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TABLE OF CONTENTS

Introduction 2

Objective 2

Block Diagram 2

Chemical Etching 2

Schematics 3

PCB Top Layout 4PCB Back Layout 4

Components List 5

Components Working 6Applications 9Trouble Shooting 10

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Introduction:

The LM386 IC is a low voltage audio power amplifier with a default voltage gain of 20, which can however be increased to any value between 20 and 200 by simply placing an external series RC circuit between pins 1 and 8.So pin 1 and 8 are gain controlling pins. In the amplifier circuit, the output AC power is clearly larger than the input AC power reflecting the voltage, and thus power, gain. The increase in AC power in going from the input terminals of the amplifier to the output terminals are provided by the DC voltage source biasing the circuit. In the case of the LM386 IC, the operating DC power source must have a voltage between 4V and 12V and supply a current of 100 mA. So I provide it a power supply of 9 volt and 220 mA. These values of DC voltage and current are readily provided by a battery so that an audio amplifier based on the LM386 IC is very much amenable to battery operation.

Objective:

The purpose of the present experiment is to introduce the audio amplifiers using the popular audio amplifier integrated circuit (IC) LM386 and then measuring the amplifier performance, including its gain. How we control the gain and remove the noises by using LM386.

Block Diagram:

Chemical Etching:

There are two methods of making PCB

By CNC Machine By Chemical Etching

The CNC Machine of NU_FAST University is out of order so I made PCB by Chemical Etching.

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The Method of Chemical Etching is given below.

Take a print of PCB layout and paste it on PCB board with Iron. After 5 minutes remove the print of PCB layout then the traces will be combining on the Board. Put some quantity of Ferret Chloride in a plastic box then mix it into water. Then put the board into the mixture of Ferret Chloride. After 5 hours all the copper remove except traces because Ferret Chloride does not react with Black carbon.

Now made holes in PCB board and put the components with the help of soldering wire and iron.

Schematic:

PCB Top Layout:

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PCB Bottom Layout:

COMPONENTS LIST:

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S.NO. COMPONENT VALUE/MODEL QTY. PRICE1 Low Voltage Audio power IC LM386 12 Voltage regulator IC LM7809 13 Transformer 12-0-12 1 704 Speaker 8 ohm 1 705 Bridge rectifier IC KBL406G 1 156 Variable Resistor 10k , 5K 2 307 Capacitors 10uF/25V 4 5 x 48 Capacitor 100uF 1 29 Capacitor 2200uF/35V 1 1010 Non-polar Capacitor 1uF 1 1011 Non-polar Capacitor 100nF 1 212 Non-polar Capacitor 1nF 1 213 Non-polar Capacitor 47nF 1 214 Diode 1N4001 1 215 Resistor 1.2k 1 116 Resistor 10 ohm 1 117 Resistor 470 ohm 1 118 Wire --- 1 2019 Switch --- 1 1520 Audio Jack Male Connector Stereo 2 4021 Audio Jack Female Connector Stereo 2 4022 PCB Board --- 1 2023 Heat sink --- 1 524 Jumper Wires --- --- 1025 Soldering Wire --- 1 8026 Soldering iron --- 1 15027 Casing Material --- --- 10028 Battery 9V 1 20

Components Working:

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LM386 IC:

The LM386 is a power amplifier IC designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.So pin 1 and 8 are gain controlling pins.  I give input to pin no 3(positive) so out is non-inverting. If I give input to pin no 2 the output will be out of phase.

LM7809 IC:

Voltage regulator gives constant voltage. In this project I used LM7809 IC which gives constant 9v. So I obtained 9V DC signal at output of Voltage Regulator IC.

Bridge Rectifier IC:

Bridge rectifier converts AC signal into DC signal. So this rectifier took 24v from transformer and converted it into full wave pulsating DC signal.

Transformer:

In this project center tapped transformer is used. I do not use the center ground wire I used only (+12,-12). Step down transformer decreased the given voltage. It converts 220v into

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24v. Remember that it does not convert AC signal to DC signal. It only gives 24v AC signal to Bridge Rectifier.

Speaker:

It is used to hear the sound of audio signal. It is of 8 ohm and 3 watt.

Battery

It is used to give 9v DC voltage.

Variable Resistor:

It is used to give variable resistance to input signal. By increasing or decreasing the resistance by variable resistor we can control the amount of input signal. In this circuit we control input signal in such a way that output signal controlled automatically. I also used it as a gain controller

Capacitors:

It stores the charges. It also uses as a filter and reduces the ripple of DC. In Amplifier it is also used to reduce the noises of sounds.

Diode:

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It is used in the circuit for safety purpose. It is reverse biased in circuit. If we even connected the circuit in opposite direction it saves the others component from destroying.

Switch:

It is used to ON/OFF the amplifier. In this amplifier is used SPDT switch. SPDT stands for single pole double through. In mid state the amplifier is OFF when I push the botton on left side the amplifier beagan to work with DC battry and when I push the button on right side it will began to work with DC power supply.

Audio Jack Male Connector:

Audio jack male connector is used to give or receive the input or output signal.

Audio Jack Female Connector:

Audio jack Female connector is used to give or receive the input or output signal.

PCB Board:

It is used to made traces for components. We connect the components with the help of traces on this board. Its surface is made of copper. So by chemical etching only traces left on PCB.

Heat Sink:

It is used to cool down the IC. It takes heat from ICS and leave it in environment. In this way ICS become safe from damaging due to heat.

Jumper Wires:

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Jumper wires are used to connect the PCB to those Components which are placed in casing such as transformer, switch, speaker and LEDs.

Soldering Wire:

It is used to join the Pins of components on PCB with the help of soldering wire.

Soldering Iron:

It is used to join the pins of components on PCB with the help of soldering wire.

Casing:

To make a suitable casing for PCB of amplifier is much difficult. I worked very hard to make it. It was much difficult to place the external components for example variable resistor and button etc. in the casing. I made casing with wood material.

Applications:

The use of this amplifier is given below

It is used as Computer speakers. It is used as Mobile speakers. It is used in radio. Portable consumer products (toys, games, etc. Used as a AM/FM amplifiers Used as a Dc power supply of 9 v.

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Trouble Shooting:

First of all I made Circut on Bread Board and check the working of amplifier. Some of noises produced in the sound. I remove this noise by putting a capacitor and resistor between pin 1 and 8. When my circuit began to work completely then I put my circuit on PCB board after making PCB layout and Chemical Etching. In the end I complete my project it was not working. I was so worried and began to trouble shot the circuit. Finally I found the error of the circuit , the 1 uF capacitor was short interlay because of giving lot of heat during soldering.

When I was checking my project I face a 220V shock from the input wires of transformer. One of my cousins immediately switches off the AC voltage.