9 Circuits typo

After I launched my new eBook 9 Circuits, Warren made me aware of a typo.

In project 5, The Blinking LED, I wrote that the IC has 16 pins.

But it has only 14.

The error was also in the circuit diagram, and that made it confusing.

Anyway, I’ve updated the eBook to correct it.

If you’ve already bought the book, you can download the updated version by using the link from your order email.

If you haven’t bought it, but are interested, then learn all about it here: http://ift.tt/2rkHzJS

For each project in the book, you’ll find a resource page.

Use this if you get stuck, if you find a typo, or if there’s something you don’t understand.

I hope there’s no more confusing typo’s like that, but let me know if there is and I’ll update the book again.

Keep On Soldering!
Oyvind

Copyright Build Electronic Circuits

Magnetoelectric memory cell increases energy efficiency for data storage

Researchers have now developed a magnetoelectric random access memory (MELRAM) cell that has the potential to increase power efficiency, and thereby decrease heat waste, by orders of magnitude for read operations at room temperature. The research could aid production of devices such as instant-on laptops, close-to-zero-consumption flash drives, and data storage centers that require much less air conditioning.

New method of characterizing graphene

Scientists have developed a new method of characterizing graphene's properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials.

Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible

The first graphene-based camera has now been developed. It is capable of imaging visible and infrared light at the same time. The camera will be useful for many applications such as night vision, food inspection, fire control, vision under extreme weather conditions, among others.

A new spin on electronics: Study discovers a 'miracle material' for field of spintronics

A new class of 'miracle materials' has been discovered by a team of researchers who say that these organic-inorganic hybrid perovskites could be a game changer for future spintronic devices.

Printed, flexible and rechargeable battery can power wearable sensors

Nanoengineers have developed the first printed battery that is flexible, stretchable and rechargeable. The zinc batteries could be used to power everything from wearable sensors to solar cells and other kinds of electronics.

Magnetic switch turns strange quantum property on and off

A research team has developed the first switch that turns on and off a quantum behavior called the Berry phase. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices.

One-dimensional crystals for low-temperature thermoelectric cooling

Researchers studied the thermal and electrical properties of one-dimensional crystals composed of tantalum, silicon and tellurium for thermoelectric cooling at temperatures below 250 K (-23°C). The thermoelectric characteristics of these crystals were varied at temperatures ranging from the cryogenic level of 50 K up to room temperature by doping with molybdenum and antimony. The crystals' thermoelectric power factors greatly exceeded those of conventional materials around room temperature, indicating their suitability for low-temperature applications.

Scientists borrow from electronics to build circuits in living cells

Synthetic biology researchers have demonstrated a new method for digital information processing in living cells, analogous to the logic gates used in electric circuits. The circuits are the largest ever published to date in eurkaryotic cells and a key step in harnessing the potential of cells as living computers that can respond to disease, efficiently produce biofuels or develop plant-based chemicals.

Global Positioning System (GPS)

Global Positioning System or GPS is a Global Navigation Satellite System (GNSS) that provides positioning, navigation, and timing system (PNT). It was developed by the United States’ Department of Defense (U.S. DoD) in the early 1970s.

There are other Satellite based Navigation systems like Russia’s GLONASS, Europe’s Galileo and China’s BeiDou, but United States’ Global Positioning System (GPS) and Russian Global Navigation Satellite System (GLONASS) are the only fully functional Satellite based Navigation system with 32 satellite constellation and 27 satellite constellation respectively.

Before the development of GPS Technology, the main aid for navigation (in sea, land or water) are maps and compass. With the introduction of GPS, the navigation and location positioning became very easy with a position accuracy of two meters or less.

History of GPS

Before the development of GPS, ground based navigation systems like LORAN (Long Range Navigation) by the U.S. and Decca Navigator System by the U.K. are the main technologies for navigation. Both these techniques are based on Radio Waves and the ranges were limited to few hundreds of kilometers.

In the early 1960s, three of United States Government Organizations namely National Aeronautics and Space Administration (NASA), Department of Defense (DoD) and Department of Transportation (DoT) along with several other organizations started developing a satellite based navigation system with the aim of providing high accuracy, weather independent operation and global coverage.

This program evolved in to Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR Global Positioning System). This system was first developed as a military system to fulfil the needs of United States Military.
The U.S. Military used NAVSTAR for navigation as well as weapon system targeting and missile guiding systems. The possibility of enemies using this navigation system against the United States is the main reason why civilians were not given access to it.

The first NAVSTAR satellite was launched in 1978 and by 1994 a full constellation of 24 satellites were placed in the orbit and thus making it completely operational.

In 1996, the U.S. Government recognised the importance of GPS to civilians and declared a dual use system, allowing access to both military and civilians.

GPS Structure Overview

The fundamental technique of the satellite based navigation system Global Positioning System (GPS) is to measure the distances between the receiver and a few satellites that are simultaneously observed.

The positions of these satellites are already known and hence by measuring the distance between four of these satellites and the receiver, the three coordinates of the GPS receiver’s position i.e. latitude, longitude and altitude can be established. Since the change in position of the receiver can be determined very accurately, the velocity of the receiver can also be determined.

GPS Segments

The structure of this complex Global Positioning System is divided into three major segments: The Space Segment, The Control Segment and The User Segment. In this, the control segment and the space segment are developed, operated and maintained by the United States Air Force. The following image shows the three segments of the GPS system.

Space Segment

The Space Segment (SS) of the GPS consists of a constellation of 24 satellites that are orbiting around Earth in approximately circular orbits. The satellites are placed in six orbital planes with each orbital plane consisting of four satellites. The inclination of the orbital planes and the positioning of the satellites is arranged in a particular ways such that a minimum of six satellites are always in line of sight from any location on Earth.

Coming to the arrangement of the constellation in the space, the GPS Satellites are placed in the Medium Earth Orbit (MEO) at an altitude of approximately 20,000 KM. To increase the redundancy and improve accuracy, the total number of GPS Satellites in the constellation have been increased to 32, out of which 31 satellites are operational.

Control Segment

The Control Segment (CS) of the GPS consists of a network of worldwide monitoring and control and tracking stations. The primary task of the control segment is to track the position of the GPS Satellites and maintain them in proper orbits with the help maneuvering commands.

Additionally, the control system also determine and maintain the on board system integrity, atmospheric conditions, data from atomic clocks and other parameters.

The GPS Control Segment is again divided into four subsystems: a New Master Control Station (NMCS), an Alternate Master Control Station (AMCS), four Ground Antennas (GAs) and a worldwide network of Monitor Stations (MSs).

The central control node for the GPS Satellite Constellation is the Master Control Station (MSC). It is located at Schriever Air Force Base, Colorado and operates 24×7.

The main responsibilities of the Master Control Station are: Satellite maintenance, Payload monitoring, synchronizing atomic clocks, Satellite maneuvering, managing GPS Signal performance, uploading Navigation Message data, detecting GPS Signaling failures and responding to those failures.

There are several Monitor Stations (MS) but six of them are important. They are located at Hawaii, Colorado Springs, Ascension Island, Diego Garcia, Kwajalein and Cape Canaveral. These Monitor Stations continuously track the position of the satellites and the data is sent to Master Control Station for further analysis.

In order to transmit data to satellites, there are four Ground Antennas (GA) located as Ascension Island, Cape Canaveral, Diego Garcia and Kwajalein. These antennas are used to uplink data to satellites and the data can be anything like Clock correction, Telemetry Commands and Navigation Messages.

User Segment

The User Segment of the GPS system consists of end user of the technology like civilians and military for navigation, precise or standard positioning and timing. Generally, in order to access the GPS services, the user has to be equipped with GPS Receivers like Stand – alone GPS Modules, Mobile Phones that are GPS enabled and dedicated GPS Consoles.

With these GPS Receivers, civil users can know standard position, accurate time and speed while the military uses them for precise positioning, missile guidance, navigation, etc.

Working Principle of GPS

With the help of GPS Receivers, we can calculate the position of an object anywhere on Earth either in two – dimensional or three – dimensional space. For this, GPS receivers use a Mathematical method called Trilateration, a method using which the position of an object can be determined by measuring the distance between the object and few other object with already known positions.

So, in case of GPS Receivers, in order to find out the location of the receiver, the receiver module has to know the following two things:

• Location of the Satellites in the space and

• Distance between the Satellites and the GPS Receiver

Determining the Location of the Satellites

In order to determine the location of the satellites, the GPS Receivers makes use of two types of data transmitted by the GPS Satellites: the Almanac Data and the Ephemeris Data.

The GPS Satellites continuously transmit its approximate position. This data is called the Almanac data, which is periodically updated as the satellite moves in the orbit. This data is received by the GPS Receiver and stored in its memory. With the help of Almanac data, the GPS Receiver can be able to determine the orbits of the satellites and also where the satellites are supposed to be.

The conditions in the space cannot be predicted and there is a huge chance that the satellites might deviate from their actual path. The Master Control Station (MCS) along with the dedicated Monitor Stations (MS) track the path of the satellites along with other information like altitude, speed, orbit and location.

If there is any error in any of the parameters, the corrected data is sent to the satellites so that they stay in exact position. This orbital data sent by the MCS to satellite is called Ephemeris Data. The satellite, upon receiving this data, corrects its position and also sends this data to the GPS Receiver.

With the help of both the data i.e. Almanac and Ephemeris, the GPS Receiver can be able to know the exact position of the satellites, all the time.

Determining  Distance between the Satellites and GPS Receiver

In order to measure the distance between the GPS Receiver and the Satellites, time place a major role. The formula for calculating the distance of the satellite from the GPS Receiver is given below:

Distance = Velocity of Light x Transit Time of the Satellite Signal

Here, the Transit Time is the Time taken by the Satellite Signal (Signal in the form of Radio Waves, sent by the Satellite to GPS Receiver) to reach the Receiver.

The velocity of the light is a constant value and is equal to C = 3 x 108 m/s. In order to calculate the time, first we need to understand the signal sent by the Satellite.

The Transcoded Signal transmitted by the Satellite is called Pseudo Random Noise (PRN). As the satellite generates this code and starts transmitting, the GPS Receiver also starts to generate the same code and tries to synchronize them.

The GPS Receiver then calculates the amount of time delay the Receiver generated code has to undergo before getting synchronised with the satellite transmitted code.

Once the location of the satellites and their distance from the GPS Receiver are known, then finding out the position of the GPS Receiver in either 2D Space or 3D Space can be done using the following method.

Position of Receiver in 2-D Plane

In order to find the position of the object or GPS Receiver in 2 – Dimensional space i.e. an X-Y Plane, all we need to find is the distance between the GPS receiver and two of the satellites. Let D1 and D2 be the distance of the Receiver from Satellite 1 and Satellite 2 respectively.

Now, with the satellites at the center and a radius of D1 and D2, draw two circles around them on an X-Y Plane. The pictorial representation of this case is shown in the following image.

From the above image, it is clear that the GPS Receiver can be located at either of the two points where the two circles intersect. If the area above the satellites is excluded, we can pin point the position of the GPS Receiver at the point of intersection of the circles beneath the satellites.

The distance information from two satellites is sufficient in order to determine the position of the GPS Receiver in a 2-D or X-Y Plane. But the real world is a 3 – Dimensional Space and we need to determine the 3 – Dimensional position of the GPS Receiver i.e. its Latitude, Longitude and Altitude. We will see a step – by – step procedure to determine the 3 Dimensional location of the GPS Receiver.

Position of the Receiver in 3D Space

Let us assume that the locations of the satellites with respect to the GPS Receiver are already known. If Satellite 1 is at a distance of D1 from the Receiver, then it is clear that the position of the receiver can be anywhere of the surface of the sphere that is formed with satellite 1 as center and D1 as its radius.

If the distance of a second satellite (Satellite 2) from the receiver is D2, then the position of the receiver can be limited to the circle formed by the intersection of two spheres with radii D1 and D2 with Satellites 1 and 2 at the centres respectively.From this image, the position of the GPS Receiver can be narrowed down to a point on the circle of intersection. If we add a third satellite (Satellite 3) with a distance D3 from the GPS Receiver to the existing two satellites, then the location of the receiver is confined to the intersection of the three spheres i.e. either of the two points.

In real time situations, having the ambiguity of GPS Receiver located at one out of the two positions is not viable. This can be resolved by introducing a fourth satellite (Satellite 4) with a distance D4 from the receiver.

The fourth satellite will be able to pin point the location of the GPS Receiver from the possible two locations which were determined earlier with only three satellites. Hence, in real time, a minimum of 4 satellites are required to determine the exact location of the object.

Practically, the GPS System works such that at least 6 satellites are always visible to an object (GPS Receiver) located anywhere on Earth.

Types of GPS Receivers

The GPS is utilized by both civilians and military. Hence, the types of GPS receiver can be classified in to Civilian GPS Receivers and Military GPS Receivers. But the standard way of classification is based on the type of code that the receiver can be able to detect.

Basically, there are two types of codes that a GPS Satellite transmits: Coarse Acquisition Code (C/A Code) and P – Code. The consumer GPS Receiver units can detect only C/A Code. This code is not accurate and hence the civilian positioning system is called Standard Positioning Service (SPS).

The P – Code, on the other hand is used by the Military and is a highly accurate code. The positioning system used by the military is called Precise Positioning Service (PPS). The GPS Receivers can be classified based on the ability to decode these signals.

Another way to classify commercially available GPS receivers is based on the capability of receiving signals. Using this method, GPS Receivers can be divided into:

• Single – Frequency Code Receivers
• Single – Frequency Carrier – Smoothed Code Receivers
• Single – Frequency Code & Carrier Receivers
• Dual – Frequency Receivers

Applications of Global Positioning System (GPS)

GPS has become an essential part of the Global Infrastructure, similar to the Internet. GPS has been the key element in the development of a wide range of application spreading across different aspects of modern life. Increase of large scale manufacturing and miniaturisation of components has reduced the price of GPS Receivers. A small list of applications where GPS plays an important role is mentioned below.

• Modern agriculture has seen a boost in production with the help of GPS. Farmers are using GPS Technology along with modern electronic devices to get precise information about field area, average yield, fuel consumption, distance covered, etc.
• In the field of automobiles, automated guided vehicles are the most often used in the industrial or consumer applications. GPS enables these vehicles in navigation and positioning.
• Civilians use GPS Receivers for navigation purpose. The GPS receiver can be a dedicated module or an embedded module in mobile phones and wrist watches. They are very helpful in trekking, road trips, driving, etc. Additional features include accurate time and speed of the vehicle.
• Emergency services like fire and ambulance benefit from the accurate positioning of the disaster location by GPS and can be able to respond on time.
• Military uses high precision GPS receivers for navigation, target tracking, missile guidance systems, etc.
  There are numerous other applications where GPS is being used or a huge scope of use in the future.

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Off-the-shelf, power-generating clothes are almost here

A lightweight, comfortable jacket that can generate the power to light up a jogger at night may sound futuristic, but a materials scientist could make one today. In a new paper, she and colleagues outline a way to apply breathable, pliable, metal-free electrodes to fabric and off-the-shelf clothing so it feels good to the touch and also transports enough electricity to power small electronics.

Ceramic Capacitor Working, Construction and Applications

The Capacitor is an electronic device that stores energy in the form of an electric field. It consists of two metal plates separated by a dielectric or non-conducting substance. The capacitor types broadly divided based on fixed capacitance and variable capacitance. The most important are the fixed capacitance capacitors, but capacitors with variable capacitance also […]

The post Ceramic Capacitor Working, Construction and Applications appeared first on ElProCus - Electronic Projects for Engineering Students.

555 Timer Circuits in Proteus

555-Timer is one of the most popular and mostly used ICs. It best suits for timing/timekeeping related circuits. It consists of two operational amplifiers operated in an open loop or comparator mode, RS Latch with additional Reset input, a discharge transistor, an inverting buffer and an amplifier in the output stage. It has a voltage [...]

The post 555 Timer Circuits in Proteus appeared first on Electronic Circuits and Diagram-Electronics Projects and Design.

Get sponsorship for your project

Do you have a non-profit project that you’d like to build? For example for a competition or a school project?

Now you can get free printed circuit boards for your project.

A printed circuit board, or a PCB, is a board specifically designed for your project. And it makes it much easier to create projects that need a lot of connections.

To make a PCB you first need to create the schematics for your circuit. Then draw the connections you need in a PCB design software such as Eagle, KiCAD or Fritzing.

This drawing is then sent to a PCB manufacturer that will produce the final board for you. Then all you have to do is to solder the parts onto your board.

How to get sponsorship

PCBWay has a sponsorship program where they offer to create printed circuit boards for free for non-profit projects. All you have to do is to describe your project, and they will send you a code you can use for ordering your PCB.

Get free PCBs for your project here:
http://ift.tt/2rcD1b3

Learn how to design your own PCBs

Designing your own PCBs is one of the most important skills to have in electronics after you’ve learned the basics. When you want to build an idea you have in your head in real life, you’ll often see that it requires a lot of connections.

If you don’t know how to design a PCB, this can become an obstacle that keeps you from building what you really want. That’s why learning PCB design was the first course I ever created after starting my teaching career in electronics.

Do you want to learn to design your own PCBs?

This is just one of many skills you’ll learn when you join Ohmify, my online platform for teaching electronics. Learn more about Ohmify here: http://ift.tt/2pf0W5f

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Arc-Fault Circuit Interrupters (AFCI) and Its Functions

An arc fault circuit interrupter (AFCI) is a circuit protection device designed to protect against fires caused by arcing faults in electrical wiring. An arc fault circuit interrupter is defined as “a device proposed to provide protection from the effects of arc faults by recognizing arcs and by functioning to de-energize the circuit when an […]

The post Arc-Fault Circuit Interrupters (AFCI) and Its Functions appeared first on ElProCus - Electronic Projects for Engineering Students.

Switch Mode Power Supply (SMPS)

Switch Mode Power Supply or simply SMPS is a type of Power Supply Unit (PSU) that uses some kind of switching devices to transfer electrical energy from source to load. Usually the source is either AC or DC and the load is DC.

The most common application of an SMPS is the power supply unit of a computer. Switching Mode Power Supply (SMPS) has become a standard type of power supply unit for electronic devices because of their high efficiency, low cost and high power density.

The following image shows an SMPS unit from an old desktop computer. This particular SMPS is rated for 90W of power.

A Power Supply Unit is an important part of an electric circuit as it provides the power to the circuit for a proper operation. Almost all electronic devices require a constant voltage without any fluctuations. A power supply will take an unregulated power and converts it into a stable regulated power. There are basically two categories of Power Supplies: Linear Regulated Power Supply and Switching Mode Power Supply (SMPS).

Linear Regulated Power Supply is a type of power supply that regulates the output voltage with the help of a series pass control element. The basic example of a series pass element is a resistor. But the frequently used series pass elements are BJT or MOSFET in active or Linear Mode and is connected in series with the load.

Depending on the changes in either input or load, the current through the transistor changes in order to keep the output constant. The difference between the input and output (load) voltages is dropped across the transistor and this excess power i.e. difference between the input and output (load) power is dissipated as heat by the transistor.

The following image shows a basic structure of a Linear Regulated Power Supply.

From the above image, the input AC source is given to a rectifier and filter to convert it into DC. But this DC Supply is unregulated as it is susceptible to change with the changes in input. This unregulated DC supply is given as input to the Linear Regulator.

SMPS is a type of regulated power supply that uses a high frequency switching regulator to convert the power supply and also regulate the output in a highly efficient way.

The switching regulator is again a transistor (like a power MOSFET) just like in Linear Regulator but the difference is that the pass transistor in SMPS doesn’t continuously stay in saturation or fully ON state but rather switches between fully ON and fully OFF states at a very high frequency. Hence the name Switching Mode Power Supply.

Since the average time the switching element i.e. the transistor stays in active state is less, the amount of power wasted or dissipated as heat is very less when compared to Linear Regulators. This in turn leads to high efficiency of SMPS as the voltage drop across the pass transistor (or switching element) is very less.

The switching action of the transistor is controlled using a technique called Pulse Width Modulation (PWM) and the output voltage can be regulated by the duty cycle of the PWM.

The above image shows a basic structure of an SMPS unit. In this, the unregulated DC supply is given to a Switched Mode DC – to – DC Chopper Circuit and the output is a regulated DC Supply.

The main difference between the structures of Linear Regulated Power supply and Switch Mode Power Supply shown here is that in case of Linear Power Supply, the input AC is stepped down, rectified and filtered to get unregulated DC and in case of SMPS, the input AC is directly rectified and filtered and the unregulated high voltage DC is given to a High Frequency DC – to – DC Converter.

Usually, a high frequency transformer will be a part of this DC – to – DC converter for scaling and isolation.

Specification	Linear	SMPS
Efficiency	Typical efficiency of 30-40%	Typical efficiency of 60-95% can be achieved with good design
Output Voltage	Always less than Input	Can be more or less than Input
Regulation Method	By dissipating excess power	By varying duty cycle of PWM
Circuit Complexity	Less complex; consists of regulator and filter as main components	Very complex; consists of switching element, high frequency transformer, rectifiers and filters, feedback circuit
Noise and Interference	Less electronic noise at output and mild high frequency interference	High interference and noise due to frequent switching od current
Size and weight	Bulky because of transformer and heat sink	No transformer at input but requires a tiny high frequency transformer
Applications	Low power, simple and low cost systems	High power, complex and stable power requirements

Even though the design of Switch Mode Power Supply (SMPS) is more complex than a Linear Regulated Power Supply, its high efficiency, high power capabilities and stability are the main factors in choosing SMPS as the power supply unit for sensitive electronic devices.

What is the purpose of SMPS?

Majority of Electronic DC Loads like Microprocessors, Microcontrollers, LEDs, Transistors, ICs, Motors etc. are supplied with standard power sources like batteries for example. Unfortunately, the prime problem with batteries is the voltage is either too high or too low. Hence, an SMPS will provide a regulated DC output.

SMPS is a versatile power supply as we can choose from different topologies like Step – up (Boost), Step – down (Buck), power supplies with isolation at input and output depending on the type of application.

Coming to the major factor of why we need SMPS, the efficiency of a good SMPS design can be as high as 90% or even more. In contrast, the efficiency of a Linear Regulated Power Supply is dependent on the voltage drop at the pass transistor.

For example, assume we have a 3V Lithium Cell that must be stepped down to a 1.8V load drawing a current of 100mA. The power wasted in the transistor as heat is 0.12W and hence the efficiency of the power supply is 40%.

SMPS ICs come with more or less all the features of a discrete SMPS design allowing engineers to experiment with design for custom projects.

SMPS Design

The design of Switched Mode Power Supply or SMPS is fairly complex when compared to linear regulated power supply. But this complexity in design has an advantage as it will result in stable and regulated DC supply that is capable of delivering more power in an efficient way for a given physical specification (size, weight and cost).

A simplified block diagram of an SMPS which converts AC input to a regulated DC is shown in the following image.

Although there are many number of design types for an SMPS power supply, all the designs will be more or less similar to the structure shown above. The main design types in SMPS are:

• AC to DC, where AC mains is given as input and we get a regulated DC at the output,
• DC to DC Step up converter, where an input DC voltage is stepped up i.e. output voltage is greater than input and
• DC to DC Step down converter, where the input DC voltage is stepped down i.e. output voltage is less than or equal to input voltage.

In case of DC to DC SMPS systems, the input DC is usually given from a battery and hence, both the DC to DC converter circuits (Step up and Step down) are commonly found in battery operated systems.

Coming back to SMPS design in the above image, it represents a typical AC to DC converter. We will see the basic working of this SMPS design. The input AC supply is given to rectifier and filter circuits. This step will convert the High Voltage AC to High Voltage DC.

This high voltage DC is given to a High Speed Switching Element like a Power MOSFET. The output of this switch, which is a High Frequency, High Voltage Pulsating AC, is given to a High Frequency Step down Transformer.

The output of this transformer is a Low Voltage AC signal which is in turn given to a rectifier and a filter circuit to obtain Low Voltage DC.

Important Points to Note:

• The common feature of any SMPS design is to convert input AC to High Voltage DC and convert this High Voltage DC to High Voltage, High Frequency Square Wave (AC). This High Voltage and Frequency AC is converted to Regulated DC.
• Square Wave Oscillator and High Speed Electronic Switch (like a MOSFET) are responsible for converting DC to High Frequency AC. The same principle is also used in Square Wave Inverters.
• By converting the input AC or DC (after rectifying and filtering the AC) to High Frequency AC, the size and price of the components like inductors, transformers and capacitors can reduced i.e. they can be smaller and cheaper.
• As the High Frequency AC signal generated at the switch is a square wave, the output voltage can be regulated with the help of Pulse Width Modulation (PWM). There is a voltage feedback through an isolator circuit to the control circuit (which controls the PWM). With this feedback, the duty cycle of the PWM from the oscillator can be varied and hence the output is perfectly regulated without any over voltages.
• A sample current from the High Frequency AC (signal after the switch) and a reference current are compared and given to the control circuit and hence provides an over current protection.
• Also note that the output DC is completely isolated from the input mains and even the feedback signal is isolated with the help of an Opto coupler.
• Driving the Switching Transistor (MOSFET) with square wave ensures that the power dissipation is very less when compared to the Transistor being operated as a series pass transistor in Linear Regulated Power Supplies.
• Since there is a High Frequency AC Signal in the SMPS, there is a chance of high frequency harmonics and as a result, SMPS is more susceptible to RF Interference.

SMPS Topologies

We have seen the basic design of a Switched Mode Power Supply (SMPS) in the above section. Now we will see the different types or topologies of SMPS. Switched Mode Power Supplies or SMPS can be classified into two types based on its circuit topology: Non-isolated Converters and Isolated Converters.

Non – isolated Converters are a type of SMPS Topology where the switching circuit and output are not isolated i.e. they have a common terminal. The three basic and important types in Non – isolated SMPS are:

• Buck Converter or Step – down Converter
• Boost Converter or Step – up Converter
• Buck – Boost Converter

There are other non – isolated SMPS designs like Switched Capacitors, Cuk Converter and SEPIC Converter but these three types are very important. They are the simplest of SMPS designs and use a single inductor as an energy storing element and two switches, out of which one is an active switch (a Transistor – Power MOSFET) while the other can be a diode.

The output voltage can be higher (Boost or Step – up) or lower (Buck or Step – down) and can be controlled by the duty cycle of the high frequency square wave (that is applied to the switch). One main drawback of Non – isolated Topology is that the efficiency of the switches falls as the duty cycle is reduced. Isolated Topology will suit better for larger voltage changes.

Isolated Topology in SMPS uses a transformer as an isolator between the switching element and output. Depending on the transformer’s turns ratio, the output voltage can be higher or lower than the input. Transformer based SMPS topologies can be designed to generate multiple output voltage by using multiple windings at the transformer.

The energy storage element can be transformers secondary winding or a separate inductor. The two important Isolated Topology based SMPS converters are:

• Flyback Converter
• Forward Converter

Some of the other commonly used isolated SMPS topologies are Half – bridge, Full – bridge, Push – Pull, Half – Forward, Isolated Cuk, etc.

Buck Converter or Step – down Converter

Buck Converter is a type of SMPS circuit and DC to DC Converter, where the output voltage is less than input voltage. Hence, a Buck Converter is also known as a Step – down Converter.

It is one of the simplest SMPS power converter techniques and is often used in RAM, CPU, USB etc. The input DC in buck converter can be a rectified AC or a battery. A simple buck converter using two switches (one transistor and one diode) and an energy storing element (inductor) is shown in the image below.

Buck Converter Operation

A simple Buck Converter or Step down Converter is shown in the above image and it consists of a switching transistor, diode, inductor and capacitor. The combination of Inductor , Diode and Capacitor is called as Flywheel Circuit.

The operation of the Buck Converter is explained with respect to square wave pulse. The following image shows the operation of the Buck Converter when the input pulse is HIGH i.e. the switching Transistor is ON.

When the pulse input to the Gate terminal of the MOSFET is HIGH, the Transistor is turned ON. As a result, the transistor will supply current to the load. During this time, the Diode D is reverse biased and will not be a part of the circuit during this period.

Initially, the inductor resists the change in current and hence, the current to the load will increase gradually with expanding magnetic field. Also, the charge on the capacitor is built up gradually up to the supply voltage. The next image is for the condition where the pulse becomes LOW i.e. the Transistor is OFF.

When the pulse becomes LOW, the switching Transistor is turned OFF. The magnetic field that is built up during the Transistor ON state, starts collapsing now and releases the energy back in to the circuit. The polarity of the voltage across the inductor i.e. its back e.m.f is now reversed. The energy from the inductor starts collapsing and keeps the current flowing in the circuit through load and the diode, as the diode D is forward biased.

Once the energy from the inductor is completely utilized, the capacitor starts discharging and acts as the main source of supply until the transistor is turned ON. When the transistor is turned ON, it will once again supply current to inductor, capacitor and load and the process continues.

The output voltage is dependent on the ON and OFF time i.e. the Duty Cycle of the square wave pulse and the formula for output voltage is

VOUT = D x VIN, where D = TON/(TON+TOFF)

With Buck Converters, we can achieve more than 90% efficiency and as a result, they often employed in computer systems where they convert 12V supply to typically 1.8V (for RAM, CPU and USB).

Boost Converter or Step – up Converter

In the previous section, we have seen a Buck Converter type SMPS. Now, we will see about another type of SMPS called Boost Converter or Step – up converter. A Boost Converter, as the name suggests, is type of switched mode power supply, which boosts or increases the output voltage with respect to the input voltage. Boost Converters are also known as Step – up Converters as the output voltage is higher than the input voltage.

One of the best known application for Boost Converters is in electric cars. The supply from electric cars batteries won’t be sufficient for its working as they require voltages that are much higher (typically in region of 500V) than those supplied by the batteries. Another important application of Boost Converters is Laptop Chargers in Cars.

Typical Car batteries provide 12V and Laptops require anywhere between 18 to 22V. The following image shows a simple Boost Converter.

Boost Converter Operation

This simple Boost Converter consists of a Switching Transistor (BJT or MOSFETS can be used), an energy storing element i.e. inductor, another switch (Diode or another Transistor), capacitor and a high frequency square wave oscillator with controllable duty cycle.

The input to this Boost converter is unregulated DC, which can be given from rectified AC, batteries, Solar, DC Generators, etc. We will see the working operating of this Boost Converter. First we will see for period when the Transistor is ON for the first time. The following image shows this condition.

When the pulse is HIGH for the first time, the transistor is turned ON and it closes a part of the circuit consisting of Inductor, Transistor and input supply. Current flows from the input through the inductor and transistor.

The inductor, initially resists the change in current but the magnetic field will increase gradually allowing inductor to store energy. The impedance of the rest of the circuit i.e. Diode, Capacitor and Load is much higher and hence, there will be no flow of current in that part of the circuit.

When the square wave pulse goes LOW, the transistor is turned OFF. This action will cause a drop in the current through the inductor, producing a back e.m.f in the circuit due to collapsing magnetic field. Also, the polarity of the voltage across the inductor is now reversed and will be in series with the input voltage.

The combination of the input voltage and Inductor Back e.m.f cannot pass through the inductor as it is turned OFF. Hence, the diode is forward biased and charges the Capacitor and also supplies current to load.

An important point to note here is that the voltage supplied to the capacitor and load during the Transistor OFF state is a combination of input voltage and inductors back e.m.f, which is higher than the input voltage.

When the transistor is turned ON again, the current flows again through the inductor and transistor. As the diode is reverse biased, the capacitor discharges it potential, which is sum of input voltage and inductor voltage, through the load acting as its source during this period. The output voltage is given by the formula

VOUT= VIN x 1/(1-D) where D = TON/(TON+TOFF)

Flyback Converter

Flyback Converter is a type of Switch Mode Power Supply typically used in low power applications. Flyback Converter is an Isolated Type SMPS where the input and output are isolated with a transformer. The following is the circuit of a simple Flyback Converter.

The main components of a Flyback Converter are a Switching Transistor, Oscillator Circuit, Transformer, switch (like a Diode) and a Capacitor. The Transformer is different from a normal transformer and is called a Flyback Transformer. In this transformer, the Primary and Secondary do not conduct simultaneously.

Flyback Converter Operation

When the Transistor is turned ON, the current flows through the primary of the transformer with the dot being higher potential. As a result, the polarity of the voltage induced in the secondary will be reverse to that of primary. Hence, the diode D gets reverse biased.

If the capacitor got charged in the previous cycle, it will discharge through the load. The following image shows this period of operation in the flyback converter.

The operation of the Flyback converter in the other period i.e. Transistor OFF period is illustrated in the following image. When the pulse becomes LOW, the transistor is turned OFF and the primary of the transformer do not conduct.

The energy in the secondary of the transformer will be released into the circuit and also the polarity in the secondary is reversed i.e. it becomes positive. Hence, the diode is forward biased allowing the energy stored in the secondary coil acting as the source. It recharges the capacitor and also supplies the current to load.

The output voltage in Flyback Converter can be higher or lower than the input voltage and is dependent on the turns ratio of the primary and secondary of the transformer.

Forward Converter

Another important switch mode power supply is Forward Converter. It is another isolated type SMPS and produces controlled and regulated DC from an unregulated DC supply.

The efficiency of Forward Converter is slightly more than that of Flyback Converter and is often used in application where the power requirements are a little higher (typically around 200W). The design of Forward Converters is slightly complex than Flyback Converters and a simple structure is shown below.

The simple circuit of Forward Converter consists of a fast switching transistor, a control circuit to control the duty cycle of the Square Wave, a normal transformer, two diodes for rectifying the AC, an inductor and a capacitor for filtering.

Forward Converter Operation

The following image shows the operation of the Forward Converter when the Transistor is turned ON. When the pulse is HIGH, the transistor is turned ON and as a result, the primary coil of the transformer starts conducting. As a result, a voltage is induced in the secondary coil of the transformer.

The polarity of the voltage induced in the secondary is similar to that of the primary and hence, the diode D1 gets forward biased. The voltage from the secondary will start to flow through the diode D1, inductor, capacitor and finally the load. During this period, both the inductor and capacitor store energy in the form of magnetic field and electric field respectively.

When the pulse becomes LOW, the transistor is turned OFF and as a result, the primary coil stops conducting. This will in turn stop inducing current in the secondary. This sudden change (or drop) in current will generate a back e.m.f of the inductor and polarity of its voltage is reversed.

This period of operation of the Forward Converter is shown in the image below. The energy in the inductor start collapsing in the circuit through the load and Diode D2 (as it is forward biased). As soon as the energy in the inductor finishes, the capacitor starts discharging through the load and acts as a temporary source to the load. This continues until the transistor is turned ON again

The output voltage of the Forward Converter is dependent on the transformer turns ratio as well as the duty cycle of the Pulse Width Modulator. The output voltage is given by

VOUT = VIN x D x NS/NP

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Researchers create first significant examples of optical crystallography for nanomaterials

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Roll-up computer screens and other flexible electronics are getting closer to reality as scientists improve upon a growing number of components that can bend and stretch. One team now reports another development that can contribute to this evolution: a low-cost conductive paper that would be easy to manufacture on a large scale.

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Stretching the limits of elastic conductors

A newly developed printable elastic conductor retains high conductivity even when stretched to as much as five times its original length, says a team of scientists. The new material, produced in paste-like ink form, can be printed in various patterns on textiles and rubber surfaces as stretchable wiring for wearable devices incorporating sensors, as well as give human skin-like functions to robot exteriors.

Common Emitter Amplifier (CE) Circuit Working and Applications

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Fast, simple way to create two-dimensional electronic circuits

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Electrostatic design of materials: A fundamentally new approach

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How a Thermostat Works – Tutorial

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Can the motion of checking your smartwatch charge it?

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3D-printed 'bionic skin' could give robots the sense of touch

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Laser pulses reveal the superconductors of the future

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Transistors that can switch between two stable energy states

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Dual-channel biological function generator

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Programmable Logic Controller

Programmable Logic Controllers or PLCs are microprocessor based controllers that are used in automation of machine control in industries. PLC is a member of the computer family with Programmable Memory that stores instruction to perform different tasks like logic, timing, counting, sequencing and arithmetic in order to control machines and automating the processes.

In the olden days, industrial automation was done with complex relay based control systems. These electromechanical relay based control system consumed a lot of power, huge wear and tear and have to be regularly serviced and replaced.

As an alternative to these complex relay control systems, a new system has been developed by General Motors (GM) with the following requirements: Simple Programming, low maintenance cost and reliable relay control system. And thus the first ever Programmable Logic Controller (PLC) was developed in 1968.

PLCs are the best choice for cost-effective automation solutions to perform industrial operations with requirement ranging from simple to complex. Nowadays, PLCs becomes an integral part of industrial process control and factory automation systems.

PLCs can provide perfectly optimized solutions to the industrial environment due to the wide variety of advantages, like high and robust performance, excellent flexibility to connect I/Os (input/outputs), greater accuracy and reliability through built-in functional blocks, etc.

Hardware of Programmable Logic Controller

A Programmable Logic Controller (PLC) is an industrial computer that accepts real time parameters from various sensors and operates the output devices based on the logic implemented in its program. PLC replaces hardwired controlled devices like timers, relays, counters and sequencers with programmed instructions and solid state components.

The below figure shows the basic hardware components of a PLC. A typical PLC system consists of components like Power Supply, CPU, Memory Unit, Programming Device, Input and Output modules.

CPU, Processor or Controller: The operations within the PLC is controlled and processed by a main Central Processing Unit (CPU). It contains arithmetic and logic unit to perform data manipulation and logical operations. The CPU reads the status of the Input Devices and executes the control program in order to control the load.

Memory Unit: It stores the instructions needed to run the program, the data to be processed from input sensors and the data to be sent for output devices. It consists of ROM as a permanent storage for operating system and other data used by the CPU. RAM is used for storing the user program, status of various input and output devices and history data of various devices.

Power Supply Unit: Power Supply Unit provides the necessary power to the PLC. It converts the mains AC voltage to the low DC voltage as per the requirements needed to power the processor and the other circuits in input, output and communication modules. Most PLC systems work at 230V AC or 24V DC.

Input / Output Modules: Input and Output Modules form the physical connections to the field modules to the main controller. I/O modules i.e. sensors and actuators allow the PLC system to interface with the outside world. PLCs typically consists of many number of channels for input and output devices with integrated isolation and signal conditioning circuits so that each sensor and actuator can be connected directly to the PLC without any external circuitry.

I/O Modules can be either fixed i.e. controller and I/O are packed together or modular i.e. I/O can be easily fitted into removable racks. The most commonly used I/O devices include

1. Digital input modules
2. Digital output modules
3.  Analog input modules
4. Analog output modules
5. Special purpose modules

Program and Programming Device: The heart of the PLC is the CPU and we need to program the CPU as per the requirement. Usually, the programming part of the PLC is implemented using a dedicated language and is generally a Graphical Method. The Program for PLC can be designed by the operating engineers without vast knowledge in computers or programming.

The program must be loaded into the memory of the PLC using external programmers and the controller monitors the input and output devices according to this program.

Additional Hardware: In addition to the above mentioned components, some additional components like connectors for connecting external modules (USB, RS232, SD Card, etc.), communication interface for connecting with the network (Ethernet), chassis, etc.

Basic Working of a PLC

The working of PLC can be categorized into four basic stages of operation

• Initial Setup
• Reading data from the Inputs
• Executing the Instructions
• Commanding the Output peripherals

The following image shows a basic flowchart of the working of the PLC. This flow is just a typical working and doesn’t necessarily represent the actual work flow.

Whenever PLC is turned ON, it loads all the necessary instructions and functions and correspondingly checks the faults in hardware and software. This stage is called self test, during which checking for errors in all cards is performed.

If there are no errors, PLC processor reads the input values from various input modules (to which various sensors are connected) and copies their values into the memory. This is called input scan stage.

The next stage is to execute the program which is also termed as logic scan. During this, input data from memory is compared and processed by the logic program (ladder logic program or any other type of program) and correspondingly output values are updated in the temporary memory.

And the final stage is the output scan during which outputs connected to the output module will be updated using the values stored in temporary memory during logic scan. Usually, this whole process repeats 10 to 100 times in a second.

We will see a real time example of PLC operating in a wood cutter industry. The following figure illustrates the operation of a programmable logic controller to perform the automatic operation of wood cutter.

This system consists of a rotary encoder, cutting blade with pneumatic piston arrangement and a programmable logic controller unit. PLC is programmed in such a way that for a desired length of wooden peace, output will drive the pneumatic piston.

PLC also offers to vary the program, according to the desired length of the wooden piece. It scans the input from a rotary encoder which measures moving distance of the wooden block. Based on the program, PLC compares the input data and correspondingly sends the output to the cutter.

Advantages of PLC

• PLCs are built ruggedly and are used in industries where they must withstand rigorous temperatures, humidity, vibrations and other extreme operating conditions.
• PLCs eliminate the complex hard wiring associated with traditional relay based control systems.
• PLCs are fast and the response time is very less.
• Programmable Logic Controllers or PLCs can have a modular design and plug and play modules.
• The program for PLC can be easily modified and update its functionality that to rewire the relay circuits. Also the troubleshooting process for hardware and software modules in easy.

Applications of Programmable Logic Controllers (PLC)

• Programmable Logic Controllers or PLCs are optimized for industrial environment in order to control processes.
• PLCs are used in almost all industries like automotive, chemical, food, metal, mining, power, etc. for different tasks like batch processing, material conveyors, packaging, operating cranes, waste management etc.

PLC Programming Languages

PLC programming is not very difficult compared to other computer programming languages. The major advantage of PLC is that it allows multiple languages within the same controller to program it.

So the user (or program developer) has to select the best suited language to develop logic for specific application. The software model and programming languages of a PLC are dealt by IEC standard 1131-3. The five languages recommended by this standard for a PLC are discussed below.

Instruction List (IL)

It is a low level language and it is similar to assembler language programming. IL consists of many lines of code where each line represents exactly one operation. If this program is written using IEC defined instructions, the program can be moved easily to different IEC compliant PLCs. IL is well suited for small applications which involve simple mathematical functions. This language is much more compact and requires less space in the PLC memory.

However, this language is not user friendly and not very powerful. Also, implementing complex functions like PID and complex mathematical computations involves greater effort. Instruction list program for controlling the load from two sources by implementing OR logic is given below with corresponding ladder diagram.

LD % I1.1 (*Load input bit*)

OR % M1 (*OR of the M1 with the result of previous result*)

ST %Q2.3 (*Set the output bit*)

Structured Text (ST)

It is a high level textual language similar to BASIC and Pascal. It can handle the complexity of program by implementing process control functions, calculus, trigonometry and data analysis far easier than ladder and IL programming.

Also, it runs much faster than IL and easily gets transferable to any other IEC hardware PLCs with very few changes. Users who trained in high level text languages would be comfortable with structure text language.

However, it is unsuitable for troubleshooting and somewhat unfamiliar for the service and maintenance personnel. The following is the structure text programming language for heater and cooler ON and OFF based on the temperature.

IF (TEMP > 20) THEN

HEATER: = OFF;

COOLER: = ON;

ELSIF (TEMP > 19)

HEATER: = ON;

COOLER: = OFF;

END_IF;

Ladder Diagrams (LD)

The most widely used programming language for a PLC is the ladder logic, which is invented to replace the hardwired relay control systems.

It is the simple and widespread adopted language, even a non programmer with electrical background able to understand and troubleshoot the pogram. It is a graphical type of language consisting of several logic functions between rungs and power rails.

The above image shows the hardwired ladder diagram for pump control system in which horizontal lines are called as rungs while vertical two lines at rung extremities are called power rails. The left rail is the line or hot wire of the power supply while the right side rail is the neutral power rail (common terminal of power supply).

In the equivalent PLC program for pump control is given below which is similar to the hardwired logic consisting of rungs and power rails. Each individual rung consists of one or more input instructions on its left-hand side and one or more output instructions on its right-hand side.

In this, the input instructions Examine If open (XIO) and Examine If Closed (XIC) are analogous to relay contacts while the output instruction Output Energize (OTE) is analogous to relay coil. These output and input instructions connected with wires as shown in figure.

Function Block Diagram

It is also a graphical language and is the second most widely used programming language. It consists of various functional blocks which are reusable software elements consisting of one or more inputs and one or more outputs.

These function blocks include logic gates, counters, timers, PID, data conversion blocks, etc. However a large amount of screen space is required by this style of programming.

The image above shows the function block diagram of a simple lamp control unit from two input sources, i.e., from start and stop switches. Three Boolean functional blocks OR, NOT and AND are wired in this example to produce the control logic. If the start button is pressed, the output becomes true and glows the blub.

The system run output is applied at the OR Boolean function, thereby once the start button is pressed the bulb will continue to glow even if start button is OFF provided the stop button must be in OFF state as shown below.

Sequential Function Chart

It is a graphical programming language that resembles computer flow charts. This type of program controls the system as a series of steps and transitions.

It consists of action boxes, where each box can be programmed with any language that we discussed above. Each box is active until next transition step is activated. Once the current box is turned OFF, next step in the sequence is active and so on.

The figure above shows the flow chart programming of a mixing process where the process is divided into transitions. Each transition is executed sequentially before the condition for each transition is satisfied.

Suppose if a stirrer tank is to be filled by two liquids up to a certain level, then mixer has to be turned ON for a several minutes and finally mixed content passed (emptying the tank) to another tank.

This sequential process is executed by the below figure. Each transition can be programmed with any programming language.

The post Programmable Logic Controller appeared first on Electronics Hub.

Tracking devices may improve quality of life for parents of children with autism

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Discovery of new transparent thin film material could improve electronics and solar cells

Scientists have discovered a new nano-scale thin film material with the highest-ever conductivity in its class. The new material could lead to smaller, faster, and more powerful electronics, as well as more efficient solar cells.

Ohmify open for enrollment

Hey, I’ve just reopened Ohmify:

http://ift.tt/2pf0W5f

Ohmify is an online platform that helps you learn and build real things with electronics.

It gives you access to more than 30 courses for both building fun projects and learning electronics.

And today or tomorrow, depends how productive I am today, I’m releasing a new course where you’ll learn to really understand what’s going on in a circuit diagram.

I’m continually creating new courses for you.

See the growing list of courses here:

http://ift.tt/2pFTy5m
(Note: Only members can access the courses)

I recently bought a new camera and next week I’ll invest in a better microphone. Also, I’ve convinced my wife (yes, I got married a couple of months ago!) to help me with video production as she’s a professional.

The plan is to create more and better ways of showing how to do different things in electronics.

If you’re not sure if Ohmify is for you or not, check out some videos and read more about what Ohmify is here:

http://ift.tt/2pf0W5f

Or you can take it from Doug, a beginner and one of the newest members on Ohmify, who sent me the following message a couple of days ago:

“I have to say that your site and your courses are perfect for me, almost as if you wrote them specifically for me.”
-Doug Roberson

Keep On Soldering!
Oyvind

Copyright Build Electronic Circuits

New self-sustained multi-sensor platform for environmental monitoring

A research team has engineered a self-sustaining sensor platform to continuously monitor the surrounding environment without having an external power source.

LM386 Audio Amplifier Circuit

In this project, we will show you how to build LM386 Audio Amplifier Circuit. It is a very low cost audio amplifier and can power any speaker. For the cost and size of the circuit, the sound from the LM386 Audio Amplifier can be adequately loud.

There are many Audio Amplifier Circuits designed using LM386 IC. The main problem with these circuits is noise and interference. The noise from the Amplifier Circuit designed in this project is considerably less and if designed on a proper circuit board, this will make a great Audio Amplifier.

The Audio Amplifier using LM386 is a low power circuit that can deliver a maximum power of 1 Watt (1W) and can be used in a wide range of applications like portable speakers, laptop speakers, etc.

LM386 Audio Amplifier Image 1

LM386 Audio Amplifier Image 2

LM386 Audio Amplifier Image 3

LM386 Audio Amplifier Image 4

LM386 Audio Amplifier Image 5

Circuit Diagram of LM386 Audio Amplifier

Components Required

• LM386 Audio Amplifier IC
• 1000 µF Capacitor
• 100 µF Capacitor
• 10 µF Capacitor
• 0.05 µF Capacitor (two 0.1 µF Ceramic Capacitors in series would do the job)
• 10 KΩ Potentiometer (for input volume control – We did not connect this)
• 10 Ω Resistor (1/4 Watt)
• 4 Ω Speaker
• 12V Power Supply
• Connecting Wires
• Breadboard

Introduction to LM386

The LM386 is an all – in – one Class AB Audio Amplifier IC that can be used in a variety of applications. LM386 IC has been in use for decades and is still being used as Amplifier in Computer speakers and Portable Stereos.

LM386 is a low voltage power amplifier with an inactive power draw of 24mW, which makes it suitable for battery controlled applications. The most common package for LM386 is an 8 – pin DIP. The following image shows the pinout diagram of the IC LM386

.

From the pin diagram, it is clear that LM386 is a simple Amplifier IC with possibly minimum external connections. The following table shows the functions of each pin in the LM386 Amplifier IC.

Pin Number	Pin Name	Function
1	Gain	Gain Setting Pin
2	Input –	Inverting Input
3	Input +	Non – Inverting Input
4	GND	Ground
5	Vout	Output
6	Vs	Power Supply Voltage
7	Bypass	Bypass decoupling path
8	Gain	Gain Setting Pin

Pins 1 and 8 are Gain Control Pins. By default, the Gain of the LM386 Amplifier is set to a factor of 20. When a capacitor is placed between pins 1 and 8, it bypasses the internal resistor (which is responsible for setting the gain to 20) and increases the gain to 200.

Pins 2 and 3 are the inverting and non – inverting inputs of the amplifier (internally, they are connected to an OP-AMP). Audio input from devices like microphone, mobile phones, laptops, etc. is given through these pin.

NOTE: The inverting input (Pin 2) of LM386 is usually connected to Ground.

Pins 6 and 4 are the power supply pins. The maximum power supply to LM386 is 15V. We have used a 12V Power supply in this project.

Pin 7 sets the path for decoupling and a capacitor must be connected between Pin 7 and Ground. Pin 5 is the output pin. Proper filtering must be done before connecting the output to a speaker as any DC signal might permanently damage the speaker.

Functional Block Diagram of LM386

Functionally, the LM386 Audio Amplifier IC can be divided in to Amplifier, Gain Control, Bypass, Power and Output. The following image shows the functional block diagram of LM386.

Design of LM386 Audio Amplifier Circuit

The design of LM386 Audio Amplifier Circuit is very simple. First, connect the power supply pins (Pins 6 and 4) to 12V and Ground respectively. Note that the maximum power supply for LM386 is 15V.

Next, we need to connect the input. The input can be given from any audio source like mobile phone or a microphone. We have given the audio input from a mobile phone using the 3.5mm connector.

NOTE: Simple 3.5mm connector (without microphone) will have three connections: Left Audio, Right Audio and Ground. Since LM386 is a Mono Audio Amplifier, we need to connect either the Left audio or the Right Audio from the source along with ground. Alternatively, both the channels can be combined to produce a mono channel using appropriate resistors.

If we want to control the level of the input, we need to connect a 10 KΩ Potentiometer at the input. Since we are doing this project on a breadboard, we did not connect any input volume control POT. Additionally, a small capacitor can be connected in series with the input to filter out the DC Components.

Internally, the gain of the LM386 Audio Amplifier is set to 20 (without any gain control circuitry). We connected a 10 µF Capacitor between the gain control pins i.e. pins 1 and 8. Hence, the gain is now set to a factor of 200.

Although the data sheet of LM386 says the bypass capacitor at Pin 7 is optional, we found that connecting a 100 µF capacitor was really helpful as it helps in reducing the noise. It can be left open for normal operation.

Finally, for the output, first connect a 0.05 µF Capacitor and a 10 Ω Resistor in series between the output pin (Pin 5) and ground. This forms a Zobel Network, a filter consisting of resistor and capacitor in series and is used to fix the input impedance of the driver.

Next is the speaker connection. LM386 can drive any speaker within the impedance range of 4 Ω to 32 Ω. We have used a 4 Ω Speaker. Connecting the speaker through a big 1000 µF capacitor was really helpful as it filtered out the unnecessary DC signals.

Working of LM386 Audio Amplifier Circuit

A simple but efficient Audio Amplifier is designed using LM386 Audio Amplifier IC. The working of the circuit is very straight forward as all the work is done by the LM386 IC itself.

When the system is powered on and proper audio input is given at the input, the LM386 Amplifier the input signal by a factor of 200 and drives the output speaker.

One of the main problems with audio amplifiers like LM386 is the noise. Surprisingly, even though the circuit is built on a breadboard, there was very less noise from the speaker.

Applications

• LM386 is already one of the important IC in audio department and is featured commonly portable speakers and laptop speakers.
• The LM386 Audio Amplifier Circuit can be used for recording voice from microphone, building small speakers that are battery operated, in FM Radio Devices, etc.
• They can also be used in TV Sound Systems, Line Drivers, Servo Drivers, Ultrasonic Drivers, etc.

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