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 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…

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 their data lines are connected to Port0  of the microcontroller. Transistors Q1 and Q2 drives the corresponding displays D1 and D2….

Voltmeter using 8051. A simple 0-5V voltmeter using 8051 is shown in this article. This digital voltmeter has a sensitivity of  200mV which is a bit low but this project is meant for demonstrating how an ADC and seven segment display can be interfaced to 8051 to obtain a digital readout of the input voltage. A 31/2 digit high end voltmeter will be added soon. ADC0804 is the ADC and AT89S51 is the controller used in this project. Before attempting this project, go through these projects Interfacing ADC to 8051 and Interfacing seven segment display to 8051 which will give you a…

ADC (Analog to digital converter) forms a very essential part in many embedded projects and this  article is about interfacing an ADC to 8051 embedded controller. ADC 0804 is the ADC used here and before going through the interfacing  procedure, we must neatly understand how the ADC 0804 works. ADC 0804. ADC0804 is an 8 bit successive approximation analogue to digital converter from National semiconductors. The features of ADC0804 are  differential analogue voltage inputs, 0-5V input voltage range, no zero adjustment, built in clock generator, reference voltage can be externally adjusted to convert smaller analogue voltage span to 8 bit resolution…

Water level controller using 8051. A water level controller based using 8051 is shown in this article. A lot of water level controller projects have been published in this website but the is the first one based on a microcontroller. This water level controller monitors the level of the over head tank  and automatically switches on the water pump when ever the level goes below a preset limit. The level of the over head tank is indicated using 5 leds and the pump is switched of when the over head tank is filled. The pump is not allowed to start…