The world around us is full of sounds. In the city these are mainly sounds associated with the development of technology. Nature gives us more pleasant sensations - the singing of birds, the sound of the sea surf, the crackling of a fire on a hiking trip. Often, some of these sounds need to be reproduced artificially - imitated, simply out of desire, or based on the needs of your technical modeling club, or when staging a play in a drama club. Let's look at descriptions of several sound simulators.

Intermittent siren sound simulator

Let's start with the simplest design, this is a simple siren sound simulator. There are single-tone sirens, which produce a sound of one tone, intermittent ones, when the sound gradually increases or decreases, and then is interrupted or becomes single-tone, and two-tone ones, in which the tone of the sound periodically changes abruptly.

A generator is assembled using transistors VT1 and VT2 using an asymmetrical multivibrator circuit. The simplicity of the generator circuit is explained by the use of transistors of different structures, which made it possible to do without many of the parts necessary to build a multivibrator using transistors of the same structure.

Siren sound simulator - circuit with two transistors

Oscillator oscillations, and hence the sound in the dynamic head, appear due to positive feedback between the collector of transistor VT2 and the base of VT1 through capacitor C2. The tonality of the sound depends on the capacitance of this capacitor.

When switch SA1 supplies supply voltage to the generator, there will be no sound in the head yet, since there is no bias voltage based on transistor VT1. The multivibrator is in standby mode.

As soon as the SB1 button is pressed, capacitor C1 begins to charge (through resistor R1). The bias voltage at the base of transistor VT1 begins to increase, and at a certain value the transistor opens. The sound of the desired tonality is heard in the dynamic head. But the bias voltage increases, and the tone of the sound changes smoothly until the capacitor is fully charged. The duration of this process is 3...5 s and depends on the capacitance of the capacitor and the resistance of resistor R1.

As soon as you release the button, the capacitor will begin to discharge through resistors R2, R3 and the emitter junction of transistor VT1. The tone of the sound changes smoothly, and at a certain bias voltage based on transistor VT1, the sound disappears. The multivibrator returns to standby mode. The duration of discharge of the capacitor depends on its capacitance, the resistance of resistors R2, R3 and the emitter junction of the transistor. It is selected in such a way that, as in the first case, the tonality of the sound changes within 3...5 s.

In addition to those indicated in the diagram, the simulator can use other low-power silicon transistors of the corresponding structure with a static current transfer coefficient of at least 50. In extreme cases, germanium transistors are also suitable - MP37A, MP101 can work in place of VT1, and instead of VT2 - MP42A, MP42B with possibly large static transmission coefficient. Capacitor C1 - K50-6, C2 - MBM, resistors - MLT-0.25 or MLT-0.125. Dynamic head - power 0.G...1 W with a voice coil with a resistance of 6...10 Ohms (for example, head 0.25GD-19, 0.5GD-37, 1GD-39). The power source is a Krona battery or two 3336 batteries connected in series. The power switch and button are of any design.

In standby mode, the simulator consumes a small current - it depends mainly on the reverse collector current of the transistors. Therefore, the switch contacts can be closed for a long time, which is necessary, say, when using the simulator as an apartment bell. When the contacts of the SB1 button close, the current consumption increases to approximately 40 mA.

Looking at the circuit of this simulator, it is easy to notice an already familiar unit - a generator assembled on transistors VT3 and VT4. The previous simulator was assembled using this scheme. Only in this case the multivibrator does not operate in standby mode, but in normal mode. To do this, a bias voltage from the divider R6R7 is applied to the base of the first transistor (VT3). Note that transistors VT3 and VT4 have swapped places compared to the previous circuit due to a change in the polarity of the supply voltage.

So, a tone generator is assembled on transistors VT3 and VT4, which sets the first tone of the sound. On transistors VT1 and VT2 a symmetrical multivibrator is made, thanks to which a second tone of sound is obtained.

It happens like this. During operation of the multivibrator, the voltage at the collector of transistor VT2 is either present (when the transistor is closed) or disappears almost completely (when the transistor is opened). The duration of each state is the same - approximately 2 s (i.e., the multivibrator pulse repetition rate is 0.5 Hz). Depending on the state of transistor VT2, resistor R5 bypasses either resistor R6 (through resistor R4 connected in series with resistor R5) or R7 (through the collector-emitter section of transistor VT2). The bias voltage at the base of transistor VT3 changes abruptly, so a sound of one or another tone is heard from the dynamic head.

What is the role of capacitors C2, SZ? They allow you to get rid of the influence of the tone generator on the multivibrator. If they are absent, the sound will be somewhat distorted. The capacitors are connected in back-to-back series because the polarity of the signal between the collectors of transistors VT1 and VT2 periodically changes. A conventional oxide capacitor under such conditions performs worse than a so-called non-polar one, for which the polarity of the voltage at the terminals does not matter. When two polar oxide capacitors are connected in this way, an analogue of a non-polar capacitor is formed. True, the total capacitance of the capacitor becomes half that of each of them (of course, with their capacitance being the same).

Siren sound simulator using four transistors

This simulator can use the same types of parts as the previous one, including the power supply. To supply the supply voltage, both a regular switch with a fixed position and a push-button switch are suitable if the simulator will work as an apartment bell.

Some of the parts are mounted on a printed circuit board (Fig. 29) made of single-sided foil fiberglass. Installation can also be hinged, performed in the usual way - using mounting racks for soldering the leads of the parts. The board is placed in a suitable housing in which the dynamic head and power supply are installed. The switch is placed on the front wall of the housing or mounted near the front door (if there is already a bell button there, its terminals are connected by insulated conductors to the corresponding circuits of the simulator).

As a rule, a simulator installed without errors starts working immediately. But if necessary, it is easy to adjust to obtain a more pleasant sound. Thus, the tonality of the sound can be slightly lowered by increasing the capacitance of capacitor C5 or increased by decreasing it. The range of tone changes depends on the resistance of resistor R5. The duration of the sound of a particular key can be changed by selecting capacitors C1 or C4.

This can be said about the next sound simulator if you listen to its sound. Indeed, the sounds produced by the dynamic head resemble the exhausts characteristic of a car, tractor or diesel locomotive engine. If the models of these machines are equipped with the proposed simulator, they will immediately come to life.

According to the circuit, the engine operation simulator is somewhat reminiscent of a single-tone siren. But the dynamic head is connected to the collector circuit of transistor VT2 through the output transformer T1, and the bias and feedback voltages are supplied to the base of transistor VT1 through variable resistor R1. For direct current it is connected by a variable resistor, and for feedback formed by a capacitor - by a voltage divider (potentiometer). When the resistor slider is moved, the frequency of the generator changes: when the slider is moved down the circuit, the frequency increases, and vice versa. Therefore, a variable resistor can be considered an accelerator that changes the rotation speed of the “engine” shaft, and therefore the frequency of sound exhaust.

Engine sound simulator - circuit with two transistors

Transistors KT306, KT312, KT315 (VT1) and KT208, KT209, KT361 (VT2) with any letter indices are suitable for the simulator. Variable resistor - SP-I, SPO-0.5 or any other, possibly smaller in size, constant - MLT-0.25, capacitor - K50-6, K50-3 or other oxide, with a capacity of 15 or 20 μF for the rated voltage not below 6 V. The output transformer and dynamic head are from any small-sized (“pocket”) transistor receiver. One half of the primary winding is used as winding I. The power source is a 3336 battery or three 1.5 V cells connected in series.

Depending on where you will use the simulator, determine the dimensions of the board and case (if you intend to install the simulator not on the model).

If, when you turn on the simulator, it works unstably or there is no sound at all, swap the leads of capacitor C1 with the positive lead to the collector of transistor VT2. By selecting this capacitor you can set the desired limits for changing the speed of the “engine”.

Drip... drip... drip... - sounds come from the street when it rains or in the spring drops of melting snow fall from the roof. These sounds have a calming effect on many people, and according to some, they even help them fall asleep. Well, perhaps you will need such a simulator for the soundtrack in your school drama club. The construction of the simulator will take only a dozen parts.

A symmetrical multivibrator is made on transistors, the loads of which are the high-impedance dynamic heads BA1 and BA2 - “drop” sounds are heard from them. The most pleasant “drop” rhythm is set with variable resistor R2.

Drop sound simulator - circuit with two transistors

To reliably “start” a multivibrator at a relatively low supply voltage, it is advisable to use transistors (they can be of the MP39 - MP42 series) with the highest possible static current transfer coefficient. Dynamic heads should have a power of 0.1 - 1 W with a voice coil with a resistance of 50 - 100 Ohms (for example, 0.1GD-9). If such a head is not available, you can use DEM-4m capsules or similar ones that have the specified resistance. Higher impedance capsules (for example, from TON-1 headphones) will not provide the required sound volume. The remaining parts can be of any type. Power source - 3336 battery.

The simulator parts can be placed in any box and dynamic heads (or capsules), a variable resistor and a power switch can be mounted on its front wall.

When checking and adjusting the simulator, you can change its sound by selecting constant resistors and capacitors within a wide range. If in this case you need a significant increase in the resistances of resistors R1 and R3, it is advisable to install a variable resistor with a high resistance - 2.2; 3.3; 4.7 kOhm to provide a relatively wide range of droplet frequency control.

Bouncing ball sound simulator circuit

Want to hear a steel ball bounce off a ball bearing on a steel or cast iron plate? Then assemble the simulator according to the diagram shown in Fig. 32. This is a variant of an asymmetrical multivibrator, used, for example, in a siren. But unlike a siren, the proposed multivibrator does not have pulse repetition frequency control circuits. How does the simulator work? Just press (briefly) the SB1 button - and capacitor C1 will charge to the voltage of the power source. After releasing the button, the capacitor will become the source that powers the multivibrator. While the voltage on it is high, the volume of the “blows” of the “ball” reproduced by the dynamic head BA1 is significant, and the pauses are relatively long.

Simulator of the sound of a bouncing ball - transistor circuits

Gradually, as capacitor C1 discharges, the nature of the sound will change - the volume of the “beats” will begin to decrease, and the pauses will decrease. Finally, a characteristic metallic rattling sound will be heard, after which the sound will stop (when the voltage on capacitor C1 drops below the opening threshold of the transistors).

Transistor VT1 can be any of the MP21, MP25, MP26 series, and VT2 can be any of the KT301, KT312, KT315 series. Capacitor C1 - K.50-6, C2 - MBM. The dynamic head is 1GD-4, but another one with good diffuser mobility and a possibly larger area will do. The power source is two batteries 3336 or six cells 343, 373 connected in series.

The parts can be mounted inside the simulator body by soldering their leads to the pins of the button and the dynamic head. Batteries or cells are attached to the bottom or walls of the case with a metal bracket.

When setting up the simulator, the most characteristic sound is achieved. To do this, select capacitor C1 (it determines the total duration of the sound) within 100...200 µF or C2 (the duration of pauses between “beats” depends on it) within 0.1...0.5 µF. Sometimes, for the same purposes, it is useful to select transistor VT1 - after all, the operation of the simulator depends on its initial (reverse) collector current and the static current transfer coefficient.

The simulator can be used as an apartment bell if you increase the volume of its sound. The easiest way to do this is to add two capacitors to the device - SZ and C4 (Fig. 33). The first of them directly increases the sound volume, and the second gets rid of the tone drop effect that sometimes appears. True, with such modifications the “metallic” sound tint characteristic of a real bouncing ball is not always preserved.

Transistor VT3 can be any of the GT402 series, resistor R1 - MLT-0.25 with a resistance of 22...36 Ohms. In place of VT3, transistors of the MP20, MP21, MP25, MP26, MP39 - MP42 series can operate, but the sound volume will be somewhat weaker, although significantly higher than in the original simulator.

Sea surf sound simulator circuit diagram

By connecting a small set-top box to the amplifier of a radio, tape recorder or TV, you can get sounds reminiscent of the sound of the sea surf.

The diagram of such a simulator attachment is shown in Fig. 35. It consists of several nodes, but the main one is the noise generator. It is based on a silicon zener diode VD1. The fact is that when a constant voltage exceeding the stabilization voltage is applied to the zener diode through a ballast resistor with a high resistance, the zener diode begins to “break through” - its resistance drops sharply. But thanks to the insignificant current flowing through the zener diode, such a “breakdown” does not cause any harm to it. At the same time, the zener diode seems to go into noise generation mode, the so-called “shot effect” of its pn junction appears, and at the zener diode terminals one can observe (of course, using a sensitive oscilloscope) a chaotic signal consisting of random oscillations, the frequencies of which lie in a wide range.

This is the mode in which the zener diode of the set-top box works. The ballast resistor mentioned above is R1. Capacitor C1, together with a ballast resistor and a zener diode, provides a signal of a certain frequency band, similar to the sound of surf noise.

Sea surf sound simulator circuit with two transistors

Of course, the amplitude of the noise signal is too small to feed it directly to the radio amplifier. Therefore, the signal is amplified by a cascade on transistor VT1, and from its load (resistor R2) goes to an emitter follower made on transistor VT2, which eliminates the influence of subsequent cascades of the set-top box on the operation of the noise generator.

From the emitter follower load (resistor R3), the signal is supplied to a cascade with a variable gain, assembled on transistor VT3. Such a cascade is needed so that it is possible to change the amplitude of the noise signal supplied to the amplifier, and thereby simulate the increase or decrease in the volume of the “surf”.

To carry out this task, transistor VT4 is included in the emitter circuit of transistor VT3, the base of which receives a signal from a control voltage generator - a symmetrical multivibrator on transistors VT5, VT6 - through resistor R7 and integrating circuit R8C5. In this case, the resistance of the collector-emitter section of transistor VT4 periodically changes, which causes a corresponding change in the gain of the cascade on transistor VT3. As a result, the noise signal at the cascade output (at resistor R6) will periodically rise and fall. This signal is supplied through the capacitor SZ to connector XS1, which is connected during operation of the set-top box to the input of the amplifier used.

The pulse duration and repetition frequency of the multivibrator can be changed by resistors R10 and R11. Together with resistor R8 and capacitor C4, they determine the duration of the rise and fall of the control voltage supplied to the base of transistor VT4.

All transistors can be the same, KT315 series with the highest possible current transfer coefficient. Resistors - MLT-0.25 (MLT-0.125 is also possible); capacitors Cl, C2 - K50-3; NW, S5 - S7 - K.50-6; C4 - MBM. Other types of capacitors are suitable, but they must be designed for a rated voltage not lower than that indicated in the diagram.

Almost all parts are mounted on a circuit board (Fig. 36) made of foil material. Place the board in a case of suitable dimensions. Connector XS1 and clamps XT1, XT2 are fixed on the side wall of the case.

The set-top box is powered from any DC source with a stabilized and adjustable output voltage (from 22 to 27 V).

As a rule, there is no need to set up the console. It starts working immediately after power is applied. It is easy to check the operation of the set-top box using high-impedance headphones TON-1, TON-2 or other similar ones, plugged into the sockets of the XS1 “Output” connector.

The nature of the sound of the “surf” is changed (if necessary) by selecting the supply voltage, resistors R4, R6, as well as bypassing the sockets of the XS1 connector with a capacitor C7 with a capacity of 1000...3000 pF.

And here is another such sound simulator, assembled according to a slightly different scheme. It contains an audio amplifier and a power supply, so this simulator can be considered a complete design.

The noise generator itself is assembled on transistor VT1 according to the so-called super-regenerator circuit. It is not very easy to understand the operation of a superregenerator, so we will not consider it. Just understand that this is a generator in which oscillations are excited due to positive feedback between the output and input of the cascade. In this case, this connection is carried out through the capacitive divider C5C4. In addition, the super-regenerator is not excited constantly, but in flashes, and the moment of occurrence of the flashes is random. As a result, a signal appears at the output of the generator, which is heard as noise. This signal is often called “white noise”.

Sea surf sound simulator, a more complex version of the circuit

The DC operating mode of the superregenerator is set by resistors Rl, R2, R4. Inductor L1 and capacitor C6 do not affect the operating mode of the cascade, but protect the power circuits from the penetration of noise signals into them.

The L2C7 circuit determines the frequency band of “white noise” and allows you to obtain the largest amplitude of the allocated “noise” oscillations. Next, they pass through the low-pass filter R5C10 and capacitor C9 to the amplifier stage assembled on transistor VT2. The supply voltage to this stage is supplied not directly from source GB1, but through a cascade assembled on transistor VT3. This is an electronic key that periodically opens with pulses arriving at the base of the transistor from a multivibrator assembled on transistors VT4, VT5. During periods when transistor VT4 is closed, VT3 opens, and capacitor C12 is charged from source GB1 through the collector-emitter section of transistor VT3 and trimming resistor R9. This capacitor is a kind of battery that powers the amplifier stage. As soon as transistor VT4 opens, VT3 closes, capacitor C12 is discharged through trimming resistor R11 and the collector-emitter circuit of transistor VT2.

As a result, at the collector of transistor VT2 there will be a noise signal modulated in amplitude, i.e., periodically increasing and decreasing. The duration of the rise depends on the capacitance of capacitor C12 and the resistance of resistor R9, and the decline - on the capacitance of the specified capacitor and the resistance of resistor R11.

Through the capacitor SP, the modulated noise signal is supplied to an audio amplifier made on transistors VT6 - VT8. At the input of the amplifier there is a variable resistor R17 - a volume control. From its engine, the signal is supplied to the first stage of the amplifier, assembled on a VT6 transistor. This is a voltage amplifier. From the cascade load (resistor R18), the signal is supplied through capacitor C16 to the output stage - a power amplifier made using transistors VT7, VT8. The collector circuit of transistor VT8 includes a load - dynamic head BA1. From it you can hear the sound of “sea surf”. Capacitor C17 weakens the high-frequency, “whistle” components of the signal, which somewhat softens the sound timbre.

About the details of the simulator. Instead of the KT315V transistor (VT1), you can use other transistors of the KT315 series or the GT311 transistor with any letter index. The remaining transistors can be any of the MP39 - MP42 series, but with the highest possible current transfer coefficient. To obtain greater output power, it is advisable to use the VT8 transistor of the MP25, MP26 series.

Throttle L1 can be ready-made, type D-0.1 or another.

Inductance 30... 100 µH. If it is not there, you need to take a rod core with a diameter of 2.8 and a length of 12 mm from ferrite 400NN or 600NN and wind on it turn to turn 15...20 turns of PEV-1 0.2...0.4 wire. It is advisable to measure the resulting inductance of the inductor on a standard device and, if necessary, select it within the required limits by decreasing or increasing the number of turns.

Coil L2 is wound on a frame with a diameter of 4 and a length of 12 ... 15 mm from any insulating material using PEV-1 wire 6.3 - 24 turns with a tap from the middle.

Fixed resistors - MLT-0.25 or MLT-0.125, tuning resistors - SPZ-16, variable - SPZ-Zv (it has a litany switch SA1). Oxide capacitors - K50-6; C17 - MBM; the rest are KM, K10-7 or other small-sized ones. Dynamic head - power 0.1 - I W with the highest possible voice coil resistance (so that the VT8 transistor does not overheat). The power source is two 3336 batteries connected in series, but the best results in terms of operating time will be obtained with six 373 cells connected in the same way. A suitable option, of course, is power supply from a low-power rectifier with a constant voltage of 6...9 V.

The simulator parts are mounted on a board (Fig. 38) made of foil material 1...2 mm thick. The board is installed in a case, on the front wall of which a dynamic head is mounted, and a power source is placed inside. The dimensions of the case largely depend on the dimensions of the power source. If the simulator is used only to demonstrate the sound of the sea surf, the power source can be a Krona battery - then the dimensions of the case will be sharply reduced, and the simulator can be mounted in the case of a small-sized transistor radio.

The simulator is set up like this. Disconnect resistor R8 from capacitor C12 and connect it to the negative power wire. Having set the maximum sound volume, select resistor R1 until characteristic noise (“white noise”) is obtained in the dynamic head. Then restore the connection between resistor R8 and capacitor C12 and listen to the sound in the dynamic head. By moving the slider of the tuning resistor R14, the most reliable and pleasant-to-hear frequency of the “sea waves” is selected. Next, by moving the slider of resistor R9, the duration of the rise of the “wave” is set, and by moving the slider of resistor R11, the duration of its decline is determined.

To get a high volume of “sea surf”, you need to connect the extreme terminals of the variable resistor R17 to the input of a powerful audio amplifier. A better experience can be achieved by using a stereo amplifier with external speakers operating in mono playback mode.

Rain noise sound simulator simple circuit

If you want to listen to the beneficial effects of the measured noise of rain, forest or sea surf. Such sounds relax and calm.

Rain noise sound simulator - operational amplifier and counter circuit

The rain noise generator is made on a TL062 chip, which includes two operational amplifiers. Then the generated sound is amplified by transistor VT2 and sent to the speaker SP. For greater compliance, the HF audio spectrum is cut off by capacitance C8, which is controlled by field-effect transistor VT1, which essentially works as a variable resistance. Thus, we obtain automatic control of the imitator's tone.

The CD4060 counter has a timer with three shutdown time delays: 15, 30 and 60 minutes. Transistor VT3 is used as a generator power switch. By changing the values ​​of resistance R16 or capacitance C10, we obtain different time intervals in the operation of the timer. By changing the value of resistor R9 from 47k to 150k, you can change the speaker volume.

RADIO signal:

MULTIVIBRATOR-3
A SMALL SELECTION OF SIMPLE PRACTICAL DIAGRAMS

From RADIO magazine:
1967, No. 9, p. 47, Multivibrator and its application: sound generator, tachometer, metronome

1974, No. 2, p. 38, Multivibrator in radio toys: a gourmet cat, a duck with ducklings, electronic nightingales

1975, No. 11, p. 54, New Year's garlands: switches for one and five garlands

1977, No. 2, p. 50, Game library on reed switches: sensors and a dozing kitten

1978, No. 11, p. 50, Garland switches: on thyristors, with a flickering glow


1980, No. 11, p. 50, Pulsating voltage source for Christmas tree garlands

This is one of the few surviving devices that I collected a long time ago. Around 1982

The device still works fine.
1981, No. 11, p. 34, New Year's garlands

1983, No. 3, p. 53, Game “Reaction”, “Cuckoo” on transistors


1984, No.7, p.35, Readers suggest: light pulse generator from the Emitron flashlight, simulator of the sound of a bouncing ball

1985, No. 3, p. 52, On the use of a multivibrator: an intermittent signal generator

1985, No. 11, p. 52, New Year's garland switches: switch of 2 garlands, switch of 4 garlands

1985, No. 12, p. 51, Two toys with multivibrators: a “mother” generator, an electronic puppy


1986, No. 1, p. 51, AF probe generator, sound alarm

1986, No. 10, p. 52, Soldering iron power regulator


1986, No. 11, p. 55, Programmable garland switch


Another one of the few surviving devices that I collected a long time ago. Around 1992 or earlier.

In the case of a network calculator.
This device also works normally at the present time.
1987, No. 1, p. 53, Two-tone touch call


1987, No. 4, p. 50, Infra-low-frequency multivibrator-automatic


1987, No. 7, p. 34, “Polyphonic” sound simulator


1987, No. 9, p.51, Door touch bells, p.55, Probe with sound indication

1987, No. 10, p. 51, To help the radio mug: electronic siren, sound humidity alarm

1987, No. 11, p. 52, Festive garlands


1988, No. 11, p.53, Time relay for the amateur photographer, p.55, “Green or red?” on a chip

Drop sound simulator
Drip... drip... drip... - sounds come from the street when it rains or in the spring drops of melting snow fall from the roof. These sounds have a calming effect on many people, and according to some, they even help them fall asleep. Well, perhaps you will need such a simulator for the soundtrack in your school drama club. The construction of the simulator will take only a dozen parts.
A symmetrical multivibrator is made on transistors, the loads of which are the high-impedance dynamic heads BA1 and BA2 - “drop” sounds are heard from them. The most pleasant “drop” rhythm is set with variable resistor R2.

To reliably “start” a multivibrator at a relatively low supply voltage, it is advisable to use transistors (they can be of the MP39 - MP42 series) with the highest possible static current transfer coefficient. Dynamic heads should have a power of 0.1 - 1 W with a voice coil with a resistance of 50 - 100 Ohms (for example, 0.1GD-9). If such a head is not available, you can use DEM-4m capsules or similar ones that have the specified resistance. Higher impedance capsules (for example, from TON-1 headphones) will not provide the required sound volume. The remaining parts can be of any type.
When checking and adjusting the simulator, you can change its sound by selecting constant resistors and capacitors within a wide range. If in this case you need a significant increase in the resistances of resistors R1 and R3, it is advisable to install a variable resistor with a high resistance - 2.2; 3.3; 4.7 kOhm to provide a relatively wide range of droplet frequency control.

“Meow” sound simulator
This sound came from a small box, inside of which was an electronic simulator. Its circuit is a little reminiscent of the previous simulator, not counting the amplification part - an analog integrated circuit is used here.


An asymmetrical multivibrator is assembled using transistors VT1 and VT2. It produces rectangular pulses, following at a relatively low frequency - 0.3 Hz. These pulses are supplied to the integrating circuit R5C3, as a result of which a signal with a smoothly rising and gradually falling envelope is formed at the terminals of the capacitor. So, when transistor VT2 of the multivibrator closes, the capacitor begins to charge through resistors R4 and R5, and when the transistor opens, the capacitor is discharged through resistor R5 and the collector section. emitter transistor VT2.
From the capacitor SZ, the signal goes to the generator, made on transistor VT3. While the capacitor is discharged, the generator does not work. As soon as a positive pulse appears and the capacitor is charged to a certain voltage, the generator “triggers” and an audio frequency signal (approximately 800 Hz) appears at its load (resistor R9). As the voltage across the capacitor SZ increases, and therefore the bias voltage at the base of the transistor VT3, the amplitude of oscillations at the resistor R9 increases. At the end of the pulse, as the capacitor discharges, the amplitude of the signal drops, and soon the generator stops working. This is repeated with each pulse removed from the load resistor R4 of the multivibrator arm.
The signal from resistor R9 goes through capacitor C7 to variable resistor R10 - the volume control, and from its engine to the audio power amplifier. The use of a ready-made amplifier in an integrated design made it possible to significantly reduce the size of the design, simplify its setup and ensure sufficient sound volume - after all, the amplifier develops a power of about 0.5 W at the specified load (BA1 dynamic head). “Meow” sounds are heard from the dynamic head.
Transistors can be any from the KT315 series, but with a transmission coefficient of at least 50. Instead of the K174UN4B microcircuit (former designation K1US744B), you can use K174UN4A, and the output power will increase slightly. Oxide capacitors - K53-1A (C1, C2, C7, C9); K52-1 (NW, S8, S10); K50-6 is also suitable for a rated voltage of at least 10 V; the remaining capacitors (C4 - C6) are KM-6 or other small ones. Fixed resistors - MLT-0.25 (or MLT-0.125), variable - SPZ-19a or another similar one.
Dynamic head - power 0.5 - 1 W with voice coil resistance 4 - 10 Ohms. But it should be taken into account that the lower the resistance of the voice coil, the greater the amplifier power that can be obtained from the dynamic head. Power source - two 3336 batteries or six elements 343 connected in series. Power switch - any Design.
A dynamic head, a variable resistor and a power switch are installed on the front wall of the case. If you can purchase a variable resistor with a power switch (for example, type TK, TKD, SPZ-4vM), you will not need a separate switch.
The simulator usually starts working right away, but requires some adjustment to get the most similar kitten meow sounds. Thus, the duration of the sound is changed by selecting resistor R3 or capacitor C1, and the pauses between sounds are changed by selecting resistor R2 or capacitor C2. The duration of the rise and fall of the sound volume can be changed by selecting the capacitor SZ and resistors R4, R5. The sound timbre is changed by selecting parts of the frequency-setting chains generator- resistors R6 - R8 and capacitors C4 - Sat.

The cricket chirping simulator consists of a multivibrator and an RC oscillator. The multivibrator is assembled using transistors VT1 and VT2. Negative pulses of the multivibrator (when transistor VT2 closes) are supplied through diode VD1 to capacitor C4, which is the “battery” of the bias voltage for the generator transistor.
The generator, as you can see, is assembled on just one transistor and produces oscillations of a sinusoidal sound frequency. This is a tone generator. Oscillations arise due to the action of positive feedback between the collector and the base of the transistor due to the inclusion between them of a phase-shifting chain of capacitors C5 - C7 and resistors R7 - R9. This chain is also frequency-setting - the frequency generated by the generator, and therefore the tone of the sound reproduced by the dynamic head BA1, depends on the ratings of its parts - it is connected to the collector circuit of the transistor through the output transformer T1.
During the open state of transistor VT2 of the multivibrator, capacitor C4 is discharged, and there is practically no bias voltage at the base of transistor VT3. The generator does not work, there is no sound from the dynamic head.


When transistor VT2 closes, capacitor C4 begins to charge through resistor R4 and diode VD1. At a certain voltage at the terminals of this capacitor, transistor VT3 opens so much that the generator begins to work, and a sound appears in the dynamic head, the frequency and volume of which changes as the voltage across the capacitor increases.
As soon as transistor VT2 opens again, capacitor C4 begins to discharge (through resistors R5, R6, R9 and the emitter junction circuit of transistor VT3), the sound volume drops, and then the sound disappears.
The repetition frequency of the trills depends on the frequency of the multivibrator. The simulator is powered from source GB1, the voltage of which can be 8...I V. To isolate the multivibrator from the generator, a filter R5C1 is installed between them, and to protect the power source from generator signals, capacitor C9 is connected in parallel with the source. When using the simulator for a long time, it must be powered from a rectifier.
Transistors VT1, VT2 can be of the MP39 - MP42 series, and VT3 - MP25, MP26 with any letter index, but with a transmission coefficient of at least 50. Oxide capacitors - K50-6, the rest - MBM, BMT or other small-sized ones. Fixed resistors - MLT-0.25, trimmer R7 - SPZ-16. Diode - any low-power silicon. The output transformer is from any small-sized transistor receiver (half of the primary winding is used), the dynamic head is 0.1 - 1 W with a voice coil with a resistance of 6 - 10 Ohms. The power source is two 3336 batteries connected in series or six 373 cells.
Before turning on the simulator, set the trimmer resistor R7 to the lowest position according to the diagram. Apply power to switch SA1 and listen to the sound of the simulator. Make it more similar to the chirping of a cricket with trimming resistor R7.
If there is no sound after turning on the power, check the operation of each node separately. First, disconnect the left terminal of resistor R6 from parts VD1, C4 and connect it to the negative power wire. A single-tone sound should be heard in the dynamic head. If it is not there, check the installation of the generator and its parts (primarily the transistor). To check the operation of the multivibrator, it is enough to connect high-impedance headphones (TON-1, TON-2) in parallel with resistor R4 or the terminals of transistor VT2 (through a capacitor with a capacity of 0.1 μF). When the multivibrator is working, clicks will be heard in the phones, following after 1…2 s. If they are not there, look for an installation error or a faulty part.
Having achieved the operation of the generator and multivibrator separately, restore the connection of resistor R6 with diode VD1 and capacitor C4 and make sure that the simulator is working.

"Whim"
In a small toy crib sits a doll with outstretched arms - asking to be picked up. But as soon as you put her to bed, the words “Mom, mom, mom” are heard. This is what this toy looks like. An electronic sound simulator and a reed switch that turns on the power are mounted inside the crib, and a small permanent magnet is glued to the doll. When the doll is placed in the crib, power supply is supplied to the sound simulator and the sounds “Mom” are heard in the dynamic head.


The simulator consists of three multivibrators. A multivibrator is assembled on transistors VT6, VT7, generating audio frequency oscillations. They are amplified by a cascade on transistor VT8 and heard from the dynamic head BA1, connected to the cascade through the output transformer T1.
The second multivibrator is made on transistors VT4 VT5 and serves to periodically turn on the first. Since there is an integrating circuit R9, C5 between the multivibrators, the sound in the dynamic head will smoothly increase and then decrease, like a siren.
The third multivibrator is assembled on transistors VT1 and V/T2. The cascade on the transistor VTZ is a current amplifier loaded onto the electromagnetic relay K1. When this multivibrator operates, contacts K1.1 of the relay periodically connect capacitor C8 in parallel with the dynamic head, which ensures imitation of the desired word.
In the simulator you can use transistors MP39 - MP42 with a static current transfer coefficient of 30. . 100, and for transistors VT4, VT5 this parameter should be the same or close as possible. Fixed resistors - MLT-0.25 or MLT-0.125, oxide capacitors - K50-6, K50-12, K50-3 and others, for a rated voltage of at least 10V, other capacitors - BM-2, MBM or similar.
Electromagnetic relay - RES10, passport RS4.524.305, with a winding resistance of about 1800 Ohms. But the relay needs to be modified. First, carefully remove the cover from it and loosen the springs until the relay operates at a voltage of 6 ... 7 V, and then put the cover on and glue it, for example, with nitrocellulose glue. Instead of RES10, the RES22 relay, passport RF4 500 131, is suitable, but it needs to remove three groups of contacts out of four. Such a relay will have to be moved outside the board or the board will have to be increased slightly. You can use any other relay that operates at a voltage of 5 ... 7 V and a current of up to 30 mA.
An output transformer (half of the primary winding is used) from transistor receivers with an output power of 0.25 - 0.5 W is suitable as T1. If desired, you can make a homemade transformer made on a magnetic circuit Ш4Х8 (or a larger area). Its primary (collector) winding should contain 700 turns of PEV-1 0.1 wire, the secondary winding should contain 100 turns of PEV-1 0.23. Dynamic head BA1 – 0.1GD-6, 0.25GD-10. 0.5GD-17, 1GD-28 or similar, with a voice coil with a resistance of 6 ... 10 Ohms and a power of 0.1 to 1 W.
Reed switch SA1 - KEM-2 or KEM-8. If there is no reed switch, you can install ordinary contact plates that close under the mass of the lying doll. Power source - Krona battery.
Testing the toy begins with the first multivibrator and audio amplifier. The upper (according to the diagram) terminal of resistor R11 is temporarily connected to the negative power conductor, the terminals of the reed switch (or switch) are closed with a wire jumper, and contacts K1.1 are disconnected. If the parts are in good working order and there are no errors in the installation, a continuous sound will be heard in the dynamic head, the tone of which can be changed by selecting capacitors C6 and C7.
Next, the connection between resistor R11 and circuit R9 C5 is restored. You should hear a sound similar to a siren. By selecting resistors R9 R11 (sometimes R12) and capacitor C5, a smooth increase and subsequent decrease in sound is achieved. Moreover, it is recommended to change the values ​​of resistors R11, R12 only in the direction of increasing them in order to avoid the appearance of distortions. The duration of one siren sound cycle (from the beginning of the rise to the end of the fall of the sound) should be 1.5 ... 2 s - this parameter is adjusted by selecting capacitors SZ and C4.
After setting up the electronic siren, connect the contacts to 1.1 and select capacitors C1 C2 so that the contacts close for about 0.5 s and remain open for about 1 s. It is convenient to perform this operation by listening to the clicks of the relay armature. And so that the sound of the siren does not interfere, the base of the VT7 transistor is connected to the positive power conductor. After removing the jumper, the slightly drawn-out, seemingly capricious word “Mom” should be heard quite clearly in the dynamic head. The sound is corrected by more precise selection of resistors R2 and RЗ.

Bouncing ball sound simulator (add-ons)Want to hear how a steel ball bounces from a ball bearing on a steel or cast iron plate? Then assemble the simulator according to the diagram shown in Fig. below. This is a variant of an asymmetrical multivibrator, used, for example, in a siren. But unlike a siren, the proposed multivibrator does not have pulse repetition frequency control circuits. How does the simulator work? Just press (briefly) the SB1 button - and capacitor C1 will charge to the voltage of the power source. After releasing the button, the capacitor will become the source that powers the multivibrator. While the voltage on it is high, the volume of the “blows” of the “ball” reproduced by the dynamic head BA1 is significant, and the pauses are relatively long.


Rice. 1. Circuit diagram of a bouncing ball sound simulator
Rice. 2. Variant of the simulator circuit
Rice. 3. Simulator circuit with increased volume

Gradually, as capacitor C1 discharges, the nature of the sound will change - the volume of the “beats” will begin to decrease, and the pauses will decrease. Finally, a characteristic metallic rattling sound will be heard, after which the sound will stop (when the voltage on capacitor C1 drops below the opening threshold of the transistors).
Transistor VT1 can be any of the MP21, MP25, MP26 series, and VT2 can be any of the KT301, KT312, KT315 series. Capacitor C1 - K.50-6, C2 - MBM. The dynamic head is 1GD-4, but another one with good diffuser mobility and a possibly larger area will do. Power supply - two batteries 3336 or six elements 343, 373 connected in series.
The parts can be mounted inside the simulator body by soldering their leads to the pins of the button and the dynamic head. Batteries or cells are attached to the bottom or walls of the case with a metal bracket.
When setting up the simulator, the most characteristic sound is achieved. To do this, select capacitor C1 (it determines the total duration of the sound) within 100...200 µF or C2 (the duration of pauses between “beats” depends on it) within 0.1...0.5 µF. Sometimes, for the same purposes, it is useful to select transistor VT1 - after all, the operation of the simulator depends on its initial (reverse) collector current and the static current transfer coefficient.
The simulator can be used as an apartment bell if you increase the volume of its sound. The easiest way to do this is to add two capacitors to the device - SZ and C4 (Fig. 33). The first of them directly increases the sound volume, and the second gets rid of the tone drop effect that sometimes appears. True, with such modifications the “metallic” sound tint characteristic of a real bouncing ball is not always preserved.
A more complex device, assembled as shown in Fig., will allow you to increase the sound volume and maintain the sound effect. 34 scheme. In it, transistors VT2 and VT3 form a composite transistor operating in the power amplification stage.
Transistor VT3 can be any of the GT402 series, resistor R1 - MLT-0.25 with a resistance of 22...36 Ohms. In place of VT3, transistors of the MP20, MP21, MP25, MP26, MP39 - MP42 series can work, but the sound volume will be somewhat weaker, although significantly higher,

Sound probe

The sound probe is made according to the classic scheme of an asymmetrical multivibrator using two low-power transistors VT1 and VT2 of different structures. This scheme is a real “bestseller” in amateur radio literature. By connecting certain external circuits to it, you can assemble more than a dozen structures. Without sensors, this is a sound probe, a generator for learning Morse code, a device for repelling mosquitoes, the basis of a single-voice electric musical instrument. The use of external sensors or control devices in the base circuit of transistor VT1 allows you to turn the probe into a watchdog device, an indicator of humidity, light or temperature, and many other designs.

By pressing the telegraph key SB1, you can “transmit” dots and dashes in Morse code: with a short press, a very short sound (dot) is heard in the dynamic head, with a long press, a longer sound (dash). Having studied the telegraph alphabet, you can think about your own amateur radio station, which allows you to communicate with radio amateurs living almost anywhere in the world.
By connecting sockets XI, X2 instead of the telegraph key, the probe is used to check the installation, integrity of fuses, transformer coils, etc.
If you change the frequency of the multivibrator to the ultrasonic frequency range (20...40 kHz) and increase the power of the circuit, the probe functions as a device for repelling mosquitoes and small rodents.
Capacitor C1 can be of the KLS, KM5, KM6, K73-17 and other types. Resistors MJIT-0.25, MJIT-0.125.
The dynamic head BA1 is low-impedance, say type 1GD-6, you can use a TK-67 telephone capsule. If desired, the tone of the generator can be easily changed by selecting the capacitance of capacitor C1. With the indicated values ​​of the elements, it is about 1000 Hz.

"INTERNAL COMBUSTION ENGINE"
This can be said about the next simulator if you listen to its sound. Indeed, the sounds produced by the dynamic head resemble the exhausts characteristic of a car, tractor or diesel locomotive engine. If the models of these machines are equipped with the proposed simulator, they will immediately come to life.
According to the circuit, the simulator somewhat resembles a single-tone siren. But the dynamic head is connected to the collector circuit of transistor VT2 through the output transformer T1, and the bias and feedback voltages are supplied to the base of transistor VT1 through variable resistor R1. For direct current it is connected by a variable resistor, and for feedback formed by a capacitor - by a voltage divider (potentiometer). When you move the resistor slider, the frequency changes generator: When the motor is moved down the circuit, the frequency increases, and vice versa. Therefore, a variable resistor can be considered an accelerator that changes the rotation speed of the “engine” shaft, and therefore the frequency of sound exhaust.

Transistors KT306, KT312, KT315 (VT1) and KT208, KT209, KT361 (VT2) with any letter indices are suitable for the simulator. Variable resistor - SP-I, SPO-0.5 or any other, possibly smaller in size, constant - MLT-0.25, capacitor - K50-6, K50-3 or other oxide, with a capacity of 15 or 20 μF for the rated voltage not below 6 V. The output transformer and dynamic head are from any small-sized (“pocket”) transistor receiver. One half of the primary winding is used as winding I. The power source is a 3336 battery or three 1.5 V cells (for example, 343) connected in series.
Depending on where you will use the simulator, determine the dimensions of the board and case (if you intend to install the simulator not on the model).
If, when you turn on the simulator, it works unstably or there is no sound at all, swap the leads of capacitor C1 with the positive lead to the collector of transistor VT2. By selecting this capacitor you can set the desired limits for changing the speed of the “engine”.

Two tone siren
Looking at the circuit of this simulator, it is easy to notice an already familiar unit - a generator assembled on transistors VT3 and VT4. The previous simulator was assembled using this scheme. Only in this case the multivibrator does not operate in standby mode, but in normal mode. To do this, a bias voltage from the divider R6R7 is applied to the base of the first transistor (VT3). Note that transistors VT3 and VT4 have swapped places compared to the previous circuit due to a change in the polarity of the supply voltage.
So, a tone generator is assembled on transistors VT3 and VT4, which sets the first tone of the sound. On transistors VT1 and VT2 a symmetrical multivibrator is made, thanks to which a second tone of sound is obtained.
It happens like this. During operation of the multivibrator, the voltage at the collector of transistor VT2 is either present (when the transistor is closed) or disappears almost completely (when the transistor is opened). The duration of each state is the same - approximately 2 s (i.e., the multivibrator pulse repetition rate is 0.5 Hz). Depending on the state of transistor VT2, resistor R5 bypasses either resistor R6 (through resistor R4 connected in series with resistor R5) or R7 (through the collector-emitter section of transistor VT2). The bias voltage at the base of transistor VT3 changes abruptly, so a sound of one or another tone is heard from the dynamic head.
What is the role of capacitors C2, SZ? They allow you to get rid of the influence of the tone generator on the multivibrator. If they are absent, the sound will be somewhat distorted. The capacitors are connected in back-to-back series because the polarity of the signal between the collectors of transistors VT1 and VT2 periodically changes. A conventional oxide capacitor under such conditions performs worse than a so-called non-polar one, for which the polarity of the voltage at the terminals does not matter. When two polar oxide capacitors are connected in this way, an analogue of a non-polar capacitor is formed. True, the total capacitance of the capacitor becomes half that of each of them (of course, with their capacitance being the same).


This simulator can use the same types of parts as the previous one, including the power supply. To supply the supply voltage, both a regular switch with a fixed position and a push-button switch are suitable if the simulator will work as an apartment bell.
As a rule, a simulator installed without errors starts working immediately. But if necessary, it is easy to adjust to obtain a more pleasant sound. Thus, the tonality of the sound can be slightly lowered by increasing the capacitance of capacitor C5 or increased by decreasing it. The range of tone changes depends on the resistance of resistor R5. The duration of the sound of a particular key can be changed by selecting capacitors C1 or C4.

Multivibrator based on FET transistors


This multivibrator uses domestic n-channel field-effect transistors with an insulated gate and an induced channel. Inside the case, between the gate and source terminals, there is a protective zener diode, which protects the transistor in case of improper handling. Of course, not 100%.
Multivibrator switching frequency 2 Hz. It is set, as usual, C1, C2, R1, R2. Load - incandescent lamps EL1, EL2.
Resistors connected between the drain and gate of the transistors provide a “soft” start of the multivibrator, but, at the same time, somewhat “delay” the switching off of the transistors.
Instead of incandescent lamps, the load in the drain circuits can be LEDs with additional resistors or telephones like TK-47. In this case, of course, the multivibrator must operate in the audio frequency range. If one capsule is used, then a resistor with a resistance of 100-200 Ohms must be connected to the drain circuit of the other transistor.
Resistors R1 and R2 can be made up of several connected in series, or, if none are available, capacitors of larger capacity can be used.
capacitors can be non-polar ceramic or film, for example, the KM-5, KM-6, K73-17 series. Incandescent lamps for voltage 6V and current up to 100 mA. Instead of transistors of the specified series, which are designed for direct current up to 180 mA, you can use more powerful switches KR1064KT1 or KR1014KT1. If you use a more powerful load, for example, car lamps, you should use other transistors, for example, KP744G, rated for current up to 9A. In this case, protective zener diodes for a voltage of 8-10V (cathode to the gate) - KS191Zh or similar should be installed between the gate and source. For large drain currents, the transistors will have to install heat sinks.
Setting up a multivibrator comes down to selecting capacitors to obtain the desired frequency. To operate at audio frequencies, capacitances should be in the range of 300-600 pF. If you leave the capacitors with the capacity indicated on the diagram, then the resistance of the resistors will have to be significantly reduced, down to 40-50 kOhm.
When using a multivibrator as a component in the design being developed, a blocking capacitor of 0.1-100 μF should be connected between the power wires.
The multivibrator is operational at a supply voltage of 3-10V (with an appropriate load).

I did not try to present here very complex circuits in which the multivibrator is a component element. As you can see from the above, I took mostly simple patterns that can be easily repeated.
Of course, the scope of application of multivibrators is far from completely covered by the examples given; it is much wider. But this is a slightly different story, which goes beyond the scope of the topic I have outlined.

When developing amateur automation devices, an audible alarm is often required that attracts attention with its sound and volume. The proposed device can serve as such a signaling device. It simulates a siren - the frequency of the signal periodically gradually increases and then decreases, etc.

The prototype was the radio designer "Master KIT" NM5031 "Air Raid Siren", but the functionality was expanded, and the sound, in the author's opinion, became more interesting. The device diagram is shown in the figure. Its basis is an asymmetrical multivibrator on transistors VT2, VT3. A capacitor SZ is included in the positive feedback circuit, the generation frequency depends on the capacitance of this capacitor, the resistance of resistors R5, R6 and the operating mode of transistor VT2, which, in turn, depends on the voltage on capacitor C2 . The multivibrator load is the dynamic head BA1.

A rectangular pulse generator is assembled on logic elements DD1.1, DD1.2, the repetition frequency of which is determined by the capacitance of capacitor C1, the resistance of resistor R1 and is about 0.5 Hz, logic element DD1.3 is a buffer. An electronic key is assembled on transistor VT1. When the output of element DD1.3 is high, transistor VT1 is open and capacitor C2 is charged through resistor R4. In this case, the operating mode of transistor VT2 changes - it opens more and the frequency of the asymmetrical multivibrator increases. When the output level of element DD1.3 is low, transistor VT1 is closed and capacitor C2 is discharged through resistors R5, R6 and the base of transistor VT2, which smoothly closes, and the frequency of the asymmetrical multivibrator decreases. Since transistor VT1 periodically opens and closes, the frequency of the multivibrator also changes, simulating a siren signal.

The volume of the signal within small limits and the operating mode of the multivibrator can be changed using trimming resistor R7. The generator and multivibrator are powered by a voltage stabilizer using zener diode VD1, transistor VT4 and resistor R10. Capacitors C4-C6 smooth out ripples on the power line and suppress interference.

The simulator uses fixed resistors MLT, S2-23, tuning resistors SPZ-Z, SP4, oxide capacitors - K50-35 or imported, the rest - K10-17. We can replace the KT315B transistor with any transistors of the KT312, KT315, KT3102 series, and KT361B with any KT3107 series. Replacing the KT815B transistor - transistors of the KT815, KT817 series with any letter indices. Dynamic head - with a coil resistance of 8... 16 Ohms and a power of 1...2W. Most parts are mounted on a wire-assisted prototyping circuit board, which is housed in a suitably sized enclosure. A dynamic head is attached to one of the walls of the housing, for which holes are made for the sound signal to pass through.

The device can be powered from an unstabilized mains power supply with a voltage of 12...18 V and a current of up to 500 mA. If you use a stabilized unit with an output voltage of 9 V, the device can be simplified by eliminating elements VT4, VD1, R10, C6 and applying the supply voltage directly to capacitor C5. When the supply voltage is more than 14 V, transistor VT4 is installed on a heat sink with an area of ​​10...20 cm2.

The device can be supplemented with a light indication; for this, a series-connected LED (anode to pin 10 of DD1) and a resistor with a resistance of 3...5.1 kOhm are connected between the output of element DD1.3 and the common wire. It is advisable to use an LED with increased brightness. The adjustment comes down to the selection of capacitors C1 - SZ. The overall tonality of the siren sound is changed by the selection of capacitor SZ, the rate of rise and fall of the frequency - by capacitor C2, and the period of its change - by capacitor C1.
Download: Siren sound simulator
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Robotics based on Lego Mindstorms EV3. Part 1

Year of publication: 2017

This manual is intended for young lovers of design and robotics. With its help, you can create various models of robots at school and at home. For this activity you will need the LEGO MINDSTORMS Education EV3 educational construction set. LEGO MINDSTORMS Education EV3 technologies will open up a wide range of opportunities for you to get acquainted with robotics.

Widely known to the reader from previous editions, the monograph by famous American specialists is devoted to the rapidly developing areas of electronics. It presents the most interesting technical solutions, and also analyzes the errors of hardware developers; The reader's attention is focused on the subtle aspects of electronic circuit design and application.

Electronics for beginners. The simplest step-by-step tutorial (2018)
Paolo Aliverti

“Electronics is easy!” – says the famous Italian robotics engineer Paolo Aliverti. If you have never dealt with electrical engineering and want to start somewhere, or your knowledge just needs to be refreshed, this book is for you!

A series of video lessons is presented for the beginning radio amateur, which outlines in an accessible form the principles of operation of both individual radio components and discusses the operation of a single radio circuit using a specific example.
A very informative video with excellent graphics will be useful for a novice radio amateur.

Arduino MKR WIFI 1010 Development Workshop
Agus Kurniawan

Arduino MKR WIFI 1010 is a new Arduino board with WiFi capability that enables to build IoT application. This book was written to help anyone want to get started with Arduino MKR WIFI 1010 development. It describes the basic elements of the development of Arduino MKR WIFI 1010.

100 TV malfunctions

The one hundred faults discussed in this book were selected based on real-world examples. Their analysis would be incomplete without taking into account the statistics of defects of individual TV components. By taking into account the limitations imposed by the operation of components, more effective solutions to technical problems can be found.

Nine television chassis are considered, including six chassis based on CRT (MS-64A, MS-71B, MS-84A, MS-019A, MS-991A, MS-994A) and three chassis based on LCD panels (ML-012A , ML-024C and ML-024E). More than 80 TV models with screen diagonals from 13 to 29 inches are produced on these chassis. For each model, a block diagram, a circuit diagram, oscillograms of signals at control points are provided, the operation of all its components, and the procedure for adjustment in service mode are described in detail.

Radio and TV Electronics

Year: 2017

Know the operation of the Televisions, what components of a Television, what are the most common defects of a television set and how to arrange.

This manual provides an example of assembling a laboratory regulated power supply with 1.3 - 30V and a current of 0 - 5A.
When assembling a laboratory power supply with their own hands, many are faced with the problem of choosing a circuit. When setting up homemade transmitters or receivers, switching power supplies can produce unwanted interference on the air, and linear power supplies are often unable to develop high power. A simple linear power supply with 1.3 - 30V and a current of 0 - 5A, which will operate in current and voltage stabilization mode, can become an almost universal unit. If desired, they can both charge the battery and power the sensitive circuit.

Powerful bipolar transistors for switching power supplies; TV receivers and monitors.
Directory

The electrical characteristics of high-power bipolar transistors with high switching speed are given. These devices are used in switching power supplies for various purposes, in industrial equipment, in household and professional video and audio equipment.

Golubeva N.S., Mitrokhin V.N.

The fundamentals of the theory of linear and nonlinear electromagnetic processes in passive and active media are outlined. The interaction of the electromagnetic field with the electron flow, dielectric, magnetic and plasma media, as well as issues of frequency conversion, amplification and generation are considered. The theory of waveguides, including inhomogeneous, complex configurations containing magnetized ferrites, is presented; resonators; ferrite devices of ultrahigh frequencies.

Signal receiving and processing devices (2nd edition)
E. A. Kolosovsky
Video cameras and video recorders for home and car

The book describes how to select, install and use modern video monitoring tools, ensuring the safety of the individual, movable and immovable property. Reviews of popular models of video cameras and the features of their operation are given for building a video surveillance system for small objects: apartment, dacha, country house. Ways to improve visibility, color rendition and improve video capture range in open space and rough terrain are considered. Practical devices for working together with video cameras and DVRs are described, recommendations for connection, maintenance are given, and alternative operating options are given.

Servo Magazine is a popular American magazine dedicated to robotics and cybernetics, offering a huge number of examples of creating robots of various types - from toys to serious devices, as well as various circuit, technical, theoretical and practical solutions for creating, configuring, adjusting and practical use of robots.

The device, the diagram of which is shown in the figure below, produces a complex audio frequency signal reminiscent of birdsong. The basis for it was a somewhat unusual asymmetrical standby multivibrator, assembled on two bipolar silicon transistors of different conductivities. The power source GB1 (Corundum battery) is constantly connected through connector X1 to the cascade on transistor VT2, which is separated from the first stage on transistor VT1 by a normally open button SB1. A special feature of the device is the presence of three timing circuits, which, in fact, determines the nature of the sound effect. The simulator does not have a general power switch, since the current consumption in standby mode does not exceed 0.1 μA, and this is significantly less than the self-discharge current of the battery.

This is how the device works. One has only to press the SB1 button, and capacitor C1 will be charged to the voltage of battery GB1. After releasing the button, the capacitor will power transistor VT1. It will open, and the base current VT2 will flow through its collector-emitter junction, which will also open. Here the RC positive feedback circuit, composed of resistor R2 and capacitor C2, comes into effect, and the generator is excited. Since the generator input is relatively high-resistance, and resistor R2 connected in series with capacitor C2 has a high resistance, a current pulse of considerable duration will follow. It, in turn, will be filled with a “pause” of shorter pulses, the frequency of which lies within the audio range. These oscillations occur due to the presence of a parallel LC circuit consisting of the inductance of the BF1 capsule winding, its own capacitance and the capacitance of the capacitor C3, connected via alternating current in parallel to the BF1 winding. Due to the nonlinearity of the charge-discharge process of capacitors C2 and C3, sound vibrations will be additionally modulated in frequency and amplitude. As a result, a sound is formed, reproduced by the BF1 phone as a whistle, which continuously changes timbre, and then breaks off - followed by a pause.

After the discharge of capacitor C2, a new cycle of its charge begins - generation resumes. With each subsequent sound, as the voltage on capacitor C1 decreases, the melody of the whistle becomes different, increasingly interspersed with a clicking sound characteristic of birdsong, and the volume gradually decreases. At the end of the “trill,” several quiet, gentle, fading whistles are heard. After which the voltage at the base of VT1 will drop below its opening threshold (about 0.6-0.7 V), both galvanically connected transistors close, and the sound stops.

After some time, capacitor C1 will be completely discharged (through its own internal resistance, resistor R1, transistor VT1 and emitter junction VT2), the circuit formed by elements R1, C1, VT1 is connected between the base and emitter of transistor VT2, further blocking it and thereby ensuring high efficiency of the device in standby mode. The operation of the simulator is resumed by pressing the button again.

The device can use transistors of the KT201, KT301, KT306, KT312, KT315, KT316, KT342 (VT1) series; KT203, KT208, KT351, KT352, KT361 (VT2) with a static current transfer coefficient of at least 30. Any small-sized resistor R1, for example MLT-0.125, tuning resistor - SPO-0.4, SP3-9a. Capacitors C2, C3 - MBM (KLS, K10-7V), C1-oxide, for example K50-6. Phone BF1 - capsule DEMSH-1, miniature “earphone” TM-2A (the plastic attachment is removed in it - the sound guide) or another, but always electromagnetic, with a winding resistance of up to 200 Ohms; button KM1-1 or MP3.

Adjustment comes down to selecting the position of the trimmer resistor slider, which produces the desired sound effect.

The nature of “singing” can be easily changed by empirically selecting the following elements: C1 within 20-100 µF (determines the total duration of the sound), C2 within 0.1-1 µF (duration of each individual sound). In addition, C2 and R1 (within 470 kOhm - 2.2 MOhm) determine the duration of pauses between the first and subsequent sounds. The timbre coloring of sounds depends on the capacitance of capacitor C3 (1000 pF-0.1 µF).

Modeler-Constructor No. 8, 1989, p. 28