Sometimes files appear on the computer in formats unknown to us, which we have never heard of before. Now we will help you deal with one of the types of such files.LAY. First you need to know that this is a file that contains an electrical circuit diagram or printed circuit board design. This extension also has several varieties at the same time. They are used to calculate various types of problems, and they are created using the Sprint Layout utility.
How to run a file
Before opening .LAY, you will have to understand what type of file it is.
The simplest method, but not always effective, is to double-click on the file. In this case, the computer itself will select the program to open the file. But there may not be a utility on the PC that can open .LAY, so we will need to download additional software.
What software are we talking about?
There are several programs that work with this type of file. But before that, figure out what type of file you are going to work with. There are 5 types of .LAY files:
- Developed by Apple.
- Variant of the Tecplot program.
- Option "Rhino 3D".
- Template "MAME"
Now let's talk about everything in order!
Sprint Layout utility
- a special utility from Apple. It is used on Mac OS, with the help of which DVD projects are created. To create a project, no programming knowledge is required at all, because the program has several ready-made templates, with the help of which even a beginner can create his own DVD project without any problems. But experienced users may not use templates, but create them themselves. You can also test a DVD project without creating a disk image.
Important! The .LAY file in this case is located in the VIDEO_TS directory, but when converting the finished project to disk, it will not be written because it belongs to the project design.
Tecplot program
is a program used by engineers to create objects in flat and three-dimensional formats. It is used in engineering plotting and contains a wide range of functions.
LAY includes page layout, color and graphics settings. It stores participant data, parameters that determine the appearance of each frame, and the visual layout of the project workspace.
The author of the program is Tecplot.
Option "Rhino 3D"
Rhinoceros is a commercial software for volumetric NURBS design. This program is used in shipbuilding, architecture, automotive, industrial design, jewelry, etc. It helps create objects that require incredible precision. Therefore, this utility is used in the fields of CAD/CAM design and multimedia.
Advice! NURBS is used to convey the shapes of objects in .3DM format, so it became the basis of the Rhino 3D program. NURBS generates complex 3D objects from 2D models (quadrangles, circles, polylines, lines, etc.).
Rhino 3D stores state information for the layer where the 3D models are located. All models can be changed at the same time. This is done to simultaneously change the color or structure, and to simultaneously turn layer objects on or off.
Authors of the program:
- Robert McNeel.
- Associates.
Updated: 04/27/2016
An excellent amplifier for home can be assembled using the TDA7294 chip. If you are not strong in electronics, then such an amplifier is an ideal option; it does not require fine tuning and debugging like a transistor amplifier and is easy to build, unlike a tube amplifier.
The TDA7294 microcircuit has been in production for 20 years and has still not lost its relevance and is still in demand among radio amateurs. For a novice radio amateur, this article will be a good help in getting to know integrated audio amplifiers.
In this article I will try to describe in detail the design of the amplifier on the TDA7294. I will focus on a stereo amplifier assembled according to the usual circuit (1 microcircuit per channel) and will briefly talk about the bridge circuit (2 microcircuits per channel).
TDA7294 chip and its features
TDA7294 is the brainchild of SGS-THOMSON Microelectronics, this chip is an AB class low-frequency amplifier, and is built on field-effect transistors.
The advantages of the TDA7294 include the following:
- output power, with distortion 0.3–0.8%:
- 70 W for 4 ohm load, conventional circuit;
- 120 W for 8 ohm load, bridge circuit;
- Mute function and Stand-By function;
- low noise level, low distortion, frequency range 20–20000 Hz, wide operating voltage range - ±10–40 V.
Specifications
| Technical characteristics of the TDA7294 chip | |||||
|---|---|---|---|---|---|
| Parameter | Conditions | Minimum | Typical | Maximum | Units |
| Supply voltage | ±10 | ±40 | IN | ||
| Frequency range | Signal 3 db Output power 1W |
20-20000 | Hz | ||
| Long-term output power (RMS) | harmonic coefficient 0.5%: Up = ±35 V, Rн = 8 Ohm Up = ±31 V, Rн = 6 Ohm Up = ±27 V, Rн = 4 Ohm |
60 60 60 |
70 70 70 |
W | |
| Peak music output power (RMS), duration 1 sec. | harmonic factor 10%: Up = ±38 V, Rн = 8 Ohm Up = ±33 V, Rн = 6 Ohm Up = ±29 V, Rн = 4 Ohm |
100 100 100 |
W | ||
| Total harmonic distortion | Po = 5W; 1kHz Po = 0.1–50W; 20–20000Hz |
0,005 | 0,1 | % | |
| Up = ±27 V, Rн = 4 Ohm: Po = 5W; 1kHz Po = 0.1–50W; 20–20000Hz |
0,01 | 0,1 | % | ||
| Protection response temperature | 145 | °C | |||
| Quiescent current | 20 | 30 | 60 | mA | |
| Input impedance | 100 | kOhm | |||
| Voltage Gain | 24 | 30 | 40 | dB | |
| Peak output current | 10 | A | |||
| Operating temperature range | 0 | 70 | °C | ||
| Case thermal resistance | 1,5 | °C/W | |||
Pin assignment
| Pin assignment of the TDA7294 chip | |||
|---|---|---|---|
| IC output | Designation | Purpose | Connection |
| 1 | Stby-GND | "Signal Ground" | "General" |
| 2 | In- | Inverting input | Feedback |
| 3 | In+ | Non-inverting input | Audio input via coupling capacitor |
| 4 | In+Mute | "Signal Ground" | "General" |
| 5 | N.C. | Not used | – |
| 6 | Bootstrap | "Voltage boost" | Capacitor |
| 7 | +Vs | Input stage power supply (+) | |
| 8 | -Vs | Input stage power supply (-) | |
| 9 | Stby | Standby mode | Control block |
| 10 | Mute | Mute mode | |
| 11 | N.C. | Not used | – |
| 12 | N.C. | Not used | – |
| 13 | +PwVs | Output stage power supply (+) | Positive terminal (+) of the power supply |
| 14 | Out | Exit | Audio output |
| 15 | -PwVs | Output stage power supply (-) | Negative terminal (-) of the power supply |
Note. The microcircuit body is connected to the power supply negative (pins 8 and 15). Do not forget about insulating the radiator from the amplifier body or insulating the microcircuit from the radiator by installing it through a thermal pad.
I would also like to note that in my circuit (as well as in the datasheet) there is no separation of input and output lands. Therefore, in the description and in the diagram, the definitions of “general”, “ground”, “housing”, GND should be perceived as concepts of the same sense.
The difference is in the cases
The TDA7294 chip is available in two types - V (vertical) and HS (horizontal). The TDA7294V, having a classic vertical body design, was the first to roll off the production line and is still the most common and affordable.
Complex of protections
The TDA7294 chip has a number of protections:
- protection against power surges;
- protection of the output stage from short circuit or overload;
- thermal protection. When the microcircuit heats up to 145 °C, the mute mode is activated, and at 150 °C the standby mode is activated;
- protection of microcircuit pins from electrostatic discharges.
Power amplifier on TDA7294
A minimum of parts in the harness, a simple printed circuit board, patience and known good parts will allow you to easily assemble an inexpensive TDA7294 UMZCH with clear sound and good power for home use.
You can connect this amplifier directly to the line output of your computer sound card, because The nominal input voltage of the amplifier is 700 mV. And the nominal voltage level of the linear output of the sound card is regulated within 0.7–2 V.
Amplifier block diagram
The diagram shows a version of a stereo amplifier. The structure of the amplifier using a bridge circuit is similar - there are also two boards with TDA7294.
- A0. power unit
- A1. Control unit for Mute and Stand-By modes
- A2. UMZCH (left channel)
- A3. UMZCH (right channel)
Pay attention to the connection of the blocks. Improper wiring inside the amplifier may cause additional interference. To minimize noise as much as possible, follow several rules:
- Power must be supplied to each amplifier board using a separate harness.
- The power wires must be twisted into a braid (harness). This will compensate for the magnetic fields created by the current flowing through the conductors. We take three wires (“+”, “-”, “Common”) and weave them into a pigtail with a slight tension.
- Avoid ground loops. This is a situation where a common conductor, connecting blocks, forms a closed circuit (loop). The connection of the common wire must go in series from the input connectors to the volume control, from it to the UMZCH board and then to the output connectors. It is advisable to use connectors isolated from the housing. And for input circuits there are also shielded and insulated wires.
List of parts for TDA7294 power supply:
When purchasing a transformer, please note that the effective voltage value is written on it - U D, and by measuring it with a voltmeter you will also see the effective value. At the output after the rectifier bridge, the capacitors are charged to the amplitude voltage - U A. The amplitude and effective voltages are related by the following relationship:
U A = 1.41 × U D
According to the characteristics of the TDA7294, for a load with a resistance of 4 Ohms, the optimal supply voltage is ±27 volts (U A). The output power at this voltage will be 70 W. This is the optimal power for the TDA7294 - the distortion level will be 0.3–0.8%. There is no point in increasing the power supply to increase power because... the level of distortion increases like an avalanche (see graph).
We calculate the required voltage of each secondary winding of the transformer:
U D = 27 ÷ 1.41 ≈ 19 V
I have a transformer with two secondary windings, with a voltage of 20 volts on each winding. Therefore, in the diagram I designated the power terminals as ± 28 V.
To obtain 70 W per channel, taking into account the efficiency of the microcircuit of 66%, we calculate the power of the transformer:
P = 70 ÷ 0.66 ≈ 106 VA
Accordingly, for two TDA7294 this is 212 VA. The nearest standard transformer, with a margin, will be 250 VA.
It is appropriate to state here that the power of the transformer is calculated for a pure sinusoidal signal; corrections are possible for a real musical sound. So, Igor Rogov claims that for a 50 W amplifier, a 60 VA transformer will be sufficient.
The high-voltage part of the power supply (before the transformer) is assembled on a 35x20 mm printed circuit board; it can also be mounted:
The low-voltage part (A0 according to the structural diagram) is assembled on a 115x45 mm printed circuit board:
All amplifier boards are available in one.
This power supply for the TDA7294 is designed for two chips. For a larger number of microcircuits, you will have to replace the diode bridge and increase the capacitor capacity, which will entail a change in the dimensions of the board.
Control unit for Mute and Stand-By modes
The TDA7294 chip has a Stand-By mode and a Mute mode. These functions are controlled through pins 9 and 10, respectively. The modes will be enabled as long as there is no voltage on these pins or it is less than +1.5 V. To “wake up” the microcircuit, it is enough to apply a voltage greater than +3.5 V to pins 9 and 10.
To simultaneously control all UMZCH boards (especially important for bridge circuits) and save radio components, there is a reason to assemble a separate control unit (A1 according to the block diagram):
Parts list for control box:
- Diode (VD1). 1N4001 or similar.
- Capacitors (C1, C2). Polar electrolytic, domestic K50-35 or imported, 47 uF 25 V.
- Resistors (R1–R4). Ordinary low-power ones.
The printed circuit board of the block has dimensions of 35×32 mm:
The control unit's task is to ensure silent switching on and off of the amplifier using the Stand-By and Mute modes.
The operating principle is as follows. When the amplifier is turned on, along with the capacitors of the power supply, capacitor C2 of the control unit is also charged. Once it is charged, Stand-By mode will turn off. It takes a little longer for capacitor C1 to charge, so Mute mode will turn off second.
When the amplifier is disconnected from the network, capacitor C1 discharges first through diode VD1 and turns on the Mute mode. Then capacitor C2 discharges and sets the Stand-By mode. The microcircuit becomes silent when the power supply capacitors have a charge of about 12 volts, so no clicks or other sounds are heard.
Amplifier based on TDA7294 according to the usual circuit
The microcircuit's connection circuit is non-inverting, the concept corresponds to the original one from the datasheet, only the component values have been changed to improve the sound characteristics.
Parts List:
- Capacitors:
- C1. Film, 0.33–1 µF.
- C2, C3. Electrolytic, 100-470 µF 50 V.
- C4, C5. Film, 0.68 µF 63 V.
- C6, C7. Electrolytic, 1000 µF 50 V.
- Resistors:
- R1. Variable dual with linear characteristic.
- R2–R4. Ordinary low-power ones.
Resistor R1 is double because stereo amplifier. Resistance of no more than 50 kOhm with a linear rather than logarithmic characteristic for smooth volume control.
Circuit R2C1 is a high-pass filter (HPF) that suppresses frequencies below 7 Hz without passing them to the amplifier input. Resistors R2 and R4 must be equal to ensure stable operation of the amplifier.
Resistors R3 and R4 organize a negative feedback circuit (NFC) and set the gain:
Ku = R4 ÷ R3 = 22 ÷ 0.68 ≈ 32 dB
According to the datasheet, the gain should be in the range of 24–40 dB. If it is less, the microcircuit will self-excite; if it is more, distortion will increase.
Capacitor C2 is involved in the OOS circuit; it is better to take one with a larger capacitance to reduce its effect on low frequencies. Capacitor C3 provides an increase in the supply voltage of the output stages of the microcircuit - “voltage boost”. Capacitors C4, C5 eliminate noise introduced by wires, and C6, C7 supplement the filter capacity of the power supply. All amplifier capacitors, except C1, must have a voltage reserve, so we take 50 V.
The amplifier's printed circuit board is single-sided, quite compact - 55x70 mm. When developing it, the goal was to separate the “ground” with a star, ensure versatility and at the same time maintain minimal dimensions. I think this is one of the smallest boards for TDA7294. This board is designed for installation of one microcircuit. For the stereo option, accordingly, you will need two boards. They can be installed side by side or one above the other like mine. I’ll tell you more about versatility a little later.
The radiator, as you can see, is indicated on one board, and the second, similar one, is attached to it from above. Photos will be a little further.
Amplifier based on TDA7294 using a bridge circuit
A bridge circuit is a pairing of two conventional amplifiers with some adjustments. This circuit solution is designed for connecting acoustics with a resistance of not 4, but 8 ohms! Acoustics are connected between the amplifier outputs.
There are only two differences from the usual scheme:
- the input capacitor C1 of the second amplifier is connected to ground;
- added feedback resistor (R5).
The printed circuit board is also a combination of amplifiers according to the usual circuit. Board size – 110×70 mm.
Universal board for TDA7294
As you have already noticed, the above boards are essentially the same. The following version of the printed circuit board fully confirms the versatility. On this board you can assemble a 2x70 W stereo amplifier (regular circuit) or a 1x120 W mono amplifier (bridged). Board size – 110×70 mm.
Note. To use this board in a bridge version, you need to install resistor R5 and install jumper S1 in a horizontal position. In the figure, these elements are shown as dotted lines.
For a conventional circuit, resistor R5 is not needed, and the jumper must be installed in a vertical position.
Assembly and adjustment
Assembling the amplifier will not pose any particular difficulties. The amplifier does not require any adjustment as such and will work immediately, provided that everything is assembled correctly and the microcircuit is not defective.
Before first use:
- Make sure the radio components are installed correctly.
- Check that the power wires are connected correctly, do not forget that on my amplifier board the ground is not centered between plus and minus, but on the edge.
- Make sure that the microcircuits are isolated from the radiator; if not, then check that the radiator is not in contact with ground.
- Apply power to each amplifier in turn, so there is a chance you won’t burn out all the TDA7294 at once.
First start:
- We do not connect the load (acoustics).
- We connect the amplifier inputs to ground (connect X1 to X2 on the amplifier board).
- We serve food. If everything is fine with the fuses in the power supply and nothing smokes, then the launch was a success.
- Using a multimeter, we check the absence of direct and alternating voltage at the output of the amplifier. A slight constant voltage is allowed, no more than ±0.05 volts.
- Turn off the power and check the chip body for heating. Be careful, the capacitors in the power supply take a long time to discharge.
- We send a sound signal through a variable resistor (R1 according to the diagram). Turn on the amplifier. The sound should appear with a slight delay, and disappear immediately when turned off; this characterizes the operation of the control unit (A1).
Conclusion
I hope this article will help you build a high-quality amplifier using the TDA7294. Finally, I present a few photos of the assembly process, do not pay attention to the quality of the board, the old PCB is unevenly etched. Based on the assembly results, some edits were made, so the boards in the .lay file are slightly different from the boards in the photographs.
The amplifier was made for a good friend, he came up with and implemented such an original housing. Photos of the assembled stereo amplifier on the TDA7294:
On a note: All printed circuit boards are collected in one file. To switch between “signatures”, click on the tabs as shown in the figure.
list of files
Sprint-Layout is a simple program for designing both single-sided and double-sided printed circuit boards, providing almost all the necessary functions for such tasks. There is an export of files to professional formats Gerber and Excellon, which are used for industrial production of circuit boards, including etching and drilling.
Sprint-Layout allows you to draw spots, paths, foil areas, inscriptions and much more. You can choose a variety of shapes and sizes of elements, and also create them yourself.
You can open the file Example.LAY in the SprintLayout directory, it contains two boards with different examples of what can be created in the program.
Download
Program sPlan - a simple and convenient tool for drawing electronic and electrical circuits, it allows you to easily transfer symbols from element libraries onto the diagram and tie them to a coordinate grid. IN sPlan there are many tools for drawing and editing, which make the development of diagrams convenient and efficient, such as auto-numbering of elements, compilation lists of elements and others.
Download
Program “Circuit Builder 2003” designed for constructing elementary electrical circuits. It is a good replacement for bulky analogues. It includes about 50 vector objects (elements) of electrical circuits with the exception of integrated circuits
Download
QuickPic SchemCreator- raster graphic sprite-oriented editor of electrical circuit diagrams and any other pictures in bmp, gif, jpg formats.
Sprites - pictures (blanks, templates, library components) in bmp, gif, jpg, ico, cur formats.
Program features:
The program interface is focused on quick and convenient creation of pictures (diagrams) from ready-made sprites;
Built-in editor for new sprites;
The number of “Undo” steps (undoing the last action) is limited only by the free space on your disk;;
Magnification mode 2, 4, 8 times;
Various units of measurement: pixels, millimeters, inches;
Measuring rulers (as in MS Word);
Preview before printing;
Saving in BMP and GIF format;
Functions for convenient manipulation of sprites and picture size;
New in the latest version 2.4x:
Saving a list of the 10 most recently used sprites for quick access to them;
Expanded capabilities for inserting text symbols of radio elements;
Radio element number auto-increment function;
Exporting a list of elements to a text file;
Selecting the color resolution of the image when saving; Now, by default, pictures are saved in a palette of 16 colors - this is quite enough for schemes, but if you really want, you can choose 256 or 16 or 2 colors.
Download
Device diagram
It makes no significant difference whether we lay out the board on a piece of paper in a checkered pattern, cutting out templates of parts with pins from cardboard (although I deeply doubt that anyone will use this method in the 21st century, when every home has a computer), or use some program for PCB layout, for example sprint layout. Of course, with the help of sprint layout it will be much easier to do this, especially in large schemes. In both cases, first we place on the working field the part with the largest number of pins; in our case it is a transistor, let’s say VT1, this is our KT315. (A link to the sprint layout user manual will be provided below). Moreover, at first, when designing, your printed circuit board may resemble a circuit diagram, that’s okay, I think everyone started out that way. We installed it, then we connect its base and emitter with tracks to resistor R1, we also have the base VT1 connected to the output of capacitor C1 and the output of resistor R2. Instead of lines on the diagram, we connect the pins of the parts with a track on the printed circuit board. I also made it a rule to count the number of pins of parts connected on the diagram and on the printed circuit board; we should get the same number of connected patches.
As you can see, we have 3 more pins connected to the base on the board, just like in the diagram; in the diagram they are marked with red rings. Next, we install transistor VT2 - this is a KT361 transistor, it has a pnp structure, but we don’t care at the moment, since it also has 3 outputs and is in a housing exactly the same as KT315. We installed the transistor, then connect its emitter to the second terminal R2, and the second terminal of capacitor C1 to the collector VT2. We connect the VT2 base to the VT1 collector, install patches on the board to connect the BA1 speaker, we connect it with one terminal to the VT2 collector, the other terminal to the VT1 emitter. Here's what everything I described looks like on the board:
We continue further, we install the LED, connect it to the BA1 pin and to the VT2 emitter. Afterwards we install transistor VT3, this is also KT315 and connect it with the collector to the cathode of the LED, we connect the emitter of VT3 to the minus of the power supply. Next, we install resistor R4 and connect it with tracks to the base and emitter of transistor VT3; we connect the output from the base to probe X1. Let's see what happened on the board:
And finally we install the last few parts. Let's install the power switch, connecting it to the power plus with a path from one patch and to the VT2 emitter, with a path from the other patch connected to the switch. We connect this switch terminal with resistor R3, and connect the second patch of the resistor to the contacts of probe X2.
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