Sound dial indicator. Radio constructor - LED indicator of low-frequency signal level Do-it-yourself LED audio frequency indicator
- 08.10.2014
2N3819 Domestic analogue of OU 741 K140UD7, 2N3819 analogue of KP307B This amplifier provides a constant level of the output signal even with a significant change in the input signal. The op-amp is used as a direct current amplifier whose gain depends on the ratio R2/R1 and the voltage divider on R4 and the resistance of the field-effect transistor. The transistor plays the role of a resistor in this circuit, its resistance...
- 20.09.2014
Classification of magnetic materials Magnetic materials are most widely used in electrical engineering; without them, electrical machines, transformers, and electrical measuring instruments are currently unthinkable. Depending on the application, magnetic materials are subject to different, sometimes contradictory, requirements. Based on their application, magnetic materials are classified into two large groups: soft magnetic and hard magnetic. Let us briefly consider their characteristics. ...
- 20.09.2019
The alarm clock consists of an Arduino Nano (Uno) board, a 1602 LCD indicator with an I2C module based on the PCF8574 chip, and a DS3231 real-time clock module (ZS-042). The LCD 1602 displays hours and minutes in large numbers and seconds in regular numbers. There is only one alarm clock, it allows you to set the alarm time in minutes...
- 05.10.2014
Dynamic range - 25...150Hz, the author used a 75GDN-3 low-frequency head. Body fig. 1.2. made of chipboard 20mm thick. The walls of the housing are connected to each other with 20*20mm slats using glue and screws. An acoustic panel with holes for the woofer head is mounted inside the speaker cabinet. The rear wall of the case is removable, on it woofers are installed...
When making my amplifier, I firmly decided to make an 8-10 cell LED output power indicator for each channel (4 channels). There are plenty of schemes of such indicators, you just need to choose according to your parameters. At the moment, the choice of chips on which you can assemble an ULF output power indicator is very large, for example: KA2283, LB1412, LM3915, etc. What could be simpler than buying such a chip and assembling an indicator circuit) At one time I took a slightly different route...
Preface
To make output power indicators for my ULF, I chose a transistor circuit. You may ask: why not on microcircuits? - I will try to explain the pros and cons.
One of the advantages is that by assembling on transistors, you can debug the indicator circuit with maximum flexibility to the parameters you need, set the desired display range and smoothness of response as you like, the number of indication cells - at least a hundred, as long as you have enough patience to adjust them.
You can also use any supply voltage (within reason), it is very difficult to burn such a circuit, and if one cell malfunctions, you can quickly fix everything. Of the minuses, I would like to note that you will have to spend a lot of time adjusting this circuit to your tastes. Whether to do it on a microcircuit or transistors is up to you, based on your capabilities and needs.
We assemble output power indicators using the most common and cheap KT315 transistors. I think every radio amateur has come across these miniature colored radio components at least once in his life; many have them lying around in packs of several hundred and idle.
Rice. 1. Transistors KT315, KT361
The scale of my ULF will be logarithmic, based on the fact that the maximum output power will be about 100 Watts. If you make a linear one, then at 5 Watts nothing will even glow, or you will have to make a scale of 100 cells. For powerful ULFs, it is necessary that there be a logarithmic relationship between the output power of the amplifier and the number of luminous cells.
Schematic diagram
The circuit is outrageously simple and consists of identical cells, each of which is configured to indicate the desired voltage level at the ULF output. Here is a diagram for 5 display cells:
Rice. 2. Circuit diagram of the ULF output power indicator using KT315 transistors and LEDs
Above is a circuit for 5 display cells; by cloning the cells you can get a circuit for 10 cells, which is exactly what I assembled for my ULF:
Rice. 3. Diagram of the ULF output power indicator for 10 cells (click to enlarge)
The ratings of the parts in this circuit are designed for a supply voltage of about 12 Volts, not counting the Rx resistors - which need to be selected.
I’ll tell you how the circuit works, everything is very simple: the signal from the output of the low-frequency amplifier goes to the resistor Rin, after which we cut off a half-wave with diode D6 and then apply a constant voltage to the input of each cell. The indication cell is a threshold key device that lights up the LED when a certain level at the input is reached.
Capacitor C1 is needed so that, even with a very large signal amplitude, the smooth switching off of the cells is maintained, and capacitor C2 delays the lighting of the last LED for a certain fraction of a second to show that the maximum signal level - peak - has been reached. The first LED indicates the beginning of the scale and is therefore constantly lit.
Parts and installation
Now about the radio components: select capacitors C1 and C2 to your liking, I took each 22 μF at 63 V (I don’t recommend taking it for a lower voltage for ULF with an output of 100 Watt), the resistors are all MLT-0.25 or 0.125. All transistors are KT315, preferably with the letter B. LEDs are any that you can get.
Rice. 4. Printed circuit board for ULF output power indicator for 10 cells (click to enlarge)
Rice. 5. Location of components on the printed circuit board of the ULF output power indicator
I didn’t mark all the components on the printed circuit board because the cells are identical and you can figure out what to solder and where without much effort.
As a result of my labors, four miniature scarves were obtained:
Rice. 6. Ready-made 4 indication channels for ULF with a power of 100 Watts per channel.
Settings
First, let's adjust the brightness of the LEDs. We determine what resistor resistance we need to achieve the desired brightness of the LEDs. We connect a 1-6 kOhm variable resistor in series to the LED and supply this power chain with the voltage from which the entire circuit will be powered, for me - 12V.
We twist the variable and achieve a confident and beautiful glow. We turn off everything and measure the resistance of the variable with a tester, here are the values for R19, R2, R4, R6, R8... This method is experimental, you can also look in the reference book for the maximum forward current of the LED and calculate the resistance using Ohm's law.
The longest and most important stage of setup is setting the indication thresholds for each cell! We will configure each cell by selecting the Rx resistance for it. Since I will have 4 such circuits of 10 cells each, we will first debug this circuit for one channel, and it will be very easy to configure others based on it, using the latter as a standard.
Instead of Rx in the first cell, we put a variable resistor of 68-33k in place and connect the structure to an amplifier (preferably to some stationary, factory one with its own scale), apply voltage to the circuit and turn on the music so that it can be heard, but at a low volume. Using a variable resistor, we achieve a beautiful wink of the LED, after that we turn off the power to the circuit and measure the resistance of the variable, solder a constant resistor Rx into the first cell instead.
Now we go to the last cell and do the same thing only by driving the amplifier to the maximum limit.
Attention!!! If you have very “friendly” neighbors, then you can not use speaker systems, but get by with a 4-8 Ohm resistor connected instead of the speaker system, although the pleasure of setting it up will not be the same))
Using a variable resistor, we achieve a confident glow of the LED in the last cell. All other cells, except the first and last (we have already configured them), you configure as you like, by eye, while marking the power value for each cell on the amplifier indicator. Setting up and calibrating the scale is up to you)
Having debugged the circuit for one channel (10 cells) and soldered the second one, you will also have to select resistors, since each transistor has its own gain. But you don’t need any amplifier anymore and the neighbors will get a small timeout - we simply solder the inputs of two circuits and supply voltage there, for example from a power supply, and select the Rx resistances to achieve symmetry in the glow of the indicator cells.
Conclusion
That's all I wanted to tell you about making ULF output power indicators using LEDs and cheap KT315 transistors. Write your opinions and notes in the comments...
UPD: Yuri Glushnev sent his printed circuit board in SprintLayout format - Download.
Hello. The holidays are over and you can start working again. Probably many have already seen our photos of the LED level indicator - bollards on smart LEDs WS2812B. I decided to tell you more about the columns. Moreover, my colleagues look at me with a blank look: it’s a cool thing, but few people know about it. We need to fix it.
I thought about where to start and decided that from the very beginning. Level indicator, or as it is also called VU -meter, we've been wanting to get one with LEDs for a long time. It can be successfully used as decoration, for example, built into amplifiers, placed next to audio equipment or a computer monitor. We didn’t find any ready-made solutions that we liked, so we had to make our own VU meter.
The first development looked like this:
This level indicator was made by my colleague Konstantin M. and given to me for revival. Two channels of 16 single-color LEDs each were controlled by an ATmega8 microcontroller via two 8-bit shift registers. For economy and convenience, dynamic indication was used: only 16 LEDs of one column could light up at the same time. I launched the scarf, everything worked on it, but for some reason I could not make the change in the level of the columns beautiful.
Soon after this, the development of a level indicator more interesting than the previous one appeared:
Konstantin I made it, first of all, for myself. I launched it on some holidays, but took it apart without showing any results. Of course, I then took the boards to try it myself. As a prototype, only one channel of the level indicator was manufactured. The column itself consists of 32 RGB LEDs in the form of a module. It is connected to another module with 4 shift registers, through which control is carried out. Hmmm... Due to the dynamic display, the control is very unique. Four 8-bit registers control the selection of LEDs that should light up at a given time, and three pins set the color (R, G or B). All that remains is to add a board with a microcontroller and go ahead. Here we managed to go further than in the previous version of the columns. First I tried to do everything using Arduino Due:
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A microcontroller operating at 84 MHz with Arm architecture inside was just right, I thought. The column itself supported 8 gradations of brightness for each LED color (R, G and B). Only one color could be lit at a time, so it was necessary to transmit one of 24 combinations of values to the LEDs every 1 ms. In addition, it was necessary to work with the ADC, perform decimal logarithm calculations and other calculations. Except in the Arduino environment I haven’t had a chance to work with this microcontroller, so it turned out to be unoptimized Arduino -code. But even despite this,coped well.
Why are we writing a program for some little-known Arm controller? We thought about it and took a debug board on the STM8S105C6T6 microcontroller:
Everything started without problems. This time the code was transparent and therefore optimized. There were several modes of operation of the column, but the algorithms were not fully developed, and, nevertheless, we already liked the level indicator. Just what to do with this armful of wires, who needs it, and who wants to connect it? Need to come up with something...
We had a solution, but this time we didn’t get around to implementing it. Because one day - it was an ordinary Thursday - the following happened: another of my, no less valuable, colleagues Denis V. uttered his catchphrase:"Look what a cool thing I found"! It was a strip of smart LEDs WS2812B:
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It needs only 3 wires to connect (signal, 5 V power and common wire). Cool, goodbye to an armful of extra wires - we thought and ordered a tape for testing:
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A lot has been said about this WS2812B LED strip on the Internet - you can always find something interesting and suitable. Mostly people make various “lights” out of it. It turns out beautifully - of course, consumption"white-hot"LED is 40 mA. If the tape is long, you cannot connect it to the computer’s USB port. A sufficiently powerful power source is required - a problem that had to be solved. Despite this complexity, I was attracted by the convenience of controlling the posts using one wire. Why not make a level indicator constructor from this tape so that you can change color schemes, switch modes... And the Arduino Pro Mini board on the ATmega328 microcontroller will help with this. It is easy to program using a UART-USB adapter. There was another difficulty: very short timings between data loading."Lights" , of course, people succeeded... But while sending data, we still wanted to have time to take values from the ADC, read from memory, save, perform calculations... Therefore, while the tape was on the way, we considered the possibility of using hardware SPI, or rather a signal MOSI for organizing transmission with interruptions. Will the controller keep up with everything? Or we'll have to optimize the code, get creative somehow, get into assembly language - this had to be found out. But we already knew for sure and from the last implementation of the column we approved: the number of LEDs per channel will be 32 pieces. In total, it was necessary to process 64 smart fireflies for two columns. Looking ahead, I want to say that the WS2812B have been mastered. I will still suffer with the software part, I’ll tell you about the hardware - there will be a continuation.
P.S. Another development of columns has appeared. The same solution that was postponed for a while due to the discovery of WS2812B, but, thanks to it, was modernized and simplified. It will allow you to use any conventional LEDs (single-color and RGB) and more powerful lighting: even spotlights. Moreover, the bars are a small part of what can emerge from our idea. More about this some other time.
P.P.S. The following post will show a diagram of how to connect an audio signal line to a level meter. And those who are interested and can’t wait to see what kind of columns we got can watch this video:
Best regards, Nikita O.
Many sound-reproducing devices, whether tape recorders or amplifiers of the end of the last century, were equipped with a dial indicator on the front panel. Its hand moved to the beat of the music, and although it had no practical meaning, it looked very beautiful. Modern equipment, in which compactness and high functionality come first, no longer has such luxury as a dial indicator for sound. However, it is now quite possible to find a pointer head, which means that such an indicator can be easily assembled with your own hands.
Scheme
Its basis is the Soviet K157DA1 microcircuit, a two-channel full-wave average signal rectifier. The supply voltage of the circuit lies in a wide voltage range, from 12 to 16 volts, because the circuit contains a 9 volt stabilizer (VR1 in the diagram). If you use a stabilizer in a metal case TO-220, then the voltage can be supplied up to 30 volts. Trimmer resistors R1 and R2 regulate the signal level at the input of the microcircuit. The circuit is not critical to the ratings of the components used. You can experiment with the capacitances of capacitors C9, C10, which affect the smooth movement of the needle, as well as with resistors R7 and R8, which set the return time of the needle. In L and In R in the diagram are connected to a sound source, which can be any device with a linear output - be it a computer, player or telephone.(downloads: 265)
Circuit assembly
The indicator board is manufactured using the LUT method on a piece of textolite measuring 30 x 50 mm. Just in case, the microcircuit should be installed in the socket, then it can be replaced at any time. After etching, the board must be tinned, then it will look beautiful from the side of the tracks, and the copper itself will not oxidize. First of all, small parts are sealed - resistors, ceramic capacitors, and only then electrolytic capacitors, trimming resistors, and a microcircuit. Lastly, all connecting wires are soldered. The board contains two channels at once and involves the use of two arrow heads - for the right and left channel, however, you can use one arrow head, then the input and output contacts for the other channel on the board can simply be left empty, as I did. After installing all the parts on the board, be sure to wash off all remaining flux and check adjacent tracks for short circuits. To connect the board to the signal source, it is most convenient to use a 3.5 jack plug. In this case, if the length of the wires from the board is large (more than 15 cm), a shielded wire should be used.
arrow head
Finding Soviet pointer heads on sale now is not difficult; there are many types of them, different shapes and sizes. I used a small M42008 pointer head, it doesn't take up much space and looks nice. Any head with a total deflection current of 10-100 microamps is suitable for this circuit. To complete the picture, you can also replace the native scale, calibrated in microamps, with a special sound scale, calibrated in decibels. However, you need to connect the pointer head to the circuit not directly, but through a trimming resistor with a nominal value of 1-2 megaohms. Its middle contact is connected to any of the outer ones and connected to the board, and the remaining contact is connected directly to the head, as can be seen in the photo below.
Setting up the indicator
When the board is assembled, the pointer head is connected, you can begin testing. First of all, by applying power to the board, check the voltage at pin 11 of the microcircuit, there should be 9 volts. If the supply voltage is normal, you can apply a signal from a sound source to the board input. Then, using resistors R1 and R2 on the board and a trimming resistor at the pointer head, achieve the required sensitivity so that the pointer does not go off scale, but is approximately in the middle of the scale. This completes the basic setting, the arrow will move smoothly to the beat of the music. If you want to achieve sharper arrow behavior, you can install resistors with a resistance of 330-500 Ohms parallel to the arrow heads. Such an indicator will look great in the housing of a homemade amplifier, or as a stand-alone device, especially if you illuminate the indicator with a pair of LEDs. Happy building!An LED signal level indicator simulating a dial indicator is not a new idea, and it would seem that what new can be invented here? Well, in this regard, I did not invent anything.. I even find it difficult to indicate the original source. The goal is different: to make a simple circuit using available elements. The circuit doesn't even include the ubiquitous microcontrollers. Moreover, it’s not easy to solder the board, but to make a complete structure that can be installed in an amplifier without damaging the appearance. And also, based on this circuit, make your own version of the indicator, taking into account your skills in electronics, or, for example, color music. For this purpose, the indicator is made on two boards: an LED control board and an indication board. In this article, I propose 3 indicator options, let’s call them “arrow”, “6E1P lamp” and “arc”. There are also 2 scale illumination options to choose from (A and B). And all this can be done on 5mm, 3mm or SMD 0805 LEDs. Like any other, this circuit has its advantages and disadvantages. Advantage: cheap element base, with high interchangeability, tolerances, relatively simple circuit. Display options, as they say, for every taste. Disadvantages: selection of many elements, otherwise you would have to stick to one type of LEDs. Small dynamic range, i.e. on a powerful amplifier at low volume the indicator will be “silent”. Visual bifurcation of the “arrow”, which is caused by smooth switching of the LM3915 comparators in the “dot” mode. Elimination of this phenomenon is possible, but requires complication of the circuit. High density and thin thickness of tracks on the board. The solution is to buy ready-made boards, but I did it myself using photoresist.
The scheme works as follows. The input signal is supplied to VT1. The input signal level is controlled by R1. After amplification and rectification, the input signal is fed to the input of LM3915. LEDs (1 line) are directly connected to the MS outputs. Through transistor switches on VT2-VT11 there are additional 6 lines of LEDs. Transistor switches are used because The thermal resistance of the MS package is 55 °C/W, which allows a maximum power of 1365 mW at an ambient temperature of 25 °C. However, we won’t delve into the boring world of numbers, I’ll just say that no more than 2 LEDs can be connected to each output of the LM3915. Otherwise the MS will overheat. The S1 button switches between the “column” and “dot” display modes. Button S2 turns on additional lines of LEDs, which makes it possible to implement 2 more operating modes of the indicator. As can be seen from the diagram, many elements (R and C) need to be selected. This can be attributed to the scheme's disadvantage and advantage. The selection allows you to use any LEDs without being tied to Vsupply. 12V and adjust the brightness of the indicator LEDs and backlight to your taste. R6 ensures that the “arrow” glows at “zero” in the absence of an input signal. As a rule, selecting R6 is not required when powering the circuit with 12V. If the “arrow” at “zero” is not needed, then we do not install R6. By selecting R7, we set the required brightness of the LEDs connected directly to LM3915 according to the scheme HL7, 14, 21, 26, 35, 42, 49, 56, 63, 70. The smaller R7, the greater the current through the LEDs, the minimum permissible value of R7 is 20 kOhm . Resistor R8 adjusts the brightness of the backlight LEDs. R8 power is at least 1W. Using resistors R9-R18 we adjust the brightness of the remaining LEDs. Approximately 10 kOhm for LEDs with a luminous intensity of 1000 mcd, 1 kOhm for LEDs with a luminous intensity of 200-300 mcd. Capacitor C3 can be used to regulate the inertia of the “arrow”. The device is powered from a stabilized voltage source of 12V with a current of 0.2-0.3A for the mono version. The supply voltage can be increased to 18V.
External design and differences between indicator options. External design is described in the video report. I will add that when selecting the current of the LEDs, you need to achieve a balanced glow of the indicator and backlight. Then the indicator will look beautiful. The illumination of option “A” looks more beautiful than “B”, but is more difficult to manufacture. Find the stencil for the indicator in the LAY file with the board. There is no need to “mirror” boards and stencils when printing. Mount the indicator in the amplifier in any convenient way, behind the front panel window. Do not place near very hot elements. You can slightly tint the front panel glass to hide possible minor defects in the external design. The indicator input is connected in parallel to the output of the volume control or the input of the final amplifier. The setting consists of setting the tuning resistor R1 of the “arrow” of the indicator to +3db at the rated power of the amplifier.
Please note that the sizes of the indicator boards are different and the size of the board is significantly larger than the working window of the indicator. On the “Arc” indicator, the number of yellow and red LEDs used is 26 pcs. for stereo option. This is not reflected in the diagram, but assembly and adjustment are no different. Also, the backlight in various versions uses from 3 to 10 LEDs (see LAY). This is also not reflected in the diagram to avoid confusion.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| U1 | LED driver | LM3915 | 1 | To notepad | ||
| VT1 | Bipolar transistor | KT315A | 1 | To notepad | ||
| VT2-VT11 | Bipolar transistor | KT361B | 10 | Any PNP | To notepad | |
| VD1, VD2 | Diode | KD522A | 2 | 1N4148, any pulse | To notepad | |
| HL1-HL6 | Light-emitting diode | DFL-3014BD-1 | 6 | blue | To notepad | |
| HL7-HL62 | Light-emitting diode | DFL-3014GD-1 | 56 | green | To notepad | |
| HL63-69 | Light-emitting diode | DFL-3014YD-1 | 7 | yellow | To notepad | |
| HL70-HL76 | Light-emitting diode | DFL-3014RD-1 | 7 | red | To notepad | |
| C1-C3 | Capacitor | 1 µF | 3 | To notepad | ||
| R1 | Trimmer resistor | 50 kOhm | 1 | To notepad | ||
| R2 | Resistor | 220 kOhm | 1 | To notepad | ||
| R3 | Resistor | 3 kOhm | 1 | To notepad | ||
| R4 | Resistor | 10 kOhm | 1 |
