Electronic Circuits and Diagram-Electronics Projects and Design

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…

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…

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…

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…

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,…

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…

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…

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 accepts this signal, performs necessary processing and displays the corresponding distance on the 3 digit seven segment display. This circuit finds…

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 that) glued on the rotating surface and the meter shows the rev/sec on the display. The circuit diagram of the digital…

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. In simple words, the most outstanding features of the PWM based lamp dimmers are high efficiency and low physical size. The…