A voltage stabilizer is the most important radio element of modern radio-electronic devices. It provides a constant voltage at the output of the circuit, which is almost independent of the load.
Stabilizers of the LM family
In our article we will look at voltage stabilizers of the LM78XX family. The 78XX series is produced in metal cases TO-3 (left) and in plastic cases TO-220 (right). Such stabilizers have three terminals: input, ground (common) and output.
Instead of “XX”, manufacturers indicate the stabilization voltage that this stabilizer will give us. For example, a 7805 stabilizer will produce 5 Volts at the output, 7812 will produce 12 Volts, and 7815 will produce 15 Volts. Everything is very simple.
Connection diagram
And here is the connection diagram for such stabilizers. This circuit is suitable for all stabilizers of the 78XX family.
Characteristics of LM stabilizers
What voltage should be supplied for the stabilizer to work as it should? To do this, we are looking for a datasheet for stabilizers and studying it carefully.We are interested in these characteristics:
Output voltage- output voltage
Input voltage- input voltage
We are looking for our 7805. It gives us an output voltage of 5 Volts. Manufacturers noted a voltage of 10 volts as the desired input voltage. But it happens that the output stabilized voltage is sometimes either slightly underestimated or slightly overestimated. 
For electronic trinkets, fractions of volts are not felt, but for precision (accurate) equipment it is better to assemble your own circuits. Here we see that the 7805 stabilizer can give us one of the voltages in the range of 4.75 - 5.25 Volts, but the conditions must be met that the output current in the load will not exceed 1 Ampere. An unstabilized DC voltage can “fluctuate” in the range from 7.5 to 20 Volts, while the output will always be 5 Volts.
The power dissipation on the stabilizer can reach up to 15 Watts - this is a decent value for such a small radio component. Therefore, if the load at the output of such a stabilizer consumes a decent current, I think it’s worth thinking about cooling the stabilizer. To do this, it must be placed on the radiator through KPT paste. The greater the current at the output of the stabilizer, the larger the radiator should be. It would be ideal if the radiator was also blown by a fan.
LM work in practice
Let's look at our ward, namely the LM7805 stabilizer. As you already understand, at the output we should get 5 Volts of stabilized voltage.
Let's assemble it according to the diagram
We take our Breadboard and quickly assemble the connection diagram suggested above. The two yellow ones are capacitors, although it is not necessary to install them.
So, wires 1,2 - here we drive the unstabilized input DC voltage, remove 5 Volts from wires 3 and 2.
On the Power Supply we set the voltage in the range of 7.5 Volts and up to 20 Volts. In this case, I set the voltage to 8.52 Volts.
And what did we get at the output of this stabilizer? 5.04 Volts! This is the value we will get at the output of this stabilizer if we supply voltage in the range from 7.5 to 20 Volts. Works great!
Let's check one more of our stabilizers. I think you have already guessed how many volts it is.
We assemble it according to the diagram above and measure the input voltage. According to the datasheet, you can supply it with an input voltage from 14.5 to 27 Volts. We set 15 Volts with kopecks.
And here is the output voltage. Damn, some 0.3 Volts is not enough for 12 Volts. For radio equipment operating on 12 Volts this is not critical.
How to make a power supply for 5, 9.12 Volts?
How to make a simple and highly stable power supply for 5, 9 or even 12 Volts? Yes, very simple. To do this, you need to read this article and install a stabilizer on the radiator at the output! That's all! The circuit will be approximately like this for a 5 Volt power supply:
Two electrolytic capacitors to eliminate ripple and a highly stable 5 volt power supply at your service! To get a power supply for a higher voltage, we also need to get a higher voltage at the output of the transformer. Aim for the voltage on capacitor C1 to be no less than in the datasheet for the stabilizer being described.
To ensure that the voltage stabilizer does not overheat, apply the minimum voltage specified in the datasheet to the input. For example, for the 7805 stabilizer this voltage is 7.5 Volts, and for the 7812 stabilizer the desired input voltage can be considered a voltage of 14.5 Volts. This is due to the fact that the voltage difference, and therefore the power, will be dissipated by the stabilizer.
As you remember, the power formula is P=IU, where U is voltage and I is current. Consequently, the higher the input voltage of the stabilizer, the greater the power consumed by it. And excess power is heating. As a result of heating, such a stabilizer may overheat and enter a protection state, in which further operation of the stabilizer stops or even burn out.
Conclusion
An increasing number of electronic devices require high-quality, stable power without any voltage surges. The failure of one or another electronic equipment module can lead to unexpected and not very pleasant consequences. Use the achievements of electronics to your health, and don’t worry about powering your electronic trinkets.
Buy a voltage stabilizer
You can buy these integrated stabilizers cheaply as a whole set on Aliexpress at this
link. There are absolutely any values here, even for negative voltage.
Devices that are included in the power supply circuit and maintain a stable output voltage are called voltage stabilizers. These devices are designed for fixed output voltages: 5, 9 or 12 volts. But there are devices with adjustment. They can be set to the desired voltage within certain accessible limits.
Most stabilizers are designed for a certain maximum current that they can withstand. If you exceed this value, the stabilizer will fail. Innovative stabilizers are equipped with a current blocking, which ensures that the device is turned off when the maximum current in the load is reached and are protected from overheating. Along with stabilizers that maintain a positive voltage value, there are also devices that operate with negative voltage. They are used in bipolar power supplies.
The 7805 regulator is manufactured in a transistor-like package. Three conclusions are visible in the figure. It is designed for a voltage of 5 volts and a current of 1 ampere. There is a hole in the case for fixing the stabilizer to the radiator. The 7805 is a positive voltage device.
The mirror image of this regulator is its 7905 negative voltage counterpart. There will be a positive voltage on the case, a negative value will be sent to the input. -5 V is removed from the output. In order for the stabilizers to work in normal mode, 10 volts must be supplied to the input.
Pinout
The 7805 stabilizer has a pinout, which is shown in the figure. The common terminal is connected to the housing. This plays an important role during installation of the device. The last two digits indicate the voltage output by the microcircuit.
Stabilizers for powering microcircuits
Let's consider methods for connecting digital devices made independently using microcontrollers to power. Any electronic device requires a proper power connection to function properly. The power supply is designed for a certain power. A capacitor of significant capacity is installed at its output to equalize voltage pulses.
Power supplies without stabilization, used for routers, cell phones and other equipment, are not directly combined with power supply to microcontrollers. The output voltage of these blocks varies and depends on the connected power. An exception to this rule are chargers for smartphones with a USB port that outputs 5 V.
Scheme of operation of the stabilizer, compatible with all microcircuits of this type:
If you disassemble the stabilizer and look at its insides, the diagram would look like this:
For electronic devices that are not sensitive to voltage accuracy, such a device is suitable. But for accurate equipment you need a high-quality circuit. In our case, the 7805 stabilizer produces a voltage in the range of 4.75-5.25 V, but the current load should not be more than 1 A. The unstable input voltage fluctuates in the range of 7.5-20 V. In this case, the output value will always be equal to 5 B. This is an advantage of stabilizers.
When the load that the microcircuit can deliver increases (up to 15 W), it is better to provide the device with cooling by a fan with an installed radiator.
Efficient stabilizer circuit:
Technical data:
- Maximum current 1.5 A.
- Input voltage range – up to 40 volts.
- Output – 5 V.
To avoid overheating of the stabilizer, it is necessary to maintain the lowest input voltage of the microcircuit. In our case, the input voltage is 7 volts.
The microcircuit dissipates the excess power onto itself. The higher the input voltage on the chip, the higher the power consumption, which is converted into heating the case. As a result, the microcircuit will overheat and the protection will trip and the device will turn off.
Voltage stabilizer 5 volts
This device differs from similar devices in its simplicity and acceptable stabilization. It uses the K155J1A3 chip. This stabilizer was used for digital devices.
The device consists of working units: a trigger, a reference voltage source, a comparison circuit, a current amplifier, a transistor switch, an inductive energy storage device with a diode switch, input and output filters.
After connecting the power, the starting unit, which is made in the form of a voltage stabilizer, begins to operate. A voltage of 4 V appears at the emitter of the transistor. Diode VD3 is closed. As a result, the reference voltage and current amplifier are turned on.
The transistor switch is closed. A voltage pulse is generated at the output of the amplifier, which opens a switch that passes current to the energy storage device. The negative connection circuit in the stabilizer is turned on, and the device goes into operation mode.
All used parts are carefully checked. Before installing a resistor on the board, its value is set to 3.3 kOhm. The stabilizer is first connected to 8 volts with a load of 10 ohms, then, if necessary, set it to 5 volts.
Schematic diagram of a simple and reliable voltage stabilizer from 8...15V to stable 5V. Built on the L7805 integrated circuit. The stabilizer is suitable for powering digital equipment, microcontrollers, for charging phones and other devices from a stable voltage of 5V.
78XX series chips contain several built-in protections:
- Output voltage and current protection;
- Thermal protection (against overheating above +125 °C);
- Built-in powerful diode (protects against reverse current).
Schematic diagram
Figure 1 shows a schematic diagram of a homemade voltage stabilizer based on the L7805 chip. The circuit does not contain a large number of parts, which can be further reduced if reverse polarity protection at the input (D1) and voltage indication at the output (R1, LED1) are not needed.
Rice. 1. Schematic diagram of a simple and reliable 5V voltage stabilizer (L7805).
Details
A Schottky diode can be installed as D1; in the circuit it acts as protection against power supply reverse polarity, or as a rectifier if the circuit is connected directly to the secondary winding of a step-down network transformer. Diode D2 protects the output of the microcircuit from reverse voltage.
Capacitors C2 and C3 are film or ceramic, non-polar. Electrolytic capacitor C1 can be installed with a capacity of 50 µF or more, and for C4 10-22 µF will be sufficient. LED1 is used to indicate the presence of 5V voltage; any LED with a green glow will do here.
This scheme is simple and time-tested. Instead of the L7805 microcircuit, you can install other microcircuits of this series and thus obtain a voltage stabilizer for other voltages.
This short article is dedicated to the three-terminal stabilizer voltage L7805. The microcircuit is available in two types: plastic - TO-220 and metal - TO-3. Three pins, looking from left to right - input, minus, output.
The last two digits indicate stabilized voltage microcircuits- 7805-5 volts, respectively, 7806-6v.... 7824 - we can probably already guess how much. You may also be interested in vests for the boys' choir, more details on the website at the link.
Here connection diagram stabilizer, which is suitable for all chips in this series:
We don’t look at small capacitors; it is advisable to install larger ones.
Well, this is the stabilizer from the inside:
It's awesome, right? And all this fits.....A miracle of technology.
So, we are interested in these characteristics. Output voltage - output voltage. Input voltage - input voltage. We are looking for our 7805. It gives us an output voltage of 5 Volts. Manufacturers noted the desired input voltage to be 10 Volts. But it happens that the output stabilized voltage is sometimes either slightly underestimated or slightly overestimated. For electronic trinkets, fractions of volts are not felt, but for precision (precision) equipment it is better to assemble your own circuits. Here we see that the 7805 stabilizer can give us one of the voltages in the range of 4.75 - 5.25 Volts, but the conditions must be met that the output current in the load will not exceed one Ampere. An unstabilized DC voltage can “fluctuate” in the range from 7.5 to 20 Volts, while the output will always be 5 Volts. This is the big advantage of stabilizers.
Under heavy load, and this microcircuit is capable of delivering a power of as much as 15 Watts, it is better to equip the stub with a radiator and, if possible or desired, for greater and faster cooling, attach a cooler to it, like in a computer.
Here is the normal stabilizer circuit:
Technical specifications
Housing...to-220
Maximum load current, A... 1.5
Range of permissible input voltages, V... 40
Output voltage, V... 5
to help.
In order to prevent the stabilizer from overheating, you need to adhere to the required minimum voltage at the input of the microcircuit, that is, if we have L7805, then we allow 7-8 volts at the input, if 12 - 14-15 volts.
This is due to the fact that the stabilizer will dissipate excess power on itself. As you remember, the power formula is P=IU, where U is voltage and I is current. Consequently, the higher the input voltage of the stabilizer, the greater the power consumed by it. And excess power is heating. As a result of heating, such a stabilizer may overheat and enter a protection state, in which further operation of the stabilizer stops.
I converted the speaker amplifier to a cheap D-class module on PAM8403. The speakers began to play louder, and a type of bass appeared. Satisfied. But one problem arose - if power was supplied to the speakers from regular (pulse) charging at 5V, there were large distortions in the power supply. It was still possible to listen at a low volume, but impossible at a high volume. I decided to solder a power supply with linear stabilization.
The circuit diagram of such a power supply is simple:
The first impulse is to buy all the parts at the local Electronics and quickly solder the power supply circuit on a breadboard. I only calculated the price of the stabilizer parts - it turned out to be about 700 rubles. The toad strangled. Let's look at the ready-made options on Ali and eBay. Everything here is chocolate. There are cheap construction kits (you can solder them onto a printed circuit board yourself), there are ready-made modules for 110 rubles. I ended up buying it on eBay - it was cheaper there. It arrived in three weeks. The stabilizer was hanging on the radiator - I screwed it on tighter. 
The remaining parts are a transformer, a fuse, a housing, a power button, legs for the housing, a USB connector in “Electronics”. It took about 500 rubles for everything.
Characteristics of the module and stabilizer LM7805:
1. Board size. 57mm*23mm
2. Input voltage input voltage polarity, AC and DC can, range. 7.5-20V
3. The output voltage 5V
4. The maximum output current. 1.2A
5. Provided fixed bolt hole, convenient installation
As you can see, the module can be supplied with voltage from 7.5V to 20V. The output is 5V.
The stabilizer inside is quite complex: 
I bought a transformer like this TP112 (7.2 W) 2*12V xx - 
I took this 220V power button - it’s quite large. 
Button with fixation and backlight. I don’t understand how to connect the backlight when pressed (maybe anyone who knows can tell me?). I did it without backlight. 
Assembled a stand for testing: 
The speakers play without distortion at maximum volume. Nothing in the PSU gets very hot. Goal achieved: 
I tried to charge the phone - the current is 0.5A 
With a 1 A resistor, everything is completely sad: 
Conclusion - this power supply cannot be used as a charger. Apparently the transformer needs to be more powerful.
I collected everything into the case: 
I made a hole on top so that the LED indicator on the module could be seen to indicate operation. I sealed the hole on the reverse side with transparent film.
Thank you for your attention.
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