it on. I applied 220 volts, we see 7 volts on our device and we begin to rotate the variable resistor. The voltage has risen to 24 volts and we rotate smoothly and smoothly, it drops - 17-15-14, that is, it drops to 7 volts. In particular, it is installed at 3.3 com. And our rework was quite successful. That is, for purposes from 7 to 24 volts, voltage regulation is quite acceptable.

This option turned out. I put a variable resistor. The handle turned out to be an adjustable power supply - quite convenient.

Video of the Tekhnar channel.

It is easy to find such power supplies in China. I came across an interesting store that sells used power supplies from different printers, laptops and netbooks. They disassemble and sell the boards themselves, completely serviceable for different voltages and currents. The biggest plus is that they disassemble proprietary hardware and all power supplies are of high quality, with good details, all have filters.
Photos - different power supplies, cost a penny, almost a freebie.

Simple block with adjustment

Simple option homemade device for power supply of devices with regulation. The scheme is popular, it is widespread on the Internet and has been shown to be effective. But there are also limitations, which are shown on the video along with all the instructions for making a regulated power supply.

Homemade regulated unit on one transistor

What is the simplest regulated power supply you can make? This can be done on the lm317 microcircuit. She already with herself is almost a power supply. It can be used to manufacture both a voltage-regulated power supply and a flow. This video tutorial shows a voltage regulated device. The master found a simple scheme. Input voltage maximum 40 volts. Output from 1.2 to 37 volts. Maximum output current 1.5 amps.

Without a heat sink, without a heat sink, the maximum power can be as little as 1 watt. And with a 10 watt radiator. List of radio components.

Let's start assembling

Let's connect an electronic load to the output of the device. Let's see how well the current holds. We set it to the minimum. 7.7 volts, 30 milliamps.

Everything is regulated. Let's set 3 volts and add current. On the power supply, we will only set more restrictions. We translate the toggle switch to the top position. Now 0.5 amperes. The microcircuit began to warm up. There is nothing to do without a heat sink. Found some kind of plate, not for long, but that's enough. Let's try again. There is a drawdown. But the block works. Voltage regulation is in progress. We can insert an offset to this scheme.

Radioblogful video. Solder video blog.

Hello friends. Today I made a small selection of material for assembling a regulated power supply. LT1083CP is used as a regulating element, voltage regulation limits are in the range from 1.5 to 30V, current is up to 7 Amperes. This scheme can be found in the form of constructors (KIT) on Aliexpress, and so, on some selling sites. The set looks like this:

View of the board from both sides:

By photo printed circuit board, taken from Ali, I made a copy in LAY6 format for making it myself, but first, I will give a schematic diagram:

Immediately I want to draw your attention to how the LED is connected in the diagram. As I understand it, it serves as an indicator of the on state of the power supply. If we have an adjustable voltage value at the output, and the regulator of this value will be unscrewed to the minimum value, the LED will simply not light up, therefore, I consider it advisable to connect the LED + R3 chain to the input of the stabilizer U1, where the voltage is more or less constant, not counting the possible drawdown during high currents. It is this option for connecting the LED that is implemented in the watering can, which looks like this:

There is nothing special to explain in the diagram, the standard inclusion of a linear stabilizer, the only thing I want to focus on is the self-healing fuse that comes in the KIT-set, the board is marked with FU. If you decide to make an external fuse, you can bring it out with wires by connecting it to the same place, but for those who decide to make an exact copy, I will give appearance such an element:

You can easily buy it on Ali for 100 rubles for a dozen with free shipping. See the rest of the list of elements below, there are not many of them, so the list will be single:

LT1083CP - 1 pc.
R1 - 100R / 2W - 1 pc.
R2 - variable resistor 5k (multiturn in the set, you can bring the usual one to the front panel of the case)
R3 - 5k6 / 0.25W - 1 pc.
C1, C5 - 105 = 1mF / 50 ... 63V NON-POLAR - 1 pc.
C2 - 4700mF / 50V - 1 pc. (You can supply 6800mF or 10000mF / 50V if it fits in size)
C3 - 10mF / 50V - 1 pc.
C6 - 1000mF / 50V - 1 pc. (470mF / 50V installed on the KIT board)
D1, D4, D6, D7 - 10A10 (diodes 10A) - 1 pc.
D2, D3 - 1N4007 - 2 pcs.
LED1 - red LED 3mm - 1 pc.
Connector 2Pin (Connector Terminal block 2 pins) - 2 pcs.
Transformer - secondary winding 24V 8A (not included)

Who will find it more convenient to place the regulating potentiometer on the board - the watering can looks like this:

Well, the last thing I wanted to add is a way to connect two identical boards to implement a bipolar source:

The archive contains sources and datasheets for 10A10 10A10 diodes and a linear stabilizer LT1083.

The size of the archive with materials for assembling a regulated power supply unit for LT1083 is 1.3 Mb.

Buy this power supply with a set is cheaper (330 rubles), and you do not need to make the board yourself, the link to Ali is LT1083 KIT

Voltage regulator LM338, manufactured by Texas Instruments, is a general purpose integrated circuit that can be connected in a variety of ways to obtain high quality power circuits.

LM Stabilizer Specifications 338 :

• Providing an output voltage from 1.2 to 32 V.
• Load current up to 5 A.
• Availability of protection against possible short circuit.
• Reliable protection of the microcircuit against overheating.
• Output voltage error 0.1%.

The LM338 integrated circuit is available in two package options - a metal TO-3 package and a plastic TO-220:

Pinout of the LM338 stabilizer pins

Main technical characteristics of LM338

Calculator for LM338

The calculation of the parameters of the LM338 stabilizer is identical to the calculation of the LM317. An online calculator is located.

Application examples of the LM338 stabilizer (connection diagrams)

The following examples will show you some very interesting and useful power circuits built with the LM338.

Simple regulated power supply on LM338

This diagram is a typical connection of the LM338 strapping. The power supply circuit provides an adjustable output voltage from 1.25 to the maximum input voltage supplied, which should not exceed 35 volts.

Variable resistor R1 is used for modulating the output voltage.

Simple 5 Amp Regulated Power Supply

This circuit produces an output voltage that can be equal to the input voltage, but the current varies well and cannot exceed 5 amps. Resistor R1 is precisely sized to maintain the safe 5 amps of limiting current that can be drawn from the circuit.

Regulated 15 amp power supply

As mentioned earlier, the LM338 microcircuit alone can only handle 5A maximum, however, if it is necessary to obtain a higher output current, in the region of 15 amperes, then the connection diagram can be modified as follows:

In this case, three LM338s are used to provide a high current load with the ability to adjust the output voltage.

Variable resistor R8 is designed for smooth adjustment of the output voltage

Digital controlled power supply

In the previous power supply circuit, a variable resistor was used to regulate the voltage. The diagram below allows the required output voltage levels to be obtained by means of a digital signal applied to the base of the transistors.

The value of each resistance in the transistor collector circuit is selected in accordance with the required output voltage.

Lighting controller circuit

In addition to power supply, the LM338 microcircuit can also be used as a light controller. The circuit shows a very simple design where a phototransistor replaces a resistor that is used as a component to regulate the output voltage.

The lamp, the illumination of which must be kept at a stable level, is powered by the LM338 output. Its light falls on a phototransistor. When the illumination increases, the resistance of the photoresistor decreases and the output voltage decreases, which in turn reduces the brightness of the lamp, keeping it at a stable level.

The following circuit can be used to charge 12 volt lead acid batteries. The RS resistor can be used to set the required charging current for a specific battery.

By selecting the resistance R2, the required output voltage can be adjusted according to the type of battery.

Smooth start circuit (soft start) of the power supply

Some sensitive electronic circuits require a smooth power-up. The addition of a capacitor C2 to the circuit makes it possible to smoothly increase the output voltage to the specified maximum level.

The LM338 can also be configured to keep the heater temperature at a certain level.

Here, another important element has been added to the circuit - the LM334 temperature sensor. It is used as a sensor which is connected between adj LM338 and ground. If the heat from the source rises above a predetermined threshold, the resistance of the sensor decreases accordingly, and the output voltage of the LM338 decreases, subsequently decreasing the voltage across the heating element.

(729.7 Kb, downloaded: 5 150)