Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry"s standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five http://jquery2dotnet.com/ centuries , but also the leap into electronic typesetting, remaining essentially unchanged. It was popularized in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
power unit- This is an indispensable attribute in the amateur radio workshop. I also decided to build myself an adjustable power supply, because I was tired of buying batteries every time or using random adapters. Here is its brief description: The power supply regulates the output voltage from 1.2 Volts to 28 Volts. And it provides a load of up to 3 A (depending on the transformer), which is most often enough to test the functionality of amateur radio designs. The circuit is simple, just right for a beginner radio amateur. Assembled on the basis of cheap components - LM317 and KT819G.
LM317 regulated power supply circuit
List of circuit elements:
Pinout of the microcircuit and transistor
The case was taken from the computer's power supply. The front panel is made of PCB, it is advisable to install a voltmeter on this panel. I haven't installed it because I haven't found a suitable one yet. I also installed clamps for the output wires on the front panel.
I left the input socket to power the power supply itself. A printed circuit board made for surface-mounted mounting of a transistor and a stabilizer chip. They were secured to a common radiator through a rubber gasket. The radiator was solid (you can see it in the photo). It needs to be taken as large as possible - for good cooling. Still, 3 amperes is a lot!
The microcircuit has been a hit among novice radio amateurs for decades due to its simplicity and reliability. Based on this chip, you can assemble an adjustable power supply based on LM317, a current stabilizer, an LED driver and other power supplies. This will require several external radio components; for LM317, the switching circuit works immediately, no configuration is required.
The LM317 and LM317T datasheet microcircuits are completely identical, differing only in the housing. There are no differences or differences, not at all.
I also wrote reviews and datasheets of other popular ICs. With good illustrations, clear and simple diagrams.
The main purpose is to stabilize positive voltage. The adjustment occurs in a linear manner, unlike pulse converters.
The LM317T is also popular, I haven’t come across it, so I had to search for a long time for the correct datasheet for it. It turned out that they are completely identical in parameters; the letter “T” at the end of the marking indicates the TO-220 1.5 Ampere housing.
Download datasheets:
Characteristics
Even with integrated protection systems, it should not be operated at its maximum capacity. If it fails, it is not known how many volts will be at the output, it will be possible to burn an expensive load.
I will give the main electrical characteristics from the LM317 datasheet in Russian. Not everyone knows technical terms in English.
The datasheet indicates a huge scope of application; it’s easier to write where it is not used.
There are many microcircuits that have almost the same functionality, domestic and foreign. I will add more powerful analogues to the list to avoid including several in parallel. The most famous LM317 analogue is the domestic KR142EN12.
Complete analogues:
Regulator 1.25 - 20 Volts with adjustable current
To make calculations as easy as possible based on the LM317T, many LM317 calculator programs and online calculators have been developed. By specifying the initial parameters, you can immediately calculate several options and see the characteristics of the required radio components.
A program for calculating voltage and current sources taking into account LM317 characteristics of LM317T. Calculation of circuits for switching on powerful converters using transistors, TL431, M5237. Also IC 7805, 7809, 7812.
The LM317 stabilizer has proven itself to be a universal microcircuit capable of stabilizing voltage and Amperes. Over decades, hundreds of LM317T switching circuits for various applications have been developed. The main purpose is a voltage stabilizer in power supplies. To increase the number of amperes at the output there are several options:
To build a bipolar power supply, negative voltage stabilizers LM337 are used.
I think that parallel connection is not the best option due to the difference in the characteristics of the stabilizers. It is impossible to set several pieces to exactly the same parameters in order to distribute the load evenly. Due to the spread, one will always have more load than the others. The probability of failure of a loaded element is higher; if it burns, the load on others, which may not be able to withstand it, will sharply increase.
In order not to connect in parallel, it is better to use transistors at the output for the power part of the DC-DC voltage converter. They are designed for high current and have better heat dissipation due to their large size.
Modern pulse chips are inferior in popularity, but their simplicity is hard to beat. The lm317 current stabilizer for LEDs is easy to set up and calculate, and is currently still used in small-scale production of electronic components.
Bipolar power supply LM317 and LM337, for obtaining positive and negative voltage.
For beginner radio amateurs, I can recommend radio designers from the Chinese on Aliexpress. Such a constructor is the best way to assemble a device according to the switching diagram; there is no need to make a board and select parts. Any designer can be modified at your own discretion, the main thing is that there is a board. The cost of the designer starts from 100 rubles with delivery, the ready-made module assembled from 50 rubles.
The microcircuit is very popular, produced by many manufacturers, including Chinese. My colleagues came across LM317 with poor parameters that do not draw the declared current. We bought it from the Chinese, who like to fake and copy everything, while worsening the characteristics.
Comments (16):
#1 root March 28 2017
Additions have been made to the diagram:
It is better to make up capacitance C1 from several electrolytic capacitors; if you need a high current, then 2 pieces of 4700 μF or more are recommended.
KT819 transistors can be replaced with foreign MJ3001 or others.
#2 Victor September 12 2017
R2 - what type, sp...or. The circuit is not bad! THANK YOU!!!
#3 root September 12 2017
Resistor R2 - variable resistance, any type, power 0.5 W or more. If there is no suitable one with a resistance of 3.3K, then you can install 6.8K or another (up to 10kOhm).
#4 Dmitry October 25 2017
Thank you for the lessons, very useful.
#5 Evgeniy November 25 2017
What about overload/short circuit protection?
#6 root November 26, 2017
In the above circuit there is no protection against short circuit and overcurrent. Without improving the circuit, it would not hurt to install a fuse at its output.
#7 andrius December 15 2017
I assembled the circuit, but somehow the current at the output drops. Trans 300sch 40a I supply 31 volts and at the output with a load of 6 volts 3 volts. Maybe I assembled something wrong. I changed the transistors too - it doesn’t help.
#8 root December 15 2017
Carefully check the entire installation, especially the correct connection of the microcircuit and transistors.
Pinout of the LM317 chip: 
For transistors in plastic and metal cases - KT819 - characteristics and pinout.
#9 andrius December 15 2017
everything has been checked many times. The microcircuit is connected correctly and the transistor is also connected. I also changed the microcircuit and transistors. nothing helps, I don’t even know what else can be done.
#10 Alexander Compromister December 16 2017
Thanks to #root for the mixed internal circuit diagram of the chip: I looked everywhere, but to no avail. For the 12th Krenka it will be similar.
#11 Alexander Compromister December 17 2017
Regarding the internal circuit of LM317: how to replace the current source: probably with two (or more) silicon diodes? Is it possible to replace the transistors on the internal circuit with one composite brand, say, KT827VM? How to replace the operational amplifier? How to build current protection? - And while I was writing the questions, I immediately found the answer: use a field-effect transistor.
#12 root December 17 2017
Alexander, below is a schematic diagram of the LM117, LM317-N microcircuit crystal from the datasheet (website ti.com - Texas Instruments): 
#13 Alexander Compromister December 17 2017
Thank you: it is very reminiscent of the KR142EN circuit from . But there are no denominations.
#14 Igor December 26 2017
Is it possible to use KT827a transistors in the circuit?
#15 Alexander Compromister December 27 2017
To user #Igor: Surely this is possible, however, after the op-amp (see post #8) in the base circuit before the protection circuit, you probably need to include a quenching resistor, the value of which depends on the supply voltage: the main thing is that there is no more than five volts. The Current Protection unit can probably be replaced with a KS147A zener diode.
#16 Andrey February 06, 2018
Hello, I’m assembling a power supply for the first time - I found an old transformer in the garage. I’m trying to make it according to this diagram. Please tell me which leg of the variable resistor goes where.
Sooner or later, any novice radio amateur is faced with the need to have a simple, reliable and inexpensive regulated power supply to test his own crafts, and, of course, test new “patients”. There are few options - either buy a ready-made unit with the required characteristics in a store or from a more experienced colleague in the craft, or assemble the device yourself from scrap materials. Taking into account the prices for more or less high-quality SMPS with voltage regulation (on average from 15 to 80 USD), the conclusion suggests itself.
One of the simplest and most universal options is a power supply based on LM 317. This is a popular and inexpensive adjustable linear voltage stabilizer, usually manufactured in the TO-220 housing. You can find out which leg is responsible for what from the picture below.
The main characteristics are:
Let's take a closer look at the maximum current. The fact is that LM 317 is a linear stabilizer. The “extra” voltage on it turns into heat, and the maximum thermal package of the microcircuit with an additional cooling radiator is 20 W, without it - about 2.5 W. Knowing the formula for calculating power, we can calculate how much current can actually be obtained under various conditions. For example, Uin=20 V, Uout=5 V – voltage drop Udrop = 15V.
With a thermal package of 20 W, this means a maximum permissible current of 1.33 A (20 W/15 V = 1.33 A). And without a radiator - only 0.15A. So, in addition to radio components you should take care of finding a radiator– something more massive, from an old power amplifier, will do, and you need to approach the choice of power source wisely.
Very few details are needed:
Just in case, we will separately explain why the transformer voltage is no more than 25 V. When rectified using a filter capacitor, the output voltage increases by the root of two, that is, approximately 1.44 times. Thus, having 25 VAC at the output of the windings, after the diode bridge and smoothing capacitor the voltage will be about 35–36 VDC, which is quite close to the limit of the microcircuit. Keep this in mind when choosing capacitors and transformer!
As you can see, there is very little work - desoldering of parts can be done even by surface mounting, without compromising quality, provided that all contacts are carefully insulated and the power supply is survivable.
After assembly, do not rush to connect the load to the unit - first check the supply voltage at the output of the diode bridge, and then start the unit at idle and check the temperature of the stabilizer with your finger - it should be cool. Then connect the power from the unit to some load and check the voltage readings at the output - they should not change.
LM 317 has many analogues, both good and not so good - be careful when choosing a product on the market! If adjustment accuracy is important, you can change the value of the tuning resistor to 2.4 kOhm - the output voltage range will, of course, decrease, but accidentally touching the handle will hardly change the output voltage– and sometimes this is very important! Experiment with different ratings to make your power supply comfortable.
You also need to observe the temperature regime - the optimal operating temperature of LM 317 is 50...70 degrees Celsius, and the hotter the microcircuit heats up, the worse the accuracy of voltage stabilization.
If constant heavy loads are expected, say, powering power amplifiers or electric motors, it is advisable not only to mount the microcircuit on the radiator, but also increase the capacity of the smoothing capacitor up to 4700 µF and above. With a correctly selected capacitance, the voltage will not sag under load.
When you decide to get your own universal power supply, think about what would be better for you - to pay a decent amount for a ready-made solution or to assemble the device yourself, using inexpensive components and satisfying your own vanity with a small, but still, achievement.
The cost of a do-it-yourself regulated power supply is low - from the cost of the microcircuit itself (about 20 rubles) to 700–800 rubles when purchasing new parts in a store.
Recently, interest in current stabilizer circuits has grown significantly. And first of all, this is due to the emergence of artificial lighting sources based on LEDs as leading positions, for which a stable current supply is a vital point. The simplest, cheapest, but at the same time powerful and reliable current stabilizer can be built on the basis of one of the integrated circuits (IM): lm317, lm338 or lm350.
Before moving directly to the circuits, let's consider the features and technical characteristics of the above linear integrated stabilizers (LIS).
All three IMs have a similar architecture and are designed to build on their basis simple current or voltage stabilizer circuits, including those used with LEDs. The differences between the microcircuits lie in the technical parameters, which are presented in the comparison table below.
| LM317 | LM350 | LM338 | |
|---|---|---|---|
| Adjustable output voltage range | 1.2…37V | 1.2…33V | 1.2…33V |
| Maximum current load | 1.5A | 3A | 5A |
| Maximum permissible input voltage | 40V | 35V | 35V |
| Indicator of possible stabilization error | ~0,1% | ~0,1% | ~0,1% |
| Maximum power dissipation* | 15-20 W | 20-50 W | 25-50 W |
| Operating temperature range | 0° - 125°С | 0° - 125°С | 0° - 125°С |
| Datasheet | LM317.pdf | LM350.pdf | LM338.pdf |
* - depends on the manufacturer of the IM.
All three microcircuits have built-in protection against overheating, overload and possible short circuit.
Integrated stabilizers (IS) are produced in a monolithic package of several variants, the most common being TO-220. The microcircuit has three outputs:
The greatest use of ICs is found in power supplies for LEDs. Let's consider the simplest current stabilizer (driver) circuit, consisting of only two components: a microcircuit and a resistor. 
The voltage of the power source is supplied to the input of the MI, the control contact is connected to the output contact through a resistor (R), and the output contact of the microcircuit is connected to the anode of the LED.
If we consider the most popular IM, Lm317t, then the resistor resistance is calculated using the formula: R = 1.25/I 0 (1), where I 0 is the output current of the stabilizer, the value of which is regulated by the passport data for LM317 and should be in the range of 0.01 -1.5 A. It follows that the resistor resistance can be in the range of 0.8-120 Ohms. The power dissipated by the resistor is calculated by the formula: P R =I 0 2 ×R (2). Switching on and calculating IM lm350, lm338 are completely similar.
The resulting calculated data for the resistor is rounded up, according to the nominal series.
Fixed resistors are manufactured with a small variation in resistance value, so it is not always possible to obtain the desired output current value. For this purpose, an additional trimming resistor of appropriate power is installed in the circuit. 
This slightly increases the cost of assembling the stabilizer, but ensures that the necessary current is obtained to power the LED. When the output current stabilizes at more than 20% of the maximum value, a lot of heat is generated on the microcircuit, so it must be equipped with a heatsink.
