A selection of DC motor speed controller circuits

You can adjust the rotation speed of the shaft of a low-power commutator motor by connecting a resistor in series to its power supply circuit. But this option creates a very low efficiency, and in addition there is no possibility of smoothly changing the rotation speed.

The main thing is that this method sometimes leads to a complete stop of the electric motor at low supply voltage. motor speed controller described in this article does not have these disadvantages. These circuits can also be successfully used to change the brightness of 12-volt incandescent lamps.

What is a 220V voltage regulator

The abbreviated name of the device in question is RN 0-220 V. The simplest device of this type is a dimmer for incandescent lamps.
The device regulates the parameters of the mains voltage, increases / decreases the degree of the output signal in the range according to the value of the potential difference at its output. Maintains the specified voltage in the consumer circuit. The device regulates (smoothly or gradually) the voltage itself, on which the power in the power range of the connected unit also depends. Works with both reactive and resistive loads, you just need to check whether a particular assembly is suitable, especially for the latter. In addition, it is always necessary to compare the operating power (W) for which the circuit is designed.

PH changes, in accordance with user settings, the level of the output signal from the 220 V network supplied to the load connected to it. Thus, a suitable parameter is set to power a particular device and, more often, to regulate its operation (reducing / increasing the speed of low-power electric motors, light brightness).

The voltage regulator is used:

• in all cases, if a certain voltage, for example 12 V, must be created in the circuit.
• change the rotation speed of small motors of household appliances (the speed of a blender, hair dryer), less often, since not all circuits are suitable, to more powerful motors (for example, drills);
• for other devices whose operation can be configured. And more often (and this is the most correct and effective use) of the lighting level (dimmer), sound volume, heating of heating elements, soldering iron,

Most often, household 0-220 V RNs are used to gradually turn on/off devices.

Factory models usually also have a voltage stabilization chip during power surges, ensuring the devices operate in any mode. According to British standards, a thyristor regulator is called a voltage controller. PH is equipped with universal power supplies on which the voltage can be adjusted.

Types, principle of operation, characteristics

The RN on our topic is intended only for alternating voltage, that is, for a regular 220 V home network.

Most often they are assembled based on the following details:

• transistor.
• thyristors;
• triac;

The circuits also contain capacitors, fixed resistors, and tuning resistors. The selectors of the latter are adjusted. Complex assemblies may include microcircuits.

PH is most effective for resistive loads (resistive, ohmic), meaning they are part of the connected/disconnected user's energy consumption. This is the resistance to the flow of current, such as in the form of a resistor, at the point where electricity is converted into heat.

Resistive loads are heating elements, heating elements, incandescent lamps (not “rulers”).

In an inductive load, the current (much lower than the resistive load) lags behind the voltage and creates reactive power. These are asynchronous electric motors, electromagnets, inductors, transformers, rectifiers. Launch vehicles will not work with them, or will work but ineffectively, creating the risk of equipment failure. There voltage regulators are not always practical.

The thyristor device cannot be used with LED (economical) and fluorescent lamps. Capacitor regulators do not allow smooth voltage fluctuations.

DC motor speed controller using 2 14 volt capacitors.

The practicality of such motors has been proven; they are used in mechanical toys, fans, etc. They have low current consumption, so voltage stabilization is required. Often there is a need to adjust the rotation speed or change the speed of the engine to adjust the fulfillment of the goal presented to any type of electric motor of any model.

This task will be performed by a voltage regulator that is compatible with any type of power supply.

To do this, you need to change the output voltage, which does not require a large load current.

Required parts:

1. 2 Capacitors
2. 2 variable resistors

Connecting the parts:

1. We connect the capacitors to the regulator itself.
2. The first resistor is connected to the negative of the regulator, the second to ground.

Now change the engine speed of the device according to the user’s wishes.

The 14 volt voltage regulator is ready.

Simple 12 volt voltage regulator

DIY thyristor charger

There are many electronic circuits, including complex ones, with a full range of adjustments and protection, a significant number of parts, often not cheap. But most car enthusiasts prefer simple thyristor chargers, made from several inexpensive components, which can often be extracted from used equipment, such as a computer.

Selection of the scheme and principle of its operation

First, it is worth noting the main advantage of the proposed thyristor charger circuit: availability and low financial costs. There are other advantages when using the inexpensive thyristor KU202 as the main component:

1. Good charging current up to 10 A.
2. The energy output is pulse type, which extends the service life of the charged battery.
3. For assembly you will need widely available inexpensive parts that are not difficult to find.
4. The circuit of a thyristor charger for a car battery can be easily repeated even by a car enthusiast with little knowledge of radio engineering, and an experienced electronics engineer will need no more than an hour to put the device into operation.

According to the principle of operation, this is a phase-pulse power regulator made on a thyristor and allows you to change the current strength. The control electrode KU202 is powered by a transistor circuit. To protect the thyristor charger circuit for a car battery from current surges, a diode VD2 is used. Resistance R5 affects the charging current, the value of which, as is known, is 1/1 of the battery capacity. To power the circuit, you will need a transformer that reduces the mains U = 220 V to 18–22 V. If you have a transformer with a high output voltage at your disposal, the resistance R7 needs to be increased to approximately 2 kOhm (you may have to select a resistor). The rectifier bridge diodes and thyristor must be installed on aluminum radiators to prevent overheating of the parts. When installing conventional elements of type D242–245, do not forget to place an insulating washer under the body.

The schematic diagram of a thyristor charger for a car battery is as follows:

Since the circuit is simple, it does not have electronic protection: its role is played by a fuse installed at the output. When charging batteries with a capacity of no more than 60 A*h, a fuse-link with a rating of 6.3 A is sufficient. Installing a series-connected device - an ammeter - will help control the charging procedure. Below is a printed circuit board that simplifies the assembly of the charger:

List of components in the circuit and selection of possible analogues

The circuit uses an electrolytic capacitor that can withstand a voltage of at least 63 V. The power of resistors R1-R6 is 0.25 W, R7 is 2 W. The diodes in the rectifier bridge pass a current of up to 10 A and maintain a reverse U of 50 V. The pulse diode VD2 must withstand the same voltage. Transistors VT1 and VT2: KT3107, KT502, KT361 and KT503, KT315, KT3102, respectively.

Calculation of transformer, thyristor and diode parameters

One of the negative aspects of thyristor charging is low efficiency, partly due to the secondary winding of the transformer, which must freely pass a current three times greater than the power consumed by the battery. How to fix it? To do this, you can move the thyristor from winding II of the transformer to winding I, as shown in the diagram of a thyristor battery charger:

The whole difference of this thyristor charger for car batteries lies in the connection of the diode bridge and the regulating thyristor to the primary winding of the transformer. Since winding current II is approximately 10 times less than the charging current, very little thermal energy is released on the diodes and thyristor: you don’t even need to use cooling radiators (but this does not apply to VD5-VD8).

Components and their analogues:

• rectifier unit KTs402.405 with any index (A, B, C);
• Zener diode type KS524, KS518, KS522;
• transistor KT117 with letters from “B” to “G”;
• the diode bridge located at the output must consist of components rated at 10 A (D242-247).

Power regulator on triac BTA 12-600

A triac is a semiconductor device, classified as a type of thyristor and used for current switching purposes. It operates on alternating voltage, unlike a dinistor and a conventional thyristor. The entire power of the device depends on its parameter.

Answer to the question. If the circuit were assembled using a thyristor, a diode or diode bridge would be needed.

For convenience, the circuit can be assembled on a printed circuit board.

The plus of the capacitor must be soldered to the control electrode of the triac, it is located on the right. Solder the minus to the third outer pin, which is on the left.

Solder a resistor with a nominal resistance of 12 kOhm to the control electrode of the triac. A substring resistor must be connected to this resistor. The remaining pin must be soldered to the central leg of the triac.

To the minus of the capacitor, which is soldered to the third terminal of the triac, you must attach the minus from the rectifier bridge.

Plus the rectifier bridge to the central terminal of the triac and to the part to which the triac is attached to the radiator.

We solder 1 contact from the cord with a plug to the required device. A 2 contact to the AC voltage input on the rectifier bridge.

It remains to solder the remaining contact of the device to the last contact of the rectifier bridge.

The circuit is being tested.

We connect the circuit to the network. Using a trimmer resistor, the power of the device is adjusted.

The power can be developed up to 12 volts for a car.

Speed ​​controller circuit for an electric motor

To assemble a speed controller for an engine, you will need a PWM pulse generator and a triac to control the engine. The diode and resistor D1 and R1 allow you to reduce the voltage to power the motor, and the capacitor C1 is designed to filter the current at the input of the electrical circuit.

Elements P1, R5 and R3 are voltage dividers with the ability to adjust its values. Resistor R2, which is indicated on the diagram of the electric motor speed regulator, allows you to synchronize the internal blocks of the regulator with the main triac (VT139), on which the speed regulator actually operates.

Below in the figure you can see a visual arrangement of all elements of the speed controller for electric motors. It is imperative to place the elements safely, since the regulator operates from a dangerous voltage of 220 Volts.

Introduction of automation

The presence of modern microcontroller control in speed controllers and frequency converters makes it possible to improve the operating parameters of the drive, and the motor itself can operate in a fully automatic mode, when the controller used smoothly or stepwise changes the rotation speed of the rotor of the power unit. Today, microcontroller control uses processors that have different numbers of outputs and inputs. You can connect various kinds of electronic keys and buttons, various signal loss sensors, etc. to such a microcontroller.

The modern electrical market offers a wide range of converters and frequency controllers for any type of electric motor. But if you have even minimal skills in working with radio components and the ability to read electrical circuits, you can assemble a device with your own hands that will gradually or stepwise change the engine speed. Additionally, you can include a control triac rheostat and a resistor in the circuit, which will make it possible to smoothly change the speed, and the presence of microcontroller control completely automates the operation of the electric drive.

How to make a current stabilizer for LEDs yourself

Making a stabilizer for LEDs with your own hands is carried out in several ways. It is advisable for a beginner to work with simple circuits.

Driver based

You will need to choose a chip that is difficult to burn out - LM317. It will act as a stabilizer. The second element is a variable resistor with a resistance of 0.5 kOhm with three terminals and an adjustment knob.

Assembly is carried out according to the following algorithm:

1. Solder the conductors to the middle and extreme terminals of the resistor.
2. Set the multimeter to resistance mode.
3. Measure the parameters of the resistor - they should be equal to 500 Ohms.
4. Check connections for integrity and assemble the circuit.

The output will be a module with a power of 1.5 A. To increase the current to 10 A, you can add a field switch.

Stabilizer for car lighting

Stabilizer L7812

To operate, you will need a linear device in the form of an L7812 microcircuit, two terminals, a 100n capacitor (1-2 pcs.), textolite material and a heat-shrinkable tube. Manufacturing is carried out step by step:

1. Selecting a circuit for L7805 from the datasheet.
2. Cut out the required size piece from the PCB.
3. Mark the paths by making notches with a screwdriver.
4. Solder the elements so that the input is on the left and the output is on the right.
5. Make a housing from a thermal tube.

The stabilizing device can withstand up to 1.5 A load and is mounted on a radiator.

DIY power supply with current and voltage regulation

Enough words, let's get down to business!

This figure shows a power supply circuit with voltage and current regulation from 2.4V to 28V and current up to 30A.

Power supply circuit with current and voltage adjustment from 2.4V to 28V 30A

An important element of this circuit is the adjustable voltage stabilizer microcircuit TL431 or, as it is also called, a controlled zener diode, which allows you to smoothly regulate the voltage from 2.4 volts to 28 volts. Thanks to four power transistors mounted on large radiators, the power supply can withstand current up to 30A. There is also current regulation and reverse polarity protection, so the power supply can and should even be used as a charger for a car battery.

A voltage divider built on a powerful 5 W resistor R1 and a variable resistor P1 limits the current at the cathode and at the control electrode of the zener diode TL431. By rotating the knob of the variable resistor P1, the output voltage of the zener diode is set; the voltage stabilizer TL431 automatically stabilizes the voltage set by the variable resistor P1. From the TL431 chip, current flows to the base of transistor T1. The transistor acts as a switch and controls two powerful bipolar transistors T2 and T3 connected in parallel to increase the output power. Equalizing resistors R2 and R3 are installed in the output stage of the transistors. Next, the current flows to the positive terminal of the power supply.

How does current regulation work?

This circuit implements the current limiting function on two powerful field-effect transistors T4 and T5 connected in parallel. Let's look at how this works. From the diode bridge, current flows to the L7812CV voltage stabilizer, the voltage drops to 12V, this is a safe value for transistor gates. Next, the current flows to a voltage divider assembled on a variable resistor P2 and a constant resistor R4. From the variable resistor P2 motor, the current passes through the current limiting resistors R5 and R6, opening the gates of field-effect transistors T4 and T5. Transistors conduct a certain amount of current through themselves depending on the resistance of the variable resistor P2. In this circuit, the current is regulated at any output voltage.

There is also protection against polarity reversal, consisting of two LEDs. The green LED indicates the correct connection of the car battery to the power supply output, and the red LED indicates a connection error. Resistors R7 and R8 limit the current for the LEDs.

Ah, here is the printed circuit board!

This figure shows a printed circuit board for a power supply with current and voltage regulation from 2.4V to 28V 30A

Printed circuit board of the power supply with current and voltage adjustment from 2.4V to 28V 30A

You can make a printed circuit board using laser ironing technology for advanced ones, as well as by hanging mounting; this method is more suitable for beginner radio amateurs and they are well aware of it. To make a printed circuit board you will need foil fiberglass laminate measuring 100x83 mm. Most of the parts are installed on the printed circuit board with the exception of transistors T2, T3, T4, T5, as well as the L7812CV voltage regulator and resistors R2, R3, P1, P2. Bipolar transistors T2 and T3 are installed on a separate radiator without insulating gaskets, because the collectors of the transistors are still connected together according to the circuit. Field-effect transistors T4, T5 must also be installed on a separate radiator without insulation.

This picture shows two radiators with transistors installed. The radiators are fastened together with two strips of double-sided automotive tape that acts as electrical insulation. A plastic fastening plate is screwed onto the top of the radiators with screws, adding rigidity to the structure. An additional plate with a printed circuit board and a fan will be attached to it.

Since the equalizing resistors R2 and R3 are quite large, a special printed circuit board is provided for them, which is shown in this figure. The size of the printed circuit board is 85x40 mm.

Resistor block printed circuit board

Thyristor control of electric motor speed

The thyristor regulator also allows you to change the speed of the power unit shaft. It is also called a dimmer or phase regulator. With this connection method, the electric motor is connected either to a break in the network cable, or behind a rectifier bridge that powers the anode thyristor circuit. This method of controlling the motor speed is considered quite reliable, provided that there are no violations of the integrity or order of contact connections in the load circuit. If you connect a commutator electric motor through a thyristor regulator, the brushes may begin to spark, since the load current will pulse.

Although, to control 12-volt DC motors of the collector type, you can adapt a thyristor regulator, which will have some features:

• the electric motor and power thyristor are connected to one of the diagonals of the rectifier bridge, and the voltage from the mains is supplied to the other diagonal;
• Thyristors are controlled not with short pulse signals, but with a wider range, which makes it possible to eliminate the detrimental effect on the operation of the regulator of short-term load drops characteristic of commutator electric motors.

The generator of short, up to several milliseconds, positive pulses is assembled on a unijunction transistor VT1. It is designed to operate the auxiliary thyristor VS1. The trapezoidal supply voltage is supplied to the generator by limiting the 100-Hz positive half-waves of the sinusoidal voltage by the zener diode VD1. Each such half-wave gradually charges capacitor C1 through the resistive chain R1-R3.

When the voltage required to open the transistor appears on the capacitor, a positive pulse is applied from resistor R5 to the electrode of the control trinistor VS1, as a result of which this trinistor opens, and the power trinistor VS2 receives a pulse signal that is longer than the control signal and Electric motor M1 receives power.

The rotation speed of the electric motor rotor is adjusted using a variable resistor R1, which is responsible for the opening moment of the power and control thyristors, and therefore for the load power. The anode of the VS2 thyristor in its circuit has an inductive load, so spontaneous opening is possible even without receiving a control signal. To prevent this from happening, a diode VD is mounted, connected in parallel with the excitation winding LB.

Main components of a regulated power supply

The transformer power supply in most cases is made according to the following block diagram.

Transformer power supply units.

A step-down transformer reduces the network voltage to the required level. The resulting alternating voltage is converted into pulsed voltage using a rectifier. The choice of its circuit depends on the circuit of the secondary windings of the transformer. The most commonly used full-wave bridge circuit is used. Less often - half-wave, since it does not allow the transformer’s power to be fully used, and the ripple level is higher. If the secondary winding has a center point brought out, then the full-wave circuit can be built with two diodes instead of four.

Full-wave rectifier for midpoint transformer.

If the transformer is three-phase (and there is a three-phase circuit to power the primary winding), then the rectifier can be assembled using a three-phase circuit. In this case, the ripple level is the lowest, and the power of the transformer is used most fully.

After the rectifier, a filter is installed that smoothes the pulse voltage to constant. Typically, the filter consists of an oxide capacitor, parallel to which a low-capacity ceramic capacitor is placed. Its purpose is to compensate for the structural inductance of the oxide capacitor, which is made in the form of a rolled strip of foil. As a result, the resulting parasitic inductance of such a coil worsens the filtering properties at high frequencies.

Next is the stabilizer. It can be either linear or pulsed. The pulse type is more complicated and negates all the advantages of a transformer power supply in the output current niche of up to 2..3 amperes. If you need an output current higher than this value, it is easier to switch the entire power supply, so a linear regulator is usually used here.

The output filter is based on an oxide capacitor with a relatively small capacitance.

Generalized block diagram of a pulse power supply.

Switching power supplies are built on a different principle. Since the current consumed is sharply non-sinusoidal, a filter is installed at the input. It does not affect the performance of the unit in any way, which is why many industrial manufacturers of Economy class power supplies do not install it. You don’t have to install it in a simple homemade source, but this will lead to the fact that devices on microcontrollers powered by the same 220 volt network will begin to fail or work unpredictably.

Then the mains voltage is straightened and smoothed out. An inverter using transistor switches in the primary winding circuit of the transformer creates pulses with an amplitude of 220 volts and a high frequency - up to several tens of kilohertz, in contrast to 50 hertz in the network. Due to this, the power transformer is compact and lightweight. The secondary winding voltage is rectified and filtered. Due to the high conversion frequency, smaller capacitors can be used here, which has a positive effect on the dimensions of the device. Also, in high-frequency voltage filters, it becomes advisable to use chokes - small-sized inductors effectively smooth out HF pulsations.

Voltage regulation and current limitation are performed through feedback circuits, which are supplied with voltage from the source output. If, due to an increase in load, the voltage begins to decrease, then the control circuit increases the interval of the open state of the keys without reducing the frequency (pulse width control method). If the voltage needs to be reduced (including to limit the output current), the time the switches are open is reduced.

Operating principle of phase control

The principle of regulation of this type is that the pulse that opens the thyristor has a certain phase. That is, the further it is located from the end of the half-cycle, the greater the amplitude will be the voltage supplied to the load. In the figure below we see the reverse process, when the pulses arrive almost at the end of the half-cycle.

Minimum power

The graph shows the time when the thyristor is closed t1 (phase of the control signal), as you can see, it opens almost at the end of the half-cycle of the sinusoid, as a result, the voltage amplitude is minimal, and therefore, the power in the load connected to the device will be insignificant (close to the minimum). Consider the case presented in the following graph.

Half power

Here we see that the pulse that opens the thyristor occurs in the middle of the half-cycle, that is, the regulator will output half the maximum possible power. Operating at close to maximum power is shown in the following graph.

Power close to maximum

As can be seen from the graph, the pulse occurs at the beginning of the sinusoidal half-cycle. The time when the thyristor is in the closed state (t3) is insignificant, so in this case the power in the load approaches the maximum.

Note that three-phase power regulators work on the same principle, but they control the voltage amplitude not in one, but in three phases at once.

This control method is easy to implement and allows you to accurately change the voltage amplitude in the range from 2 to 98 percent of the nominal value. Thanks to this, smooth control of the power of electrical installations becomes possible. The main disadvantage of devices of this type is the creation of a high level of interference in the electrical network.

An alternative to reduce noise is to switch the thyristors when the AC voltage sine wave passes through zero. The operation of such a power regulator can be clearly seen in the following graph.

Switching the thyristor through “zero”

Designations:

• A – graph of half-waves of alternating voltage;
• B – thyristor operation at 50% of maximum power;
• C – graph displaying the operation of the thyristor at 66%;
• D – 75% of maximum.

As can be seen from the graph, the thyristor “cuts off” half-waves, not parts of them, which minimizes the level of interference. The disadvantage of this implementation is the impossibility of smooth regulation, but for loads with high inertia (for example, various heating elements), this criterion is not the main one.

Video: Testing a thyristor power regulator

Introduction.

Many years ago, I made a similar regulator when I had to earn extra money repairing radios at a customer’s home. The regulator turned out to be so convenient that over time I made another copy, since the first sample was constantly installed as an exhaust fan speed regulator. https://oldoctober.com/

By the way, this fan is from the Know How series, as it is equipped with an air shut-off valve of my own design. Description of the design >>> The material can be useful for residents living on the top floors of high-rise buildings and who have a good sense of smell.

The power of the connected load depends on the thyristor used and its cooling conditions. If a large thyristor or triac of the KU208G type is used, then you can safely connect a load of 200... 300 Watts. When using a small thyristor, type B169D, the power will be limited to 100 Watts.

Construction and details

Now let's move on to the design of the device. Diode bridges, a capacitor, resistor R2 and diode VD6 are installed on a circuit board measuring 55x35 mm, made of foil getinax or textolite with a thickness of 1...2 mm (Fig. 9.7).

The following parts can be used in the device. Transistor - KT812A(B), KT824A(B), KT828A(B), KT834A(B,V), KT840A(B), KT847A or KT856A. Diode bridges: VD1...VD4 - KTs410V or KTs412V, VD6 - KTs405 or KTs407 with any letter index; diode VD5 - series D7, D226 or D237.

Variable resistor - type SP, SPO, PPB with a power of at least 2 W, constant - BC, MJIT, OMLT, S2-23. Oxide capacitor - K50-6, K50-16. Network transformer - TVZ-1-6 from tube TVs, TS-25, TS-27 - from the Yunost TV or any other low-power one with a secondary winding voltage of 5...8 V.

The fuse is designed for a maximum current of 1 A. The toggle switch is TZ-S or any other network switch. XP1 is a standard power plug, XS1 is a socket.

All elements of the regulator are housed in a plastic case with dimensions of 150x100x80 mm. A toggle switch and a variable resistor equipped with a decorative handle are installed on the top panel of the case. The socket for connecting the load and the fuse socket are mounted on one of the side walls of the housing.

On the same side there is a hole for the power cord. A transistor, transformer and circuit board are installed at the bottom of the case. The transistor must be equipped with a radiator with a dissipation area of ​​at least 200 cm2 and a thickness of 3...5 mm.

Rice. Printed circuit board of a powerful 220V mains voltage regulator.

The regulator does not need to be adjusted. With proper installation and serviceable parts, it begins to work immediately after being plugged into the network.

Dinistor and 4 types of conductivity.

This device is called a trigger diode. Has little power. There are no electrodes in its interior.

The dinistor opens when the voltage increases. The speed at which voltage increases is determined by the capacitor and resistors. All adjustments are made through it. Works on direct and alternating current. You don’t have to buy it, it is in energy-saving lamps and is easy to get from there.

It is not often used in circuits, but in order not to spend money on diodes, a dinistor is used.

It contains 4 types: PNP N. This is the electrical conductivity itself. An electron-hole transition is formed between 2 adjacent regions. There are 3 such transitions in the dinistr.

Scheme:

We connect the capacitor. It starts charging with 1 resistor, the voltage is almost equal to that in the network. When the voltage in the capacitor reaches the level of the dinistor, it will turn on. The device starts working. Don't forget about the radiator, otherwise everything will overheat.

DIY adjustable power supply

A power supply is a necessary thing for every radio amateur, because to power electronic homemade products you need a regulated power source with a stabilized output voltage from 1.2 to 30 volts and a current of up to 10A, as well as built-in short circuit protection. The circuit shown in this figure is built from the minimum number of available and inexpensive parts.

Scheme of an regulated power supply on an LM317 stabilizer with short-circuit protection

The LM317 IC is an adjustable voltage regulator with built-in short circuit protection. The LM317 voltage stabilizer is designed for a current of no more than 1.5A, so a powerful MJE13009 transistor is added to the circuit, capable of passing through itself a really high current of up to 10A, according to the datasheet, a maximum of 12A. When you rotate the knob of the variable resistor P1 by 5K, the voltage at the output of the power supply changes.

There are also two shunt resistors R1 and R2 with a resistance of 200 Ohms, through which the microcircuit determines the output voltage and compares it with the input voltage. 10K resistor R3 discharges capacitor C1 after the power supply is turned off. The circuit is powered by voltage from 12 to 35 volts. The current strength will depend on the power of the transformer or switching power supply.

I drew this diagram at the request of novice radio amateurs who assemble circuits using wall-mounted installations.

Scheme of an regulated power supply with short-circuit protection on LM317

It is advisable to carry out the assembly on a printed circuit board, so it will be beautiful and neat.

Printed circuit board of the regulated power supply on the LM317 voltage regulator

The printed circuit board is made for imported transistors, so if you need to install a Soviet one, the transistor will have to be unfolded and connected with wires. The MJE13009 transistor can be replaced with the MJE13007 from the Soviet KT805, KT808, KT819 and other npn structure transistors, it all depends on the current you need. It is advisable to reinforce the power paths of the printed circuit board with solder or thin copper wire. The LM317 voltage stabilizer and the transistor must be installed on a radiator with sufficient area for cooling; a good option is, of course, a radiator from a computer processor.

It is advisable to screw a diode bridge there. Don't forget to insulate the LM317 from the heatsink with a plastic washer and a heat conductive gasket, otherwise there will be a big boom. Almost any diode bridge can be installed with a current of at least 10A. Personally, I installed the GBJ2510 at 25A with double the power reserve, it will be twice as cool and reliable.

And now the most interesting part... Testing the power supply for strength.

I connected the voltage regulator to a power source with a voltage of 32 volts and an output current of 10A. Without load, the voltage drop at the output of the regulator is only 3V. Then I connected two series-connected halogen lamps H4 55 W 12V, the lamp filaments were connected together to create a maximum load, the result was 220 W. The voltage dropped by 7V, the nominal voltage of the power supply was 32V. The current consumed by four halogen lamp filaments was 9A.

The radiator began to heat up quickly, after 5 minutes the temperature rose to 65C°. Therefore, when removing heavy loads, I recommend installing a fan. You can connect it according to this diagram. You can not install the diode bridge and capacitor, but connect the L7812CV voltage stabilizer directly to capacitor C1 of the regulated power supply.

Connection diagram of the fan to the power supply

What happens to the power supply if there is a short circuit?

In the event of a short circuit, the voltage at the output of the regulator is reduced to 1 volt, and the current is equal to the current of the power source, in my case 10A. In this state, with good cooling, the unit can remain for a long time; after the short circuit is eliminated, the voltage is automatically restored to the limit set by the variable resistor P1. During the 10-minute short-circuit test, no parts of the power supply were damaged.

Radio components for assembling an adjustable power supply on LM317

• Voltage stabilizer LM317
• Diode bridge GBJ2501, 2502, 2504, 2506, 2508, 2510 and other similar ones designed for a current of at least 10A
• Capacitor C1 4700mf 50V
• Resistors R1, R2 200 Ohm, R3 10K all resistors with a power of 0.25 W
• Variable resistor P1 5K
• Transistor MJE13007, MJE13009, KT805, KT808, KT819 and other npn structures

Friends, I wish you good luck and good mood! See you in new articles!

I recommend watching a video on how to make an adjustable power supply with your own hands

Types of Variable Resistors

Wire

It consists of a tubular plastic or ceramic frame, on which a thin wire with high resistance (manganin or constantan) is laid in the form of a single-layer winding.

A metal slider slides along the surface of the wire, which, when moved, touches the next turn of the winding before leaving the previous one - this ensures smooth adjustment.

To ensure reliable contact between the slider and the conductive layer, the surface of the wire is carefully polished.

Thin film

It consists of a frame in the form of a horseshoe-shaped dielectric plate coated with a thin film made of carbon, boron, metallized or composite materials. A slider, firmly connected to the adjustment mechanism, slides over the surface of the film.

Simple DIY CH

Parametric voltage stabilizer

A 12-volt voltage stabilizer for LEDs, backlights of automotive on-board systems is quickly and conveniently performed using microcircuits: LM317, LD1084, L7812, KREN 8B and similar devices. Several diodes, a resistance and the microcircuit itself are the components of such a circuit.

Stabilizer on LM317

Depending on the manufacturing option of the LM317 case, the arrangement of parts on the board is selected.

LM317 with heatsink mount

Making a stabilizer comes down to the following:

• a resistance with a nominal value of 130 Ohms is soldered to the output (Vout);
• a wire supplying voltage for stabilization is connected to the input contact (Vin);
• the adjustment input (Adj) is connected to the second terminal of the resistor.

When connecting LED lights, strips, etc. as a load. no radiator required. Assembly takes 15-20 minutes with a minimum of parts. Using a simple formula, you can calculate the value of resistance R to obtain a certain value of the permissible load current.

CH circuit on LM317

Circuit on the LD1084 chip

The use of this microassembly will help maintain the 12 V voltage constant for LED illumination devices connected to the vehicle’s on-board network.

Datasheet LD1084

Here, to assemble a homemade CH, the following is included in the circuit binding circuit of the microcircuit:

• two electrolytic capacitors of 10 μF * 25 V;
• resistors: 1 kOhm (2 pcs.), 120 Ohm, 4.7 kOhm (can be constant);
• diode bridge RS407.

The device is assembled as follows:

• the voltage removed from the rectifier diode bridge is supplied to the input of LD1084;
• the emitter of the KT818 transistor is connected to the contact that controls the stabilization mode (Adj), the base of which is connected through two single-column resistors to the power supply circuits for the headlights (low and high);
• the output circuit of the microcircuit is connected to resistors R1 and R2, as well as a capacitor.

By the way. Resistor R2 can be taken not as a variable, but as a tuning one, using it to set the output voltage to 12 V.

SN for on-board network

Stabilizer on diodes and assembly L7812

A similar microcircuit in conjunction with a diode and capacitors can supply LEDs with a stable voltage of 12 V.

The scheme is built according to the principle outlined below:

• The 1N401 Schottky diode passes current from the positive terminal of the battery through itself and supplies it to the input of the microcircuit. In this case, the “+” of the electrolyte (330 μF capacitor) is also connected to the cathode of the diode;
• a load circuit and a “+” capacitor with a capacity of 100 μF are connected to the output of L7812;
• all negative terminals (from the battery and both electrolytic capacitors) are connected to the control input of the microcircuit.

Electrolytic capacitors are selected for a voltage of at least 25 V.

12 V stabilizer circuit on IC L7812

The simplest stabilizer is the KREN board

Schemes using rolls are quite popular. This is the name for ICs whose markings include combinations of the letters KR and EN. These are powerful SNs that allow you to supply a current of up to 1.5 A to the load. They have a stable 12 V output when a voltage of up to 35 V is applied to the input.

The circuit using this microcircuit is assembled like this:

• voltage from the positive terminal of the battery (rechargeable battery) to the bank input is supplied through a 1N4007 diode, it protects the battery circuit from reverse voltages;
• the negative terminal of the battery is connected to the control electrode KREN;
• The output voltage is supplied to the load.

If necessary, the microcircuit is screwed to the radiator.

KR142EN8B, connection diagram

Assembling 12 V voltage stabilizers with your own hands using linear and integrated MV circuits is not difficult. In this case, it is necessary to monitor the heating temperature of the housing of the elements and, when T0C is higher than permissible, install them on heat sinks (radiators).

Schematic diagram

When powering powerful loads with direct current, a rectifier circuit (Fig. 1) with four power valves is often used. The alternating voltage is supplied to one diagonal of the “bridge”, the output constant (pulsating) voltage is removed from the other diagonal. One pair of diodes (VD1-VD4 or VD2-VD3) operates in each half-cycle.

This property of the rectifier “bridge” is significant: the total value of the rectified current can reach twice the maximum current value for each diode. The diode voltage limit should not be lower than the amplitude input voltage.

Since the voltage class of power valves reaches fourteen (1400 V), there are no problems with this for a household electrical network. The existing reverse voltage reserve allows the use of valves with some overheating, with small radiators (do not abuse them!).

Rice. 1. Rectifier circuit with four power valves.

Attention! Power diodes marked “B” conduct current “similarly” to D226 diodes (from the flexible lead to the body), diodes marked “VL” - from the body to the flexible lead.

The use of valves of different conductivity allows installation on just two double radiators. If you connect the “housings” of the “VL” valves (minus output) to the device body, then you will only have to isolate one radiator, on which diodes marked “B” are installed. This circuit is easy to install and set up, but difficulties arise if you have to regulate the load current.

If everything is clear with the welding process (attach the “ballast”), then huge problems arise with the starting device. After starting the engine, the huge current is unnecessary and harmful, so it is necessary to quickly turn it off, since every delay shortens the battery life (batteries often explode!).

The circuit shown in Fig. 2 is very convenient for practical implementation, in which the current control functions are performed by thyristors VS1, VS2, and power valves VD1, VD2 are included in the same rectifier bridge. Installation is made easier by the fact that each diode-thyristor pair is mounted on its own radiator. Radiators can be used standard (industrial production).

Another way is to independently manufacture radiators from copper and aluminum with a thickness of over 10 mm. To select the size of the radiators, you need to assemble a mock-up of the device and “drive” it in heavy duty. It’s not bad if after a 15-minute load the thyristor and diode housings do not “burn” your hand (turn off the voltage at this moment!).

The device body must be designed in such a way as to ensure good circulation of air heated by the device. It wouldn’t hurt to install a fan that “helps” move air from bottom to top. Fans installed in racks with computer boards or in “Soviet” gaming machines are convenient.

Rice. 2. Scheme of a current regulator using thyristors.

It is possible to implement an adjustable rectifier circuit entirely using thyristors (Fig. 3). The lower (according to the diagram) pair of thyristors VS3, VS4 is triggered by pulses from the control unit.

The pulses arrive simultaneously at the control electrodes of both thyristors. This design of the circuit is “dissonant” with the principles of reliability, but time has confirmed the operability of the circuit (“the household electrical network cannot burn” thyristors, since they can withstand a pulse current of 1600 A).

Thyristor VS1 (VS2) is connected as a diode - with a positive voltage at the anode of the thyristor, an unlocking current will be supplied through diode VD1 (or VD2) and resistor R1 (or R2) to the control electrode of the thyristor. Already at a voltage of several volts, the thyristor will open and will conduct current until the end of the half-wave of current.

The second thyristor, the anode of which had a negative voltage, will not start (this is not necessary). A current pulse comes to thyristors VS3 and VS4 from the control circuit. The value of the average current in the load depends on the opening moments of the thyristors - the earlier the opening pulse arrives, the larger part of the period the corresponding thyristor will be open.

Rice. 3. Adjustable rectifier circuits are entirely based on thyristors.

Opening thyristors VS1, VS2 through resistors somewhat “dulls” the circuit: at low input voltages, the open angle of the thyristors turns out to be small - noticeably less current flows into the load than in a circuit with diodes (Fig. 2).

Thus, this circuit is quite suitable for adjusting the welding current via the secondary and rectifying the mains voltage, where the loss of a few volts is insignificant.

The circuit shown in Fig. 4 allows you to effectively use a thyristor bridge to regulate current over a wide range of supply voltages.

The device consists of three blocks:

1. power;
2. phase-pulse control circuits;
3. two-limit voltmeter.

Transformer T1 with a power of 20 W provides power to the control unit for thyristors VS3 and VS4 and the opening of “diodes” VS1 and VS2. Opening thyristors with an external power supply is effective at low (car) voltage in the power circuit, as well as when powering an inductive load.

Rice. 4. Thyristor bridge for current control over a wide range.

Rice. 5. Schematic diagram of the thyristor control unit.

Opening current pulses from the 5-volt windings of the transformer are supplied in antiphase to the control electrodes VS1, VS2. Diodes VD1, VD2 pass only positive half-waves of current to the control electrodes.

If the phasing of the opening pulses is “appropriate”, then the thyristor rectifier bridge will work, otherwise there will be no current in the load.

This shortcoming of the circuit can be easily eliminated: just turn the T1 power plug in the opposite direction (and mark with paint how to connect the plugs and terminals of the devices to the AC network). When using the circuit in a starter-charger, there is a noticeable increase in the supplied current compared to the circuit in Fig. 3.

It is very beneficial to have a low-current circuit (mains transformer T1). Breaking the current by switch S1 completely de-energizes the load. Thus, you can interrupt the starting current with a small limit switch, circuit breaker or low-current relay (by adding an automatic shutdown unit).

Read also: Do-it-yourself machine for rewinding fire hoses

This is a very important point, since it is much more difficult to break high-current circuits that require good contact for the current to pass through. It is no coincidence that we remembered the phasing of transformer T1. If the current regulator were “built-in” into the charging and starting device or into the welding machine circuit, then the phasing problem would be solved at the time of setting up the main device.

Our device is specially designed to be wide-profile (just as the use of the starting device is determined by the season of the year, welding work has to be carried out irregularly). You have to control the operating mode of a powerful electric drill and power nichrome heaters.

Figure 5 shows a diagram of the thyristor control unit. The rectifier bridge VD1 supplies the circuit with a pulsating voltage from 0 to 20 V. This voltage is supplied through the diode VD2 to the capacitor C1, which provides a constant supply voltage to the powerful transistor “switch” on VT2, VT3.

The pulsating voltage is supplied through resistor R1 to resistor R2 and zener diode VD6 connected in parallel. The resistor “ties” the potential of point “A” (Fig. 6) to zero, and the zener diode limits the peaks of the pulses at the level of the stabilization threshold. Limited voltage pulses charge capacitor C2 to power the DD1 chip.

These same voltage pulses affect the input of the logic element. At a certain voltage threshold, the logic element switches. Taking into account the inversion of the signal at the output of the logic element (point “B”), the voltage pulses will be short-term - around the moment of zero input voltage.

Rice. 6. Pulse diagram.

The next logic element inverts the voltage “B”, so the voltage pulses “C” have a significantly longer duration. While the voltage pulse “C” is in effect, capacitor C3 is charged through resistors R3 and R4.

The exponentially increasing voltage at point “E”, at the moment of crossing the logical threshold, “switches” the logical element. After inversion by the second logic element, the high input voltage at point "E" corresponds to a high logic voltage at point "F".

Two different values ​​of resistance R4 correspond to two oscillograms at point “E”:

• lower resistance R4 – greater steepness – E1;
• greater resistance R4 – lower slope – E2.

You should also pay attention to the power supply of the base of transistor VT1 with the “B” signal; when the input voltage decreases to zero, transistor VT1 opens to saturation, the collector junction of the transistor discharges capacitor C3 (preparing for charging in the next half-cycle of voltage). Thus, the logic high level appears at point "F" earlier or later, depending on the resistance of R4:

• lower resistance R4 – the pulse appears earlier – F1;
• greater resistance R4 - later an impulse appears - F2.

The amplifier on transistors VT2 and VT3 “repeats” the logical signals - point “G”. The oscillograms at this point repeat F1 and F2, but the voltage reaches 20 V.

Through isolation diodes VD4, VD5 and limiting resistors R9 R10, current pulses act on the control electrodes of thyristors VS3 VS4 (Fig. 4). One of the thyristors opens, and a rectified voltage pulse passes to the output of the block.

The smaller value of resistance R4 corresponds to the larger part of the half-cycle of the sinusoid - H1, the larger value - the smaller part of the half-cycle of the sinusoid - H2 (Fig. 4). At the end of the half-cycle, the current stops and all thyristors close.

Rice. 7. Scheme of an automatic two-limit voltmeter.

Thus, different values ​​of resistance R4 correspond to different durations of “segments” of sinusoidal voltage on the load. The output power can be adjusted practically from 0 to 100%. The stability of the device is determined by the use of “logic” - the switching thresholds of the elements are stable.

Making your own device

Initially we need a 12 volt voltage regulator circuit. It needs to be etched and cleaned before it can be used in practice. Next, you should solder the necessary parts as indicated. And as a result, here is a pulse voltage stabilizer (12 volts, 1.5 Amperes), which can be used in a car to adjust the backlight. For convenience and protection, the entire device can be placed in a special container. It is advisable to use plastic as its material, which can easily withstand significant temperatures and ensures tightness. Conductive metals should only be used if there are insulators on the wires and all parts of parts that could potentially cause an electric shock.

Adjustment features

It makes sense to talk about this or that 12 volt regulator only if you provide additional data:

• DC or AC voltage must be regulated;
• what is the maximum current in the load;
• the magnitude of the potential difference in front of the regulator;
• load voltage parameters in the regulation range.

Each of the listed parameters is associated with certain technical solutions that are reflected in the diagram. The general circuit of the regulator is a load that is connected to some device. It is conventionally indicated by a rectangle in the diagram shown below. Inside this rectangle there may be one or another diagram that corresponds to the additional data mentioned above. The simplest regulator is a variable resistor. It allows you to regulate AC voltage without distortion. This resistor is also applicable for direct current.

Circuit with variable resistor.

Elementary diagram of the regulator

Circuit with variable resistor

If the potential difference at the input is significantly greater than 12 volts at the output, energy will be lost in the regulator. The variable resistor will generate heat. To avoid heat loss, it is necessary to use variable inductance on alternating current, which can be LATR. Its throughput is limited, as in a variable resistor, by the design of the moving contact. But if switching is permissible by placing jumpers with reliable contacts between the turns, a significant current can be obtained.

Inductive regulator

Another way to regulate 12 volt alternating voltage with your own hands is to change the inductance of the regulator. To do this, manually change either the gap or the number of turns specifically designed for this. An adjustable welding transformer used to power a voltaic arc is designed according to this principle. If the 12 volt voltage regulator does not have the properties of a stabilizer and is controlled by yourself, the potential difference across the load must be monitored with a voltmeter.

A variable resistor and variable inductance can also be used as a current regulator. In this case, it is necessary to monitor the current in the load with an ammeter. If the voltage parameters at the load are not specified, with the exception of its value of 12 V, you can regulate it with a dimmer. This can be a powerful regulator since it is usually thyristor based. And modern thyristors are produced for a very wide range of potential difference and current.

Design features and operating principle of the frequency converter

Electronic frequency converters are used to control the operation of electric motors in both a three-phase 380V and single-phase 220V power supply. Their work is based on changing the amplitude and frequency of the electrical signal, which allows you to smoothly change the parameters of the rotor speed of the power unit. The design of most such devices, as a rule, is based on semiconductor-type transistors with pulse-width modulators. Speed ​​adjustment is carried out using a control unit installed on the microcontroller.

Frequently used in power tools and household appliances, commutator-type DC motors are distinguished by the fact that when directly connected to a 220-volt power supply, they begin to produce maximum speed. This increases the load on the drive and contributes to its rapid wear. In addition, at high rotor speeds, a lot of heat is generated, which leads to overheating of the working mechanisms, melting of windings and cables, and can also cause a short circuit. Therefore, it is highly recommended to install a power and frequency regulator here, even if control over the speed in the technical process and operation of the electrical installation is not provided.