Previously, they were used, and even now, in many equipment, conventional analog mechanical volume controls are used, which are variable resistors connected by potentiometers and regulate the level of the signal passing from the signal source to the ULF input. In a relatively simple way, invading the ULF circuit a little, you can introduce electronic volume control in it using a chip like DS1868.
This microcircuit is manufactured by Dallas-semiconductor and is an analogue of two variable resistors controlled by software using an external microcontroller. Adjustment is possible in 256 steps of resistance change (or rather, the position of the “slider” variable resistor). One output of the variable resistor is NO or H1, the second, which is desirable (but not necessary) to be connected to a common power supply minus - L0 or L1. Conclusion"slider" - W0 or W1, respectively.
Microcircuits are produced in three versions according to the resistance of variable resistors, - DS1868-10, - 2x10 kOhm, DS1868-50, - 2x50 kOhm, DS1868-100, -2x100 kOhm, in three types of cases: 20-pin TSSOP, 16-pin SOIC, and 14-pin DIP (Figure 1).
The block diagram of the microcircuit is shown in Figure 2. The potentiometers of one microcircuit can be used either separately, for example, to adjust the volume in different ULF channels, or they can be connected in series to increase the total resistance (Fig. 3). In this case, the general conclusion, that is,"slider" such a variable resistor becomes the output Sout. In this case, the number of adjustment steps can be doubled by software (up to 512). This option can be useful for building an electronic tuning circuit, for example, a VHF-FM receiver with an AFC system based on an IC of the K174XA34 type. The DS1868 chip, together with an external microcontroller and an LCD display, will perform the functions of a scale and a vernier device.
Chips can be cascaded up to any number to control multiple controllers on the same digital bus. In this case, the CLK pins are connected together, the RST pins are also connected together, but the controller port, which should be DQ, is connected only to the first stage. Further, the output Cout is used for transfer (Fig. 4).
For example, if the ULF uses electronic adjustment, in which the control voltage at the corresponding inputs of the preamplifier microcircuit is regulated by variable resistors, then one of« variable resistors» DS1868 chips can be used, for example, to control the volume, and the second for stereo balance. The software used in this design allows separate adjustment for each« variable resistor» microcircuits. The control body is the microcontroller D2, as well as three buttons S2-S4 and a liquid crystal display.
Button S4 (Up) is used to increase the parameter, button S3 (Down) - to decrease the parameter. With the S2 (Select) button, you can select the operating mode, adjust the left, right or both channels at the same time. The display shows two rows of rectangles along the length of which you can understand the position of the regulator. Button S1 (Reset) - for reset, it can not be displayed on the front panel (make a hole to poke it with a match if necessary).
Figure 5 shows the DS1868 in a 14-pin DIP package. You can also use the microcircuit in another package, according to Figure 1. Op-amp gain adjustment circuit (Fig. 6.1 - with a variable resistor, Fig. 6.2 - with the DS1868 microcircuit). The source code of the program in the SI programming language and the firmware of the PIC18F2550 microcontroller are available at the link below.
We offer you a simple high-quality
six-channel digital volume control
. The regulator is assembled on a TDA7448 microcircuit, manufactured by the European company STMicroelectronics. This chip has a digital I2C interface. For control through this interface, a common, cheap, high-speed RISC microcontroller from Microchip PIC16F873 was used (it is possible to replace it with PIC16F873A, PIC16F876, PIC16F876A).Developers of devices based on microcontrollers from Microchip have a unique opportunity to easily connect multiple encoders without additional wiring. This made it possible to implement a rather unusual concept of the device.
Structurally, the circuit consists of two nodes: a microcontroller control unit
And the regulator block on the TDA7448.
The regulator is supposed to be used in 5.1 format systems. This assumes the following channels: front (left and right), surround (left and right), center and subwoofer. These channels are controlled by 4 encoders. The volume and balance mode for the front and for the rear is switched by the "volume / balance" button. There are also buttons "Mute" (muting) and "StandBy" (standby mode). There is also a separate StandBy line that can be used to turn off amplifiers in hardware. Special mode - "General volume" (Master volume). The transition to this mode is carried out by the button on the reserved line. In this mode, all encoders work in parallel, i.e. uniformly change the volume levels for all channels (lines). The parameter "general loudness" does not have any specific numerical measurement, because. Each channel is set to its own volume level. Adjusting the "master volume" only synchronously reduces or increases all channels.
To visualize the direction of regulation in this mode, the indicator in the top line displays the name of the "Master volume" mode, and in the bottom line there are animated icons<<<<< или >>>>>.
All of the listed control functions can be implemented through any remote control in RC5 format (from Philips household appliances).
Printed circuit boards are made of one-sided foil textolite using the LUT method, but can be easily made on circuit boards. Board drawing files in Sprint Layout format at the end of the article. Below is a drawing and a photograph of the assembled printed circuit board of the microcontroller control unit.
The values of resistances and capacitors may differ from those indicated in the diagram by 20%.
The indicator has 2 lines of 16 characters. They are produced by many different companies and they use different microcircuits: HD44780 (HITACHI), KS0066 (SAMSUNG), KB1013VG6 (ANGSTREM) and others.
IR receiver TSOP1736 (Vishay) can be replaced with SFH-506 (Siemens), TFMS5360 (Temic), ILM5360 (Integral software).
The TDA7448 chip is made in a surface-mount package, but has a fairly wide pin pitch (1.27 mm) and is easily soldered with a sharpened soldering iron. Below is a drawing and a photograph of the assembled printed circuit board of the regulator unit on the TDA7448.
Below is a picture of the encoder board:
Mechanical incremental encoder, for example, PEC12 or from the EC11 series. When choosing an encoder, refer to the pinout documentation. You can determine the correct inclusion by scientific enumeration.
The buttons can be any to your taste - from clock to typical membrane keyboards. The membrane keyboard has a strong sticky base (like adhesive tape), which makes it easy to stick it on the device case. It is convenient to use connectors of the FB-x series, for example, FB-5R, to connect the membrane keyboard cable.
The operation of the regulator has been successfully tested with various remote controls in RC5 format. Below is a photo of one of the remotes. The left-right buttons select the adjustable parameter, and the desired level is set with the up-down buttons (the functions of the buttons correspond to the "volume" and "channel" buttons).
During operation, all settings are automatically saved and, when turned on, the last entered volume levels are smoothly set.
Setting up the device circuit is reduced to setting the required contrast with a tuning resistor. All menu dialogues are in English. Below is a photo from life.
The use of an electronic volume control in radio equipment can change its characteristics and operational properties for the better. So the advantages of electronic regulators include the absence of interference and noise arising during adjustment (squeaks, clicks). The electronic regulator can be used in combination with radio equipment with remote control devices. Instead of adjustment buttons, it is possible to install relays controlled by infrared radiation or a radio signal.
Characteristics of the stereo volume control on the KA2250 chip
Frequency range 20-20000 Hz;
Supply voltage from 6 to 16 volts;
The maximum input voltage is not more than 2.5 V;
Volume control from 0 to 64 dB;
Adjustment step 2 dB.
Schematic diagram and board for mounting an electronic volume control
The following is a diagram and its description for assembling a stereo electronic volume control. The stereo regulator is assembled on the basis of the KA2250 microcircuit, it is controlled by two buttons without fixing. A pointer indicator can be connected to the regulator through resistor R7 (see wiring diagram). With the switch VK1 through the resistor R5, the indicator can be blocked, turned off. Wires supplying sound frequency and removing it from the volume control must be shielded. The volume control, subject to proper assembly and the use of serviceable radio components, does not need to be adjusted.
Rice. 1 Schematic diagram of the volume control on the KA2250 chip (Toshiba)
Fig. 2 Placement of radio elements on the circuit board of the electronic stereo volume control
Rice. 3 Board appearance (size 40mm wide * 38mm high)
Radio elements used to assemble an electronic stereo volume control based on the KA2250 chip
Resistors:
R1 - 51 ohm - 1 pc.;
R2 - 22 k - 1 pc.;
R3 - 22 k - 1 pc.;
R4 - 100 k - 1 pc.;
R5 - 1 to - 1 pc.;
R6 - 51 k - 1 pc.;
R7 - 1 to - 1 pc.;
R8 - 33 k - 1 pc.
Resistors power - 0.25 W
Capacitors:
C1 - 22 uF / 16 volts - 1 pc.;
C2 - C8 - 4.7 uF / 16 volts - 7 pcs.;
C9 - 47 uF / 16 volts - 1 pc.
Other radio elements used in the circuit:
Diode D1, D3, D4 - RL522 - 3 pcs.;
Zener diode D2 - D814D - 1 pc.;
Chip KA 2250
The electronic regulator can be successfully used with the bass amplifier described in the article "
KA2250, TDA2030A, TC9153. The desire to make a high-quality amplifier arose a long time ago. I chose TDA because, firstly, we only have this MC on sale (from a possible variety), and secondly, 80 watts is more than enough, well, at least for me. By the way, everywhere they write that there are a lot of fakes of these MSs, but so far I haven’t come across a single one (maybe because they haven’t gotten to it yet?)
Power amplifier AF TK-1
Why TK-1? Everything is simple UMZCH is named after the first letters of the microcircuits that are used in it: and KA2250, and 1 means "first".Idea
The desire to make a high-quality amplifier arose a long time ago. I stopped my choice because, firstly, out of the possible variety, we only have this MC on sale, and secondly, 80 watts is more than enough, well, at least for me.
By the way, everywhere they write that there are a lot of fakes among TDAs, but so far I have not come across any of them. Maybe because they haven't reached 7295 yet? In total, about 10 amplifiers have been assembled on this MS to date.
First, a trial version was made according to the datasheet, and successfully tested on the S90. The sound pleased, but something was missing (maybe it's the speakers themselves). However, the owner of the S90 liked everything and the amplifiers safely went to a friend. After some time, it was decided to make an amplifier according to a modified circuit.
Modified TDA7295 switching circuit
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Thank you for your attention!
▼ 🕗 21/09/08 ⚖️ 8.7 Kb ⇣ 273 Hello reader! My name is Igor, I'm 45, I'm a Siberian and an avid amateur electronics engineer. I came up with, created and maintain this wonderful site since 2006.
For more than 10 years, our magazine exists only at my expense.
Good! The freebie is over. If you want files and useful articles - help me!
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Thank you for your attention!
Igor Kotov, editor-in-chief of Datagor magazine
Addition from Datagor
About volume level backup
A backup of the state of the volume control chip is possible. Those. the set level will be saved between power-ups of the amplifier and will not be reset to zero.
This is possible and has been tested on the original Toshibov TC9153AP chip. I can't vouch for an analogue of the KA2250 type. Try it and unsubscribe in the comments.
So, TC9153AP has control input 7 (INH). The high level required for normal operation (log.1) on it is provided by a voltage divider on resistors 10 Kom / 51 Kom. Removing the high logic level puts the MS into shutdown mode and minimum power consumption.
This allows you to use a conventional high-capacity capacitor connected to the MS power circuit to maintain the set volume.
The diode is needed to prevent the capacitor from discharging through other circuits. The resistor limits the discharge current of the capacitor, extending the "life" of the settings. The settings will reset to zero as soon as the voltage at the VDD point drops below 4.0 Volts.
Select the ratings of the supply conduit and resistor experimentally. For example, 1000 uF and 4.7 - 10 Kom. Try!
About regulator failures and erroneous decision
It is a mistake to try to increase the capacity of C3, which Ivan is trying to do. Capacitor C3 determines the frequency of the internal MC oscillator, i.e. regulation speed. And an increase in its capacitance to 220 microfarads can lead to the inoperability of the circuit.
Most likely, failures occur due to a slightly incorrect circuit design.
The fact is that the nominal supply voltage of the TC9153AP chip ranges from 6 Volts (min!) To 12 Volts (max!), 9 Volts is ideal. And in the above scheme, something strange is heaped up on nutrition! Look, a 5 V linear regulator, then everything is choked by a 4.7 V zener diode. As a result, the MS is powered by extremely low voltage, beyond the absolute minimum.
Good luck to everyone, Igor.
Reader's vote
The article was approved by 14 readers.
To participate in the voting, register and enter the site with your username and password.Option 1
LF amplifier chip TDA2030A firms ST Microelectronics fig.1.
Option 2
Amplifier on TA8215
:
Installation and selection of parts:
Option 3
Power Supply:
Option 4
Amplifier
Option 5
Let's look at the diagram:
Option 6
Option 7
bug
options:
Ipotr=25-30mA at Upit=9V
Option 8
Option 9
Option 10
Option 11
Option 12
Option 13
Option 14
Option 15
Option 16
Option 17
Power outlet radio transmitter
This scheme, with a minimum of radio components, has quite good qualities:
high sensitivity of the microphone (the ticking of the wall clock can be heard in the room),
with an antenna length of 100 cm, the range is 500 meters (when using a mobile phone with built-in FM radio).
A correctly assembled circuit should work immediately, the whole adjustment consists in adjusting the frequency, by compressing and expanding the turns of the L1 coil and in selecting the resistance R7 (100 Ohm - 1kOhm) to achieve maximum power.
C4 can be supplied with a larger capacity, in which case it will smooth out the ripples even better. The power supply should be separated from the transmitter by an aluminum screen.
I recommend experimenting with the capacitance of C6 and C3, choosing them so that there is practically no buzz in the receiver.
L1 - 6 turns of copper wire, 0.5 mm in diameter
VD1 - zener diode, type KS168 (you can use any other for a voltage of 6.8V)
VT1, VT2 - transistors, type KT315, you can KT3102, KT368.
Option 18
car radio watchman
In connection with the growth in the number of cars and the remoteness of garages from apartments, the issue of protecting cars at night in the yards of houses has become relevant. If stealing a car is quite difficult, then removing the emblem, pulling out the radio or battery is not a big deal. Most anti-theft devices only make it harder to start the car's engine, but do not protect against theft of contents.
There are devices that respond to swing, the actuating unit of which is a siren or a car signal. At night, they wake up not only the owner, but also the neighbors. Disconnecting the battery completely disables such devices.
From all these shortcomings, the proposed radio watchman is free. Let's take a look at his work.
The radio watch consists of a high-frequency generator, a modulator and a swing sensor. In standby mode, the swing sensor is open and power is supplied only to the generator. The receiver, located in the apartment, is tuned to the carrier frequency of the generator by the disappearance of noise in the loudspeaker.
Thus, even when the battery is disconnected, the operation of the radio guard is determined by a sharp increase in noise, and this is also a sign of the health of the car-apartment line.
When touching the vehicle, the rocking sensor B1 closes for a short time (Fig. 2). Through its contacts, power is supplied to the modulator and the capacitor C 1 is charged.
After opening the sensor contacts, the modulator is powered from the capacitor until the next short circuit. The voltage of damped low-frequency oscillations from the output of the modulator modulates the high-frequency generator. At the same time, a loud intermittent alarm is heard in the receiver. The frequency of the high-frequency generator is determined by the quartz frequency (3..5 harmonics) and is in the ranges of 64...75 MHz or 88...108 MHz for the European standard. Coil L1 has 6 turns of PEL 0.6 wire on a frame with a diameter of 6 mm. Communication coil L2 - 2 turns PEL 0.3. The range of the radio watchman from inside the car without a connected antenna is up to 50 m. Several of these devices have been tested in operation for 2 years and have shown reliable operation.
Option 19
Mouse Feedback
In Logitech terminology, this is iFeel - the issuance of vibration of various amplitudes and rhythms. Somehow, after reading reviews, I bought a Logitech iFeel MouseMan and tried to play - it's hard to imagine a greater disappointment. The mouse is heavy, uncomfortable, iFeel is inexpressive. Half an hour later, the brush ached, which had never happened before. It was a long time ago and I safely forgot this terrible dream. You can read more about "Feedback" technologies on the Immersion website. Recently, I caught the eye of a vibrating alert from some cell phone and had an idea - to get a similar effect, but without the terrible Immersion drivers. I made a circuit that filters low-frequency components and sends them to a vibrating alert.
The circuit consists of two parts - a low-pass filter (LPF) on the first half of the LM358 and a rectifier amplifier on the second half of the LM358. LPF is made on C3, R3, C4, R4; the circuit R1, R2, C1 sets the bias 1/2 of the supply for the normal operation of the filter. Resistor R9 regulates the signal level. Capacitor C2 removes the DC component and an AC voltage with zero on the ground comes to the rectifier input. This is very convenient, because it is necessary to get at the output not a variable, but a rectified signal. The rectifier takes feedback from the output, which reduces the harmful effect of the vibrating alert. I have a vibrating alert with an internal DC resistance of 30 Om, operating voltage 3V. The rectified voltage is not smoothed out by capacitors and this is done on purpose - this way there is less inertia and somehow the rhythm, shape and frequency affect the nature of the vibration.
Capacitors and resistors can be anything, only C3 must be with a small leakage current, i.e. not electrolytic. Transistor Q1 any npn, Q2 any pnp but with "average" collector current (0.3–2A). It’s better not to put it on Q2 completely low-current, because it provides a vibrating alert current. The vibrating alert itself is 3-5V with not very high current, because USB power is not unlimited. I have the whole circuit placed in the mouse itself, the level control is at the bottom left and does not interfere with the game, which is convenient for adjusting during the game. The vibrating alert is glued to the inside of the top cover of the mouse, there is also a diagram. Pressing the vibrating alert may not provide a reliable mechanical connection, because the vibration level is very significant. When adding the circuit, the total weight of the mouse remained almost unchanged.
Option 20
Var 22
Var 26 Radio probe
This is how we conditionally call this design, which will undoubtedly help in establishing or repairing various radio receiving, amplifying and generating devices and will allow you to check the operation of individual stages by ear.
The probe (Fig. 1) is a broadband radio receiver without tuning elements, with a three-stage radio frequency amplifier. Transistors VT1, VT2 are connected according to a common collector circuit, which provides a sufficiently large input impedance of the amplifier and allows you to connect its input sockets X1 and X2 to the corresponding circuits of the device under test without introducing a noticeable detuning of the circuits. The cascade on the transistor VT3 amplifies the voltage signal.
Fig.1 Schematic diagram of the radio probe
The RF amplifier transistor mode for DC is set by resistors R1-R6. From the amplifier load - resistor R5 - the signal goes to the detector stage, in which the diode VD1 operates. The audio frequency component of the detected signal is isolated on the resistor R7, after which it is amplified by a cascade on the transistor VT4 - the headphone BF1 serves as its load.
If you need to check the sound path of the radio receiver, electrophone, or control the operation of the AF oscillation generator, the wire with the probe at the end is connected to the X3 or X4 socket. The first of them is designed for a weaker signal, through the second a high-level signal is supplied. For any test, socket X2 is connected to the common wire of the device under test. The probe is powered by a galvanic battery GB1 connected by a SA1 switch.
The details of the probe are placed on a printed circuit board (Fig. 2) made of foil fiberglass or on a plate of ordinary textolite or getinaks.
Fig.2 PCB
For the RF amplifier, in addition to those indicated in the diagram, transistors KT361V or MP42B are suitable, any transistor from the MP39-MP41 series works well in the RF amplifier. The detector diode can be any of the D9 series, resistors - MLT, MT with a power of at least 0.125 W, oxide capacitors K50-6 (C5, C6) and KLS (the rest). It is better to take a phone of the TON-2 type, a 3336 battery is suitable as a power source.
After assembling the device and turning on the power, it is useful to check the compliance of the currents of the transistors VT3, VT4 indicated in the diagram. In case of significant differences, the resistor R1 or R8 is selected accordingly.
In conclusion, it should be noted that, if desired, you can expand the functionality of the device: adding a magnetic antenna connected to the RF amplifier with a separate switch will allow you to receive local radio stations. It is clear that in this case it will be necessary to slightly increase the dimensions of the case and the board.
Var 35 ULF
We bring to the attention of radio amateurs a simple and rather powerful ULF, which does not require adjustment. The amplifier develops an output power of 70 W into a load of 4 ohms, the reproducible frequency range is 10 ... 30000 Hz. The harmonic coefficient at rated output power is 0.1%, which is pretty good. The circuit diagram of the amplifier is shown in the figure below.  The amplifier is assembled on a high-voltage op-amp (operational amplifier) KR 1408UD1 (DA1). The final cascade is made on transistors KT972 and KT973, and the final stage on transistors KT908A. The quiescent current of the amplifier does not exceed 30 mA; to stabilize it, the diodes VD1-VD4 must be located near the radiators of the output stage transistors. To assemble the structure, MLT resistors were used, all KM-6 capacitors. Diodes d220 can be replaced by any high-frequency. The output transistors must be installed on heatsinks with an area of 400 cm^2. |
Option 1
LF amplifier chip TDA2030A firms ST Microelectronics enjoys well-deserved popularity among radio amateurs. It has high electrical characteristics and low cost, which makes it possible to assemble high-quality ULF with a power of up to 18 W at minimal cost. However, not everyone knows about its "hidden advantages": it turns out that a number of other useful devices can be assembled on this IC. The TDA2030A chip is an 18W Hi-Fi class AB power amplifier or VLF driver up to 35W (with powerful external transistors). It provides a large output current, low harmonic and intermodulation distortion, a wide bandwidth of the amplified signal, a very low level of intrinsic noise, built-in output short-circuit protection, an automatic power dissipation limiting system that keeps the operating point of the IC output transistors in a safe area. The built-in thermal protection ensures that the IC is turned off when the crystal is heated above 145°C. The microcircuit is made in a Pentawatt package and has 5 pins. First, let's briefly consider several schemes for the standard use of ICs - bass amplifiers. A typical TDA2030A switching circuit is shown in fig.1.
The microcircuit is connected according to the scheme of a non-inverting amplifier. The gain is determined by the ratio of the resistances of the resistors R2 and R3 that form the OOS circuit. It is calculated by the formula Gv=1+R3/R2 and can be easily changed by selecting the resistance of one of the resistors. This is usually done with a resistor R2. As can be seen from the formula, a decrease in the resistance of this resistor will cause an increase in the gain (sensitivity) of the ULF. The capacitance of the capacitor C2 is chosen based on the fact that its capacitance Xc=1/2?fC at the lowest operating frequency is at least 5 times less than R2. In this case, at a frequency of 40 Hz, Xs 2 \u003d 1 / 6.28 * 40 * 47 * 10 -6 \u003d 85 Ohms. The input resistance is determined by the resistor R1. As VD1, VD2, you can use any silicon diodes with a current I PR 0.5 ... 1 A and U OBR more than 100 V, for example KD209, KD226, 1N4007.
Option 2
Amplifier on TA8215
Below are its main technical characteristics:
1) Supply voltage, V……………………9…18
2) Rated output power at supply voltage 13 V, W………2*15
3) Rated output power at a supply voltage of 15 V, W……….2*18
4) Load resistance, Ohm ……………..4
5) Harmonic coefficient at output power 1 W, supply voltage 13 V, load resistance 4 Ohm, at a frequency of 1 kHz (maximum),% ……….0.04
6) Frequency response …………….20…20000
7) Output voltage in the absence of a signal, V ………….0.3
8) Operating temperature range, С* ……………………-30…+60
As mentioned earlier, the UMZCH is made on the basis of the TA8215 microcircuit inside the microcircuit consists of nine functional units - two pre-amplifiers, two phase inverters, four final power amplifiers with a bridged load switching circuit (two per channel) and a monitoring and protection unit (against overload of the final amplifiers and from exceeding the temperature of the microcircuit case, etc.).
The volume level is regulated by a variable resistor R1, and a variable resistor R2 (group A) adjusts the balance of signal levels in the channels. Resistors R3 and R4 adjust the sensitivity of the amplifier. Further, stereo signals through the conders C1 and C2 are fed to the outputs of the microcircuit. The signals amplified by the microcircuit can be fed to acoustic systems of the appropriate power. Correction circuits R7C6, R8C7, R9C8 R10C9 improve the stability of the UMZCH. The supply voltage is filtered by the C1 conder and fed to the corresponding pins of the microcircuit, the amplifier is put into operation by applying voltage to the stand-by input. Which, through the resistor R6, enters pin 4 of the DA1 microcircuit with a high level voltage. The HL1 LED signals the transition of the UMZCH to the operating mode.
For the manufacture of a stereo version of the amplifier, one TA8215H chip is used (P. max 2 * 18 W), but instead of it, you can use a cheaper analog chip from the same TA8215AN or TA8205AL line (P \u003d 2 * 18 W) with minor additions. (to terminals 2 and 7, solder 1000 pF conders connected to a common wire) preventing self-excitation of the UMZCH at high frequencies) you can use TA8210AN (P = 2 * 22 W) in similar cases, and for a load resistance of 2 ohms, TA8220N microcircuits can be recommended, TA8221AN (2*30 W). The operation of the UMZCH was tested with TA8205AN, TA8215N microcircuits.
After assembly, the UMZCH does not need to be adjusted and is operational immediately after power is applied.
Installation and selection of parts:
The power and input circuit wires must be thick enough (at least 0.75 mm). All input circuit wires must be shielded, preferably for each channel separately. It should not be allowed that the wires of the input circuits are located in parallel with the power wires and output circuits of the UMZCH. The installation of UMZCH elements can be both hinged and made on a printed circuit board. But in any case, all connecting conductors between the pins of the microcircuit and the elements of the amplifier should be as short as possible. The microcircuit must have good thermal contact with a heatsink of the appropriate size (at least 500 cm in area), to reduce the size, you can use a finned heatsink with a fan from the PC processor. The heat sink must be connected to the common wire of the electrical contact of the heat sink surface by the microcircuit amplifier! polarity must be observed when connecting speakers. It should be noted that bridge amplifiers are characterized by failure when the outputs of the microcircuit are shorted to a common wire or when the reverse polarity supply voltage is incorrectly applied to it; limits. The resistance of the resistor P1 is allowed within 10 ... 47kΩ; Capacitors C1 and C2 can be 1 ... 10 microfarads for a voltage of 6.3-100 V; P5-P 1.2 ... 2 kOhm; P7-P10 - 2 ... 10 Ohm; capacitors C3-C5 - 30 ... 100 microfarads for a voltage of 6.3-100 V; C4 - 100 ... 500 uF for a voltage of 10-100 V; C10 - 100 ... 470 microfarads at 16-100 V; C6-C9 - 0.1 ... 0.5 μF; LED NL1 of the AL102 series and the like of any color of luminescence.
Option 3
Power Supply:
To power the UMZCH, it is necessary to use a powerful stabilized power source (the TA8215N microcircuit consumes a current of about 3 A at maximum power). the power supply circuit is shown in Fig. 3. turning it on and off. Produced with one button SB1. relay RES22 (rf4.523.023-00) was used as K1. The step-down transformer must provide a voltage on the secondary winding of 17 ... 20 V at a current of at least 3 A. The voltage based on the transistor VT1 is stabilized by the DA1 microcircuit, the stabilization voltage of which is set by the construction resistor P2. before connecting the PSU to the amplifier, it is necessary to adjust this resistor to achieve a constant voltage of 15 ... 16 V at the PSU output. The PSU is not critical to details, it is only important that the voltage and power dissipation levels do not exceed the allowable values. Even with increased voltage in the network.
Option 4
Amplifier
Based on the article by A. Chivilch “Increasing the power of the amplifier on the TDA7294 chip” from the RADIO magazine No. 11, 2005, since the amplifier has been tested by me more than once and was noted for its sufficiently high reliability, high output power, and high-quality bass. The amplifier circuit is shown below. It differs from the original only by replacing the output transistors with better imported ones.
I will not delve into the principle of operation of the circuit, you can read about this in more detail in the original article. I will only tell you the fundamental patterns of drawing up a diagram. It is assembled on a board with dimensions of 125x70mm. All non-electrolytic capacitors, except for C2, are film, with an input capacity of 1 microfarad, 2.2 microfarads can be used. Resistors 0.25W, although 0.125W is enough. The output transistors are bent and pressed against the board so that their housings are parallel to the board and their heat-removing part is smeared with thermal paste and pressed to the radiator through a dielectric film. That is, the transistor cases are isolated from one another and from the radiator. The inductor L1 is frameless, wound with a wire with a diameter of 1 mm in two layers and contains 25 turns, an inner diameter of 5 mm. The fuses have been moved to the rectifier board.
Option 5
Preamplifier on KR140UD1B
Your attention is invited to a preliminary amplifier with a tone block. This amplifier is entry-level, but with its simplicity, its parameters are quite decent.
The main characteristics are as follows:
Let's look at the diagram:
As mentioned above, the amplifier is assembled on a KR140UD1B chip. The tone control is included in the feedback loop. Resistor R11 is engaged in high-frequency adjustment, and R6 is engaged in low-frequency adjustment. Well, the resistor R10 regulates the output signal level
Option 6
Electronic volume control on KA2250
The microcircuit is an electronic volume control with the following parameters:
Adjustment range, dB 0…66
Adjustment step, dB 2
Operating frequency band, Hz 20…20000
Harmonic coefficient, % 0.005
Supply voltage, V 3…16
Table with a list of elements:
| Designation on the diagram | Denomination |
| C1 | 4.7uF |
| C2 | 4.7uF |
| C3 | 4.7uF |
| C5 | 4.7uF |
| C6 | 4.7uF |
| C7 | 4.7uF |
| C4 | 22uF |
| C8 | 4.7uF |
| C9 | 100uFx15V |
| R1 | 10k |
| R2 | 22kOhm |
| R4 | 22kOhm |
| R5 | 33kOhm |
| R6 | 100kOhm |
| R3 | 51kOhm |
| R7 | 10k |
| S1 | |
| S2 | Any push-button without fixation |
| VD1 | KD503 |
| VD2 | KD503 |
| VD3 | KD 503 |
| Chip | KA2250 |
Option 7
bug
She has stable and honest options:
Ipotr=25-30mA at Upit=9V
Range 350 meters (tested in the field with a Chinese-made receiver worth 300 rubles)
Microphone sensitivity like all similar ones (in a quiet room you can hear the ticking of a wall clock)
The device is assembled: an electret microphone, as everyone knows, has a field-effect transistor in its composition, so it needs to be supplied with a supply voltage for this, a resistor R1 is installed. Capacitor C2 corrects the low-frequency component and blocks the RF connection between the microphone and the antenna. The variable component of the microphone signal is filtered by C3. Now the signal is further amplified to obtain the desired depth of deviation of the AF amplifier assembled on a transistor VT1. By selecting the bias resistor R2 in the base circuit in the transistor VT1, you need to achieve half the supply voltage at its collector, although this is not necessary. The AF amplifier and the HF generator are directly connected. The low-frequency modulation signal goes directly to the base of the transistor VT2 and the high-frequency generator is assembled on it according to the banal “three-point” scheme. You can achieve stable generation by changing the feedback capacitance C7 in small aisles or replacing the transistor with another one (but this procedure is rarely required by a crane). The RF signal is allocated on a circuit consisting of elements L1C6. This circuit is tuned to a frequency of 96 megahertz within 5-6 MHz, you can change it by shifting or pushing the turns with some non-metal object. A match, a wooden toothpick, etc. will do. Now the modulated RF signal through C8 is fed to the RF amplifier assembled on the VT3 transistor; in its base circuit, a circuit consisting of the L2 coil and capacitors C9 and C10 is included; this circuit serves as an active load of the VT3 transistor. This can be done by connecting a milliammeter to the power circuit of the entire device and adjusting it to achieve the minimum current consumption and maximum range. To connect the antenna, a capacitor divider C9 and C10 was made, which is not the best solution, but it eliminates the need to remove the RF voltage from part of the turns of the L2 coil. As a bug antenna, simple stranded wires 40 centimeters long were used.
