Audio amplifier circuit using IC LM386

                                                  Audio Amplifier using IC LM386

Amplifiers are used to boost the strength of the input signal and give an amplified version of the signal in the output. Audio amplifiers are widely used in Stereo or Home theater systems, Mini speakers etc. There are numerous ways to build a Audio amplifier but nothing is efficient as building using a dedicated Audio amplifier IC. The above circuit diagram shows the connections and components used to build a Audio amplifier.

IC LM386:

                                                       Pin diagram of LM386

LM386 is a simple low power audio amplifier used in most of the Audio circuits for its less power consumption. This IC is capable of giving a output gain of about 200 when external components are used along with it. But when you use it without adding external components its capable of delivering amplification of 20. 

The pin 1 & 8 are meant for altering the gain level by tying up a capacitor or RC pair in between them. Audio input was fed through the Non inverting input pin while inverting input tied to the ground usually. 

WORKING OF CIRCUIT:

The IC is initially powered by means of Vcc, Resistor R1 and Capacitor C2 was used to prevent oscillations in the circuit. The Resistors R2 and Capacitor C3 plays a major role in this above circuit as it alters the output gain obtained in the output. Adding a single capacitor of 10uF will help us to obtain max gain. While using along with resistor will help you obtain a gain of about 50db. The positive terminal of C3 should be connected to pin 1 and negative to pin 8 of the IC LM386.

Capacitor C3 was used to couple the output to the speaker and POT can also be used to tailor the gain of the obtained output signal. The increase gain is only used when a very low input signal is to be amplified. You can feed any Audio signals to this circuit and this works just fine to do its purpose.

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#Murugan

what is RS232 Communication??

        RS232 is Based on serial communication which means it can send or receive one bit at a time RS232 is a Standard (1987) to make a communication sophisticated RS232 connect a peripheral devices like printer,scanner,modem and mouse with computer RS232 can provide p2p communication some time called point to point-communication the speed of RS232 is not too much fast we can achieve a maximum speed of 920 Kbps during a data communication by using RS232.

           we can connect a peripheral device with computer at a maximum distance of 50 ft RS232 styles is different it,s shape is just like D so people called it a D style so it comes in two shape the one is D9 ( total 9 pins connector ) and second one is D25 ( total 25 pins connector ) but mostly three pins are using such as Tx,RX,CT

1) TXD ( Pin NO 3 ) : The function of this pin is to send or transmit data serially to a connected devices with computer

2) RXD ( Pin NO 2 ) : The function of this pin is to Receive a data serially from connected devices with computer

3) CTS&RTS ( Pin NO 7,8 ) : Clear to send and Ready to send Just to check that the channel is busy or free for the communication

4) DSR ( Pin NO 6 ) : it,s stand for Data set ready it works with device like modem to tell to computer that now i m ready to take a new data

5) DTR ( Pin NO 4 ) : The function of 

this pin is to connect or disconnect a peripheral device from computer

6) DCD: ( Pin NO 1 ) : To check that Devices is disconnected or still connected with the pc

7) RI: ( Pin NO 9 ) : it,s stand for Ring indicator the function of this pin is to inform the computer that modem is ringing 

8) SG: ( Pin NO 5 ) : it,s stand for Signal ground in a simple words a reference point of the circuitry 

How to set up your own Electronics Lab at home

Every Electronic hobbyists have a dream of setting up his own lab at home to learn, explore, widen the knowledge and of course have fun with Electronics. But most of us don't how to start setting up one and even if we did it will end up in a complete mess. So after going through several forums and asking the suggestions of pros i have prepared this article on setting up your own lab, i hope this will be helpful for all budding Electronic Engineers and Hobbyist.

WORKSPACE:

This is the first thing you need to set for your homemade lab. The workspace should consist a large wooden work bench, desk or table that fits the components and tools while you are working. Ensure that work area is well lit and comfortable to work even for long time. Your work area should be accessible to household electrical power (220V AC)

Also install a Desktop or Laptop computer in your work area which will be helpful to refer datasheets of components or IC's. Also it will come handy when you are working with Microcontrollers and makes your work a lot easier.

POWER SUPPLIES:

This comes next in the list as Power supplies hold the next priority in your Electronics Lab. When coming to power supplies you have lot of options to consider but it all depends on how much you are about to invest. Bench power supply is usually preferred but it was insanely expensive and you have to spend 40% of your budget in it.

As i said you do have options, so its best to buy some DC power supply adapters which suits your need such as 12v, 5v or 9v. You can also construct power supply for your needs, it takes bit of work but believe me it will come handy.

IMPORTANT THINGS TO BUY:

• Needle Nose Pliers
• Wire Strippers
• Tweezers
• Screwdrivers
• Knife
• Drill
• Connecting Wires
• Breadboard
• Gator Clips
• Helping Hands
• Solder Iron/Gun
• Solder
• Flux
• Multimeter
• Protoboards

These are the things which are very essential and should be in your lab if you wanna be a better worker. And many would have noticed i missed "Oscilloscope" in the above list. A decent Oscilloscope will cost around $50 and am not sure that how many of you would like to spend that much for your lab. Usage of Oscilloscope might suit certain applications but always remember Oscilloscope is not the first thing to buy.

COMPONENTS TO BUY:

When coming to the components there is not much help others can do as you need to identify your needs. The usage of components varies based on the things you are working in your lab. Here are some of the basic components you must have in your lab.

• Resistors ( 100,330,470,1k,10k,100k,1M)
• Capacitors ( 0.1uF, 22pF, 100uF, 1000uF)
• NPN & NPN Transistors (2N222,2N3906)
• Diodes (1N4001,1N4148)
• Voltage Regulators (7805,7812)
• IC's ( 555,4017)
• LED (red, Blue, white)
• Male and Female Header
• Battery
• Push Buttons

The above list is to provide a general idea about the components to buy for your lab. Also do not forget to analyze your needs and buy the components which fit your need.

IF YOU ARE WORKING WITH MICROCONTROLLERS:

You need to spend some extra bucks if you are the one who loves to play with the Microcontrollers. A Development board is the best choice for all the programmers who wants to learn and have fun with the Controllers. There are number of Development boards in the market for 8051, PIC ,AVR or ARM Controllers.

• Arduino
• Raspberry Pi
• Easy PIC
• 
  

FINAL WORDS:

I Hope the above lists and suggestions would have given you a clear idea about setting up your lab. Setting up a perfect lab at the beginning itself is quite a difficult task, so don't get disheartened keep on expanding your lab by experimenting and adding many stuffs to it. Undoubtedly you will learn a hell lot of things and   gradually it will make you a pro.

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regards,

 Murugan

I2C Protocol

Introduction

Usually embedded systems are complex design which include multiple peripherals interconnected like LED, LCD, RTC, other microcontroller, Memory card, etc with main computer or master to expand its capabilities. All these peripheral’s interfacing is done by standard rules which is called protocol. Protocol is a set of rules that defines how communication between systems and devices are done which include bit ordering, bit pattern meanings, creating data frames, error checking, etc. UART, SPI, I2C, USB and Ethernet are some of the protocols widely used in embedded systems for serial data communication. Here we are bound to I2C Protocol.

                 The Inter-integrated Circuit (I2C) Protocol was originally developed in 1982 by Philips(now known as NXP) used to connect multiple devices with only two wire. Its is also called two wire interface protocol.

Why I2C Protocol ?

Comparing I2C with UART

In UART, separate clock line is not used with data transmission so both device should agree on same Baud-rate. If differences occur between Baud-rate on either end will cause garbled data while in I2C separate clock line is used.

• UART uses hardware overheads like start bit, stop bit, partiy bit or CRC bit in each frame of transmission which will lead to increase in transmission time while I2C use only acknowledgement bit(ACK) or no acknowledgement bit.
• Another drawback of UART is that they are suited to communications between two, and only two, devices while I2C can used with multiple devices and different modes like multi-master or single master, etc.
• Data transfer speed is also an issue for UART, they are limited to some extent and maximum baud-rate is around 230400 bps.

Comparing I2C with SPI

• The first drawback of SPI is pin used to connect multiple devices. If we connect two device with SPI standard it will use four pins MISO, MOSI, SCK, CS.
• In SPI protocol, there is only single master but it can support arbitrary number of slaves. While in I2C, multiple master can be possible.
• If we compare data transmission speed of SPI and I2C, then SPI will win definitely. SPI support speed upto 10MHz (10 Mbps).

What’s good in I2C ?

• I2C requires only two line(two wire), but those two wires can support up to 1008 slave devices.
• Unlike SPI, I2C can support a multi-master system, allowing more than one master to communicate with all devices on the bus (although the master devices can’t talk to each other over the bus and must take turns using the bus lines).
• Data rates of I2C devices can communicate at the rate of 100kHz to 400kHz.

How I2C Protocol Works ?

To understand the working of I2C Protocol, Let we take some practical examples

Single Byte Transfer

                                                                 Single Byte Transaction

• Idle condition: As you can see in above figure, at the initial condition SDA and SCL both High because of both line pulled High with pull-up resister.
• Start condition: Data transfer is start when SDA line pulled down mean High to Low when SCL line is High.
• Bit Detect: Slave can understand bit reception when it receives single bit ‘1’ or ‘0’ when SCL line is High. 
• Data allowed to change: Transition of bit from 1 to 0 or 0 to 1 is only allowed when SCL line is Low as seen in pick.
• ACK Bit: Transmitter must release the SDA line after transmitting 8 bit to allow the Receiver to pull SDA line Low to acknowledgement the previous 8 bit data reception.
• Stop condition: is only understood when SDA line goes Low to High while SCL line is High.

Note: In I2C Protocol Byte is transmitted MSB to LSB. And in multi-Byte transmission, every 8 bits has a 9th bit that is an acknowledge.

Write/Read Two Byte  from Master to Slave

Start Condition

Every communication in I2C Protocol is begin with start condition which we already studied above how start condition form. This alerts all slave devices that a transmission is about to start.

Address Frame Byte

The address frame byte include device address which is of 7-bit long and Read(1)/Write(0) bit.  The address frame byte is always sent first when any new communication sequence initiate.

ACK/NACK Bit

The 9th bit of the frame is the NACK/ACK bit(here NA or A). This is the case for all frames (data or address). Once the first 8 bits of the frame are sent, the receiving device is given control over SDA. If the receiving device does not pull the SDA line low before the 9th clock pulse, it can be inferred that the receiving device either did not receive the data or some error occur. 

Data Bytes

After the address frame byte has been sent, data bytes can begin being transmitted. The master will simply continue generating clock pulses at a regular interval, and the data will be placed on SDA by either the master or the slave, depending on whether the R/W bit indicated a read or write operation. The number of data byte is arbitrary, and most slave devices will auto-increment the internal register, meaning that subsequent reads or writes will come from the next register in line.

Stop condition

Every communication in I2C Protocol is end with stop condition which we already studied above. During normal data writing operation, the value on SDA should not change when SCL is high, to avoid false stop conditions.

Speed of I2C Protocol

Common I²C bus speeds are the 100 kbit/s standard mode and the 10 kbit/s low-speed mode, but arbitrarily low clock frequencies are also allowed. Recent revisions of I²C can run at faster speeds typically 400 kbit/s Fast mode, 1 Mbit/s Fast mode plus or Fm+, and 3.4 Mbit/s High Speed mode.

More About I2C Protocol

10-bit Addressing suppor

ts more number of devices

In order to increase device address capability, 10-bit addressing scheme is introduced to I2C Protocol by which we can connect more number of devices by using I2C Protocol.

In a 10-bit addressing system, two frames are required to transmit the slave address. The first frame will consist of the code 11110xyz, where ‘x’ is the MSB of the slave address, y is  8th bit of the slave address, and z is the Read/Write bit as seen above. The first frame’s ACK bit will be asserted by all slaves which match the first two bits of the address. As with a normal 7-bit transfer, another transfer begins immediately, and this transfer contains bit 0 to bit 7 of the address. At this point, the addressed slave should respond with an ACK bit. If it doesn’t, the failure mode is the same as a 7-bit system. 

Clock stretching

• In an I2C communication the master device determines the clock speed. However, there are situations where an I2C slave is not able to co-operate with the clock speed given by the master and needs to slow down a little. This is done by a mechanism referred to as clock stretching.
• An I2C slave is stretching the clock by pull down the SCL if it needs to reduce the bus speed. The master on the other hand is required to read back the clock signal after releasing it to high state and wait until the line has actually gone high.

Repeated Start Conditions

• When we communicate through I2C bus, its obvious in most cases that first you need to send command and then you get response from slave, so each time you dont need to terminate communication by stop condition. You can use start condition reapetedly without terminating previous transaction. The I2C protocol defines a so-called repeated start condition.
• For example, After having sent the address byte (address and read/write bit) the master may send any number of bytes followed by a stop condition. Instead of sending the stop condition it is also allowed to send another start condition again followed by an address (and of course including a read/write bit) and more data. This is defined recursively allowing any number of start conditions to be sent.
• The purpose of this is to allow combined write/read operations to one or more devices without releasing the bus and thus with the guarantee that the operation is not interrupted.

Choosing between M.Tech or Job after completing Engineering(B.E)

Don't get confused between JOB and studies, " Studies is to learn and job is to earn ". Once you fall behind money you may not be truly interested in learning. Its true that you can gain practical experience in job, but it depends on the type of company you are joining.

 Knowledge of B.E engineers v/s Knowledge of M.Tech engineers :

My senior had to say this in comparison of B.E engineers v/s M.Tech Engineers,

" In my experience i have seen that, Graduate Engineers can make things work but they are not able to reason it how its working and why it didn't before. And, Masters can theoretically prove why the thing is not working, but they cant fix it".

Starting career in a MNC (More Money, Less Knowledge) :

If you join an MNC you may be working on some patch of hardware or software which is already developed by some senior guys. You may hardly get to touch the real thing. First one to two years, you will be doing more documenting work that designing and developing. MNC's follow strict designing guidelines and protocols where in you are hardly allowed to make mistakes. If you want to make money from start of your career then join an MNC. 

Joining a startup (Less Money, More Knowledge) : 

If you really want to learn doing a job then join a startup product development company, you will get huge exposure to everything that's going on in the company. You will go across everything, starting from hardware design to software development, testing, problems faced during the product development. And you will be doing everything here, if you develop the software, you are going to test it and if there are any issues , you are the one responsible to fix it. The initial growth and salary will be slow in a start-up but once you have acquired the knowledge here, there will be no limits to your growth. 

My Suggestion : 

I personally suggest that you go for higher studies if there is no burden of responsibilities on you. If you have to support your family you may have to do a job. Don't Worry, You will get to learn in both places.

These are totally my personal opinions based on my experience.

Frequently Asked Questions in Electronics

1.Why is the letter I used to represent current?

                The letter I seems to be an odd choice for the English language, but it was chosen in the early days of electricity to represent intensity of current which we simply call current today. The unit of current, the ampere, is named after the French scientist André-Marie Ampère in recognition of his work on the relationship between electric current and magnetism. Ampère referred to electric current as "l'intensité du courant électrique", so I was a logical choice to represent intensité (intensity). I am grateful to Barry Caruth for suggesting a search of the internet for "Ampère" and "l'intensité du courant électrique" which returns many sites as evidence (most of them French) enabling me to answer this question with confidence. 

2.What is a "short circuit"?

A "short circuit" is a connection of very low resistance such as a wire (almost 0) which provides a very easy path for current. Think of it as an electrical short-cut. It is normally used to describe a fault or accidental connection rather than a deliberate one. 
For example: if the leads from a battery touch one another they create a very low resistance connection across the battery, so we say they have caused a short circuit across the battery. Current will flow through this short circuit rather than through the proper circuit. This stops the circuit working and it may cause a fire because the leads and battery will become hot with a large current flowing. 

3.What does "open circuit" mean?

"Open circuit" means no connection. It is usually used to describe a break in some part of a circuit which could be deliberate (such as a switch in the open or off position) or a fault (such as a broken wire or burnt out component). 

4.My project has a resistor labelled 47, does that mean 47k?

No, it means 47 which is a much smaller resistance. 47k would be shortened to 47k (or 47K). The ohm () symbol is often omitted from circuit diagrams and component layouts but the k (meaning kilo = 1000) will always be included if it is needed. 

5.A project on another website lists a 10kW resistor! What does it mean?

It almost certainly means a 10k resistor. This is a common error which occurs when the web page specifies a Greek font. If this font is not available on your computer you see the character in your standard font and it happens to be W which is the symbol for watt, the unit of power. I avoid the problem on this website by using a small image for . In a few projects a low value resistor with a high power rating is required but the power will be something smaller like 5W, never 10kW which is more powerful than an electric heater! 

6.Where can I buy heatproof cable to replace the ordinary cable on my soldering iron?

Silicone heat resistant cable is sold in 1.5 metre lengths for exactly this purpose by Rapid Electronics, part number 85-0590 (look in the Soldering Equipment section). If you use another supplier make sure you buy 3-core mains flex with a current rating of 3A (the proper name for mains appliance leads is flex, not cable). Please note that to change over to the new flex you will need to borrow a second soldering iron! This is because the flex is soldered to the iron's element. Make sure that you connect the wires correctly in the iron and in the mains plug which should have a 3A fuse. 

7.My soldering iron was supplied with a hook, do I really need to buy a stand as well?

For safety you must buy (or make) a stand for your soldering iron. Please don't use the hook because it leaves exposed the very hot element and tip of the iron - it is too easy to accidentally touch them and burn yourself. If you can't afford to buy a stand you could try making your own with a spiral of stiff galvanised iron wire (a coat-hanger?) screwed to a block of wood. Ideally the stand should include a damp sponge for safely wiping the tip of the iron when it needs cleaning. 

8. What component has a black stripe in the centre (it looks like a diode)?

A small component about the size of a resistor or signal diode with a single black stripe in the centre is a zero-ohm resistor, it is really just a wire link. These components are used on commercial PCBs because they are easier for machines to handle than small pieces of wire. The single black stripe is logical because it means zero in the resistor colour code. Ordinary resistors have at least four stripes. Diodes have a single stripe near one end, not in the centre. 

9.How do I choose a relay to use with one of our projects?

The 555 timer IC used in many projects can supply current up to 200mA so it can power most relays directly. However, you must connect a signal diode (a 1N4148 for example) in parallel across the relay coil to protect the 555. Note that this diode is connected 'backwards' so that it will normally not conduct.

10.I want to use a large number of LEDs, do I need a resistor for each one?

No, you can usually connect a few LEDs of the same type in series and just use one resistor. The number of LEDs you can connect in series depends on the circuit's supply voltage. This arrangement has the advantage of reducing the total current required by the circuit. 

If you wish to have several LEDs on at the same time it may be possible to connect them in series. This prolongs battery life by lighting several LEDs with the same current as just one LED.

All the LEDs connected in series pass the same current so it is best if they are all the same type. The power supply must have sufficient voltage to provide about 2V for each LED (4V for blue and white) plus at least another 2V for the resistor. To work out a value for the resistor you must add up all the LED voltages and use this for V_L.

Example calculations: 

A red, a yellow and a green LED in series need a supply voltage of at least 3 × 2V + 2V = 8V, so a 9V battery would be ideal. 

V_L = 2V + 2V + 2V = 6V (the three LED voltages added up). 

If the supply voltage V_S is 9V and the current I must be 15mA = 0.015A, 

Resistor R = (V_S - V_L) / I = (9 - 6) / 0.015 = 3 / 0.015 = 200, 

so choose R = 220 (the nearest standard value which is greater).

11.What is a Darlington pair?

A Darlington pair is two transistors connected together so that the current amplified by the first is further amplified by the second transistor, giving a very high gain of 10000 or so. 

12.What does 'sinking a current' mean?

It means current is flowing into the output of an IC. This happens when the output is low (0V) if there is a device connected between the positive supply (+Vs) and the output. It is the opposite of sourcing a current which means current is flowing out of the output. Most IC outputs can both sink and source current. 

13.Are 'time period' and 'time constant' the same thing?

No, they have different meanings although both are time. Time period is the duration of a single pulse or the time for one cycle of a repeating electrical signal. Time constant is a property of a changing system, such as a capacitor charging and discharging. 

14.What does 'SMD' mean?

'SMD' means Surface Mount Device. SMDs are components with small pads instead of leads for their contacts. They are designed for soldering by machine onto specially designed PCBs and are not suitable for educational or hobby circuits constructed on breadboard or stripboard. Do not buy SMD components for your projects.

15.I'm interested in electronics, where should I start?

I suggest that you start with a few simple projects, learning how to solder and how to identify the common components. You will need some tools to construct the projects. It is best to buy kits to be sure you have the correct parts.

Many people then want to start learning how the circuits work and maybe try designing their own, usually by adapting a published circuit. You can read through the study section of this website. At this stage it is worth buying a breadboard for trying out circuits without soldering so that changes can be easily made and the parts re-used. The 555 timer circuits are great for simple projects.