Pulse Width Modulation – What is it?

Anish August 17, 2013 6 Comments
The good definition of Pulse Width Modulation (PWM) is in the name itself. It means modulating/varying the width of the pulse (Not the frequency). To best understand what PWM is, let us first see some basic terminologies. Microcontrollers are intelligent digital components which live on binary signals. Best representation of a binary signal is a square wave. The following diagram explains the basic terminologies associated with a square wave signal. As the shown in the above diagram, the important...
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The Story of PN Junction Diode

jojo August 27, 2013 7 Comments
I am really excited by the amazing comments & responses I got for my two articles on PN Junction. If you have not read them yet, here they are – 1) Understanding the PN Juction and 2) PN Junction Diode Characteristics. In those 2 articles, I have tried to demystify PN Juction and explain it in very simple words. From those good responses, I assume my attempt has been successful to some extent. In this article, my objective is...
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Breathalyzer circuit using 8051

admin March 12, 2014 15 Comments
Alcohol Breathalyzer circuit using 8051 microcontroller (AT89S51). This article is about a breathalyzer circuit using 8051 microcontroller which outputs the blood alcohol content (BAC) from the breath. The BAC is displayed in percentage on a 3 digit seven segment display. The microcontroller used if AT89S51 which belongs to the 8051 family and the alcohol sensor is MQ135 gas sensor from Futurelec. MQ135 gas sensor. MQ135 is a stable and sensitive gas sensor which can detect  ammonia, carbon dioxide, alcohol,...
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What are the Different Types of LED’s available

jojo May 30, 2013 9 Comments
This article is a guide for any one who is interested in knowing about the different types of LED’s available in the market. This can be considered as a general informational guide on LED and a buying guide for hobbyists as well.  One important challenge I faced while writing this guide was to incorporate consumer LED’s and professional/hobbyist LED’s into a single article. Let your comments say if I have been successful in this attempt. Over the years semiconductor...
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How to start your career in Web Development & Web Technologies

jojo May 4, 2013 7 Comments
Usually we publish articles that are of interest only to the “electronics” community. However today I thought of publishing an article about career opportunities in Web Development & Web Technologies. The reason being the wide opportunities it provides for fresh engineers & graduates. “Cloud Computing” is making a wave and plenty of new job opportunities are posted every week in this area. “Web Development” is a general term which can be used in connection with anything that is related...
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VLSI Books for Beginners

john November 2, 2017 4 Comments
Very Large Scale Integration (VLSI), is a very vast domain and is known to be the best and most sought after field among all branches in electronics. Our idea is to bring in the basic knowledge on VLSI to our readers and for those who are interested is pursuing this field for a career. As an introduction, we shall take you readers to some of our earlier posts which gives the very basic knowledge of VLSI. VLSI mainly consists...
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Heart rate monitor using 8051

admin January 23, 2018 105 Comments
This article is about a simple heart rate monitor using 8051 microcontroller. Like the previous 8051 projects, AT89S51 is the microcontroller used here. The device senses the heart rate from the finger tip using IR reflection method and displays it on a three digit seven segment display in beats per minute. The circuit has an accuracy of 4 beats per minute and it is very easy to use. In medical terms, the technique used here for sensing heart rate...
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Interfacing hex keypad to 8051

admin March 8, 2013 15 Comments
This article is about interfacing a hex key pad to 8051 microcontroller. A clear knowledge on interfacing hex key pad to 8051 is  very essential  while designing embedded system projects which requires character or numeric input or both. For example projects like digital code lock, numeric calculator etc. Before going to the interfacing in detail, let’s have a look at the hex keypad. Hex keypad. Hex key pad is essentially a collection of 16 keys arranged in the form...
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8051 Microcontroller Projects & Circuits

admin November 2, 2017 46 Comments
This article is a compilation of all 8051 based Electronic Projects and Circuits we have developed at CircuitsToday till date. We have one of the biggest collection of 8051 based Projects – which range from very Advanced one’s like Electronic Voting Machine, Heart Rate Monitor, RFID based Access Control (and a lot more) to Medium Level and Easy one’s like Water Level Controller, Solar Panel Tracker, Ultrasonic Range Finder etc. Note:- We have listed Project Kits of all our...
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Ultrasonic range finder using 8051

admin October 31, 2017 84 Comments
Ultrasonic range finder using 8051 . A simple ultrasonic range finder using 8051 microcontroller is presented in this article. This ultrasonic rangefinder can measure distances up to  2.5 meters at an accuracy of 1 centi meter. AT89s51 microcontroller and the ultrasonic transducer module HC-SR04 forms the basis of this circuit. The ultrasonic module sends a signal to the object, then picks up its echo and outputs a wave form whose time period is proportional to the distance. The microcontroller...
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Digital tachometer using 8051

admin April 20, 2015 39 Comments
Contactless digital tachometer using 8051. A three digit contact less digital tachometer using 8051 microcontroller which can be used for measuring the revolutions/second of a rotating wheel, disc, shaft or anything like that is introduced in this project. The tachometer  can measure up to a maximum of 255 rev/sec at an accuracy of 1 rev/sec. What you just need to do is to align the sensor close to the reflective strip  (aluminium foil, white paper or some thing like...
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PWM lamp dimmer using NE555

admin January 22, 2014 20 Comments
PWM lamp dimmer. A simple and efficient PWM lamp dimmer using timer IC NE555 is discussed in this article. Yesterdays linear regulator based dimmers can only attain a maximum efficiency  of 50% and are far inferior when compared to the PWM based dimmers which can hit well over 90% efficiency. Since less amount of power is wasted as heat, the switching elements of PWM dimmers require a smaller heat sink and this saves a lot of size and weight....
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PN Junction Diode and its characteristics

jojo August 15, 2013 54 Comments
In chapter 1 – Understanding the PN junction , we have seen how a PN junction is formed from a p-type and n-type semiconductor. We have also learned about diffusion current, depletion region, drift current and barrier potential. If you find these terms foreign, just read the chapter about “understanding the pn junction” once more. Lets just make some questions. What is the use of a PN junction? Why have scientists created a pn junction device? What kind of...
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Simple audio circuits

jojo December 2, 2012 9 Comments
This article is a compilation of the simple and popular audio circuits we have published over years in CircuitsToday. This list involves a collection of simple amplifier circuits that you can try at home and some other audio related circuits with specific applications.  Image Source 1. 150 Watt amplifier circuit – This circuit is the most popular amplifier we have ever published. It has received over 700+ comments and is still counting. This amplifier has been tested by many...
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Understanding the PN Junction

jojo July 21, 2014 30 Comments
Whenever someone decides to learn electronics, the first question that comes to his mind may be – “Where shall I begin?“. I would say, one shall begin at a junction 😉 the “pn junction“. We know semiconductor devices like transistors and diodes are the basic building units of any equipment that involves electronics, say tablet computers to the sophisticated MRI machines! How these basic units like transistors and diodes are formed ? or how are they made ? The...
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Delay using 8051 timer

admin November 28, 2012 11 Comments
Delay using 8051 timer.  The 8051 microcontroller has two independent 16 bit up counting timers named Timer 0 and Timer 1 and this article is about generating time delays using the 8051 timers. Generating delay using pure software loops have been already discussed here but such delays are poor in accuracy and cannot be used in sensitive applications. Delay using timer is the most accurate and surely the best method. A timer can be generalized as a multi-bit counter...
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The Best & Free Android Applications for the Electronics & Electrical Engineers

jojo November 28, 2012 11 Comments
The world around us is changing at a much faster pace than any one can anticipate. The world of “computing” has already seen great shifts from Desktops to Notebooks to Smartphones and Tablets. The coming decade will be more focused on mobile computing and cloud computing. Here in this article, I am listing some of the best and really useful applications released in Android market (aka Google Play), that comes handy for any one who is working in Electrical...
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How to debug in Keil Microvision

Nilay Banker November 21, 2012 4 Comments
In this article we will take a look at Debugging feature of Keil uVision. In Previous Article we had seen how to create project, hex file and building Project. Once you build your project and if you see 0 errors and 0 warnings you are half way through your project. Now what is debugging? Debugging is to identify and fix bugs in your project e.g. logical or synchronization problems in the code, or a design error in the hardware.First go...
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What is Image Processing?An Introduction to basics

Avaneet Ranjan November 21, 2012 3 Comments
Sight/vision is one of the greatest powers of a human being. Our eyes can tell us the shape, size, color of any and everything which comes in front of it.An Image is a 2 D light intensity function f(x,y). A digital image f(x,y) is discretized both in spatial coordinates and brightness.It can be considered as a matrix whose row, column indices specify a point in the image and the element value identifies the intensity value at that points. These...
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Software delay routine in 8051 microcontroller

admin November 16, 2012 4 Comments
Software delay routine in 8051 In an 8051 microcontroller, it requires 12  cycles of the processor clock for executing a single instruction cycle.  For an 8051 microcontroller clocked by a 12MHz crystal, the time taken for executing one instruction cycle is 1µS and it is according to the equation,  Time for 1 instruction cycle= 12 /12MHz = 1µS.  The shortest instructions will execute in 1µS and other instructions will take 2 or more micro seconds depending up on the...
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Raspberry Pi-Getting started with the revolutionary computer

jojo November 6, 2012 3 Comments
Are you hearing the name “Raspberry Pi” for the first time? Then you must really recheck your reading habits! I must say that you are not up to date with the latest happenings around the world 😉 Well, Raspberry Pi is nothing more than a small,customizable computer. When you read “computer“, dont think that its something like an Ipad or a Samsung Galaxy Note. Raspberry Pi is an educational product designed for students/hobbyists to learn computer easily.  It is available in...
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Getting Started with Keil uVision

Nilay Banker November 4, 2012 21 Comments
An Introduction to Keil MicroVision Embedded system means some combination of computer hardware and programmable software which is specially designed for a particular task like  displaying message on LCD. If you are still wondering about an embedded system, just take a look at these circuit applications using 8051 microcontroller. You can call these applications embedded systems as it involves hardware (8051 microcontroller) and software (the code written in assembly language). 1. Voltmeter using 8051 2. Thermometer using 8051 3....
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Random number generator using 8051

admin December 13, 2012 9 Comments
Random number generator using 8051. A  random number generator using 8051 that  displays a random number between 0 & 99 is shown in this article. The circuit it self is very simple and may not find any applications in serious embedded projects and this article is just an illustration. The circuit is based on AT89S51 microcontroller, two seven segment LED displays, two transistors and few passive components. Circuit diagram. The two seven segment LED displays are multiplexed together and...
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Digital thermometer using 8051

admin December 13, 2012 29 Comments
Thermometer using 8051. This article is about a simple 0-100°C digital thermometer with 1°C resolution using 8051. The circuit is based on LM35 analog temperature sensor, ADC0804 and AT89S51 microcontroller. LM35 is an analogue temperature sensor IC which can measure a temperature range of -55 to 150°C. Its output voltage varies 10mV per °C change in temperature. For example, if the temperature is 32°C, the output voltage will be 32 x 10mV = 320mV. ADC 0804 is used to convert...
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Most Popular Simple Electronic Circuits

jojo January 3, 2018 3 Comments
In this article we are attempting to list the most popular electronic circuits we have published over the last couple of years.  We know, its a little difficult task! First hurdle to cross is selecting the criteria to decide – “what makes a circuit popular ?“. Next hurdle is listing all of them in an ordered and categorized manner. Some circuits may seem so silly and simple for an experienced hobbyist/electronics geek, while some other circuits may seem so...
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