Category: Electronics Projects

Relay Tester Circuit

Engineeering Projects
circuit diagram of relay tester

Here is the relay tester circuit using timer IC 555 which is used to measure pull-in and release voltage of relays ranging from 6V to 28V DC. Relays are probably the simplest electromechanical devices, yet they are the most important components of many industrial and domestic electrical equipment. All too often, it is a hardship for the equipment manufacturers to discover that the commercial quality relays of similar types have a wide range of operating voltage. Many times, it is found that the relay contacts will not close properly. Many…

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JFET Op-Amp Based Stereo Control Preamp

Engineeering Projects
circuit diagram of jfet stereo control preamplifier

Almost all pre-amplifier circuit uses ordinary op-amp, which is not as good as JFET op-amp. JFET op-amp has very low noise and a very high input impedance due to which they can be used in a large number of circuits. The circuits are shown here fulfill the need for a handy, high-performance simple control preamp. Circuit Description of JFET Op-Amp Based Stereo Control Preamp Based on LF353N bi-FET op-amp the circuit is ideal for the stereo application for which quad LF347 or four LF351s can also be used is shown in…

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Electronics Thermometer Using Op-amp 741 IC

Engineeering Projects
electronic thermometer circuit using op-amp 741

Here is the circuit diagram of an electronics thermometer using op-amp 741 IC and a silicon diode having a range of -20oC to 125oC. Various types of temperature measuring and controlling circuits either using a microcontroller or discrete component are already posted on bestengineeringprojects.com. Circuit Diagram of Electric Thermometer Using OP-AMP 741 The entire circuit of the electric thermometer is built around two op-amp 741 IC, a silicon diode, and a few passive components, where silicon diode D1 is used as a temperature sensor. The diode 4148 has a voltage…

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Single Phasing Preventer Circuit

Engineeering Projects
installation of the preventer

If we have been familiar with machinery, we all know how important it is to follow safety measures to mitigate injuries and accidents. A single phasing preventer circuit is one of the solutions we can look forward to. The phrase ‘preventer circuit’ itself portrays it. The single-phase preventer circuit is also a high low and unbalanced-supply voltage cut-off relay. To ensure complete safety for 3-phase machinery, the preventer circuit has been known to be handy. Generally, an induction motor burns out due to excessive voltage during an off-hour, a very…

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Electronic Fuse Using Op-amp 741

Engineeering Projects
op-amp 741 based electronic fuse

Here is an electronic fuse using op-amp 741 which features slow-blow properties, a variable current limit, and a ‘live’ indication of its operation. Moreover, it is simple to restore. The electronic fuse using op-amp 741 allows the gadget to draw a higher current initially but keeps a watch on it. if the gadget continues to draw more current beyond the set time limit, it disconnects the supply. The fuse, therefore, acts as a cut-out and indicates this by a neon glow. It is replaced by simply resetting the circuit once.…

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RFID Based Security System Using Microcontroller AT89C52

Engineeering Projects
circuit diagram of RFID Based security system

RFID Based Security System Using Microcontroller AT89C52 Different concepts of security systems have flourished along with different techniques and different types of equipment. RFID; Radio-Frequency identification (RFID) is another achievement we are relying on for optimum security facility in multiple projects. It makes use of electromagnetic fields to detect unique tags assigned to objects in the vicinity. There is a reason why it has mustered more popularity in comparison to other security systems that use bar codes and conventional methods. It is because RFID traces tags hidden inside objects, unlike…

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Electric guitar preamp circuit

Engineeering Projects
author prototype of guitar pre-amplifier box

The entire circuit of the ‘Electric guitar preamp circuit’ is divided into small sections to ensure simplicity and easy understanding of the project. The first section comprises a single transistor that serves as a common-emitter amplifier. Be it in melodious songs or in rock songs, the guitar is an inseparable part of music in today’s world. To extend the level of sound such that it can be heard by every individual in a mass, amplifier circuits are extensively incorporated into the music system. And this circuit represents a similar concept.…

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Frequency Counter Schematic using Microcontroller AT89C51

Engineeering Projects
circuit diagram of frequency counter

Frequency Counter Schematic using Microcontroller AT89C51 is a simple yet mostly used frequency counter schematic used. The reason behind its simplicity also lies somewhere in the fact that this project uses only two components-AT89C2051 microcontrollers and a 16*2 LCD. Frequency is a crucial subject matter in every project. Precise and accurate frequency generation is another challenge we face in varieties of project design. As per the design of this project, this circuit can withstand frequency ranges between 1 Hz to ~16.5 Mhz, and the rest depends on the characteristics of…

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AC Motor Speed Controller Circuit Using AT89C51

Engineeering Projects
author prototype of ac motor speed controller

Here is a simple circuit “AC Motor Speed Controller Circuit Using Microcontroller” which is used to control the speed of AC motor using microcontroller At89c51. The circuit uses the principle of changing the firing angle of TRIAC to control the speed of the motor. Here, in this project, we had to use various switches to control the speed whereas an LED bar graph is used to indicate the speed of the motor. Circuit Description of AC Motor Speed Controller Circuit Using AT89C51 The circuit diagram of the signal phase AC…

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Sound detector circuit using op-amp 741

Engineeering Projects
sound detector circuit using 741 IC

The circuit diagram of the sound detector circuit using op-amp 741 is shown in figure 1. The heart of the circuit is op-amp 741 which is used in order to sense the vibrations of sound waves condenser microphones. Introduction of Sound detector circuit using op-amp 741 Sometimes due to lack of concentration and our ignorance, we are unable to hear anything around us. And, that could lead to unfortunate misfortunes which could have been avoided with appropriate precautions. This circuit called ‘Sound Detector’ is what detects vibrations of the sound waves…

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