Electronic volume control on Microchip PIC18F2550 and DS1868. Digital volume control on a microcontroller Sound processing using an atmega microcontroller

Once upon a time, in 2005-2006, I made a volume and tone control on a TDA8425 with a remote control.
The article was posted on some website with a demo version of the MK firmware.

I decided to post it here full version, may be useful to someone.
I see no point in rewriting what is written in the attached article (pdf).
In short, the TDA8425 is a volume and tone control controlled via the I2C bus; accordingly, the controller is made on ATMEL.
The controller, in addition to directly adjusting the volume, allows you to control it remotely from the remote control RC-5 and the like, there is a smooth increase in volume at the moment of switching on, and temperature control.

From the editor: You can download the full article, firmware and other files at the bottom of this page. I will give some excerpts from the article and photographs, so that the respected reader can decide for himself how interesting this scheme is to him and how difficult it is to repeat. -- Datagor

What are we talking about?

This article describes how to make a two-channel (stereo) volume and tone control with remote control on the TDA8425. Specifications devices correspond to the characteristics of the TDA8425 chip and are indicated in the Data Sheet. This device can be assembled as a separate unit or inserted into the amplifier housing.

Sound processor unit

That's it, the board is ready. Be sure to check the quality of installation. The TDA8425 chip is controlled via the I2C bus using a controller.

Microcontroller

The following is a diagram and description of the controller (control circuit).
The main task of this circuit is to transfer data to the TDA8425 chip (I2C bus). However, there are also a number of additional functions. Further short description scheme.

1. “LCD panel and buttons” - everything that goes to the front panel is connected here. This is a two-line 16-character LCD panel with backlight, four buttons for control from the panel and a photodetector for remote control.

2. “Thermal sensor 1” and “Thermal sensor 2” - installed on amplifier radiators (ULF), monitor the temperature and, when the maximum (set) temperature is reached, turn on the cooling coolers (fans) connected respectively to “To cooler 1”, “To cooler 2” work independently, any fans operate at +12V. It is possible to connect instead of a fan, for example, an LED to indicate the high temperature of the radiator or a relay to turn off the load, etc.
Contacts “A1” and “A2” for enabling or disabling the temperature control system. “A1” and “A2” are closed; the microcontroller controls the temperature. “A1” and “A2” are open - the microcontroller does not control the temperature. A transistor (any n-p-n) is used as a sensor.

3. “To LCD backlight” - connects to the minus of the LCD panel backlight, after completing the adjustments, the backlight goes out after about 15-20 seconds.

4. “Mute signal” - in mute mode, in addition to reducing the volume (in TDA8425), +5V appears on contacts M1 and M2 (for amplifiers that have a mute mode).

If there is no need for additional functions, parts related to them do not need to be installed.
When using coolers (fans) with high operating current, it is necessary to supply more powerful transistors VT2 and VT3.

Front Panel

The front panel contains: LCD panel, control buttons and photodetector. The connection diagram is shown below. It makes no sense to include any printed circuit boards since the arrangement of the elements depends on the design of the case.

Be sure to pay attention to the connection of the LCD panel; the diagram above uses WH1602D. +5 V power is supplied to pin 1 and the body to 2. For other manufacturers of LCD panels, it may be the other way around +5 V pin 2, body pin 1.

power unit

For power supply, you can use any stabilized +12V source, or do it according to the diagram below

Parts used

The boards are designed for installation of the following parts:
Non-polar, output capacitors K10-17. “Chip” elements with standard size 1206. Diodes KD522 or similar. Zener diodes at 5.1V or 5.6 V. Any photodetector used in new generation TVs. It is advisable to install resistors R23, R24 of the same value. The boards are designed to install standard (2.5 mm pitch) connectors.

Settings

Before setting up, program the microcontroller (firmware is given below).

1. Connect the pins of the same name on the I2C bus (SDA SDA, etc.) of the two boards. Turn on the power.
By rotating the trimming resistor R1, set the desired brightness of the LCD panel reading (quality of letter output).

2. If you plan to use a radiator temperature control system, then you need to determine the limits for turning on and off coolers (fans). This need is associated with the scatter of parts (resistors, stabilizers). I will give an example of the procedure for determining the limits (the numbers given below are the result of my measurements).

We connect the temperature sensors and fix them on a metal plate along with a thermocouple connected to the tester (the tester must be able to measure temperature).

Contacts A1 and A2 must be closed (place a jumper).

Turn on the power, simultaneously press the “+” and “-“ buttons, the readings T1=117 and T2=117 will be displayed on the LCD panel screen (the readings will be the same if R23, R24 do not differ from each other in value, maybe for example T2=114, but this is not important). We look at the temperature on the tester. For me T1 = 117 corresponds to 28 degrees C (room temperature).

Place the plate with temperature sensors on the soldering iron and heat it up. At the desired temperature, write down the values ​​of T1 and T2. These are the minimum values. T1=T1min=110, T2=T2min=110 corresponds to 45 degrees C. Heat further and record the maximum values. T1=T1max=97, T2=T2 max =97 corresponds to 75 degrees C. (you choose the temperature limits yourself).

We obtained the values ​​of T1 and T2 in decimal form, convert them to hexadecimal. T1=T1min=110=6E, T2=T2min=110=6E, T1=T1max=97=61, T2=T2 max=97=61. We write the resulting hexadecimal values ​​into the ROM of the microcontroller at the address:

05 - Т1max, 06 - Т1min, 07 - Т2max, 09 - Т2 min.

When the ULF radiator heats up to T1max = 75 degrees C, cooler 1 will turn on and cool the radiator to a temperature T1min = 45 degrees, when the temperature reaches 45 degrees C, cooler 1 will turn off.

As a result, when the radiators are slightly heated (small output power ULF) coolers do not turn on; with high ULF output power, the heating of the radiators increases and the coolers work. This system allows you to reduce the size of ULF radiators and not create unnecessary noise when coolers operate at low volume levels (at high power the noise is not audible :)).

Description of work

1. The device uses remote control using any remote control compatible with the RC5 or RC6 command system. All commands are executed while holding the VCR button

2. When you turn it on for the first time, due to the lack of initial settings, you will see “Volume MUTE” on the LCD screen, take the remote control and while holding the VCR button, press the MUTE button (mute). The volume values ​​will appear on the LCD screen, press the “Write” button on the front panel (write to memory).

3. Front panel.
Buttons "+" and "-" for adjusting and changing values.
“Select” - menu selection
“Write” - writing to memory.
Using the listed buttons, set the levels and values ​​you need in all menus. Click "Write". The next time you turn on the device, all the values ​​stored in memory will be set.

When connected to the network, the volume is set to minimum, +5V appears at the “Mute Signal” output of the “Control Circuit” board. After about 2 seconds - a smooth increase in volume to the value recorded in memory

4. Remote control.
“+” and “-” buttons
“Select” - menu selection.
Perform the same functions as the buttons on the front panel.
The following buttons work only from the remote control: “MUTE” - turn off the sound (the sound in the TDA8425 and “Mute signal” from the microcontroller are turned off). “PP” - setting initial values ​​(values ​​stored in memory are set).

5. In any menu, if more than one button is not pressed, after about 10 seconds return to the “Volume” menu, and after the same time, turn off the LCD backlight.

ULF TDA2050

Below, as an example, the circuit and boards of a low-frequency amplifier on a microcircuit are shown (output power 20-25W). The amplifier works with this volume and tone control.

The circuit shown in the figure is an amplifier for the Subwoofer. The left and right channel signals are fed to LI and RI respectively, filtered, summed and amplified. To obtain an amplifier for the left or right channel, the following changes must be made:
R1, R3, R6, C1, C4 are not installed.
Instead of resistor R4, place a jumper.
R10 = 1kOhm.
The signal is sent to LI.
One channel is shown, for stereo you need two such channels. The amplifier's radiator is small and is used for cooling by fans.

An unstabilized, unipolar power supply is used to power the amplifier. It is necessary to use a transformer with a power of 70-100W with an output voltage of no more than 30-33V.
Power supply for volume and tone control from a separate winding (~15-18V), or a separate transformer. Be sure to follow the rules for installing grounds and high-current circuits (there are many articles about this).

Files

Actually, the article itself, 2005
▼ 🕗 07/29/08 ⚖️ 3.09 Mb ⇣ 649 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 have been maintaining this wonderful site since 2006.
For more than 10 years, our magazine has existed only at my expense.

Good! The freebie is over. If you want files and useful articles, help me!

We bring to your attention a simple, high-quality

six-channel digital volume control

. The regulator is assembled on a TDA7448 chip manufactured by the European company STMicroelectronics. This microcircuit has a digital I2C interface. To control via this interface, a common, cheap, high-speed RISC microcontroller from Microchip PIC16F873 was used (can be replaced with PIC16F873A, PIC16F876, PIC16F876A).
Developers of microcontroller devices from Microchip have the unique ability to easily connect multiple encoders without additional wiring. This made it possible to implement a rather unusual concept for the device.
Structurally, the circuit consists of two components: a microcontroller control unit

And the regulator unit on TDA7448.

The regulator is intended to be used in 5.1 format systems. This assumes the following channels: front (left and right), rear (left and right), center and subwoofer. To control these channels, 4 encoders are used. The volume and balance mode for the front and rear can be switched with the "volume/balance" button. There are also “Mute” and “StandBy” buttons. There is also a separate StandBy line, which can be used to hardware disable amplifiers. A special mode is “Master volume”. The transition to this mode is carried out using a button on a reserved line. In this mode, all encoders operate in parallel, i.e. change the volume levels evenly across all channels (lines). The "overall volume" parameter does not have any specific numerical measurement, because Each channel is set to its own volume level. Adjusting the "overall volume" only simultaneously decreases or increases all channels.
To visualize the direction of regulation in this mode, the indicator shows the name of the “Master volume” mode on the top line, and animated icons on the bottom line<<<<< или >>>>>.

All of the above control functions can be performed via any remote control in RC5 format (from Philips household appliances).
Printed circuit boards are made of single-sided foil PCB using the LUT method, but can easily be made on circuit boards. Files of board drawings in Sprint Layout format are at the end of the article. Below is a drawing and photograph of the assembled printed circuit board 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 symbols. They are produced by many different companies and they contain different microcircuits: HD44780 (HITACHI), KS0066 (SAMSUNG), KB1013VG6 (ANGSTREM) and others.
The 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 lead pitch (1.27 mm) and is easily soldered with a sharpened soldering iron. Below is a drawing and photograph of the assembled printed circuit board of the regulator unit on the TDA7448.

Below is a picture of the encoder board:

Mechanical incrementing encoder, for example, PEC12 or from the EC11 series. When choosing an encoder, refer to the pinout documentation. The correct inclusion can be determined by scientific enumeration.

The buttons can be anything you like - from clock buttons to standard film keyboards. The membrane keyboard has a strong adhesive base (like adhesive tape), which makes it easy to stick it to the device body. To connect a film keyboard cable, it is convenient to use FB-x series connectors, for example, FB-5R.
The operation of the regulator has been successfully tested with various remote controls in RC5 format. Below is a photo of one of the remote controls. Use the left-right buttons to select the adjustable parameter, and use the up-down buttons to set the desired level (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 comes down to setting the required contrast with a trimming resistor. All dialogue in the menu is in English. Below are photos from life:

About catering.
It is advisable to supply a voltage of 6-7 volts to the 7805 stabilizer towards the microcontroller control unit so that it does not heat up when the voltage drops. The TDA7448 should be supplied with a voltage of 9 volts from a stabilized power source, for example, assembled on the 7809 stabilizer. We recommend connecting the common grounds on the side of the power supply.
For fans of synthetic modeling, a project has been compiled in Proteus Professional 7.2 SP6, in which you can evaluate some of the functions of the volume control.

If there are already blocking capacitors at the input of your amplifier, then in this circuit you can safely throw out the output electrolytes and put jumpers in their place.

With the development and improvement of microcircuits for audio amplifiers (both preliminary and final), there is a desire to modernize control. The best way to do this is to use a controller. This project interested me very much in terms of functionality; the author of the controller circuit and the firmware itself put a lot of effort into bringing the control program to perfection (for which many thanks to him!). Next, I copy the author’s description with minor abbreviations.

Schematic diagram of the main unit

Microcontroller controlled preamplifier Atmega16 It is built on a modular principle, that is, everyone can create individual modules according to their wishes and preferences. This especially applies to output power amplifiers, power supplies, and speaker protection. In this material we will look at the input module on the chip TDA7313 and a processor control unit. Chip TDA7313 is included according to the standard scheme and has no special features. The unit is powered by a +9 Volt power supply. This block has no more features. PCB files for this and other modules archived on the forum, there is also circuit diagrams for connecting a keyboard, final amplifier and power supply.

Main module parameters:

1. Volume adjustment (16 levels);
2. Gain adjustment (4 levels);
3. Bass tone adjustment (16 levels);
4. HF tone control (16 levels);
5. Adjustment of the balance of the front speakers (16 levels);
6. Adjustment of the balance of the rear speakers (16 levels);
7. LOUDNESS - On/off loudness;
8. MUTE mode;
9. STANDBY mode;
10. Show time in mode MUTE And STANDBY and also after 10 seconds, when there were no keystrokes or other control inputs;
11. Control of all functions from the keyboard, remote control (RC) The remote control operates according to the RC-5 standard, as one of the most common;
12. Control using the Valcoder (encoder);
13. Monitoring the temperature of radiators or internal temperature in the case via two channels based on sensors from DALLAS DS18x20. When the set control temperature is exceeded, the cooling fan turns on.

The module uses mainly SMD elements. Microcircuits in DIP packages. The VD10 diode is installed on the opposite side of the board. The amplifier is controlled using a keyboard, encoder and remote control. You can use any remote control that works according to the standard. The keyboard is built in the form of a matrix of 12 buttons (4x3):

INPUT1- selection of 1 channel;
INPUT2- selection of channel 2;
INPUT3- selection of channel 3;
LOUDNESS- enable/disable loudness mode;
MUTE- turn off the sound (turning off occurs smoothly, not abruptly). Pressing again turns on the sound;
STANDBY- turn off the amplifier. The power amplifier and its power supply are turned off, the processor module operates in standby mode;
MENU- a button to enter the additional menu, in it you can set Extra options, such as time, date, response temperature of radiator control temperature sensors. Pressing this button again in this mode returns to the main amplifier control menu without saving the parameters. In order for the new parameters to be saved, you need to click on the button SET.
SET- as stated above, this is saving the new parameters entered in the submenu. Basically, when you press a key SET You can see the temperature of the radiators, information is displayed within 3 seconds.
UP/DOWN- move to the previous/next menu item or submenu;
LEFT/RIGHT- decrease/increase the corresponding parameter, which is displayed on the indicator.

The main buttons are processed by the program almost instantly, but pressing and responding to the button STANDBY requires pressing for approximately 3 seconds. Buttons MUTE And LOUDNESS about 1 second. This is done to prevent activation when these buttons are accidentally pressed, especially if the remote control is used. The main menu of the amplifier control program consists of the following items:

Volume(Volume)
Attens(Gain)
Bass(LF tone)
Treble(HF tone)
Balans F(Front speaker balance)
Balans R(Balance of rear speakers)

The key also works in this mode SET, when pressed, temperature values ​​from the sensors are displayed for 3 seconds. When you press the button MENU we will be taken to an additional menu to set the time, date and maximum temperature parameters for temperature protection to trigger. This menu consists of the following items:

"Set Time: Hour" (time setting - clock),
"Set Time: Min" (time setting - minutes),
"Set Time: Sec" (time setting - seconds),
"Set Date: Day" (setting the date - day),
"Set Date: Months" (setting the date - month),
"Set Date: Year" (setting the date - year),
"Set MAX DS18x20" (setting the thermal protection response temperature).

In this mode, movement through the menu is carried out using the keys UP/DOWN(and the remote control keys), and parameter adjustment using the keys LEFT/RIGHT(and encoder). At any of the points, if we press the key MENU, then we will return to the main menu without writing new values, and if we press the key SET, then saving the entered parameters. For convenience, the author provided firmware in English, Russian and Ukrainian. As an option, I decided for myself to control only the remote control, so I don’t want to assemble and install the encoder and keyboard. The payment that the author provided was made for himself, so he decided to make his own.

I finished assembling the preamplifier - everything opens and is adjustable. Since there are no sensors, they are not defined (in the form of dashes in standby mode). I built my board for SMD, but the processor is in a Dip package, so the board fits it according to the size of the indicator - this is the main reason why I don’t put the board in Lay.

The second board will be the most preamp on TDA7313. The third board is a power supply control module and standby mode. Here is a photo:

It's time for testing. Plays great! I'm pleased with the depth of adjustment of the bass and treble, the bass is soft, the high-pitched tweeters are so loud (although with OM it will certainly be more fun), I especially liked the loudness compensation with its very impressive rise in the low frequencies. In general, I can only say one thing about the device so far - continuous advantages!

After driving for half a day, I did not find any flaws in the firmware, the operation of the remote control is clear, in general, if anyone decides to repeat this scheme, they will not regret it! Author of the scheme - Andrey Doinikov. Assembly and testing - GOVERNOR.

Discuss the article MICROCONTROLLER CONTROL IN ULF

Control circuit on a microcontroller.
Since many questions come like: is this really a working scheme? how to connect the relay? and so on. The article has been revised and expanded.

For those who are not afraid to use microcontrollers in audio devices, a control circuit is proposed Nikitin volume control on the 16F877A controller (author of the circuit and program Yuri Glotov).

The scheme allows:
1. manage six-link volume control by A. Nikitin, thanks to which you can build a regulator:

• with a step of 1 dB and a control depth of 64 dB (indication in decibels) or
• with a step of 2 dB and a control depth of 127 dB (indication is conditional - in steps).

Attention!!! The controller generates inverse relay control signals, which allows you to build a regulator without clicks on conventional (not bistable) relays.

2. manage four-channel input switch for building a pre-amplifier or full amplifier. The inputs are switched by relays K1-K4, controlled by buttons S3-S6.

3. switch inputs and control the regulator using remote control. You can use the remote control for any TV or DVD player from the company Sony. (RM-834 was tested).

4. mode "MUTE"(from the remote control) - quick mute down to -64 dB.

The device uses dynamic display. Seven-segment LED indicators with common anode.

Functionally, the design consists of three blocks:

1. volume control board— the controller, transistors for controlling the relay, and its own power supply with a surge protector are mounted on the board:

Click to enlarge

Controller printed circuit board made using LUT technology:

2. control Panel(it is also used as a false panel of the structure) - all the amplifier and regulator controls, indicators, remote control receiver and power filter for it are mounted here:

Click to enlarge

Panel printed circuit board made using LUT technology:

3. executive part - mounted on the preamplifier board or on separate input switch and volume control boards, respectively:

Click to enlarge

Construction and details:

surge protector - any from a monitor, DVD player, etc.
network transformer - any low-power one with an output voltage of 13-15V
rectifier bridge diodes - KD212 were used (because I have a lot of them)
transistors T1-T6 type 2SC2655 or 2SD667 (soldered from faulty computer power supplies)
transistors T8-T14 KT815 (KT817) - I understand that they are too powerful, but I have a lot of them and they take up little space on the board.
LEDs - any
7-segment indicators - any with a common anode. (The design used an LD4-BW56RN-A21 indicator with 4 acquaintances simply because it was available)
Stabilizer chips are installed on small radiators.

12 Volt stabilizer Can be used to power power on indicator, protection device, circuits smooth start power amplifier, etc., as well as when using 12-volt relays.
If you have 5-volt relays and there is no need for a voltage of 12 volts, then the first stabilizer can be excluded from the circuit, and a transformer can be used with a lower output voltage (7-9 volts).

Complete structure:

Click to enlarge

Photo of the completed device (on top is the SONY TV remote control, which was perfect for this scheme):

Click to enlarge

All schemes in one file (rar archive 800 kb)
All PCBs(Sprint format) (rar archive 120 kb) The archive contains two options for control unit printed circuit boards: for 5-volt relays and for 12-volt relays.
PCB option from our readers (in Sprint-Layout format, NOT CHECKED by the editors of RadioGazeta!) download (rar archive 153 kb).
Microcontroller firmware: (rar file 4kb)

Setup.

At power-up, input #1 is selected by default.
To set volume level, which will be installed when you turn on the device, you need to use the S1 and S2 buttons to set the required value and press the “Input1” and “Volume+” buttons simultaneously. The controller will remember the selected level.

1. while holding down the buttons "Volume+" And "Volume-" on the control panel, apply power. The indicator will show "0" - the controller is in code reading mode.
2. By pressing the necessary buttons on the remote control (for example: 1,2,3,4 - turning on inputs, “Volume+” and “Volume-” volume control), read the decimal button codes from the indicator.
3. convert decimal codes to hexadecimal.
4. program the obtained values ​​into the controller, as shown in the figure:

Important! For stable operation of the device when using the remote control, capacitor C4 must be installed as close as possible to the photodetector!

To be continued...

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