Remote control of the sound amplifier. Electronic volume control with remote control
The motorized potentiometer is not new for a long time, there are even ready-made devices for sale. The price for it can be said to be "space" and not affordable for many radio amateurs, like me! 🙂
The idea itself is very interesting, because such a connection has many advantages - no interference from adjustments is introduced into the sound, it can be easily connected to the remote control, for remote control, the device itself can be used anywhere, replacing it with a conventional potentiometer!
But besides the pluses, there are also minuses - For a direct connection of the potentiometer with the shaft, only a stepper motor is suitable, for a regular one you need a gearbox! During the adjustment, the sound of the motor will be heard, the motor must be controlled ...
However, with these disadvantages, there are still many benefits from this type of regulator, and I will tell you how I implemented it!
It all started with the fact that I had accumulated a lot of different motors, stepper and conventional:
I had to adapt them somewhere)) I didn’t touch the steppers, I will need them for other purposes, but I decided to twist the usual ones with a potentiometer to adjust the volume, since I had long wanted to adjust the volume with the remote control, for example, listening to the radio at work or watching a movie on the computer.. 🙂
Connecting the motor directly to the potentiometer will not work, the motor may not have enough strength to rotate the potentiometer shaft, or vice versa, the motor will have so much dope that it will turn the shaft completely in a split second! =)
For this I needed a gearbox! But it was difficult to make a gearbox on my own, I didn’t have materials ... Then fantasy went into battle ...
I went to a flea market, bought a cheap Chinese inertial machine for 10 hryvnias, removed a very necessary part from it and tried to connect it with a potentiometer:
As you can see, the motor was “embedded” in the very place where the inertial shaft stood, I removed the gear from it and put it on the motor axis, such a simple design came out!
The first tests were great! The motor exactly turned the handle of the resistor, but it still rotated it relatively quickly ... Then I needed a control circuit, but more on that later ...
Then I bit off the unnecessary parts of the axis of such a gearbox with wire cutters and with the help of a needle file I grinded off one part “for a screwdriver”:
The mount turned out to be very strong, the Chinese did not save on the material for the axis))
Actually what happened in the end:
The dimensions came out relatively small ... I fixed the gearbox on a piece of textolite with hot glue (a cool thing, by the way, very useful for housework) and simply soldered the potentiometer to the textolite with the body!
Then I took up the motor control circuit ... I needed an indication of the volume level, since the device would be inside the case, you need to see what position the regulator is in, it would not be very good to turn on the amplifier at maximum volume at night! 🙂
Here's the schematic that came out:
The option is of course “raw”, but in practice everything works very well!
Briefly describe how IT works:
A twelve-step indicator is assembled on transistors, which performs two functions - a volume level indicator (when the volume key is not pressed) and a display of the volume status for a couple of seconds after pressing the key louder or quieter and switching back to the level indication mode!
The motor control circuit itself is assembled on a “555” timer that generates pulses to control the motor, communication with the motor occurs using an “H” bridge assembled on powerful transistors (which I used and used, but I only had TIP100 and TIP106) . Transistors in the bridge which I used:
The driver always generates pulses, but in order to choose which direction to rotate the motor, we need to close one of the pairs of transistors by applying one to any of the inputs (L or R)! If you hook up an IR receiver to these inputs, as, for example, from an article about the past "Amplifier with Remote Control", then the volume can be adjusted with any remote control! I additionally put two buttons on the case, well, it’s not always possible to operate the remote control! 🙂
It may be necessary to use an additional amplifier for the level indicator input (LINE IN input), since on the mp3 player it did not have enough volume even at the maximum to show the level, but from the computer it worked at full ...
Also on the diagram there is an approximate drawing of how this system is connected!
As far as I assembled the circuit from scratch, I decided at first to do everything with a body kit ... This is how my “H” bridge and the whole device looked like:
It's scary, of course, I do not argue, but it works =))))
Later, I made a printed circuit board for it, which I posted on the forum ... I say right away - I did NOT check it, I did it in haste and there may be errors in it! I would be grateful to anyone who checks it! 🙂
Despite the terrible appearance, the device works very well, smoothly adjusts the volume, and in combination with the remote control, it turned out very conveniently!
And finally, here's the video:
On the video, it may seem that the volume is adjusted sharply, this is due to the fact that I connected the test amplifier (on the TDA8563) directly through the potentiometer to the computer! When connected via a tone block, the adjustment is much smoother!
First, the video shows an indication of the volume status, I close the “Louder” contact and the indication switches to the volume level mode, the LED strip fills up, after a couple of seconds when I release the contact, the indication returns to the signal level display mode (VU Meter). I turn on the amplifier, give a signal ... For tests, I used an amp on the TDA8563 and a car speaker, which turned everything on my table with vibration! 🙂
I made an SE amplifier on the GU-50 and, as usual, the question arose about the volume control. I didn’t want to install a regular joint venture, and it’s problematic to tie the remote control (remote control). Buying a potentiometer from a well-known APLS company is expensive, and our dealers do not have them.
I often saw circuits of regulators on resistive dividers on the Web, they are popularly called “Nikitin regulators”.
Finally got around to trying it.
Attenuator circuit
The circuits presented in various sources had an adjustment step of 1 or 2 dB, and a maximum signal attenuation of 63 or 127 dB.
I decided to make an intermediate version with a step of 1.5 dB and an attenuation of 94.5 dB. A resistance of 10 kOhm for a tube amplifier is not enough, I counted it to 33 kOhm. It turned out 6 steps with resistors of the following ratings.
On various sites offering regulator designers, it is written about the criticality of the resistors used in the divider. It is strongly recommended to use a 0.5% range, in extreme cases 1%. I have enough resistors and I just selected the ones closest to the calculated ones, paying special attention to the symmetry between the channels. Example: according to calculations, a 9.638 kΩ resistor is needed, I picked up 9.653 and 9.654 (for 2 channels).
The requirements for the relay are also not frail. I took a relay from an old PBX, a 24 volt Alcatel relay with 2 groups of contacts.
Well, they just exist.
Functions of my control unit
In terms of functionality, the volume control has evolved to a control unit with the following features:- IR remote control
- Volume control
- Turn on/off the amplifier
- Switching 4 inputs
- switching of 2 acoustic systems
- Switching the indicator mode (output voltage / anode current)
- Delay on anode voltage
- Forced on/off anode voltage from the remote control
BU scheme
When developing the circuit, I wanted to make the relay control static, without high-frequency circuits. Registers are used for this, and the indication circuit has already been used in my previous designs. The microcontroller came up with resources PIC12F675.I wrote the program in assembler from scratch, without other people's tie-ins. The operation of the device is quite simple, we measure the voltage at the analog inputs (AN0, AN1), and depending on their value, we turn on the necessary relays. At the same time, we listen to the digital port GP3 for the presence of a package from the IR remote control. We expose the data to the GP2 output, and strobe into the desired pair of registers on the GP4 and GP5 ports.
With each bit change, we write 2 bytes sequentially. Chains R25, C8, R28 filter high-frequency noise when writing to registers. Recording time 192 µs.
Design and details of BU
Structurally, the device is divided into two parts.The display unit, on which the controller is installed, is located on the front panel.
Relay module, located near the inputs.
Printed circuit boards are made by LUT technology. On the divider board, the top layer of foil is left used as a screen.
In the design, you can use a relay for a different voltage, respectively, connecting to a different power supply. Transistors can be replaced with similar ones, but it must be taken into account that a diode is built into the KT972. Registers IR23 can be series 155, 1533, 555, imported 74S374 or, if the board is changed, IR8 series 155, etc. Feature IR23 - high load capacity.
I used the KRT-30 IR receiver. You can use any other brands, the main thing is that the modulation frequency of the remote control matches the frequency of the receiver, otherwise the range of the remote control may be greatly reduced.
power unit may differ from those indicated. I have a standby voltage of 15V stabilized at 12V, it is also used to power the display unit, and 24V is taken from the main UZCH transformer. The relay for turning on the amplifier is rated for 12V and is powered by the standby PSU.
Separately, I will say about the power supply of the divider and input selector relays: it must be well stabilized, so the relay is better suited for a higher voltage (less current consumption).
The switch of the input selector, outputs on the diagram is shown under the biscuit switch, you can also use a variable resistor (similar to the volume control).
Regulator operation
After turning on the power switch, the amplifier is in standby mode, the indicator shows "--".To turn it on, you need to turn the volume knob or change the position of the input switch, the indicator shows the attenuation value in dB "32" (for example, corresponds to the position of the volume control).
The anode voltage relay turns on after about 70 seconds. Next, adjust the volume, switch inputs, i.e. we manage as we wish.
The following functions are available from the remote control:
0 - power on / off
1 - volume [+]
2 - volume [-]
3 - switching inputs around the ring [+]
4 - switching outputs
5 - switching the mode of indicators
6 - switching inputs around the ring [-]
7 - mute button
8 - turn off / turn on the anode
9 - not used
DU training
The constant use of the previous design revealed a lack of attachment to a specific remote, so here I made the remote learnable.You can use consoles of popular protocols NEC, RC-6, RC-5.
In a completely turned off device, we bring the volume to maximum attenuation, and the switch to position 2/4 (maximum).
We turn on the device, within 3 seconds you need to press any key on the remote control.
If the remote control is suitable, then "H0" is displayed on the indicator - it is proposed to select the first key (from the list above), press.
The block receives the code, the indicators show "H1", etc. Digit - function number from the list. Unnecessary functions can be scored with any already used buttons.
If within 3 seconds after turning on the key on the remote control is not pressed or the remote control does not fit according to the protocol, then the device goes into standby mode.
When the amplifier is turned on, the initial settings (volume, inputs, outputs) are taken from the position of the knobs on the front panel.
When programming, you can safely press the buttons for 1 second or more (repeat is not processed).
If desired, having read the data of the non-volatile memory of the controller by the programmer, we will see the key codes - the two most significant bits from the device code.
Simplified version
For those who only need a volume control, here is a simplified diagram.You can program two remote control buttons without an indicator. We translate SA1 into the open state, the volume control to the position of maximum attenuation, turn on the power, press any button on the remote control for 3 seconds.
If the remote control is suitable, then when switching SA1, all relays remain off (maximum attenuation).
We program the buttons themselves, press any unused button once, and then
1 - volume [+]
2 - volume [-]
Now turn off the device, or press any key on the remote control 7 times. All buttons are programmed.
results
The operation of the regulator completely satisfied me, the volume is regulated smoothly and in small steps. The switching of the relay is audible in the headphones (a slight rustle only at the moment of regulation), in the AC regulation is almost inaudible.The indicator shows the attenuation in decibels, which is very practical.
The measurement showed a completely linear frequency response, no distortion of the signal shape, attenuation error over the entire control range does not exceed 0.25 dB, asymmetry in the channels is extremely small.
Device succeeded.
Files
Files in the archives: schematics, printed circuit boards (for a complete circuit), MK firmware (NEC protocol), MK firmware (RC-6 protocol), additional materials.▼
Organization volume control in high-quality equipment has always been an important and not simple issue. The potentiometer used for this must have a high channel identity (for paired potentiometers), good wear resistance, and the absence of extraneous sounds (rustles and crackles) during adjustment. Today, conventional variable resistors are being replaced by hardwire switches, relay circuits, or integrated circuits. With significant cost and complexity, such options, solving some problems, give rise to others. Therefore, many lovers of high-quality sound still prefer "old-fashioned" potentiometers.
If you set out to find a high-quality potentiometer for your amplifier, you will definitely and quickly come across the company's products. ALPS. Indeed, their products are used in expensive devices and have high performance at a reasonable price. ALPS produces both conventional and motorized potentiometers. It is the latter that allow you to adjust the volume using remote control. You just need to connect the control circuit.
This article presents a circuit that allows you to remotely control motorized potentiometers. ALPS, as well as switch the amplifier's five inputs using a standard RC-5 remote control.
One microchip.
Apart from the supply voltage stabilizer, the circuit contains only one microcircuit - this is the Atmel ATmega microcontroller, which is responsible for decoding RC-5 signals, generating signals for motor control and input switch relay control signals.
Schematic diagram of the device is shown in the figure:
zoom on click
The scheme is quite simple and does not require detailed explanations. Let's just focus on some important points.
Ports PD2-PD6 via connector K3 can be used to control the relay of the preamplifier input switcher.
The pins of the PC and PB ports are connected in parallel to increase the output current. They are used to control the potentiometer drive through connector K1. The maximum motor current according to the ALPS documentation is 150 mA. The maximum current of the microcontroller port according to the Atmel documentation is about 40 mA. By paralleling 6 outputs, we can get a control current of more than 200 mA.
To indicate the rotation of the engine, LED D1 is connected in parallel with it. Here it is necessary to use a two-color LED and by the color of the glow it will be clear in which direction the engine rotates. If desired, it can be displayed on the front panel of the amplifier.
The structure can be powered from a separate transformer, which is connected to the K5 connector. Or constant voltage from the power supply of the amplifier itself. In this case, voltage is supplied to the board through connector K4, and elements B1 and C10-C13 can be omitted.
Design.
The figure shows the arrangement of elements on the printed circuit boards of the device:
The design is divided into two parts for ease of placement in the amplifier case. The motorized potentiometer itself is located on one board. This board is mounted in close proximity to the front panel of the amplifier.
The second board contains the power supply, microcontroller and other elements of the device. It is desirable to place this board in the amplifier case as far as possible from the audio circuits and, if possible, shield it to reduce radiated interference.
The IR signal receiver must also be placed on the front panel of the amplifier by connecting it to the board with a three-wire cable. With a long cable length, in order to exclude unstable and false alarms of the receiver, it is necessary to duplicate the capacitors C2 and C3, soldering them directly at the receiver's terminals.
All connections of the structure are implemented by connectors, which are interconnected by loops with the appropriate number of cores.
The potentiometer PCB has pins for connecting the signal cable shield and the motor control cable shield, if required.
A photo of the finished structure is shown in the figure:
zoom on click
Signals for transistor control keys of the input switch relay are taken from connector K3. To switch inputs on the remote control, use the number buttons 1...5. In this way, the desired input can be directly selected. To switch inputs sequentially on the remote control, use the up / down channel switching buttons.
Important note.
The author tested his development with a remote control from Philips devices. It is clear that not every home has products of this well-known brand, so attempts have been made to check the compatibility of other remotes. The universal remote control "EuroSky 8" turned up under the arm (in the photo it is black on the right):
This remote worked well. various devices in the house, but when it was programmed to work with audio devices, errors were observed when working out auxiliary functions. It turned out that some remotes do not work correctly with the RC-5 standard.
The editors of the magazine "Elector" carried out modernization software this device in order to minimize errors when working with different remotes from different manufacturers. The tests carried out with the Philips SBC RU 865 universal remote control showed excellent performance. With others universal remotes DU shouldn't be a problem either.
If you have a remote control tester, you can check if your remote control complies with the RC5 standard using the table below:
Here, for example, incorrect codes are presented, which were transmitted by the "EuroSky 8" remote control. The right column shows the correct command codes.
The article was prepared based on the materials of the Elector magazine.
Successful creativity!
Editor-in-Chief of the Radio Newspaper.
A bit of history
This design appeared after I assembled the famous OM 2.5 amplifier. Naturally, the question arose of choosing a volume control, protection and other service functions. Of course, I also wanted to have a digital input and remote control, but it already seemed like a completely inaccessible space. I have never been involved in programming controllers or designing electronic circuits before. However, as they say, the walker will master the road, and the Atmega16 controller with the PGA2311 volume control chip settled on the breadboard. As a result, the process fascinated me so much that it was very difficult to complete the project. While there was free memory and controller legs, ideas appeared to expand functions and add new modules. Boards for all modules were originally bred in DipTrace and made by hand using photoresist. Then I tried to order part of the boards in production. Therefore, in the photo there is a combined hodgepodge of blue home-made and green factory boards. So, in this article I tried to describe what I ended up with.
System functions.
- Soft start, delay adjustable from 0 to 30 sec.
- AC turn-on delay, adjustable from 0 to 30 sec.
- NEC standard remote control with remote control settings from the menu system
- Switching speakers using protection boards: zones A / B (button, remote control), left / right (remote control) or just on / off.
- Input selector control for 4 inputs (buttons, remote control)
- Volume and balance control using the PGA23XX chip or Nikitin's relay RG (encoder, remote control)
- Control of the Matyushkin tone block with relay adjustment of bass and treble (encoder, remote control)
- Management - transmission of commands stop/start/rewind/tracks (RC)
- Thermal control on digital sensor LM75, one or two channels, shutdown in case of overheating, turning on fans
- Power, speaker switch, four input selector and mute buttons
- Adjusting the brightness of the screen backlight (remote control)
- Screen savers: screen blanking, level meter and spectrum analyzer
Composition and configuration of the system.
The system consists of a front panel controller with a 4x20 character display and several executive modules. The display is installed parallel to the controller board on four racks and connected to it with PLS-PBS connectors, a fairly compact "sandwich" 12mm high is obtained. All connections are made around the perimeter of the controller board using XH angled connectors.
The modules carry out the necessary adjustments/switching and are installed in the amplifier housing, taking into account the minimization of the length of the signal circuits:
- Volume control based on PGA23XX with input selector for 4 inputs and connector for USB-dac PCM2705
- Volume control Nikitin
- Input selector for 4 inputs (for use with RG Nikitin)
- Matyushkin tone control with relay adjustment of bass and treble
- AC protection against DC voltage with switching of two zones A/B
- Thermal sensors
- Standby power supply with input filter and soft start control
The configuration of the modules used is determined by the dip switch on the controller board. It is read when power is applied to the controller and determines the algorithm for the further operation of the system:
The volume controls, tone block and input selector are connected to the SPI controller bus in series; for this, the module boards have Control IN and Control Out connectors. When using Nikitin's RG, two such modules can be connected to adjust the balance. This allows you to flexibly configure the control system for a specific device. The range and step of volume control for PGA23xx and Nikitin's RG can differ significantly, so they are set in the system setup menu. Important - the firmware does not check the entered values for adequacy, so you should not set the maximum volume to +32db for Nikitin's RG. All possible options for connecting modules to the SPI bus:
- controller ->
- controller -> TB Matyushkina -> WG on PGA23XX with input selector and DAC
- controller -> RG Nikitin -> input selector
- controller -> RG Nikitin -> RG Nikitin -> input selector
- controller -> TB Matyushkina -> RG Nikitin -> input selector
- controller -> TB Matyushkin -> RG Nikitin -> RG Nikitin -> input selector
Thermal sensors are connected to the controller via the I2C bus. Their presence and quantity is also set by the dip-switch. Three options are possible - thermal control is disabled, one sensor is used or two sensors are used for each channel of the amplifier. If the thermal control is enabled, you can set the maximum temperature at which the device will turn off. The on and off temperatures are also adjustable. When using two thermal sensors, it is possible to organize independent blowing of each channel.
Indication.
All information is displayed on a 4x20 character display on the well-known HD44780 controller. The first line indicates the status of the AC switch. The same line displays the temperature of the radiators, received from the thermal sensors, when it exceeds the airflow switch-on temperature. The second line displays the attenuation of the RG in decibels. The third line is the state of balance. When adjusting bass or treble, their status is also displayed in this line instead of balance. The last line displays the names of the inputs and the current input.
Another indication organ is the LED. It glows when the system is online and in standby mode. When turned on, it goes out and indicates by blinking the reception of commands from the remote control.
If no controls are used for a certain amount of time, the screen may switch to screensaver mode. The simplest is to reduce the brightness of the screen backlight. If you connect an input or output audio signal to the corresponding inputs of the controller, you can use the “Level Indicator” or “Spectrum Analyzer” splash screens based on the Fourier transform.
Control.
For control, non-latching buttons are used that close the corresponding controller inputs to ground, an encoder with a button, and a remote control with the NEC protocol. The encoder controls the volume control. When you press its button, the encoder sequentially switches to adjusting the balance / timbre of the bass / timbre of the treble. At the same time, the symbols corresponding to the current mode flash on the screen. Only the minimum set of commands is implemented on the buttons and the encoder, the full functionality of 26 commands is available only from the remote control. Some functions, such as changing the volume, support receiving auto-repeat commands from the remote control (when the remote control button is held down). For functions such as On / Off, auto-repeat is intentionally disabled - to repeat the command, you must press the button on the remote control again.
The minimum required kit for starting and configuring the system is a power button, an encoder and a remote control. When power is applied to the controller, it will be in standby mode. A long press on the power button (from 2 seconds) switches the controller to the setting mode. In this case, only the screen turns on, the soft start relays remain off. Navigating through the setup menu and changing parameter values is done by rotating the encoder. To select menu items, enter editing and confirm the selection, you must press the encoder button.
The remote control command codes in the corresponding setup submenu can be simply entered if you know them. But it's easier to read them from the existing remote control. To do this, you need to enter the editing code of the desired command and press the corresponding button on the remote control. If the controller was able to accept the command, it will blink the standby LED and enter the code in the edit field. To confirm the code, it remains only to press the encoder. All configurable parameters and commands are shown in the table below:
| System | General system settings | |
| Lcd Brigtness | Display brightness, 0-16 | |
| speaker delay | AC turn-on delay, 0-30 sec. | |
| SS Delay | Soft start duration, 0-30 sec. | |
| Screen Saver | Screen saver: off-disabled, LcdOff-decreasing screen brightness, Level-level indicator, Spektr-spectrum analyzer | |
| SaverDelay | Screensaver on time: 5-100 sec. | |
| Volume | Adjust volume and balance controls. | |
| volume min | Minimum volume: -94db - -64db | |
| Volume Max | Maximum volume: -32db - -32db | |
| volume step | Volume control step: 1-4db | |
| Balance | Balance adjustment range: 4-16db | |
| selector | Selecting input names displayed on the screen | |
| In1 | Login 1 | |
| In2 | Login 2 | |
| In3 | Login 3 | |
| In4 | Login 4 | |
| TermoControl | Thermal control setting | |
| power off | Shutdown temperature: 60-90 degrees | |
| Cooler ON | ||
| Cooler OFF | Blow off temperature: 40-70 degrees | |
| Remote | Remote control codes | |
| System | Console system code common to all commands | |
| On | Turn on/off | |
| Enter | Analogue of pressing the encoder button | |
| Vol+ | Volume up | |
| Vol- | Volume down | |
| Balleft | Balance left | |
| BalRight | Balance right | |
| Bass+ | Boost bass | |
| Bass- | Reduce bass | |
| Treb+ | Increase treble | |
| Treb- | Reduce bass | |
| In1 | Input selection 1 | |
| In2 | Input selection 2 | |
| In3 | Input selection 3 | |
| In4 | Input selection 4 | |
| In+ | Next entry | |
| In- | Previous entry | |
| SpeakerNext | Next AC. Switching is performed depending on the configuration, On->Off or A->B->Off | |
| SpeakerPrev | Previous AS. Switching is performed depending on the configuration, Off->On or Off->B->A | |
| Speaker L/R | Speaker switch right/left/both | |
| DacPlayPause | HID command for USB DAC - play/pause | |
| DacStop | HID command for USB DAC - stop | |
| DacNext | HID command for USB DAC - next track (short press) / fast forward (long press) | |
| DacPrev | HID command for USB DAC - previous track (short press) / rewind (long press) | |
| Bright+ | Increasing display brightness | |
| Bright- | Decreasing display brightness | |
| Mute | Temporarily decrease the volume to Volume | |
Controller Diagram
Power is supplied through a protective diode D1 and a 5V stabilizer U1. Keys Q1 and Q2 control the soft start relay. R9 adjusts the contrast of the display, for a blue backlit screen on the third leg of the X9 connector, you need to set the voltage to about 0.85-0.9V. Q3 is the PWM key for adjusting the brightness of the display backlight.
All buttons and the S1 configuration dip-switch are connected to the controller via the I2C bus using PCF8574 port expanders (U3, U4). Pressing any button causes an interruption on the PB2 leg of the Atmega and, as a result, polling U3 for the code of the button pressed. An encoder (x6) and an IR receiver (PH1) are also connected to the controller legs that support external interrupts - PD2 and PD3.
Operational amplifier U5 is used to supply the analog signal of the right and left channels to the inputs of the ADC. Based on the data received from the ADC, the functions of the level indicator and spectrum analyzer are implemented. The ADC inputs work with a signal in the range of 0-5V, so the audio signal needs to be amplified / attenuated to an amplitude of 2.5V and a 2.5V DC component added. The gain is determined by R15/R19 and R16/R20. R17 and R18 provide the required 2.5V bias. U5 must be rail to rail in and out and run on 5v power. When setting resistors R13, R14, it is necessary to achieve the maximum possible amplitude of the analog signal on PA6, PA7 (U2) without signs of a clip.
Firmware, Fuses, Modeling
The X2 connector is used for firmware. When flashing the controller, be sure to disconnect any modules from the X3 connector. After flashing the program, the file with the Eeprom data must be uploaded. When installing fuses, you must disable the JTAG debugger (JTAGEN) and set the frequency to 8 MHz (CKSEL0, CKSEL1, CKSEL2, CKSEL3), everything else is default.
The model of the controller in Proteus 8 is attached to the article. With its help, you can get acquainted with the controller, test functions, indications, control signals without assembling the device. I could not find the LM75 digital thermometer model, so another similar sensor and firmware are used, taking into account this replacement. To emulate the NEC remote control, a simple model and firmware was made, I found the encoder emulator model in an open project. The firmware of these models are included with the Proteus file.
Thermal sensor
Thermal sensors are pressed against the radiators with the side with the microcircuit. On the other side of the board, jumpers set the addresses of the sensors on the I 2 C bus. The address of the left channel is 000, the right one is 001. If one sensor is used, the address of the left channel is set. An important limitation is that the OS airflow switch-on outputs are low-current, they can pass current up to 100 μA. This must be taken into account when connecting keys that control fans to the controller.
Volume control Nikitin
The scheme used is inverse to the original one - when the relays are off, the attenuation of the regulator is maximum. Shift register U1 receives volume data from the controller (X9). Its outputs are reinforced with darlington switches with protective diodes U2, because register 74HC595 cannot supply the required current to all relays. In addition, thanks to the ULN2003A, it is possible to use a relay not necessarily 5V. The relay windings can be powered from the controller board, but it is better to power them from a separate source, X11 connector is provided for this. If relays with windings over 5V are used, external power is the only option. The choice of power supply is set by jumpers J1 and J2.
When all relays are installed, an attenuation of up to -128 db and a control step of - 1db are provided. If -64db attenuation is sufficient, relay K7 can be omitted. In this case, the output signal is taken from connectors X6,X8. It is possible to increase the control step up to 2db, for this it is enough not to install the relay K1 and apply the input signal to the connectors X2,X4.
Resistors R15 and R16 are needed to match the output impedance of the regulator with the input impedance of the amplifier. R15 is set if -64db output is used, R16 for -128db output. The value of the resistors is determined based on the output resistance of the RG 10 kOhm and the value of the input load resistance. If an input selector is not used, resistors R20,R21,R22 must be installed to connect digital and analog ground. If there is an input selector, it is better to connect the grounds on its board.
The input selector control scheme is similar to Nikitin's RG, but with some simplifications. Since only one relay is energized at any time, the U1 register current is sufficient and the ULN2003 was abandoned. Therefore, only 5V relays can be used in the input selector. When using conventional relays, jumper J1 is soldered. Jumper J2 is for experimenting with bistable relays for the future.
RG Nikitin can be installed on the input selector. In this case, the analog inputs/outputs and the control bus are connected using PLS-PBS connectors. To do this, the selector has two outputs per channel, corresponding to the inputs of Nikitin's RG with a control step of 1db and 2db. R1, R2, R3 connect analog and digital ground. The jumper on the J3 board allows you to connect the grounds to the device case through a plated mounting hole on the board.
In the original TB Matyushkin circuit, high frequencies are regulated by a variable resistor. This did not fit into the concept of my design, so the resistor was replaced with a relay divider. But it was necessary to reduce the number of relays so that the adjustment of bass, treble and the inclusion of a direct fit into 7 legs of the ULN2003. I borrowed the switching circuit for three relays, instead of four, from. To minimize the board, Epcos lavsan capacitors for 63V with a 5mm pitch of legs were used.
The relay switching control scheme is completely similar to Nikitin's RG. The only addition is the X4 Direct output for an external tone block bypass relay. The Direct relay turns on when all timbres are set to 0. The controller does not yet have an additional Direct turn on command, but it is not difficult to add it.
This is the first module from which the development of the controller began. PGA2311 (U2) for control consists of two eight-bit shift registers connected in series. Each register controls the volume of its channel. The microcircuit has a data output, to which another regular register U3 was connected. It controls four input relays. The remaining four legs of the register through a 3V divider transmit USB commands to the DAC - play / pause, stop, rewind right / left, prev / next. track. This makes it possible to control the playback of playlists on a computer from the amplifier's remote control, which is quite convenient. Analog and digital power is separate and is carried out from three stabilizers - U4, U5, U6. Diode bridges and filters are installed on the board, you only need to connect a transformer. Instead of PGA2311, the PGA2310 chip can be used, for this it is enough to replace the stabilizers U4 and U5 with similar ones with an output voltage of 12V. An important feature is that digital and analog power must be supplied synchronously. The design of the module involves installation on the rear wall of the amplifier.
Instead of the first analog input, a PCM2706 USB DAC can be installed. I posted all the materials on it on. In this case, instead of the X1 RS-813 connector, a connector for 3 RS-613 inputs is installed. The operational amplifier U1 has an additional filter for the DAC. In addition, it amplifies the output of the DAC to the standard 1.2v.
measurements
The quality of the modules after assembly was checked using measurements by the program. As sound card used EMU-0404. Thanks to this, I was able to detect and correct some errors in the layout of the boards. I will not clutter up the article with pictures with measurement results, they are attached to the project files. In general, we can say that the noise and harmonics of the modules lie on the edge of the measuring capabilities of the EMU-0404.
List of radio elements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad | |
|---|---|---|---|---|---|---|---|
| Controller | |||||||
| U1 | Linear Regulator | LM7805 | 1 | To notepad | |||
| U2 | MK AVR 8-bit | ATmega16 | 1 | To notepad | |||
| U3, U4 | I2C interface IC | PCF8574A | 2 | To notepad | |||
| U5 | Operational amplifier | LMC6482QML | 1 | To notepad | |||
| Q1, Q2 | bipolar transistor | MMBT3904 | 1 | To notepad | |||
| Q3 | bipolar transistor | BC807 | 1 | To notepad | |||
| R1, R2 | Resistor | 1.8 kOhm | 1 | SMD 1206 | To notepad | ||
| R3, R4, R5, R17, R18, R19, R20, R21, R22 | Resistor | 10 kOhm | 9 | SMD 1206 | To notepad | ||
| R6, R8 | Resistor | 100 ohm | 2 | SMD 1206 | To notepad | ||
| R9 | Trimmer resistor | 10 kOhm | 1 | 3296x | To notepad | ||
| R10, R11 | Resistor | 4.7 kOhm | 2 | SMD 1206 | To notepad | ||
| R12 | Resistor | 10 ohm | 1 | SMD 1206 | To notepad | ||
| R13, R14 | Trimmer resistor | 47 kOhm | 2 | 3296x | To notepad | ||
| R15, R16 | Resistor | 5.1 kOhm | 2 | SMD 1206 | To notepad | ||
| C1, C2, C3, C4, C5, C6, C7 | Capacitor | 10 microfarad | 7 | SMD 1206 | To notepad | ||
| D1 | Diode | SMA4007 | 1 | SMA | To notepad | ||
| PH1 | IR receiver | TSOP34838 | 1 | 38MHz 2.5mm, 1-Out, 2-Gnd, 3-Vs | To notepad | ||
| S1 | DIP switch | DS1040-08RT | 1 | To notepad | |||
| X1,X6 | Angled connector | S4B-XH-A | 2 | XH 2.5 mm, 4 pins | To notepad | ||
| X2 | Male plug | PLS-6R | 1 | 2.54mm 1x6 | To notepad | ||
| X3, X11, X12 | Angled connector | S5B-XH-A | 3 | XH 2.5 mm, 5 pins | To notepad | ||
| X4, X5, X7, X10, X13 | Angled connector | S3B-XH-A | 5 | XH 2.5 mm, 3 contacts | To notepad | ||
| X8 | Male plug | PLS-9R | 1 | 2.54mm 1x9 | To notepad | ||
| X9 | socket for board | PBS-16 | 1 | 2.54mm 1x16 | To notepad | ||
| Display | WH2004 | 1 | HD44780 | To notepad | |||
| Thermal sensor | |||||||
| U1 | temperature sensor | LM75AD | 1 | To notepad | |||
| C1 | Capacitor | 10 microfarad | 1 | smd | To notepad | ||
| R1 | Resistor | 100 kOhm | 1 | SMD 1206 | To notepad | ||
| U1 | shift register | SN74HC595 | 1 | To notepad | |||
| U2 | Composite transistor | ULN2003 | 1 | To notepad | |||
| R1 | Resistor | 1.1 kOhm | 2 | SMD 1206 | To notepad | ||
| R2 | Resistor | 82 kOhm | 2 | SMD 1206 | To notepad | ||
| R3 | Resistor | 2 kOhm | 2 | SMD 1206 | To notepad | ||
| R4 | Resistor | 36 kOhm | 2 | SMD 1206 | To notepad | ||
| R5 | Resistor | 3.6 kOhm | 2 | SMD 1206 | To notepad | ||
| R6 | Resistor | 16 kOhm | 2 | SMD 1206 | To notepad | ||
| R7 | Resistor | 6.2 kOhm | 2 | SMD 1206 | To notepad | ||
| R8 | Resistor | 6.8 kOhm | 2 | SMD 1206 | To notepad | ||
| R9 | Resistor | 8.2 kOhm | 2 | SMD 1206 | To notepad | ||
| R10 | Resistor | 1.8 kOhm | 2 | SMD 1206 | To notepad | ||
| R11 | Resistor | 9.1 kOhm | 2 | SMD 1206 | To notepad | ||
| R12 | Resistor | 240 ohm | 2 | SMD 1206 | To notepad | ||
| R13 | Resistor | 10 kOhm | 2 | SMD 1206 | To notepad | ||
| R14 | Resistor | 6.2 ohm | 2 | SMD 1206 | To notepad | ||
| R15 | Resistor | * | 2 | SMD 1206 | To notepad | ||
| R16 | Resistor | * | 2 | SMD 1206 | To notepad | ||
| R17 | Resistor | 100 kOhm | 1 | SMD 1206 | To notepad | ||
| R18, R19 | Resistor | 0 ohm | 2 | SMD 1206 | To notepad | ||
| R20, R21, R22 | Resistor | 15 ohm | 3 | SMD 1206 | To notepad | ||
| C1 | Capacitor | 10 microfarad | 1 | SMD 1206 | To notepad | ||
| K1, K2, K3, K4, K5, K6, K7 | Relay | G6H-2F | 7 | TQ2SA or similar | To notepad | ||
| X1, X2, X3, X4, X5, X6, X7, X8, X11 | connector | B2B-XH-A | 5 | XH 2.5 mm, 2 pins | To notepad | ||
| X9 , X10 | connector | B5B-XH-A | 2 | XH 2.5 mm, 5 pins | To notepad | ||
| U1 | shift register | SN74HC595 | 1 | To notepad | |||
| D1, D2, D3, D4 | rectifier diode | PMLL4148L | 4 | To notepad | |||
| R1, R2, R3 | Resistor | 10 ohm | 3 | SMD 1206 | To notepad | ||
| C1 | Capacitor | 10 microfarad | 1 | SMD1206 | To notepad | ||
| K1, K2, K3, K4 | Relay | G6H-2F | 4 | TQ2SA 5v or similar | To notepad | ||
| X1, X2, X3, X4 | connector | PBS-2 | 3 | 2.54mm 1x2 | To notepad | ||
| X5 | connector | PBS-5 | 1 | 2.54mm 1x5 | To notepad | ||
| U1 | shift register | SN74HC595 | 1 | To notepad | |||
| U2 | Composite transistor | ULN2003 | 1 | To notepad | |||
| R1 | Resistor | 100 kOhm | 1 | SMD 1206 | To notepad | ||
| R2, Rl20, Rr20 | Resistor | 0 ohm | 3 | SMD 1206 | To notepad | ||
| R3, R4, R5 | Resistor | 10 ohm | 3 | SMD 1206 | To notepad | ||
| Rl1, Rr1 | Resistor | 7.5 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl2, Rr2 | Resistor | 680 ohm | 2 | SMD 1206 | To notepad | ||
| Rl3, Rr3 | Resistor | 940 ohm | 2 | SMD 1206 | To notepad | ||
| Rl4, Rr4 | Resistor | 6.8 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl5, Rr5 | Resistor | 820 ohm | 2 | SMD 1206 | To notepad | ||
| Rl6, Rr6 | Resistor | 1.3 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl7, Rr7 | Resistor | 2.7 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl8, Rr8 | Resistor | 10 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl9, Rr9 | Resistor | 1.5 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl10, Rr10 | Resistor | 1.8 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl11, Rr11 | Resistor | 3 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl12, Rr12 | Resistor | 14 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl13, Rr13 | Resistor | 1 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl14, Rr14 | Resistor | 4.7 kOhm | 2 | 3296W | To notepad | ||
| Rl15, Rl16, Rl17, Rr15, Rr16, Rr17 | Resistor | 16 kOhm | 6 | SMD 1206 | To notepad | ||
| Rl18, Rr18 | Resistor | 36 kOhm | 2 | SMD 1206 | To notepad | ||
| Rl19, Rr19 | Resistor | 12 kOhm | 2 | SMD 1206 | To notepad | ||
| C1 | Capacitor | 10 microfarad | 1 | SMD 1206 | |||
