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1Vumeter using lm324

Abstract

VU Meters are used in many applications like in discotheques to measure the level of audio signals. This level or magnitude of sound signal is termed as loudness. They are basically used to measure the loudness of sound signals or measure the noise signal. There are two ways to measure sound level of a signal.Another way is displayed the loudness or sound level of the signal using visualized display. This is usually done using consecutive LEDs to indicate the sound level.This circuit can be used to display the variation of an audio signal in a group of 8 LEDs, behaving like a VU meter. We could use an specific integrated circuit used for VU meters, but we decided to use a readily available integrated circuit: The LM324 op amp.

Dept of ECE kluniversity


INTRODUCTIONThe VU meter is calibrated in volume units that are numerically equal to the number of decibels above the reference level. The circuit is conventional To turn on the LEDs at different audio levels, the 1K ohm resistor is necessary because higher values might cause some LEDs not to function properly even if LED has very low internal resistance. The design is flexible where additional op-amps is allowed and is not limited to LM324 amplifier.To keep a low level signal input to the circuit, a resistor around 33K ohm may be utilized. The potentiometer can also be employed to adjust the sensitivity of the circuit. The negative audio is used for signal input while the positive input is connected to the main positive rail. The VU meter’s design considers the following such as scale of the instrument, dynamic characteristics, response vs frequency, sensitivity, impedance, harmonic distortion, and overload.

The VU meters were used to monitor audio power levels in recording and broadcast studios, so that the signal can be weakened or amplified to bring it within the optimal range for recording or broadcast. The meter effectively connects in parallel with the input of the receiver or amplifier. In some VCRs, they only included VU meters when it includes a manual level control which is required for recording live music rather than compressed television or radio broadcasts. In earlier times, the VU meter was used in speech research prior to the advent of computers and modern signal processing methods.



CIRCUIT DIAGRAM

List of components

IC1 = IC2: LM324 operational amplifier

D1 = D2: Red LED

D3 = D4: Yellow LED

D5 = D6 = D7 = D8: Green LED

R1 = R2 = R3 = R4 = R5 = R6 = R7 = R8: 1K, 1/4 Watt resistor

R9 = R10: 20K, 1/4 Watt resistor

R11 = R12 = R13 = R14 = R15 = R16 = R17 = R18: 330 ohms, 1/4 Watt Resistor

P1: 50K potentiometer



COMPONENTS DESCRIPTION1.LM324

The LM324 IC is derived high popular that used in many circuit diagram. Which is a package of four operational amplifiers (OP-AMP) that can be powered by a battery or other single-polarity supply(positive and negative only) over a very wide voltage range.The four op-amps are installed in a single 14-pin package.You can use only one of the op-amps or all four.The current consumption is unaffected by the power supply voltage.

The circuit was conventionally designed with eight LED audio level meter made out of two low power quad op-amps which utilizes LM324.

Volume Unit – an entity equal to a decibel for expressing the magnitude of a complex audio; it states the level of complex, nonrecurrent, and non-periodic signals such as music and speech

Decibel – a logarithmic unit of measurement that expresses the magnitude of a physical quantity of power or intensity relative to a specified or implied reference level

Op-Amp – a differential amplifier having a large voltage gain, very high input impedance and low output impedance

LM324 – has internal frequency compensated for unity gain, large DC voltage gain, wide bandwidth, wide power supply range, very low supply current drain, low input biasing current, low input offset voltage, large output voltage swing and differential input voltage range equal to the power supply voltage



2. LED’S

LEDs are simply diodes that are designed to give off light. When a diode is forward-biased so that electrons and holes are zipping back and forth across the junction, they're constantly combining and wiping one another out. Sooner or later, after an electron moves from the n-type into the p-type silicon, it will combine with a hole and disappear. That makes an atom complete and more stable and it gives off a little burst of energy (a kind of "sigh of relief") in the form of a tiny "packet" or photon of light.The output signal of an audio amplifier (which is connected to the input to the speaker), is applied to all the inverting inputs of the operational amplifiers, through resistor R1. R1 and R9 form a voltage divider to reduce the amplitude of the input signal. This signal will vary according to changes of music and make the LEDs light, according to the voltage level of the audio signal.

The non-inverting pin of operational amplifiers are connected to a voltage divider network,

composed of several resistors in series. This means that the non-inverting operational

terminals have predetermined fixed voltages. Whenever the input signal into an operational

(in the inverter pin) exceeds the voltage corresponding non-inverting pin, the output is set

low, lighting the LED. A light-emitting diode (LED) is a two-lead semiconductor light

source. It is a pn-junction diode, which emits light when activated.[4]When a

suitable voltage is applied to the leads, electrons are able to recombine with electron

holes within the device, releasing energy in the form of photons. This effect is

called electroluminescence, and the color of the light (corresponding to the energy of the

photon) is determined by the energy band gap of the semiconductor.An LED is often small in

area (less than 1 mm2) and integrated optical components may be used to shape its radiation

pattern.


http://en.wikipedia.org/wiki/Radiation_pattern

http://en.wikipedia.org/wiki/Radiation_pattern

http://en.wikipedia.org/wiki/Band_gap

http://en.wikipedia.org/wiki/Electroluminescence

http://en.wikipedia.org/wiki/Photon

http://en.wikipedia.org/wiki/Electron_holes

http://en.wikipedia.org/wiki/Electron_holes

http://en.wikipedia.org/wiki/Electrons

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Light-emitting_diode#cite_note-4

http://en.wikipedia.org/wiki/Diode

http://en.wikipedia.org/wiki/Pn-junction

http://en.wikipedia.org/wiki/Light_source

http://en.wikipedia.org/wiki/Light_source

http://en.wikipedia.org/wiki/Semiconductor


3.RESISTORS

The principal job of a resistor within an electrical or electronic circuit is to “resist” (hence the nameResistor), regulate or to set the flow of electrons (current) through them by using the type of conductive material from which they are composed. Resistors can also be connected together in various series and parallel combinations to form resistor networks which can act as voltage droppers, voltage dividers or current limiters within a circuit.

Resistors are what are called “Passive Devices“, that is they contain no source of power or amplification but only attenuate or reduce the voltage or current signal passing through them. This attenuation results in electrical energy being lost in the form of heat as the resistor resists the flow of electrons through it.

Then a potential difference is required between the two terminals of a resistor for current to flow. This potential difference balances out the energy lost. When used in DC circuits the potential difference, also known as a resistors voltage drop, is measured across the terminals as the circuit current flows through the resistor.

Most types of resistor are linear devices that produce a voltage drop across themselves when an electrical current flows through them because they obey Ohm’s Law, and different values of resistance produces different values of current or voltage. This can be very useful in Electronic circuits by controlling or reducing either the current flow or voltage produced across them we can produce a voltage-to-current and current-to-voltage converter.

There are many thousands of different Types of Resistor and are produced in a variety of forms because their particular characteristics and accuracy suit certain areas of application, such as High Stability, High Voltage, High Current etc, or are used as general purpose resistors where their characteristics are less of a problem.



4.50K POTENTIOMETER

Normally, potentiometers are wired as variable voltage dividers: connect +V to one side, connect the other side to ground, and the middle pin will output a voltage between 0 and +V However, by only connecting two pins (one outside pin and one center pin) of a potentiometer to your circuit, you can turn a pot into a variable resistor. Think about it this way: the potentiometer is filled with resistive material and turning the knob changes the amount of this material that the electrons must travel through before leaving the pot. This means that the maximum resistance of this variable resistor is the total resistance of the pot. In figure 1 the pot has a total resistance of 10kOhms, so if the pot is turned all the way to the left the resistance between the two black wires is 10kOhms. If the pot is turned all the way to the right the amount of resistive material between the two black leads drops to zero and the resistance goes to zero as well. Any position in the middle will give a resistance between 0 and 10kOhms. If I'd soldered a wire to the left lead instead of the right all of this will flip: turning all the way to the left is 0Ohms and all the way to the right is 10kOhms.


http://en.wikipedia.org/wiki/Voltage_divider


WORKING PROCEDURE

The output signal of an audio amplifier (which is connected to the input to the speaker), is

applied to all the inverting inputs of the operational amplifiers, through resistor R1. R1 and

R9 form a voltage divider to reduce the amplitude of the input signal. This signal will vary

according to changes of music and make the LEDs light, according to the voltage level of the

audio signal.The non-inverting pin of operational amplifiers are connected to a voltage

divider network, composed of several resistors in series. This means that the non-inverting

operational terminals have predetermined fixed voltages. Whenever the input signal into an

operational (in the inverter pin) exceeds the voltage corresponding non-inverting pin, the

output is set low, lighting the LED.

The principle of operation lies with the working of LM324. It basically consists of a buffer amplifier which drives a series of ten comparators. The input to the amplifier is the input analog voltage. Each comparator receives a reference voltage signal through a 1:10 potential divider arrangement and compares the input voltage with the reference voltage. Accordingly the corresponding LED connected to each comparator is driven incase the input voltage is more than the reference voltage. LM324 can be operated in dot or bar mode, wherein the former means a single LED glows at one time and the latter means LEDs glow in continuous fashion. In other words dot mode represents the instantaneous value of audio wave.



ADVANTAGES AND DISADVANTAGES

A VU meter is designed to gauge the strength of the sound. The meter was created in the 1930s, and it was originally used for sound transmissions regulation on telephone lines. The device was later adopted as conventional tool to measure and record sound in music industry. For those who have an old stereo design and assembly, it usually includes an analog VU meter. VU meters are popular with those who are interested in the best sound quality.

ADVANTAGES

1.Ability to Regulate Sound

People who use the analog VU meter understand its significance, and appreciate its advantages. First is that you will be able to determine the power of volume on your recordings, and you will be able to regulate its sound. This has already been demonstrated in the music industry. It is widely used even until now. Sounds are regulated or standardized with the help of an analog VU meter.

2.Consumes Little Power

Another advantage is that it only consumes a very small amount of power. So there is actually nothing to worry about when it comes to power consumption. Analog VU meters are also sturdy, and malfunctions due to operational conditions are rare. The usual and commonly known malfunction of the device is when its gauge needles wouldn’t move while the device is in use. The solution for this problem is actually simple. All you have to do is clean the device, and lubricate some of its mechanical parts. The device will function as expected after that. The durability of the analog VU meter has been proven by people who are still using them, and keeps them under their care.

DISADVANTAGES

1.Maintenance Required

Although analog VU meter are wonderful devices, there are also downsides when you use them. This type of device requires some maintenance every 6 months. If you fail to have the mechanical parts lubricated, there is a high chance that your VU meter will not function as it should until such time that you do perform maintenance. To address the concern you will need to purchase a lubricating fluid that is appropriate for the device. You have to take time when doing maintenance on VU meters. In some cases, owners will open the cover of the device to brush off dust particles that may hinder its optimal operating condition.

2.Rarity of Replacement Parts

In the event that the analog VU meter is broken. You may have difficulty searching for the replacement of some parts. This is especially so if you have an original vintage design that is



branded, which at times may require for original parts replacements. Furthermore, analog VU meters may require some space to have them accommodated, and most are not portable. So they may actually have mobility as one of the concerns.



APPLICATIONS

The VU meters were used to monitor audio power levels in recording and broadcast studios, so that the signal can be weakened or amplified to bring it within the optimal range for recording or broadcast.

The meter effectively connects in parallel with the input of the receiver or amplifier. In some VCRs, they only included VU meters when it includes a manual level control which is required for recording live music rather than compressed television or radio broadcasts.

In earlier times, the VU meter was used in speech research prior to the advent of computers and modern signal processing methodsSince a VU meter is a mechanical device it can never reflect the instantaneous signal peaks of complex audio signals. The designers of the VU meter therefore took a different approach. They created a meter that did NOT measure peaks but simply inferred them. A real VU meter has a very specific "ballistic characteristic". This means it responds to changing audio signals at a very precise speed, rising from no signal to 99% of "0VU" when a 1 kHz sine wave tone is applied for 300 milli-seconds.

When using a VU meter the audio system is calibrated with a sine wave tone at a "reference

level" for the system. At the reference level the VU meter will show "0" for a sine wave tone,

but the engineer must know that with music or speech the Peak levels will always be

"inferred" to be between 6dB to 10dB higher than the reference level. The genius of the VU

meter is that for most types of audio sources the system engineer can count on these peaks

being within this range and can design the audio system with confidence. Good engineering

practice is to always build in a little extra "headroom" as it's called, to cover the strange

conditions where an audio signal might exceed normal peak levels or the equipment operator

fails to adjust the levels correctly.

CONCLUSION



This project is about VU meter using LM324 which is used to drive 8 LEDs. It is a dot/bar display driver and requires a 3V-25V supply. The LEDs are driven in 3DB steps. It consists of a ten stage voltage divider such that when each stage is reached, the matching LED will be illuminated.Another way is displayed the loudness or sound level of the signal using visualized display. This is usually done using consecutive LEDs to indicate the sound level.

REFERENCES



1. http://www.hobby-hour.com/electronics/s/bfo-metal-detector.php

2. http://www.creativethinkingwith.com/Thomas-Edison.html

3.http://www.iccc.e.co.in/papers

4. www.circuitstoday.com

5. Science.howstuffworks.com

6.www.gobookee.org


http://www.circuits/

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