The simplest audio frequency generator. Signal generator: DIY function generator How to make a crystal tone oscillator

It’s better not to explain, but to see everything right away:

A funny toy, isn't it? But seeing is one thing, but doing it with your own hands is another, so let’s get started!

Device diagram:

When changing the resistance between points PENCIL1 and PENCIL2, the synthesizer produces a melody of different tones. Parts marked * may not be installed. Instead of transistor T1, KT817 is suitable; BC337, instead of Q1 - KT816; BC327. Please note that the pinouts of the original and analogue transistors are different. You can download the finished printed circuit board on the author’s website.

I will assemble the circuit very compactly (which I do not advise beginners to do) on a breadboard, so here is my version of the circuit layout:

On the reverse side, everything looks less neat:

As a housing I will use a button from a surge protector:

In the case:

I attached the speaker and the crown terminal block to hot glue:

Complete device:

I also came across a simplified diagram:

In principle, everything is the same, only the squeaking will be quieter.

Conclusions:

1) It is better to use a 2M pencil (double softness), the drawing will be more conductive.

2) The toy is interesting, but got boring after 10 minutes.

3) Once you are tired of the toy, you can use it for other purposes - ring the circuit, determine the approximate resistance by ear.

And finally, another interesting video:

Low frequency generators (LFO) are used to produce undamped periodic oscillations of electric current in the frequency range from fractions of Hz to tens of kHz. Such generators, as a rule, are amplifiers covered by positive feedback (Fig. 11.7, 11.8) through phase-shifting chains. To implement this connection and to excite the generator, the following conditions are necessary: ​​the signal from the output of the amplifier must arrive at the input with a phase shift of 360 degrees (or a multiple of it, i.e. 0, 720, 1080, etc. degrees), and the amplifier must have some gain margin, KycMIN. Since the condition for the optimal phase shift for generation to occur can only be satisfied at one frequency, it is at this frequency that the positive feedback amplifier is excited.

To shift the signal in phase, RC and LC circuits are used, in addition, the amplifier itself introduces a phase shift into the signal. To obtain positive feedback in the generators (Fig. 11.1, 11.7, 11.9), a double T-shaped RC bridge is used; in generators (Fig. 11.2, 11.8, 11.10) - Wien bridge; in generators (Fig. 11.3 - 11.6, 11.11 - 11.15) - phase-shifting RC circuits. In generators with RC circuits, the number of links can be quite large. In practice, to simplify the scheme, the number does not exceed two or three.

Calculation formulas and relationships for determining the main characteristics of RC sinusoidal signal generators are given in Table 11.1. To simplify calculations and simplify the selection of parts, elements with the same ratings were used. To calculate the generation frequency (in Hz), resistance values ​​expressed in Ohms and capacitances - in Farads are substituted into the formulas. For example, let's determine the generation frequency of an RC oscillator using a three-link RC positive feedback circuit (Fig. 11.5). At R=8.2 kOhm; C = 5100 pF (5.1x1SG9 F), the operating frequency of the generator will be equal to 9326 Hz.

Table 11.1

In order for the ratio of the resistive-capacitive elements of the generators to correspond to the calculated values, it is highly desirable that the input and output circuits of the amplifier, covered by a positive feedback loop, do not shunt these elements and do not affect their value. In this regard, to construct generator circuits, it is advisable to use amplification stages that have high input and low output resistance.

In Fig. 11.7, 11.9 show “theoretical” and simple practical circuits of generators using a double T-bridge in a positive feedback circuit.

Generators with a Wien bridge are shown in Fig. 11.8, 11.10 [R 1/88-34]. A two-stage amplifier was used as a ULF. The amplitude of the output signal can be adjusted using potentiometer R6. If you want to create a generator with a Wien bridge, tunable in frequency, a dual potentiometer is switched on in series with resistors R1, R2 (Fig. 11.2, 11.8). The frequency of such a generator can also be controlled by replacing capacitors C1 and C2 (Fig. 11.2, 11.8) with a dual variable capacitor. Since the maximum capacitance of such a capacitor rarely exceeds 500 pF, it is possible to tune the generation frequency only in the region of sufficiently high frequencies (tens, hundreds of kHz). The stability of the generation frequency in this range is low.

In practice, switchable sets of capacitors or resistors are often used to change the generation frequency of such devices, and field-effect transistors are used in the input circuits. In all the given circuits there are no elements for stabilizing the output voltage (for simplicity), although for generators operating at the same frequency or in a narrow tuning range, their use is not necessary.

Circuits of sinusoidal signal generators using three-link phase-shifting RC chains (Fig. 11.3)

shown in Fig. 11.11, 11.12. The generator (Fig. 11.11) operates at a frequency of 400 Hz [P 4/80-43]. Each of the elements of a three-link phase-shifting RC chain introduces a phase shift of 60 degrees, with a four-link chain - 45 degrees. A single-stage amplifier (Fig. 11.12), made according to a circuit with a common emitter, introduces a phase shift of 180 degrees necessary for generation to occur. Note that the generator according to the circuit in Fig. 11.12 is operational when using a transistor with a high current transfer ratio (usually over 45...60). If the supply voltage is significantly reduced and the elements for setting the transistor's DC mode are not optimally selected, generation will fail.

Sound generators (Fig. 11.13 - 11.15) are close in construction to generators with phase-shifting RC circuits [Рл 10/96-27]. However, due to the use of inductance (telephone capsule TK-67 or TM-2V) instead of one of the resistive elements of the phase-shifting chain, they operate with a smaller number of elements and over a larger range of supply voltage changes.

Thus, the sound generator (Fig. 11.13) is operational when the supply voltage changes within the range of 1...15 V (current consumption 2...60 mA). In this case, the generation frequency varies from 1 kHz (ipit = 1.5 V) to 1.3 kHz at 15 V.

An externally controlled sound indicator (Fig. 11.14) also operates at 1) power supply = 1...15 V; The generator is turned on/off by applying logical levels of one/zero to its input, which should also be within the range of 1...15 V.

The sound generator can be made according to a different scheme (Fig. 11.15). Its generation frequency varies from 740 Hz (consumption current 1.2 mA, supply voltage 1.5 V) to 3.3 kHz (6.2 mA and 15 V). The generation frequency is more stable when the supply voltage changes within 3...11 V - it is 1.7 kHz ± 1%. In fact, this generator is no longer made on RC, but on LC elements, and the winding of a telephone capsule is used as inductance.

The low-frequency sinusoidal oscillation generator (Fig. 11.16) is assembled according to the “capacitive three-point” circuit characteristic of LC generators. The difference is that a telephone capsule coil is used as inductance, and the resonant frequency is in the range of sound vibrations due to the selection of capacitive elements of the circuit.

Another low-frequency LC oscillator, made using a cascode circuit, is shown in Fig. 11.17 [R 1/88-51]. As inductance, you can use universal or erasing heads from tape recorders, windings of chokes or transformers.

The RC generator (Fig. 11.18) is implemented on field-effect transistors [Рл 10/96-27]. A similar circuit is usually used when constructing highly stable LC oscillators. Generation occurs already at a supply voltage exceeding 1 V. When the voltage changes from 2 to 10 6, the generation frequency decreases from 1.1 kHz to 660 Hz, and the current consumption increases, accordingly, from 4 to 11 mA. Pulses with a frequency from a few Hz to 70 kHz and higher can be obtained by changing the capacitance of capacitor C1 (from 150 pF to 10 μF) and the resistance of resistor R2.

The sound generators presented above can be used as economical status indicators (on/off) of components and blocks of electronic equipment, in particular light-emitting diodes, to replace or duplicate light indications, for emergency and alarm indications, etc.

Literature: Shustov M.A. Practical circuit design (Book 1), 2003

This article describes a simple audio frequency generator, in other words, a tweeter. The circuit is simple and consists of only 5 elements, not counting the battery and button.

Description of the circuit:
R1 sets the offset to the base of VT1. And with the help of C1 feedback is provided. The speaker is the load of VT2.

Assembly:
So, we will need:
1) A complementary pair of 2 transistors, that is, one NPN and one PNP. Almost any low-power ones will do, for example KT315 and KT361. I used what I had on hand - BC33740 and BC32740.
2) Capacitor 10-100nF, I used 47nF (marked 473).
3) Trimmer resistor about 100-200 kOhm
4) Any low-power speaker. You can use headphones.
5) Battery. Almost any one is possible. Finger, or crown, the difference will only be in the generation frequency and power.
6) A small piece of foil fiberglass, if you plan to do everything on the board.
7) Button or toggle switch. I used a button from a Chinese laser pointer.

So. All parts have been collected. Let's start making the board. I made a simple surface mount board mechanically (that is, using a cutter).

So, everything is ready for assembly.

First we install the main components.

Then we solder in the power wires, a battery with a button and a speaker.

The video shows the operation of the circuit from a 1.5V battery. The tuning resistor changes the generation frequency

List of radioelements

E. KUZNETSOV, Moscow
Radio, 2002, No. 5

Tone pulses can be used to test the dynamic parameters of meters and autolevelers, as well as noise reduction devices. A stand with a tone pulse generator will also be useful when studying amplification and acoustic equipment.

The linearity of the frequency response and the accuracy of the readings of level meters can be easily checked using a conventional audio signal generator, but to check their dynamic parameters, a tone pulse generator (TPU) is required. Such generators offered by radio amateurs often do not comply with the standards, where, to test level meters (IU), the frequency of the sinusoidal signal in pulses is assumed to be 5 kHz, and the beginning and end of the pulses coincide with the signal’s “zero” transitions.

Similar problems arise when setting up auto-controllers for audio signal levels. The recovery time of 0.3...2 s is easy to see on the oscilloscope screen, but the response time of the limiter or compressor can be less than 1 ms. To measure and observe transient processes in audio equipment, it is convenient to use GTI. In this case, it is advisable to change the pulse filling frequency using an external tunable generator. For example, with a filling frequency of 10 kHz, the duration of one period is 0.1 ms, and when observing the actuation process, determining the actuation time is not difficult. Sound pulses from the output of the GTI must have a level difference of 10 dB.

In foreign literature, it is usually proposed to measure the response time with a stepwise increase in the signal level by 6 dB above the normalized value, but real signals have a significantly larger level difference. The use of this technique often explains the “clicking” of imported autolevel regulators. In addition, in almost any sound generator you can jump the level by 10 dB; using such a level difference is convenient for observation. Therefore, in domestic practice, it is customary to measure the dynamic parameters of autoregulators when the levels change by 10 dB.

Unfortunately, the signal level switches of many generators produce a short-term surge of voltage at the moment of switching, and they cannot be used to measure the response time, since the autoregulator “shuts up”. In this case, GTI can be very useful.

Most radio amateurs have to carry out such measurements infrequently, and it is advisable to include such a device in a measuring stand with wider capabilities. Its front panel contains switching elements that are very convenient for connecting measuring instruments and custom equipment. In Fig. Figure 1 shows the approximate location of connectors (terminals or sockets) and switches. The bench diagram (Fig. 2) shows these switching circuits.

Device diagram

To enlarge, click on the image (opens in a new window)

Input jacks X1 ("ВХ.1") and Х2 ("ВХ.2") are intended for connecting inputs of configurable equipment. Toggle switches SA1 and SA2 allow you to connect the inputs to connectors X2 and X3 or short them to a common wire when measuring the level of integral noise. Compared to buttons, toggle switches provide a more visual representation of input connections. An audio frequency generator and a voltmeter are connected to the central sockets X2 and XZ to monitor the input voltage. Connectors X5 and X8 are intended for connecting the outputs of configurable equipment. One of the outputs can be connected by toggle switch SA3 to connectors X6 and X7 for measuring instruments. When setting up audio equipment, it is convenient to use a nonlinear distortion meter and an oscilloscope.

Switching circuits do not require any power sources, so with such switching it is very convenient to test various equipment.

If the double toggle switch SA4 (Fig. 1) is in the “POST” position, a constant level signal supplied to X2, X3, depending on the position of the toggle switches SA1 or SA2, is sent to connectors X1, X4 to the inputs of the equipment under test. If you move SA4 to the upper position, the signal from the generator will go to inputs 1 and 2 through the GTI circuits. In this case, the stand must be connected to a 220 V AC network.

The power switch SA5 is located on the rear panel, and only LEDs HL1, HL2 (indication “+” and “-”) are located on the front panel, indicating the presence of a bipolar supply voltage of ╠15 V.

To generate tone pulses, an electronic switch DA4 is used. At pins 16 and 4, the signal voltage value changes from the normalized value to zero, and at pins 6, 9, the level difference during setup is set by a variable resistor R15. The mode is selected using the SA9 toggle switch.

The pulse filling tone signal comes from the generator to the electronic switch through the buffer op-amp DA1.1. The second op-amp DA1.2 is used as a comparator, producing a synchronization signal for the start of the pulse when the filling signal passes through “zero”. Pulses from the comparator are fed to the clock input of the D-flip-flop DD2. At input D (pin 9) a pulse comes from a one-shot device assembled on the second trigger DD2.

The pulse duration is changed using switch SA8.2, which changes the resistance in the charging circuit C15, connected to the R input (pin 4) of the monostable. To set the pulse duration, a regular oscilloscope is sufficient. The one-shot device is triggered by signals coming from the square pulse generator on inverters DD1.1 ≈ DD1.3, or in manual mode with the SA6 “START” button. If toggle switch SA7 is set to the "AUTO" position, the duty cycle (period) of the pulses is set using variable resistor R11 "SCR."

It is very difficult to observe transient processes on the oscilloscope screen with a tone pulse duration of 3 ms and a high duty cycle. The task is simplified for oscilloscopes that have an external trigger during a standby sweep. To synchronize them, the X9 “SYNC.” socket is located on the rear panel of the stand. The triggering pulse is supplied to the electronic key with a certain delay relative to the synchronizing one, determined by the choice of parameters R13, C13.

The high level at which the electronic switch DA4 passes the tone signal appears with a positive voltage drop from the comparator after the appearance of a pulse from the monostable and ends after the end of this pulse (at the next signal drop from the comparator). This ensures that the beginning of the tone pulse coincides with the transition of the fill signal through “zero” and the requirement of generating an integer number of periods is satisfied. When the switch SA8 is in the "U Out" position, the voltage at the control input DA4 is zero and the generator output voltage can be set to correspond to the nominal input level. In switch position SA8 "TACT." The DA4 chip is controlled by voltage coming directly from the clock generator. Its switching frequency is set by variable resistor R11.

After the electronic switch, through repeater DA1.3 and toggle switches SA1 and SA2, tone pulses are supplied to the inputs of the configured equipment. The device also has an inverter DA1.4 and a switch SA10, which can be used to change the phase of the signal at one of the inputs relative to the other. Such an inverter is needed, for example, when checking the common mode of signals in stereophonic systems, in speakers, but perhaps instead it is more useful to assemble a built-in tone signal generator on this op-amp according to the circuit shown in Fig. 3. With such a generator it is easy to obtain Kg less than 0.2% and for many tests it is possible to do without the use of a generator external to the stand.

To test level meters, you need to connect the inputs of two channels (for stereo meters) to the corresponding input connectors. Then, in the “U Ex” position of switch SA8, set the normalized value of the signal level at the generator output with F = 5 kHz and check the readings of both channels of the meter. For example, in a level meter, the LEDs corresponding to the “O dB” value should light up simultaneously, and the scale error here should not exceed 0.3 dB. Toggle switch SA9 is set to the “-80 dB” position. Then switch SA8 is switched alternately to the positions “10 ms”, “5 ms” and “3 ms” and check that the readings of the DUT comply with the standards. The “200 ms” position of SA8 is used when testing average level meters, which, unfortunately, prevail in household equipment.

In order to accurately control the value of the return time, the variable resistor R11 (“SCR”) sets the frequency of the square-wave generator signals, at which the next pulse would follow immediately after the LED is turned off, corresponding to a value of -20 dB on the DUT scale. Then determining the period of the signals using an oscilloscope is not difficult. The LEDs in both channels should go out synchronously.

When checking the dynamic parameters of auto signal level regulators, use the “-10 dB” position of switch SA9. Inputs and outputs are connected to the appropriate connectors. The channel outputs are monitored one at a time, although with a two-channel oscilloscope nothing prevents you from monitoring both outputs simultaneously. At the output of the audio frequency generator, in the “U Out” position of switch SA8, a signal is set with a level 10 dB higher than the normalized value. Then switch SA8 to pulses of any duration, and switch SA7 to the “MANUAL” position. The key remains turned off and allows you to control the voltage on connectors X1 and X2, which must correspond to the normalized value. Then, using switch SA7, the GTI is switched to the automatic operating mode and, having selected the desired pulse duration and duty cycle, transient processes are observed at the output of the autoregulator. If the oscilloscope is running in clock-triggered standby mode, it is easy to determine the trigger time and the presence of trigger noise or overshoot.

The GTI uses four microcircuits, and the current consumption is very low. This allows you to use simple parametric voltage stabilizers using zener diodes instead of integrated stabilizers. On the other hand, by installing more powerful integrated stabilizers DA2, DA3 of the dA7815 and dA7915 series, they can be used to power prototypes of custom devices by placing an additional connector on the rear panel (not shown in the diagram). The microcircuits provide protection against short circuits, which are common during experiments.

The front panel of the stand has dimensions of 195x65 mm. The stand body is made of steel.

To connect the equipment under test, ZMP-type socket-terminals are convenient. In addition to them, depending on the equipment being tested, connectors of the appropriate design can be installed on the stand panel, for example, tulip, jack, ONTs-VG sockets or others.

Double toggle switch SA4 ≈ PT8-7, P2T-1-1 or similar. Switch SA2 ≈ biscuits PG2-8-6P2NTK. Button SA6 "START" can be of any type without locking, for example, KM1-1.

The DA2 K590KN7 microcircuit can be replaced with a similar one in functionality. As DA1, you can use a microcircuit with four op-amps of types LF444, TL084, TL074 or K1401UD4.

Mounting of the device board is printed or mounted on a breadboard.

The GTI stand can be used for testing compander noise reduction systems, dynamic filters and other audio equipment.

LITERATURE
1. Kuznetsov E. Sound signal level meters. - Radio, 2001, No. 2, p. 16, 17.
2. Microcircuits for household radio equipment. Directory. - M.: Radio and communication, 1989.
3. Turuta J. Operational amplifiers. Directory. - M.: Patriot, 1996.

Radio 1987, No. 5

Multi-voice EMRs with one tone generator have already proven themselves to be reliable and practical devices. However, their capabilities are often not fully realized due to the characteristics of the generators used in them. As a rule, the tone generator is built on the basis of a highly stable quartz resonator or RC circuits. In this case, electronic frequency control is either excluded or extremely difficult.

The device described below is a voltage controlled tone generator. The control signal is removed from various shapers and EMR controls. These can be frequency vibrato generators, envelope generators (for automatic tuning changes), glissando (tuning sliding) regulators with manual or foot (pedal) control.

The features of the generator include a high operating frequency. The use of a digital microcircuit made it possible to implement a relatively simple and cheap VCO with an operating frequency of up to 7.5...8 MHz (Fig. 1). For most digital tone generators with an evenly tempered musical scale, usually consisting of 12 identical counters with different interval conversion factors, a clock (leading) frequency is required in the range of 1...4 MHz. Therefore, the characteristics of the generator must be such as to provide the necessary linearity within these frequency limits.

The principle of operation of the generator is based on the formation of pulses, adjustable in duration, by two identical voltage-controlled shapers closed in a ring. Thus, the decline of a pulse at the output of one shaper causes the appearance of the front of the next pulse at the output of another, etc. The operation of the device is illustrated by the timing diagrams shown in Fig. 2. Until moment t 0, the control voltage is zero. This means that at points A and B a signal with a logical level of 0 has been established, since the flowing input current of elements DD1.1 and DD1.2 (it does not exceed approximately 1.6 mA) is closed to a common wire through resistors R1 and R2 and a small output resistance of the control voltage source. Level 1 is active at the output of inverters DD1.1 and DD1.2 at this time, so the RS trigger on elements DD1.3 and DD1.4 will be set arbitrarily to one of the stable states. Let us assume, for definiteness, that the direct (upper in the circuit) output has a signal of 1, and the inverse output has a signal of 0.

When a certain positive voltage appears at the control input at the moment t 0, current will flow through resistors R1 and R2. In this case, at point A the voltage will remain close to zero, since current flows through resistor R1 to the common wire through the low resistance of diode VD1 and the output circuit of element DD1.4. At point B, the voltage will increase, since diode VD2 is closed at a high level from the output of element DD1.3. The current through resistor R2 will charge capacitor C2 to 1.1... 1.4 V in a time depending on its capacity, the resistance of resistor R2 and the value of the control voltage. As U ynp increases, the charging rate of the capacitor increases and it charges to the same level in less time.

As soon as the voltage at point B reaches the switching threshold of element DD1.2, its output will set to level 0, which will switch the RS trigger. Now the direct output will have a level of 0, and the inverse output will have a level of 1. This will lead to a rapid discharge of capacitor C2 and a decrease in voltage, and capacitor C1 will begin to charge. As a result, the trigger will switch again and the whole cycle will repeat.

An increase in the control voltage (time period t 1 ...t 2, Fig. 2) leads to an increase in the charging current of the capacitors and a decrease in the oscillation period. This is how the generator oscillation frequency is controlled. The flowing input current of the TTL elements is added to the current of the control voltage source, which makes it possible to expand the limits of the control signal, since with a high resistance of resistors R1 and R2, generation can be maintained even at U ynp = 0. However, this current is characterized by temperature instability, which affects the stability of the generation frequency. To some extent, the temperature stability of the generator can be increased by using capacitors C1 and C2 with positive TKE, which will compensate for the increase in the uncontrolled flowing input current of elements DD1.1 and DD1.2 with temperature changes.

The oscillation period depends not only on the resistance of resistors R1 and R2 and the capacitance of capacitors C1 and C2, but also on many other factors, so an accurate assessment of the period is difficult. If we neglect the time delays of the signals in the elements DD1.1-DD1.4 and take the value of their logical voltage 0, as well as the threshold voltage of the diodes VD1 and VD2 equal to zero, then the operation of the generator can be described by the expression: T 0 =2t 0 =2RC*ln( (I e R+U control)/(I e R+U control -U sp)), obtained based on the solution of the differential equation:

dUc/dt = I e /C + (U control -Uс)/(RC),

where R and C are the ratings of timing circuits; Uc - voltage on capacitor C; Usp - maximum (threshold) voltage value Uc; U ynp - control voltage; I e - average value of the input leaking current of the TTL element; t 0 - pulse duration; T 0 - period of oscillation. Calculations show that the first of these formulas very accurately agrees with the experimental data at Uynp>=Usp, and the average values ​​were chosen: I e = 1.4 mA; Usp = 1.2 V. In addition, based on the analysis of the same differential equation, we can come to the conclusion that

(I e R+U control)/(I e R+U control -Usp)>0,

i.e., if I e R/(I e R-Usp)>0, then the device is operational at Uynp≥0; This conclusion is confirmed by experimental testing of the device. Nevertheless, the greatest stability and accuracy of VCO operation can be achieved with Ucontrol ≥ Usp = 1.2..1.4 V, i.e., within the frequency range of 0.7...4 MHz.

A practical tone generator circuit for polyphonic EMI or EMC is shown in Fig. 3. Operating frequency limits (with U control ≥ 0.55...8 V) - 0.3...4.8 MHz. The nonlinearity of the control characteristic (at a frequency within 0.3...4 MHz) does not exceed 5%.

Input 1 receives a signal from the envelope generator to automatically control audio frequency sliding. With a slight modulation depth (5...30% of the tone), an imitation of the sound shades of a bass guitar, as well as other plucked and percussion instruments is achieved, in which the pitch of intonation of sounds at the moment of their extraction deviates slightly from the norm (usually increases abruptly during the attack of the sound and then quickly decreases to its normal value).

Input 2 is supplied with a constant control voltage from a manual or pedal glissando controller. This input is used to adjust or change (transpose) the tonality within two octaves, as well as to slide along the pitch of chords or tonal sounds that imitate, for example, the timbre of a clarinet, trombone or voice.

Input 3 is supplied with a sinusoidal, triangular or sawtooth signal from the vibrato generator. Variable resistor R4 regulates the level of vibrato within 0...+-0.5 tones, as well as the level of frequency deviation up to +-1 octave or more when switch SA1 is closed. With a high modulation frequency (5...11) Hz) and a depth of +-0.5...1.5 octaves, tonal sounds lose their musical qualities and acquire the character of a noise signal, reminiscent of a dull rumble or rustling of fan blades. At a low frequency (0.1...1 Hz) and the same depth, a very colorful and expressive effect is achieved, similar to the “floating” sound of a ukulele.

The signal from the output of the tone generator must be fed to the input of a digital signal conditioner of equal temperament musical scale.

An active adder of control signals is assembled on the operational amplifier DA1. The signal from the output of the adder is supplied to the input of the VCO, which is made using logic elements DD1.1-DD1.4. In addition to the VCO, the device contains an exemplary quartz oscillator assembled on elements DD2.1, DD2.2, as well as a circuit of two octave frequency dividers on triggers of the DD3 microcircuit. clocked by this generator. The generator and triggers generate three sample signals with a frequency of 500 kHz, 1 and 2 MHz. These three signals and the signal from the VCO output are supplied to the input of electronic switches assembled on open-collector elements DD4.1-DD4.4.

These switches, controlled by switches SA2-SA5, have a common load - resistor R13. The output circuits of the elements form a device with a logical OR function. When one of the switches passes its clock signal to the output, the rest are closed at a low level from the switches. The high level for supply to the R-inputs of D-flip-flops DD3.1 and DD3.2 and to the contacts of switches SA2-SA5 is removed from the output of element DD2.4.

A quartz oscillator with frequency dividers play an auxiliary role and serve mainly for operational adjustment of the VCO or “drive” the instrument in the “Organ” mode, with switches SA3, SA4, SA5 (“4”, “8”, “16”” ) allow you to shift the pitch of the EMR, respectively, from the lowest register by one or two octaves up. In this case, of course, there can be no adjustment or change in the pitch of sounds.

The disadvantages of the generator include relatively low temperature stability, which in this case is not of great importance, and significant nonlinearity of the VCO control characteristic at the edges of the range, especially in the lower frequencies of the generator operating range.

In Fig. Figure 4 shows the experimentally measured dependence of the generation frequency on the control voltage: 1 - for the generator according to the circuit in Fig. 1, 2 - fig. 3.

The device is assembled on a printed circuit board made of foil fiberglass laminate 1.5 mm thick.

Chips of the K155 series can be replaced with similar ones from the K130 and K133 series; K553UD1A - to K553UD1V, K553UD2, K153UD1A, K153UD1V, K153UD2. Instead of D9B, you can use diodes of this series with any letter index, as well as D2V, D18, D311, GD511A. It is better to choose capacitors C4 and C5 with positive TKE, for example. KT-P210. KPM-P120, KPM-P33, KS-P33, KM-P33, K10-17-P33, K21U-2-P210, K21U-3-P33. Capacitors C7, C10, C11 - K50-6.

Particular attention should be paid to careful shielding of the device. The output conductors must be twisted into a cord with a pitch of 10..30 mm.

A correctly installed tone generator does not require adjustment and begins to work immediately after connecting the power. The control voltage at the VCO input should not exceed 8...8.2 V. The frequency stability of the generator is negatively affected by changes in the 5 V supply voltage, so it must be powered from a source with a high stabilization coefficient.

I. BASKOV, village of Poloska, Kalinin region.

LITERATURE

1. V. Bespalov. Frequency divider for polyphonic EMR. - Radio, 1980, No. 9.
2. L. A. Kuznetsov. Fundamentals of the theory, design, production and repair of EMR. - M.: Light and food industry. 1981.