The Story & History of Transistor Invention

Transistors and its path of invention We all know “transistor” is an integral part of any electronic circuit/device. It is very rare to see any circuits built without at least one transistor. This  semiconductor device is used either for switching purposes or for amplification purposes in electronic devices. They are either packed separately or found coupled to the integrated circuits.Transistors are of two types, PNP and NPN. Most commonly NPN transistors are used. In this article, lets go deep into the interesting history of transistor invention. We have developed this article by seeking inspiration from the good responses we have…

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Pulse Width Modulation – What is it?

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 thing to note in a PWM signal is that the time-period and hence the frequency is always fixed. Only the ON…

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The Story of PN Junction Diode

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 to take you through the “invention story” of PN Junction diode.  We are going to see how a pn juction diode…

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Breathalyzer circuit using 8051

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, smoke, nitrogen dioxide etc. The sensor consists of a tin dioxide sensitive layer inside aluminium oxide micro tubes, measuring electrode and…

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What are the Different Types of LED’s available

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 technology has advanced to bigger heights. The result is what we see around us in the form of smart gadgets. LED…

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How to start your career in Web Development & Web Technologies

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 to web & internet. “Web Technologies” refers to technologies that are used to build applications for the web. Examples of technologies…

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VLSI Books for Beginners

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 of a front end and a backend. The detailed architecture is explained in VLSI DESIGN FLOW Most demanding jobs in VLSI goes…

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Heart rate monitor using 8051

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 is called photoplethysmography. Photoplethysmography. Photoplethysmography is the process of optically estimating the volumetric measurement of an organ. Pulse oximetry, cardiovascular monitoring,…

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Interfacing hex keypad to 8051

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 of a 4×4 matrix. Hex key pad usually have keys representing numerics 0 to 9 and characters A to F. The…

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8051 Microcontroller Projects & Circuits

In this article we are listing all the projects and circuits we have developed using the 8051 micro controller. We have tested all of these projects in our lab and verified the working . All these projects are made to solve a real world requirement or problem. Engineering students & other diploma students will find these projects useful for their mini project and main project requirements. All the 8051 projects listed below are made using the 8051 compliant microcontroller from Atmel – AT89S51.  We have given the correct circuit diagram, working and software code (in assembly language) for each and…

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