Krasimir Rilchev's thyristor charging unit is designed for charging batteries of trucks and tractors. It provides a continuously adjustable (resistor RP1) charging current of up to 30 A. The principle of regulation is phase-pulse based on thyristors, providing maximum efficiency, minimum power dissipation and not requiring rectifier diodes. The network transformer is made on a magnetic core with a cross-section of 40 cm2, the primary winding contains 280 turns of PEL-1.6, the secondary winding contains 2x28 turns of PEL-3.0. Thyristors are installed on 120x120 mm radiators. ...

For the circuit "Thyristor turn signal relay"

Automotive electronics Thyristor turn signal relay. Kazan A. STAKHOV A non-contact car turn signal relay can be designed using silicon controlled diodes - thyristors. The diagram of such a relay is shown in the figure. The relay is a conventional multivibrator on transistors T1 and T2;, the switching frequency of which determines the blinking frequency of the lamps, since the same multivibrator controls the DC switch on thyristors D1 and D4. Any low-power low-frequency transistors can operate in the multivibrator. When switch P1 connects the signal lamps of the front and rear sidelights, the multivibrator signal opens the thyristor D1 and the battery voltage is applied to the signal lamps. In this case, the right plate of capacitor C1 is charged positively (relative to the left plate) through resistor R5. When the triggering pulse of the multivibrator is applied to thyristor D4, the same thyristor opens and the charged capacitor C1 is connected to thyristor D1 so that it instantly receives a reverse voltage between the anode and the cathode. How to check the k174ps1 microcircuit This reverse voltage closes the thyristor D1, which interrupts the current in the load. The next triggering pulse of the multivibrator opens thyristor D1 again and the whole process is repeated. D223 diodes are used to limit negative current surges and improve the startup of thyristors. Any low-power thyristors with any letter indices can be used in a DC switch. When using KU201A, the current consumed by the signal lamps should not exceed 2 A; for KU202A it can reach up to 10 a. The relay can also operate from an on-board network with a voltage of 6 V. RADIO N10 1969 34...

For the circuit "POWER AMPLIFIER FOR CB RADIO STATION"

HF power amplifiers POWER AMPLIFIER FOR CB RADIO STATION A. KOSTYUK (EU2001), Minsk. When manufacturing a power amplifier, radio amateurs are faced with the question of what active component to use in it. The advent of transistors led to the creation of a large number of designs based on them. However, designing on such an element base at home is problematic for most radio amateurs. in the output stages of powerful modern metal-glass or metal-ceramic lamps such as GU-74B, etc. difficult due to their high cost. The output is widely used lamps, for example 6P45S, used in color TVs. The idea of ​​the proposed amplifier is not new, and was described in [I]. A simple current regulator It is made on two 6P45S beam tetrodes, connected according to a circuit with grounded grids. Technical characteristics: Power gain - 8 Maximum anode current - 800 mA Anode voltage - 600 Equivalent amplifier resistance - 500 ohms Switching to transmission occurs by applying a control voltage on relay Kl, K2. If there is no such voltage in the CB station, you can make an electronic reception/transmission key, as was done in. Parts and design Chokes LI, L5 have an inductance of 200 μH and must be rated for a current of 800 mA. The inductor L6, L7 is wound on a ring 50 VC-2 K32x20x6 with two MGShV wires with a cross-section of 1 mm2. Coils L2, L3 contain 3 turns and are wound with 0 1 mm wire on Rl, R2, respectively. The P-circuit coil L4 is wound with a wire with a diameter of 2.5 mm. The amplifier capacitors are KSO type for an operating voltage of 500 V. For forced...

For the circuit "TURNING ON POWERFUL SEVEN-ELEMENT LED INDICATORS"

For the diagram "Push-pull converters (simplified calculation)"

Power supply Push-pull converters (simplified calculation) A. PETROV, 212029, Mogilev, Schmidt Ave., 32 - 17. Push-pull converters are very critical to the asymmetrical magnetization reversal of the magnetic circuit, therefore, in bridge circuits to avoid saturation of the magnetic circuits (Fig. 1) and as a result - the occurrence of through currents, it is necessary to take special measures to balance the hysteresis loop, or in the simplest version, Figure 1 - introduce an air gap and a capacitor in series with the primary winding of the transformer. A joint solution to the problems of increasing the reliability of semiconductor switches and improving electromagnetic compatibility, helping to reduce weight and size indicators, can be achieved by organization of natural electromagnetic processes in converters, in which switching of keys occurs at currents equal to or close to zero. In this case, the current spectrum attenuates faster and the power of radio interference is significantly attenuated, which simplifies the filtering of both input and output voltages. Let's focus on the simplest half-bridge self-generating unregulated inverter with a commutating saturable transformer (Fig. 2). Triac TS112 and circuits on it Its advantages include the absence of a direct current component in the primary winding of the power transformer due to the capacitive divider. Puc.2 The half-bridge circuit provides power conversion of 0.25...0.5 kW in one cell. The voltages on closed transistors do not exceed the supply voltage. The inverter has two PIC circuits: - one - for current (proportional current control); - the second - for voltage. proportionally...

For the scheme "Use of an integral timer for automatic voltage control"

For the circuit "Power amplifier made in a bridge circuit."

AUDIO techniqueA power amplifier made using a bridge circuit. It has an output power of 60 W with a unipolar power supply of +40 V. Obtaining high output power is associated with a number of difficulties, one of which is the limitation of the power supply voltage caused by the fact that the range of high-voltage powerful transistors are still quite small. One way to increase the output power is to connect transistors of the same type in series-parallel, but this complicates the design of the amplifier and its configuration. Meanwhile, there is a way to increase the output power, allowing you to avoid application hard-to-reach elements and do not increase the voltage of the power source. This method involves using two identical power amplifiers, connected so that the input signal is supplied to their inputs in antiphase, and the load is connected directly between the outputs of the amplifiers (bridge amplifier circuit). VHF circuit A power amplifier made using such a bridge circuit has the following main technical characteristics: Rated output power...... 60 W Harmonic distortion...... 0.5% Operating frequency band.. ........ 10... 25,000 Hz Supply voltage........... 40 V Quiescent current......... 50 mA The schematic diagram of such an amplifier is shown in Fig. .1. Changing the phase of the input signal is achieved by feeding it to the inverting input of one amplifier and to the non-inverting input of the other amplifier. The load is connected directly between the amplifier outputs. To ensure temperature stabilization of the quiescent current of the output transistors, diodes VD1-VD4 are placed on a common heat sink. Puc.1 Before turning on, check the correct installation and connections of the amplifier. After connecting the power source with resistor R14, the voltage between the amplifier outputs is set to no more...

For the circuit "Simple current regulator of a welding transformer"

An important design feature of any welding machine is the possibility of adjusting the operating current. In industrial devices, different methods of current regulation are used: shunting using chokes of various types, changing the magnetic flux due to the mobility of the windings or magnetic shunting, stores of active ballast resistances and rheostats. The disadvantages of such adjustment include the complexity of the design, the bulkiness of the resistances, their strong heating during operation, and inconvenience when switching. The best option is to make it with taps while winding the secondary winding and, by switching the number of turns, change the current. However, this method can be used to adjust the current, but not to regulate it over a wide range. In addition, adjusting the current in the secondary circuit of a welding transformer is associated with certain problems. Thus, significant currents pass through the regulating device, which leads to its bulkiness, and for the secondary circuit it is almost impossible to select such powerful standard switches that they can withstand a current of up to 200 A. Triac TS112 and circuits on it Another thing is the primary winding circuit, where the currents five times less. After a long search through trial and error, the optimal solution to the problem was found - a very popular thyristor regulator, the circuit of which is shown in Fig. 1. With the utmost simplicity and accessibility of the element base, it is easy to manage, does not require settings and has proven itself in operation - it works just like a “watch”. Power regulation occurs when the primary winding of the welding transformer is periodically turned off for a fixed period of time at each half-cycle of the current (Fig. 2). The average role of the current decreases. The main elements of the regulator (thyristors) are connected back-to-back and parallel to each other. They open one by one...

For the circuit "Use of tunnel diodes"

For the amateur radio designer of tunnel diodes, Fig. Figures 1, 2 and 3 show three different circuit applications of a tunnel diode oscillator. The FM transmitter shown in Fig. 1 is very simple and provides reliable reception within a radius of 10-30 m when using a whip antenna and an FM receiver of average sensitivity. Due to the fact that the modulation scheme of the transmitter is the simplest, the output signal is somewhat distorted, and, in addition to the frequency modulation obtained by changing the generator’s natural frequency synchronously with the microphone signal, there is significant amplitude modulation. It is impossible to greatly increase the output power of such a transmitter, since it is a source of interference. Such a transmitter can be used as a portable radio microphone, calling or intercom device for short distances. Fig. 1. The simplest transmitter using a tunnel diode. Amateur radio converter circuits Coil L contains 10 turns of PEL 0.2 wire. The operating principle of the local oscillator (Fig. 2) is the same as the previous transmitter. Its distinctive feature is the incomplete inclusion of the circuit. This was done with the goal of improving the shape and stability of the generated vibrations. An ideal sinusoid can be obtained, but in practice small nonlinear distortions are inevitable. Fig. 2. Local oscillator on a tunnel diode L=200 µH. Shown in Fig. 3 tuning fork audio frequency generator can be used as a standard for tuning musical instruments or a telegraph buzzer. The generator can also operate on diodes with lower maximum currents. In this case, the number of turns in the coils must be increased, and the dynamic loudspeaker must be connected through an amplifier. For normal operation of the generator, the total ohmic resistance...

For the circuit "TRANSISTOR TUBE AM TRANSMITTER"

Radio transmitters, radio stations TRANSISTOR-TUBE AM TRANSMITTER Portable HF and VHF radio stations are now widespread. For greater efficiency, reduced weight and dimensions, transistors are widely used in them. In this case, for more or less radio stations, circuits are used that use a generator radio tube in the output stage of the transmitter. The anode voltage for it usually comes from a voltage converter. These schemes are complex and not economical enough. The proposed scheme has increased efficiency and simplicity of design. It uses a powerful modulator and rectifier as an anode voltage source (see figure). The modulation transformer has two step-up windings - modulation and supply. The voltage removed from the supply winding is rectified and fed through the modulation winding to the anode of the output stage, operating in anode-screen modulation mode. Phase-pulse power regulator on CMOS The modulator operates in mode B and has high efficiency (up to 70%). Since the anode voltage is proportional to the modulation voltage, modulation with a controlled carrier (CLC) is carried out in this circuit, which significantly increases efficiency./img/tr-la-p1.gifThe master oscillator is assembled according to a circuit with a common base on transistor T1 (range 28-29 .7 MHz) and gives an excitation voltage of approximately 25-30 V. It should be noted that transistor T1 operates at a slightly higher collector voltage, so special selection of working specimens may be required. Choke Dr1 is wound on resistor BC-2 with the conductive layer removed and has 250 turns of PEL 0.2 wire. Coils L1 and L2 each contain 12 turns of PEL 1.2 wire. The diameter of the coils is 12 mm, the winding length is 20 mm. Bends to cat...

A selection of circuits and a description of the operation of a power regulator using triacs and more. Triac power regulator circuits are well suited for extending the life of incandescent lamps and for adjusting their brightness. Or for powering non-standard equipment, for example, 110 volts.

The figure shows a circuit of a triac power regulator, which can be changed by changing the total number of network half-cycles passed by the triac over a certain time interval. The elements of the DD1.1.DD1.3 microcircuit are made with an oscillation period of about 15-25 network half-cycles.

The duty cycle of the pulses is regulated by resistor R3. Transistor VT1 together with diodes VD5-VD8 is designed to bind the moment the triac is turned on during the transition of the mains voltage through zero. Basically, this transistor is open, respectively, a “1” is sent to the input DD1.4 and transistor VT2 with triac VS1 are closed. At the moment of crossing zero, transistor VT1 closes and opens almost immediately. In this case, if the output DD1.3 was 1, then the state of the elements DD1.1.DD1.6 will not change, and if the output DD1.3 was “zero”, then the elements DD1.4.DD1.6 will generate a short pulse, which will be amplified by transistor VT2 and open the triac.

As long as there is a logical zero at the output of the generator, the process will proceed cyclically after each transition of the mains voltage through the zero point.

The basis of the circuit is a foreign triac mac97a8, which allows you to switch high-power connected loads, and to regulate it I used an old Soviet variable resistor, and used a regular LED as an indication.

The triac power regulator uses the principle of phase control. The operation of the power regulator circuit is based on changing the moment the triac is turned on relative to the transition of the mains voltage through zero. At the initial moment of the positive half-cycle, the triac is in the closed state. As the mains voltage increases, capacitor C1 is charged through a divider.

The increasing voltage on the capacitor is shifted in phase from the mains voltage by an amount depending on the total resistance of both resistors and the capacitance of the capacitor. The capacitor is charged until the voltage across it reaches the “breakdown” level of the dinistor, approximately 32 V.

At the moment the dinistor opens, the triac will also open, and a current will flow through the load connected to the output, depending on the total resistance of the open triac and the load. The triac will be open until the end of the half-cycle. With resistor VR1 we set the opening voltage of the dinistor and triac, thereby regulating the power. At the time of the negative half-cycle, the circuit's operating algorithm is similar.

Option of the circuit with minor modifications for 3.5 kW

The controller circuit is simple, the load power at the output of the device is 3.5 kW. With this homemade amateur radio you can adjust lighting, heating elements and much more. The only significant drawback of this circuit is that you cannot connect an inductive load to it under any circumstances, because the triac will burn out!

Radio components used in the design: Triac T1 - BTB16-600BW or similar (KU 208 or VTA, VT). Dinistor T - type DB3 or DB4. Capacitor 0.1 µF ceramic.

Resistance R2 510 Ohm limits the maximum volts on the capacitor to 0.1 μF; if you put the regulator slider in the 0 Ohm position, the circuit resistance will be about 510 Ohms. The capacitance is charged through resistors R2 510 Ohm and variable resistance R1 420 kOhm, after U on the capacitor reaches the opening level of dinistor DB3, the latter will generate a pulse that unlocks the triac, after which, with further passage of the sinusoid, the triac is locked. The opening and closing frequency of T1 depends on the level of U on the 0.1 μF capacitor, which depends on the resistance of the variable resistor. That is, by interrupting the current (at a high frequency) the circuit thereby regulates the output power.

With each positive half-wave of the input alternating voltage, capacitance C1 is charged through a chain of resistors R3, R4, when the voltage on capacitor C1 becomes equal to the opening voltage of dinistor VD7, its breakdown will occur and the capacitance will be discharged through the diode bridge VD1-VD4, as well as resistance R1 and control electrode VS1. To open the triac, an electrical chain of diodes VD5, VD6, capacitor C2 and resistance R5 is used.

It is necessary to select the value of resistor R2 so that at both half-waves of the mains voltage, the regulator triac operates reliably, and it is also necessary to select the values ​​of resistances R3 and R4 so that when the variable resistance knob R4 is rotated, the voltage on the load smoothly changes from minimum to maximum values. Instead of the TS 2-80 triac, you can use TS2-50 or TS2-25, although there will be a slight loss in the permissible power in the load.

KU208G, TS106-10-4, TS 112-10-4 and their analogs were used as a triac. At the moment when the triac is closed, capacitor C1 is charged through the connected load and resistors R1 and R2. The charging speed is changed by resistor R2, resistor R1 is designed to limit the maximum value of the charge current

When the threshold voltage value is reached on the capacitor plates, the switch opens, capacitor C1 is quickly discharged to the control electrode and switches the triac from the closed state to the open state; in the open state, the triac bypasses the circuit R1, R2, C1. At the moment the mains voltage passes through zero, the triac closes, then capacitor C1 is charged again, but with a negative voltage.

Capacitor C1 from 0.1...1.0 µF. Resistor R2 1.0...0.1 MOhm. The triac is switched on by a positive current pulse to the control electrode with a positive voltage at the conventional anode terminal and by a negative current pulse to the control electrode with a negative voltage at the conventional cathode. Thus, the key element for the regulator must be bidirectional. You can use a bidirectional dinistor as a key.

Diodes D5-D6 are used to protect the thyristor from possible breakdown by reverse voltage. The transistor operates in avalanche breakdown mode. Its breakdown voltage is about 18-25 volts. If you don’t find P416B, then you can try to find a replacement for it.

The pulse transformer is wound on a ferrite ring with a diameter of 15 mm, brand N2000. The thyristor can be replaced with KU201

The circuit of this power regulator is similar to the circuits described above, only the interference suppression circuit C2, R3 is introduced, and the switch SW makes it possible to break the charging circuit of the control capacitor, which leads to instant locking of the triac and disconnecting the load.

C1, C2 - 0.1 MKF, R1-4k7, R2-2 mOhm, R3-220 Ohm, VR1-500 kOhm, DB3 - dinistor, BTA26-600B - triac, 1N4148/16 V - diode, any LED.

The regulator is used to regulate load power in circuits up to 2000 W, incandescent lamps, heating devices, soldering iron, asynchronous motors, car charger, and if you replace the triac with a more powerful one, it can be used in the current regulation circuit in welding transformers.

The principle of operation of this power regulator circuit is that the load receives a half-cycle of the mains voltage after a selected number of skipped half-cycles.

The diode bridge rectifies alternating voltage. Resistor R1 and zener diode VD2, together with the filter capacitor, form a 10 V power source to power the K561IE8 microcircuit and the KT315 transistor. The rectified positive half-cycles of the voltage passing through capacitor C1 are stabilized by the zener diode VD3 at a level of 10 V. Thus, pulses with a frequency of 100 Hz follow to the counting input C of the K561IE8 counter. If switch SA1 is connected to output 2, then a logical one level will be constantly present at the base of the transistor. Because the microcircuit reset pulse is very short and the counter manages to restart from the same pulse.

Pin 3 will be set to a logical one level. The thyristor will be open. All power will be released at the load. In all subsequent positions of SA1 at pin 3 of the counter, one pulse will pass through 2-9 pulses.

The K561IE8 chip is a decimal counter with a positional decoder at the output, so the logical one level will be periodic at all outputs. However, if the switch is installed on output 5 (pin 1), then counting will only occur up to 5. When the pulse passes through output 5, the microcircuit will be reset to zero. Counting will begin from zero, and a logical one level will appear at pin 3 for the duration of one half-cycle. During this time, the transistor and thyristor open, one half-cycle passes to the load. To make it clearer, I present vector diagrams of the circuit operation.

If you need to reduce the load power, you can add another counter chip by connecting pin 12 of the previous chip to pin 14 of the next one. By installing another switch, you can adjust the power up to 99 missed pulses. Those. you can get about a hundredth of the total power.

The KR1182PM1 microcircuit has two thyristors and a control unit for them. The maximum input voltage of the KR1182PM1 microcircuit is about 270 Volts, and the maximum load can reach 150 Watts without the use of an external triac and up to 2000 W with the use, and also taking into account the fact that the triac will be installed on the radiator.

To reduce the level of external noise, capacitor C1 and inductor L1 are used, and capacitance C4 is required for smooth switching on of the load. The adjustment is carried out using resistance R3.

A selection of fairly simple regulator circuits for a soldering iron will make life easier for a radio amateur.

Combination consists in combining the convenience of using a digital regulator and the flexibility of adjusting a simple one.

The considered power regulator circuit works on the principle of changing the number of periods of the input alternating voltage going to the load. This means that the device cannot be used to adjust the brightness of incandescent lamps due to visible blinking. The circuit makes it possible to regulate power within eight preset values.

There are a huge number of classic thyristor and triac regulator circuits, but this regulator is made on a modern element base and, in addition, was phase-based, i.e. does not transmit the entire half-wave of the mains voltage, but only a certain part of it, thereby limiting the power, since the triac opens only at the required phase angle.

The article describes how a thyristor power regulator works, the diagram of which will be presented below

In everyday life, very often there is a need to regulate the power of household appliances, such as electric stoves, soldering irons, boilers and heating elements, in transport - engine speed, etc. The simplest amateur radio design comes to the rescue - a power regulator on a thyristor. Assembling such a device will not be difficult; it can become the very first home-made device that will perform the function of adjusting the temperature of the soldering iron tip of a novice radio amateur. It is worth noting that ready-made soldering stations with temperature control and other pleasant functions are an order of magnitude more expensive than a simple soldering iron. A minimal set of parts allows you to assemble a simple thyristor power regulator for wall mounting.

For your information, surface mounting is a method of assembling radio-electronic components without using a printed circuit board, and with good skill it allows you to quickly assemble electronic devices of medium complexity.

You can also order a thyristor regulator, and for those who want to figure it out on their own, a diagram will be presented below and the principle of operation will be explained.

By the way, this is a single-phase thyristor power regulator. Such a device can be used to control power or speed. However, first we need to understand this because this will allow us to understand for what load it is better to use such a regulator.

How does a thyristor work?

A thyristor is a controlled semiconductor device capable of conducting current in one direction. The word “controlled” was used for a reason, because with its help, unlike a diode, which also conducts current only to one pole, you can select the moment when the thyristor begins to conduct current. The thyristor has three outputs:

• Anode.
• Cathode.
• Control electrode.

In order for current to begin flowing through the thyristor, the following conditions must be met: the part must be in a circuit that is energized, and a short-term pulse must be applied to the control electrode. Unlike a transistor, controlling a thyristor does not require holding the control signal. The nuances do not end there: the thyristor can be closed only by interrupting the current in the circuit, or by forming a reverse anode-cathode voltage. This means that the use of a thyristor in DC circuits is very specific and often unwise, but in AC circuits, for example in a device such as a thyristor power regulator, the circuit is constructed in such a way that a condition for closing is ensured. Each of the half-waves will close the corresponding thyristor.

Most likely, you don’t understand everything? Do not despair - below the process of operation of the finished device will be described in detail.

Scope of application of thyristor regulators

In what circuits is it effective to use a thyristor power regulator? The circuit allows you to perfectly regulate the power of heating devices, that is, influence the active load. When working with a highly inductive load, the thyristors may simply not close, which can lead to failure of the regulator.

Is it possible to have an engine?

I think many of the readers have seen or used drills, angle grinders, which are popularly called “grinders,” and other power tools. You may have noticed that the number of revolutions depends on the depth of pressing the trigger button of the device. It is in this element that a thyristor power regulator is built in (the diagram of which is given below), with the help of which the number of revolutions is changed.

Pay attention! The thyristor regulator cannot change the speed of asynchronous motors. Thus, the voltage is regulated on commutator motors equipped with a brush assembly.

Scheme of one and two thyristors

A typical circuit for assembling a thyristor power regulator with your own hands is shown in the figure below.

The output voltage of this circuit is from 15 to 215 volts; in the case of using the indicated thyristors installed on heat sinks, the power is about 1 kW. By the way, the switch with the light brightness control is made according to a similar scheme.

If you don't need to fully regulate the voltage and just want an output of 110 to 220 volts, use this diagram, which shows a half-wave thyristor power regulator.

How does this work?

The information described below is valid for most schemes. Letter designations will be taken in accordance with the first circuit of the thyristor regulator

A thyristor power regulator, the operating principle of which is based on phase control of the voltage value, also changes the power. This principle lies in the fact that under normal conditions the load is affected by the alternating voltage of the household network, changing according to a sinusoidal law. Above, when describing the operating principle of a thyristor, it was said that each thyristor operates in one direction, that is, it controls its own half-wave from a sine wave. What does it mean?

If you periodically connect a load using a thyristor at a strictly defined moment, the value of the effective voltage will be lower, since part of the voltage (the effective value that “falls” on the load) will be less than the mains voltage. This phenomenon is illustrated in the graph.

The shaded area is the area of ​​stress that is under load. The letter “a” on the horizontal axis indicates the opening moment of the thyristor. When the positive half-wave ends and the period with the negative half-wave begins, one of the thyristors closes, and at the same moment the second thyristor opens.

Let's figure out how our specific thyristor power regulator works

Scheme one

Let us stipulate in advance that instead of the words “positive” and “negative”, “first” and “second” (half-wave) will be used.

So, when the first half-wave begins to act on our circuit, capacitors C1 and C2 begin to charge. Their charging speed is limited by potentiometer R5. this element is variable, and with its help the output voltage is set. When the voltage necessary to open dinistor VS3 appears on capacitor C1, the dinistor opens and current flows through it, with the help of which thyristor VS1 will be opened. The moment of breakdown of the dinistor is point “a” on the graph presented in the previous section of the article. When the voltage value passes through zero and the circuit is under the second half-wave, the thyristor VS1 closes, and the process is repeated again, only for the second dinistor, thyristor and capacitor. Resistors R3 and R3 are used for control, and R1 and R2 are used for thermal stabilization of the circuit.

The principle of operation of the second circuit is similar, but it controls only one of the half-waves of alternating voltage. Now, knowing the principle of operation and the circuit, you can assemble or repair a thyristor power regulator with your own hands.

Using the regulator in everyday life and safety precautions

It must be said that this circuit does not provide galvanic isolation from the network, so there is a danger of electric shock. This means that you should not touch the regulator elements with your hands. An insulated enclosure must be used. You should design the design of your device so that, if possible, you can hide it in an adjustable device and find free space in the case. If the adjustable device is located permanently, then in general it makes sense to connect it through a switch with a dimmer. This solution will partially protect against electric shock, eliminate the need to find a suitable housing, has an attractive appearance and is manufactured using an industrial method.

An article about various ways to connect a load to a microcontroller control unit using relays and thyristors.

All modern equipment, both industrial and domestic, is powered by electricity. At the same time, its entire electrical circuit can be divided into two large parts: control devices (controllers from the English word CONTROL - to control) and actuators.

About twenty years ago, control units were made on microcircuits with a low and medium degree of integration. These were the series of microcircuits K155, K561, K133, K176 and the like. They are called because they perform logical operations on signals, and the signals themselves are digital (discrete).

Exactly the same as ordinary contacts: “closed - open”. Only in this case, these states are called “logical one” and “logical zero”, respectively. The logical one voltage at the output of microcircuits ranges from half the supply voltage to its full value, and the logical zero voltage of such microcircuits is usually 0...0.4V.

The operation algorithm of such control units was carried out through the appropriate connection of microcircuits, and their number was quite large.

Currently, all control units are developed based on . In this case, the operating algorithm is laid down not by the circuit connection of individual elements, but by a program “stitched” into the microcontroller.

In this regard, instead of several dozen or even hundreds of microcircuits, the control unit contains a microcontroller and a number of microcircuits for interacting with the “outside world”. But, despite this improvement, the signals of the microcontroller control unit are still the same digital as those of the old microcircuits.

It is clear that the power of such signals is not enough to turn on a powerful lamp, motor, or even just a relay. In this article we will look at, what ways can you connect powerful loads to microcircuits?.

The most. In Figure 1, the relay is turned on using transistor VT1; for this, a logical unit is applied to its base through resistor R1 from the microcircuit, the transistor opens and turns on the relay, which, with its contacts (not shown in the figure), turns on the load.

Cascade shown in Figure 2 works differently: to turn on the relay, a logical 0 must appear at the output of the microcircuit, which closes transistor VT3. in this case, transistor VT4 will open and turn on the relay. Using the SB3 button you can turn on the relay manually.

In both figures you can see that diodes are connected parallel to the relay windings, and in relation to the supply voltage in the opposite (non-conducting) direction. Their purpose is to extinguish the self-induction EMF (can be ten or more times the supply voltage) when the relay is turned off and to protect the circuit elements.

If the circuit contains not one or two relays, but much more, then for connecting them a specialized chip ULN2003A, allowing connection of up to seven relays. This connection diagram is shown in Figure 3, and in Figure 4 the appearance of a modern small-sized relay.

Figure 5 shows (instead of which, without changing anything in the circuit, you can connect a relay). In this diagram, you should pay attention to the transistor switch, made on two transistors VT3, VT4. This complication is caused by the fact that some microcontrollers, for example AT89C51, AT89C2051, hold the logical 1 level on all pins for several milliseconds during the reset time when turned on. If the load is connected according to the diagram shown in Figure 1, then the load will operate immediately when the power is turned on, which can be a very undesirable phenomenon.

In order to turn on the load (in this case, the LEDs of optocoupler thyristors V1, V2) a logical 0 should be applied to the base of transistor VT3 through resistor R12, which will lead to the opening of VT3 and VT4. The latter will light the LEDs of the optothyristors, which will open and turn on the mains load. Optocoupler thyristors provide galvanic isolation from the network of the control circuit itself, which increases the electrical safety and reliability of the circuit.

A few words about thyristors. Without going into technical details and current-voltage characteristics, we can say that this is a simple diode, they even have similar designations. But the thyristor also has a control electrode. If a pulse positive relative to the cathode is applied to it, even a short-term one, the thyristor will open.

The thyristor will remain in the open state as long as current flows through it in the forward direction. This current must be no less than a certain value called the holding current. Otherwise, the thyristor simply will not turn on. You can turn off the thyristor only by breaking the circuit or applying a voltage of reverse polarity. Therefore, in order to pass both half-waves of alternating voltage, a counter-parallel connection of two thyristors is used (see Fig. 5).

In order not to make such an inclusion, triacs are also produced in bourgeois language. They already have two thyristors in one housing, connected back-to-back - in parallel. They have a common control electrode.

Figure 6 shows the appearance and pinout of thyristors, and Figure 7 shows the same for triacs.

Figure 8 shows diagram for connecting the triac to the microcontroller (chip output) using a special low-power optotriac type MOC3041.

This driver inside contains an LED connected to pins 1 and 2 (the figure shows a top view of the microcircuit) and the optotriac itself, which, when illuminated by the LED, opens (pins 6 and 4) and, through resistor R1, connects the control electrode to the anode , due to which a powerful triac is opened.

Resistor R2 is designed to prevent the triac from opening in the absence of a control signal at the moment the power is turned on, and the chain C1, R3 is designed to suppress interference at the time of switching. True, the MOC3041 does not create any special interference, since it has a CROSS ZERO circuit (voltage transition through 0), and switching on occurs at the moment when the mains voltage has just passed through 0.

All considered circuits are galvanically isolated from the supply network, which ensures reliable operation even with significant switching power.

If the power is insignificant and galvanic isolation of the controller from the network is not required, then it is possible to connect thyristors directly to the microcontroller. A similar diagram is shown in Figure 9.

This is the diagram Christmas tree garland produced, of course, in China. The control electrodes of the MCR 100-6 thyristors are connected directly to the microcontroller (located on the board under a drop of black compound). The power of the control signals is so low that the current consumption for all four at once is less than 1 milliamp. In this case, the reverse voltage is up to 800V and the current is up to 0.8A. The overall dimensions are the same as those of the KT209 transistors.

Of course, it is impossible to describe all the schemes at once in one short article, but it seems that we were able to describe the basic principles of their operation. There are no particular difficulties here, the schemes have all been tested in practice and, as a rule, do not cause any problems during repairs or self-production.

Boris Aladyshkin