Sound in the car

It is known that for many motorists machine evolved into something more than just a means of transportation. After all, the person conducting the wheel for several hours a day, not only wants to listen to the local news, but good music. However, high-quality automotive interior equipping reproducing unit, few who can manage only industrial products.

In recent years in the amateur literature appeared many publications devoted to independent manufacturing automotive audio equipment, mainly amplifiers. But even a good amplifier does not solve all the problems faced by the creator of Sound Hi-Fi class for its attitude avtomobilya.Skepticheskoe many motorists to leave such systems due primarily illiterate approach to installing speakers in the cabin.Unfortunately, in most cases, they are placed in the car according to the principle "to fit", not "where it is necessary." However, an unambiguous answer to the question - "Where else do you want?" - Does not exist. None of the known solutions does not give a guaranteed result. Much easier to answer the question "where it is not necessary?". Show rasprstranennaya error - placing powerful and high heads speakers in the rear tray. Front same state that have or nothing. Is the owner of this car prefer to sit with his back to the stage?

Contrary to popular belief, most importantly in the design of the car radio is not to achieve high power, low distortion, and not even getting a good frequency response. The main problem - the creation of a wide soundstage for listeners sitting on the front seat of the car. Its solution is directly related to the installation of the front head.

Under any reasonable version of their placement inside the difference in the signal path from the left and right radiators to the listener reaches unacceptably large. To reduce this difference may be reflected to use all or part of the signal from the windshield. So there setting with outdoor acoustics front (see Fig. 1).

Embodiment of a such a solution is quite difficult and time consuming, but the result is impressive. However, to cut the floor to install the heads dare not everyone. So really to install radiators in front passenger car is not too many places: the dashboard, windshield racks, doors, vertical bar at the bottom of the passenger compartment at the front wheels of the vehicle.

The dashboard allows you to set the emitters at a sufficient height, but head size is usually limited to 10 ... 13 cm, acoustic design is virtually absent, so low frequencies are reproduced in this case efficiently enough. To further advance the sound image can be installed on radiators racks on the side edges of the windshield, but in reality there are only fit tweeter (tweeter).

Popular because of its simplicity and low-frequency coaxial installation heads in the doors usually argued increase efficiency low frequency reproduction ready acoustic design. The result obtained is the opposite desired effect. For the reduction of phonograms most modern tools engineers is situated in the center of the bass sound stage, ie Sound signals of the left and right channels in the same frequency band are in phase and have almost the same intensity. Therefore, when installing radiators in the front door of the sound waves at frequencies 100 ... 150 Hz, critical for the subjective perception of bass attack reaches the opposite head of phase (as determined by the width of the cabin) and compensated. Hence - a dull, lifeless sound that did not fix any EQ. Installation heads in kikpanelyah decreases the difference in the signal path from the left and right radiators, but the sound picture falls unacceptably low. In addition, this embodiment carry the same effect, "blanking" bass attacks, although to a lesser extent as when installing heads in the doors, and organize a decent acoustic design easy.

It follows that the best results can be achieved, the use of multi-band dispersed front speakers. Bandpass emitters should be placed in locations where they will work with maximum efficiency. According to the author the best place to install the bass radiators - in buildings under the front Cedeno with the radiation of sound forward and upward. MF emitters best place on the front panel or in the upper front corner of the door, and HF - racks on the windshield (it picks up sound pattern).

Full bass reproduction is only possible using acoustic design of considerable size, so virtually all car audio sound frequency range is limited to the main channel 100 ... 120 Hz and lower frequencies generated by the speaker as the sum signal. Because at the lowest frequencies loudspeaker has a circular radiation pattern, the choice location for a subwoofer - question komponoki system. Most often, it is placed in the trunk. The problem is that the frequency response of the cabin, which plays here the role of acoustic design, has Wake up in the very low frequencies for each individual model of the body. Therefore, to obtain a uniform frequency response of the total system must be able to adjust only the level but also the frequency response sabfufernom channel.

Sound image formed without using surround izluchatalay certainly be incomplete. Their main value - "the creation of the hall effect" by simulating the reflected sound. Spectrum Signal rear channels (Fig. 2) for this should be limited [2], and the signal can be both traditional ("left-right" channel), and the sum or difference, or a combination thereof. Power rear channel nevilika (no more than 10% of the total capacity of the system), and in some cases, for its realization will require additional amplifying devices. The simplest case - anti-series connection of the rear head between the amplifier output left and right channels through a simple filter.

On the influence of connecting cables and sound quality lately written so much that this subject can not apply here. Wire size than the power supply current consumption and the length of the wires themselves. In any case, the voltage drop in the supply of power at maksimaonoy should be no more than 0.1 ... 0.2 V

Damping parasitic resonances and sound elements salon are also important. Noise absorbing material should be applied to all available panels and plastic body parts, focusing on the panel, located near the head speakers, or those used as part of the speaker enclosure.Resonances usually disappear when the cover 25 percent or more of the area. To absorb road noise noise canceling material should cover polsalona, ​​fireproof bulkhead area and wheels.
Original article source cxem.net

Roadblock for noise

Noise music enemy number one, and to successfully deal with it, we must first understand its nature. The first cause of outsiders (and therefore undesirable) sounds obvious. This noise transmitted from outside the cabin. The second factor leading to vehicle noise, vibration occurring when the machine is moving: vibrations propagating through structural elements are emitted into the cabin noise and form.Vibration source can be the engine, transmission, suspension and trim body resonance of individual elements, mechanical shocks, etc. By the way, the speakers work often gives rise to interference resonances.

In turn, the materials that are to become an insurmountable obstacle to the noise, separated by counter methods (reflection, absorption, damping), typical application areas (doors, engine compartment, wheel arches, floor, ceiling), and its physical structure (liquid, foam, spray, solid). Therefore specialize in this area manufacturers approach the problem in a comprehensive and usually offer a list of materials, taking each his <defense sector>. Requirements for such products is very high. Besides the fact that silencers should be as effective in fulfilling its primary function is the sine qua non of their non-toxicity, resistance to high temperatures, moisture, as well as technology and ease of use.

Now on specific examples. As a practical sample products take American company Cascade Audio Engeneering (CAE), known under the brand name V-Blok. Interestingly, the products of the company in the U.S. is gaining markets in Europe. And one of the reasons for the popularity V-Blok is that all materials CAE absolutely harmless to human health, as in the Old World, as we know, environmental issues are taken very seriously. In the Russian market, the manufacturer is also not the first year and a well-deserved reputation as one of the most irreconcilable fighters for clarity. Number 1 at CAE listed noise-proof water-based paste VB-1. It is used to eliminate vibrations large area panels, curved and irregular surfaces and also for the treatment enclosure speakers. It is noteworthy that the VB-1 is versatile and extremely well to metal, plastic and wood, extinguishing the oscillations in a wide frequency range (10 Hz to 40 kHz). For maximum effect, apply two coats of a thickness not exceeding 3 mm, the treated surface does not let the noise of the entire life of the car.

In turn, VB-2 and VB-2HD (it is thicker) are polymeric adhesive materials designed for damping SAE (converting vibration energy into thermal energy) of oscillations of sheet metal and plastic. They produced pieces of different sizes and thanks to universal adhesive layer, which can withstand heat up to 200 degrees, seize virtually any surface. It should be noted that the VB-2 and VB-2HD absorb noise is twice as good mastic asphalt-based resins, while being 40% lighter and much more manufacturable.

For floor treatment from a range of car interior Cascade Audio Engeneering best club VB-3. As its structure, it consists of two layers reinforced neoprene foam, separated by a thin plate of lead. Accordingly, the bottom layer is a suspension for lead <filling> and the upper acts as insulation. As for the movable lead plate, it is an effective barrier for the noise arising from contact with the road during movement of the machine. At the same time, despite the presence of VB-3 lead layer, this material is easy to give the necessary form.

Composite material VB-4, in principle, the same as the VB-3 application areas (floor, walls salon, wheel arches), but differs from it in structure. The first line of defense heavy, soft and flexible vinyl weight. If coming from the pavement sound waves still seep through the vinyl, they are offset by a separating layer foam. At the same time prevents the penetration of the foam into the cabin heat and moisture. For processing engine compartments Cascade Audio Engeneering advises to use VB-TS. As well as the VB-3, this composite is struggling with the noise in two ways: absorption and reflection. It consists of a heat-cm layer of soundproofing foam retention noises midrange, and polyester film which is metallized chemically pure aluminum having a high reflectance. The reflective surface allows the use of VB-TS at ambient temperatures up to 205 degrees. Other advantages of this material are the presence of a filler, water repellent, and that VB-TS is stretched by 10% and provides a wide contact surface with any complicated.

Several stand out special pads Deflex Powerpads. These items are attached to the body of the car directly behind the speaker magnet head and prevent the occurrence of standing waves inside the installation volume that prevents the destruction of the diffuser and improves sound quality. Set Powerpads easy and have a lifetime warranty.

Original article source cxem.net

K574UD1 generator audio range

In the development and research of electronic equipment in the laboratory one of the most important components of the measurement equipment is a universal source of test signals. Function generator, working in a range of sound frequencies, was developed based on a microcontroller. It is based on generator circuit described in [Radiohobby, 2000, № 5, p. 79]. The analysis of this scheme it was revealed a significant disadvantage. Because the counter is formed by two functional elements, the logic levels on the address pins are not installed simultaneously, which leads to the appearance of high-frequency emissions of the generator output. Developed device devoid of these deficiencies. Generated output waveform (saw, triangle, sine, square wave) programmed in flash-memory. The generator used firmware contained in [Radiohobby, 2000, № 5, p. 79]. Schematic diagram of the function generator is shown in Fig. 1.

The main technical parameters:

Range of generated frequencies, Hz 

0 ... 30000

Flatness dB 

<0.3

The amplitude of the output voltage, V 

4

Number of steps output 

128 128

MS 4046 on a chip (DD1) assembled an oscillator, which control the frequency tuning in the range 0 ... 4 MHz. Variable resistor R1 is a multiple of the frequency control. On-chip 556IE10 (DD2) assembled address counter which outputs signals are formed ("typed address") applied to the address inputs of the PROM Winbond W27C512 (DD4). In this flash-memory chip programmed forms of output signals. With PROM outputs signals are sent to the DAC DAC0800 (DA4), from which output signal is fed to a high-speed operational amplifier K574UD1 (DA5). SB1 button is used to select the output waveform. The components of the chip 155LAZ (DD3.2, DD3.3) Assemble debounce buttons SB1. With the terminals 5 and 9, which also receives signals from the outputs of the PROM, the signal goes to the chip decoder SN74LS156N (DD7). With its removable data outputs the selected signal that displays one of the LEDs. For indicating the selected output waveform is assembled unit to the D-flip-flop circuits 155TM2 (DD6), the input of which receives impulses originating switching button. The unit is powered from the unregulated voltage source + 12, which enters the integral timer DA1 and positive voltage stabilizer DA2. Timer DA1 implemented multivibrator, the output of which removed rectangular pulses. They are rectified and is input to the negative voltage regulator DA3. The voltage from its output is used to power a generator. When setting up the device you first need to set the frequency of the selection of C1-order 4 MHz at pin 4 chips DD1, then the resistor R11 to generate sine wave mode, controlling the output of an oscilloscope, to establish the symmetry of the signal relative to the total wire. The maximum output frequency of the oscillator is determined primarily by the speed of EEPROM, which for the chip Winbond W27C512 is approximately 4 MHz, so the maximum output frequency: 4 MGts/128 stages = 30 kHz. Measured harmonic distortion of the sinusoidal signal constitute 0.0076% at 1 kHz. This generator is designed to work with a digital oscilloscope, which displays the frequency of the input signal, so additional indication output signal frequency is not provided. The devices made on microcontrollers, promising enough. For example, the proposed generator can be increased through the use of frequency oscillator with greater frequency. Also by increasing the bit of flash-memory can increase the frequency of sampling. The generator can be connected to a PC with the ability to programmatically change the shape of the output signal due to changes in firmware flash-memory. Resistor R1 - SP5-44-1 or other reusable, R9, R11 - SPZZa or other small.
Original article source cxem.net

About audio HDMI interface

In 2002, the largest consumer electronics manufacturers such as Hitachi, Philips, Sony, Toshiba and others, proposed a new interface High-Definition Multimedia Interface (HDMI). He became the first fully digital interface for transmitting uncompressed video and audio streams, while it is backward compatible with DVI, which transmits a digital video stream.

HDMI interface is constantly evolving. Today there are several versions with different numbers. The first version of HDMI 1.0 appeared in 2002.The latest HDMI 1.3 was approved in June 2006. Each version uses the same hardware specs and cable, but offers extra capacity and the types of information that can be transmitted via HDMI. For example, HDMI 1.0 supports a maximum speed of 4.9 Gbit / s, while HDMI 1.3 - has 10.2 Gb / s.

Below is a summary of the versions of HDMI.

HDMI 1.0 - 12/2002 

One cable for transmitting digital stream audio / video with maximum throughput of 4.9 Gb / s. Supports video stream up to 165 megapixels per second (1080p @ 60 Hz or UXGA) and 8-channel 192 kHz/24-bit.

HDMI 1.1 - 5/2004 

Added support for content protection DVD Audio.

HDMI 1.2 - 8/2005 

Added support for Super Audio CD; 

HDMI Type A connector for connecting a PC as a source; 

PC sources can use the "native" mode colors RGB, color mode option saved YCbCr; 

support low-voltage sources.

HDMI 1.3 - 6/2006 

Connection Bandwidth / V was increased to 10.2 Gbit / s; 

improved support for colors, including a depth of 30, 36 and 48-bit (RGB or YCbCr); 

added support for color standards xvYCC; 

added support for automatic synchronization of sound; 

added support for the Dolby TrueHD and DTS-HD (the format used in HD DVD and Blu-ray) for decoding external receivers; 

approved a new mini connector for devices such as camcorders.

HDMI 1.3b - 3/2007 

Consumer Electronics Control.

HDMI 1.4 - 5/2009 

Added support for 4K x 2K resolution (3840 × 2160 at 24/25/30 Hz and 4096 × 2160 at 24 Hz). 

The possibility of creating Fast Ethernet-connections (100 Mbit / s) (HDMI Ethernet Channel, HEC). 

Implemented technology Audio Return Channel (ARC). 

A new interface connector for miniature devices - micro-HDMI (Type D). 

3D-capable.

HDMI 1.4a - 3/2010 

Improved support for 3D-image

HDMI 1.4b - 10/2011 

Supports 1080p video at 120 Hz. 

Increased bandwidth of a single wire up to 15 Gbit / s.

HDMI 2.0-9/2013 

Added support for resolution 4K (3840 × 2160) at 50/60 Hz 

Added support for up to 32 channels of audio 

Sound frequency is increased 1536kGts for highest sound quality 

Added support for displays with 21:9 

Added dynamic synchronization of video and audio streams

The table below shows the major improvements version 1.3 compared to 1.2.

Function HDMI 1.2 HDMI 1.3

Maximum Throughput 4.95 Gb / s 10.2 Gb / s

Maximum bandwidth 165 MHz 340 MHz

Maximum resolution 1920x1080 progressive (1080p) 2560x1440 progressive (1440p)

Maximum color depth 24-bit 48-bit

The maximum number of colors 16.7 million 281 trillion.

Support for DTS and Dolby Digital 5.1 Yes Yes

Support for Dolby TrueHD and DTS-HD No Yes

The maximum sampling frequency sound (2 channels) 192 kHz 768 kHz

The maximum sampling frequency sound (from 3 to 8 channels) 96 kHz (4 threads max.) 192 kHz (8 threads max.)

Technical information

Below is a diagram interface HDMI.

Pin 1 - TMDS Data2 + 

Contact 2 - TMDS Data2 Shield 

Pin 3 - TMDS Data2- 

Track 4 - TMDS Data1 + 

Track 5 - TMDS Data1 Shield 

Track 6 - TMDS Data1- 

Pin 7 - TMDS Data0 + 

Track 8 - TMDS Data0 Shield 

Track 9 - TMDS Data0- 

Track 10 - TMDS Clock + 

Track 11 - TMDS Clock Shield 

Track 12 - TMDS Clock- 

Track 13 - CEC 

Contact 14-Reserved (NC on device) 

Contact 15 - SCL 

Track 16 - SDA 

Track 17 - DDC / CEC Ground 

Contact 18 - +5 V Power 

Track 19 - Hot Plug Detect

Legend. 

TMDS (Transition-Minimized Differential Signaling). High-speed digital technology flows used in HDMI and DVI. Uses three channels, streamed audio / video and other data, with up to 3.4 Gb / s per channel. 

CEC (Consumer Electronics Control). Allows you to send commands and control signals between the communication participants. CEC function built by manufacturer. If all communication participants will support HDMI CEC, you can, for example, to send commands from the remote control all the connected equipment. Among the teams have on / off, play, go into standby, recording and others. 

SCL (Serial Data Clock). Responsible for synchronizing data transmission. 

SDA (Serial Data Access). Transmitting data. 

DDC (Display Data Channel). Specification allows you to send the display, such as the manufacturer's name, model number, supported formats and resolution, etc.

Supported file formats

Today, it supports all major video formats, including PAL, NTSC, ATSC, and others. Video resolution up to 1440p or maybe 2560x1440 progressive format (from Blu-ray and HD-DVD, it is a maximum, 1080p). Supported color depths up to 48 bits (over 280 trillion. Colors) with a refresh rate of 120 Hz.

Supported audio formats include. 

Compressed audio. Dolby Digital, DTS, etc. 

Multi-channel sound. SACD, DVD Audio. 

Uncompressed audio (PCM). Up to 8 channels with sampling rates up to 192 kHz at 24 bits. 

Lossless quality. Newly added support for Dolby TrueHD and DTS-HD Master Audio.

Content Protection (HDCP)

HDMI Interface was built licensed digital content protection circuitry High-Bandwidth Digital Content Protection (HDCP), which was created by Intel and a few others to fight piracy. HDCP is to be present on the HD-receivers or players / recorders DVD / HD-DVD / Blu-ray, which use HDMI.

HDMI Receivers

If you follow the development of the "home theater", then you already know that today the receiver audio / video streams must have the support of HDMI. Modern receivers typically have inputs and outputs and HDMI support the following functions. 

Multi-channel audio and video. HDMI-receiver allows you to connect a HDMI-cable source of the audio / video (HD-disc player or HD cable HDTV) to its input, and the second HDMI-cable - HDTV-TV to its output. The receiver will transmit the digital video signal from the player HD-diskov/pristavki cable HDTV to HDTV-TV and multi-channel sound via an amplifier to pass and send to the connected speakers. If the audio / video receiver does not support HDMI, then you have to use a separate cable (digital optical or coaxial) to transmit sound from a player / set-top box to the input of the receiver. Difference in quality between HDMI and a separate digital audio cable for no, but why suffer in another cable system?

In principle, the advantages of such a configuration, when you use the player with the release of HDMI, not too large. But as we add more HDMI-components advantages become more significant. Namely ... 

Switching HDMI. Most HDMI-equipped receivers two or three inputs HDMI, allowing you to connect multiple sources HDMI-audio/video him. A display HDTV-connects to HDMI-receiver with just one cable. You can switch on the receiver video source that is more convenient than peretykat HDMI-cable TV, or via HD-source. This feature will become increasingly important as they appear in your home appliances with support for HDMI.

Analog-to-digital conversion and video deinterlacing. Early versions of the HDMI-receiver stores the digital and analog signals in the form in which they were received, which required not only digital, but the analog connection HDTV-TV to the receiver. But many modern receivers HDMI-learned how to transform incoming analog audio / video signals (for example, via the composite input or S-Video) into digital form, allowing any transfer of TV streams over a single cable HDMI. Besides analog-to-digital conversion, many receivers, also provide video deinterlacing (with the 480i to 480p). Also a very useful feature since many older HDTV-TVs do not support 480i signals via input HDMI. Some modern receivers can convert the signals into formats 480i 720p, 1080i or 1080p, which helps to improve the picture quality from older video sources to your new HDTV-TVs.

Compatible HD-DVD/Blu-Ray

A very important feature of the HDMI interface is that HD-DVD players and Blu-ray will transmit a picture in full 1080p resolution only via HDMI.Such a move is a result of industry efforts to protect against piracy. Unlike other audio / video interface, HDMI to transmit at full resolution requires mandatory protection HDCP. If you use any other interface, for example, component video, the video signal is artificially deteriorated to DVD quality, or even worse.

Increased bandwidth of HDMI 1.3 can be very useful useful new technologies, which are used HD-DVD/Blu-ray. This could include increased color depth, which allows output of up to 69 billion colors (depth 30-36 bits). HDMI 1.2 can transfer image with only 16.7 million colors (24 bit depth). In addition, HDMI 1.3 supports audio formats next-generation Dolby TrueHD and DTS HD Master Audio, which use lossless compression to the number of channels to eight (96 kHz, 24-bit, up to 18 Mbit / s). All receivers without HDMI 1.3 support can play the movie with the "old" sound formats DTS and Dolby Digital.

All new features sooner or later improve the home theater enjoyment, but there is an area in which the situation with HDMI is still not very clear.We mean video recording. Data passes through uncompressed HDMI and HDCP main function is to protect the uncompressed data copy. So write information via HDMI until you get. Let's see how this problem is solved in the future.

Conclusion

In the area of ​​home theater is the time for change. Already the war between video formats 1080p standards HD-DVD and Blu-Ray, and also appeared confusion in the minds of consumers regarding the new interface for transferring digital video and audio HDMI. Especially because the HDMI specification continues to evolve.

A new version of HDMI 1.3 makes much to think about. And, perhaps, take into account the purchase of audio / video equipment. HDMI-receivers appeared on the market recently, but in a few years they have made significant progress in its capabilities. HDMI 1.3 is a major step forward compared with HDMI 1.2, so if possible, always buy hardware that supports it version 1.3. Especially that drives HD-DVD and Blu-Ray will use the advanced features HDMI 1.3. However, receivers supporting HDMI 1.3 can not be on the market until mid-2007. And who knows what price they will be sold. On the other hand, many interesting features HDMI, for example, switching and HDMI video conversion, already available on today's HDMI-receivers.

HDTV-TVs also switch to standard HDMI 1.3, and, as expected, already in the beginning of 2007 models. New televisions should use such advantages HDMI 1.3, as improved color depth, as well as solve many "problem youth" HDMI (with audio sync problems, support for Consumer Electronics Control, etc.). The result will be as follows. Before buying carefully check the capabilities of each component. Try to compare them with the current requirements, as well as possible, and with the future.
Original article source cxem.net

Stereo balance indicator

Imagine the scheme stereo balance indicator. It has 3 LEDs showing the predominance of right or left channel, or they are the same level.

Through a chain consisting of C1, VD1, R1 left and C2, VD2, R2 for the right channel signal supplied to the operational amplifier IC1 is enabled by the differential amplifier circuit. The output of IC1 is supplied to a signal noninverting inputs of IC2 and IC3. Will prevail if the right channel outputs IC2 and IC3 will have a high level and lights LD3. Otherwise would prevail if left channel outputs IC2 and IC3 will be low and lights LD1. If the signal levels are the same, the outputs of IC2 and IC3 will have a correspondingly high and low levels, and turns LD2. IC1, IC2, IC3 can apply the type LM358 or 741. Electrolytic capacitors for voltage 16V. LEDs any thin, preferably of different colors. Supply voltage 15-30V.

The whole setup is reduced to install IC2 and IC3 balance by adjusting the R8 and R9.

Original article source cxem.net

Audio level indicator on the LM324

Chip LM324 is a precision operational amplifier and contains four independent channels. She

works in a wide range of supply voltages from 3 to 30 volts. The output current of each channel does not exceed 10 mA. On the chip can construct a set number of interesting devices. 

Scheme is relatively simple indicator of the audio signal, built on a chip LM324. Because the chip contains 4 outputs, the number of LEDs for the analyzer will also be four, one for each channel. The amplifier output is connected to the input indicator LEDs will light up depending on the frequency of play, at low input frequencies LEDs will flash column. The result is a very beautiful light and music effects.

For best effect, you can use two chips, then it will be able to use 8 LEDs, we consider both options.

Installation will not work if the input is connected to the line output from the computer sound card or headphone output does not work!

During these experiments, it became clear that the chip can be adapted to the two modes of operation, the first of which is already listed above - flashing LEDs individually, besides flashing corresponds to the input frequency range, the stronger low frequency, the higher the LED lights pole.

The second mode - joint flashing. In this mode, all the LEDs light up together. In this case, the output of the power amplifier and connect the negative input of the indicator.

In the first scheme, the construction of the variant of the indicator on a single chip. The effect is not very entertaining, but I advise you to start to collect that way, and then if everything is working properly, and you can connect a second chip.

In the video clip demonstrated the operation of a single chip, the LEDs are working together, then there is a circuit connected to the second embodiment.

Indicator is able to work together with any power amplifier, regardless of the supply voltage of the amplifier power, only do not raise the maximum allowable stress indicator, which is 30 volts.

In those cases where you need to combine the light with an amplifier that runs on dual supply, you need to use a voltage of 12 to 24 volts.LEDs fit literally any colors to your taste, you can apply one color LEDs, you decide.

Variant of the indicator on two chips:

To display operated in the "column", you need to connect the output of the amplifier plus the power supply indicator and an input razhim this can only be used when the power amplifier and the indicator powered from a variety of sources, otherwise there is a danger of burn VLF output stage!

Original article sourse cxem.net

Equalizer LEDs Design

LED design is somewhat more complicated. Of course, by using a special control circuit can be simplified to the limit, but there lurked a little trouble. Most of these chips produces the output current up to 10 mA, and the brightness of the LEDs under the car may not be enough. In addition, the most common chip in yields on 5 LEDs, and it is only "minimum program". Therefore, for our conditions diagram on discrete elements is preferable, it can be extended without much effort.

The simplest LED display (Fig. 4) does not contain active elements and thus does not need power. Connection - to the unit under the scheme "mixed mono" or split capacitor, an amplifier - "mixed mono" or directly.

Fig. 4

The scheme is very simple and does not require the establishment. The only procedure - selection of R7. On the face value of the scheme to work with built-in amplifiers head unit. When working with power amplifier 40 ... 50 W resistance of this resistor should be 270 ... 470 ohms.Diodes VD1 ... VD7 - any silicon with forward voltage drop of 0.7 ... 1 and permissible current of at least 300 mA.

Any LEDs, but the same type and color glow with operating current 10 ... 15 mA. Since LEDs are "fed" by the amplifier output stage, their number and increase the operating current in this circuit is impossible. So we have to choose the "bright" LED indicator or find a place where it will be protected from direct light. Another disadvantage of the simplest design - small dynamic range.

To improve the work required indicator to the control circuit. In addition to greater freedom in the choice of the LEDs can be simple means to generate any type of scale - from linear to logarithmic, or "stretch" the only one site. Indicator diagram with a logarithmic scale is shown in Fig.5. The dotted line shows the optional items.

Fig. 5

LEDs in this scheme the control keys on the transistors VT1 ... VT5. Thresholds options specify diodes VD3 ... VD9. Picking up their number, you can change the dynamic range and scale type. Overall sensitivity of the indicator is determined at the input resistors. The figure shows the approximate thresholds for the two variants of the scheme - with single and "twin" diodes. The basic version of the measuring range - up to 30 watts into 4 ohms, with single diodes - up to 18 watts.

HL1 LED lights continuously, it means the beginning of the scale, HL6 - overload indicator. Delay capacitor C4 0.3 ... 0.5 seconds extinction LED that allows even notice briefly overloaded. Storage capacitor C3 determines the return stroke. It is, by the way, depends on the number of LEDs glowing - "column" of the maximum begins to subside quickly, and then "brakes". Capacitors C1, C2 at the input only when working with integrated amplifier recorder. When dealing with a "normal" amplifier exclude them. Number of input signals can be increased by adding a chain of resistors and a diode. The number of cells can be increased simply indicating "cloning", a major limitation - the "threshold" diodes should be no more than 10 and between the bases of adjacent transistors must be at least one diode.

LEDs can be any, depending on requirements - from single LED to LED assemblies and panels, high-brightness. Therefore, the diagram shows the current-limiting resistors ratings for different operating currents. The remaining details of any special requirements are not established, transistors can be used almost any structure with npn collector power dissipation of 150 mW at least twice and reserve current collector. Transfer coefficient of the base current of these transistors must be at least 50, but better - more than 100.

This scheme can be simplified somewhat, with the side effect of new properties appear, very useful for our purposes (Fig. 6).

Fig. 6

Unlike previous schemes, where transistor cell were connected in parallel, series connection is used here "column". Threshold elements are transistors and open themselves, they in turn - "bottom up." But in this case depends on the threshold voltage. The figure shows the approximate indicator thresholds at a supply voltage 11 V (the left edge of the rectangle) and 15 (right border). It is seen that with increasing voltage is shifted most border indicating the maximum power. In the case of the amplifier, the power of which depends on the voltage of the battery (and there are many), this "auto-calibration" can benefit.

However, the fee is - increased load transistors. Through the lower scheme transistor current flows all the LEDs, so the use of indicators with a current 10 mA transistors also require appropriate power. "Cloning" cell further increases the scale unevenness. Therefore, 6-7 cells - is the limit. Assignment of the remaining elements and their requirements - are the same as in the previous scheme.

Slightly modernized this scheme, we obtain other properties (Fig. 7). In this scheme, unlike previously discussed, there is a glowing "ruler". At any time, only one LED lights, simulating the movement of arrows on a scale. Therefore, the power consumption is minimal and in this scheme can be applied low-power transistors. The rest of the scheme does not differ from those discussed previously.

Threshold diodes VD1 ... VD6 designed to safely disconnect idle LEDs, so if there will be a weak illumination superfluous segments, you must use diodes with a large forward voltage connected in series or two diodes. "Cloning" cells reduces the brightness of the upper segments of the scheme, to address this instead of resistor R9 need to enter the current generator. And we agreed - not to complicate.Therefore, in this case, an 8-cell - is the maximum.

Original article sourse cxem.net