Device to reduce the volume of the sound during advertising. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Device to reduce the volume of the sound during advertising. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Телевидение

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Most viewers would like to get rid of the intrusive advertising that is broadcast during broadcasts on almost all channels. The author of the article published here proposes to use a device that, if the viewer wishes, allows you to reduce its volume for a while, and then automatically restore normal reception of the program.

Periodic television viewing has become an integral part of most people's lives. But since television now cannot exist without advertising technologies, all viewers, to a greater or lesser extent, become their consumers. Avalanches of advertising, following one after another during the most interesting programs, most often cause irritation, but they can also disrupt mental balance, which negatively affects the microclimate in the family and at work.

Usually, viewers who do not want to listen to advertising turn down the volume of the sound or completely turn it off using the buttons on the remote control or the front of the TV. However, after the end of the commercial, you need to set the required volume again, which is not only inconvenient, but usually slow, or turn on the missing sound in time, which is often forgotten if the viewer is briefly distracted. And some viewers switch TV to other programs during commercials and return to the original channel often after it ends, having missed part of the program of interest.

It is possible to reduce irritation, prevent undesirable consequences from advertising and reduce these inconveniences if the proposed device is used. Its schematic diagram is shown in fig. 1. It allows you to mute the volume of the sound of a working TV for a while (several minutes). The device is controlled by either a laser pointer or a touch sensor. The design can be built into any TV with analog electronic volume control, and with minor modifications to the device and the TV - to any other.

Volume down device during commercials

When the power is turned on, the device does not manifest itself in any way, and the soundtrack is carried out at the desired volume. If at least one of the phototransistors of the device is briefly illuminated with a beam of a laser pointer (and then turned off), the sound volume will immediately decrease for the time set in the device (the author has about 3 minutes). After this time, the sound volume will automatically return to the original. If there is no laser pointer nearby, do the same by briefly touching the sensor. When using the sensor, it becomes possible to turn off the low volume mode if the advertisement ends before the set exposure time

Consider the case of laser pointer control. In the initial state, when none of the phototransistors VT1-VT3 is not illuminated, their total resistance is high, the voltage across the resistor R1 is close to zero, which sets the level O at the inputs of the element DD1.2. At its output and, therefore, at the inputs of the element DD1.1 there will be level 1, and at the output of this element - level 0. The emitter follower on the transistor VT6 is closed, the capacitor C4, on which the exposure time depends, is discharged. The gate voltage of the field-effect transistor VT8 is zero, and it does not affect the sound volume level. The two-crystal LED HL1 glows green, indicating that the device is ready for operation.

If even for a short time a laser beam hits one or more phototransistors, the voltage across the resistor R1 will become more than half the supply voltage of the DD1 chip and the voltage levels are inverted at all its information outputs. Moreover, it should be remembered that this state persists as long as at least one of the phototransistors is illuminated. LED HL1 glows red, which indicates the passage of the command. The emitter follower on transistor VT6 opens, and capacitor C4 quickly charges to a voltage of 10 ... 11 V. The gate voltage of transistor VT8 becomes much higher than its opening threshold voltage, it opens by connecting series-connected shunt resistors R13, R16 to the volume control circuit , and it goes down.

After removing the pointer beam from the phototransistors or turning it off, the elements of the DDI chip and the VT6 transistor return to their original state. Capacitor C4 starts to discharge through resistor R12. When the voltage on it becomes close to the threshold voltage for opening the transistor VT8, the volume level will gradually increase to the previously set value. The smoothness of volume recovery depends on the drain current of the transistor VT8. Diode VD4 prevents the discharge of capacitor C4 through the emitter junction of transistor VT6. The inclusion of elements DD1.1, DD1.2 according to the Schmitt trigger circuit allows you to get the charge level of the capacitor C4 more stable.

If using a laser pointer is inconvenient, you can control the device with the E1 sensor. When you touch it with your finger, an alternating voltage is induced on the gate of the transistor VT5. Transistor VT4, working as a micropower zener diode, protects transistor VT5 from gate breakdown. Transistor VT5 works as a current and voltage amplifier. With a short touch (fractions of a second) to the sensor, the inputs of the DD1.1 element receive several pulses of level 0. At all information outputs of the DD1 microcircuit, the levels are inverted, the transistor VT6 opens and the capacitor C4 is quickly charged. Further, everything happens the same way. like with a laser pointer.

The sensor also allows you to turn off the low volume mode if, for example, the advertisement ended before the set time delay. To do this, hold the finger on the sensor for more than one second. During this time, the capacitor C5 will have time to charge up to a voltage of 2 ... 4 V. The transistor VT7 will open and discharge the capacitor C4. Transistor VT8 will close, the sound volume will increase. Resistor R11 limits the current surges through the transistor VT6 when the transistor VT7 is open.

The control output of the device is connected to the active input of the electronic volume control unit or node. In ZUSST-5USTST TVs with radio channel blocks SMRK-1-5, SMRK-2, the output is connected to pin 2 of these blocks (i.e., to pin 8 of the UPCHZ-2 block, or pin 7 of UMCHZ-Sh-1, or pin 5 of the microcircuit K174UR4 or TBA120U). If the TV has a UM 1-2 audio UFC submodule or a similar two-system M1-6-1 module, the device is connected to the output

7 of this block (i.e., to pin 5 of the K174UR1, K174UR1M or TBA120S chip). If the TV contains a radio channel module SMRK-41-2, the output is connected to its output 13. If the sound processing path is built on the KR1087XA5 or TDA3827 chip, its volume control input is output 16 (Horizon - CTV-601 TVs, etc.) .

The possibility of installing the device in modern domestic and imported TVs with a monochassis is determined after analyzing the schematic diagram of the device to be finalized and evaluating its own capabilities.

In some cases, to connect the structure, you can use a low-power electromagnetic relay, which at the right time would turn on the dynamic heads of the TV through an additional resistor. To implement this control option, the VT8 transistor must be more powerful.

The device can use resistors C1-4, C2-23, C2-33 and other similar ones; tuning R16 - any small-sized. Oxide capacitors - any, the rest - K10-17, KM-5, KM-6, K73-17, K73-24. Capacitor C4 should be with as little leakage current as possible. The diodes indicated in the diagram can be replaced with any of the KD503, KD510, KD521, 1N4148 series.

Transistor KT315A (VT4) - any of the same series. A zener diode is also suitable, for example, KS175A (cathode to the VT5 gate, anode to a common wire). Field-effect transistors - any of the KP501 series. ZWN2120, ZN2120 and the like. Transistor VT6 must be installed with the lowest possible initial collector current, otherwise it will be necessary to reduce the resistance of resistor R12 with a proportional increase in the capacitance of capacitor C4. Any of the KTZ102, KT6111, KT6113, BC547, BC556, SS9014, 2SC1222, 2SC1845 series will do. Chip K561LA7 is interchangeable with analogues KR1561LA7, CD4011A

L-51P3C phototransistors from Kingbright have a dark current of no more than 100 nA. They are being replaced by similar L-51P3s. Instead, you can use domestic IR photodiodes, for example, FD320, FD263, etc. Phototransistors on the front panel of the TV are installed in the corners of a certain triangle, and the HL1 LED is placed in its center, which will greatly facilitate aiming a laser pointer at them. The LED can be any similar two-chip, for example, L-93WGYC.

The current consumed by the device does not exceed 35 mA.

On a TV set, it can be connected to any secondary source of a stabilized voltage of 9 ... 12 V, which is not galvanically connected to the mains voltage. In old domestic TVs, as a rule, there is always a sufficiently powerful voltage source + 12 V, in modern ones - +9, +12 V.

The details of the device are mounted on a single-sided foil printed circuit board, the drawing of which is shown in Fig. 2. Its screening is desirable.

Volume down device during commercials

Establishing the device is reduced to the selection of the resistor R1 so that the sensitivity of the phototransistors is not enough to falsely turn on the device with the brightest lighting in the room. If the phototransistors are replaced by photodiodes, the resistor R1 can have a resistance of several tens or even hundreds of kilo-ohms. The time delay for which the volume will decrease depends on the values of the capacitor C4 and the resistor R12. The trimming resistor R16 sets the volume reduction level. The sensor, which can be used as, for example, the metal case of a miniature transistor, is connected to the device with a shielded wire.

Author: A.Butov, village of Kurba, Yaroslavl region

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