Category: Electronics Projects

Add on Device For Telephone

Engineeering Projects
circuit diagram of add on unit for telephone

This electronic project, Add on Device For Telephone has multiple applications when used with the telephone lines. Since it is added parallel on the telephone system, it is called add-on device. The circuit add on device for telephone supports three modes of operation: on-hook, off hook, and ringing modes. It also provides the audio-visual indication of these operations. Using the relay, add on device circuit can connect the telephone to a CID (caller identification device). It can also be used to indicate tapping or misuse of telephone lines with the…

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Tone Control Circuit (Active and passive)

Engineeering Projects
circuit diagram of active tone control using single transistor

Among the most popular control circuit found in an audio system is tone control. The tone control is used to modify the tonal characteristic of the signal chain i.e. it enables the listener to alter the tonal quality of the sound being reproduced. The effect of tone control has on the frequency response of the equipment and their purpose is to help remedy shortcomings in the source program material, the receiver or transducer, or in the loudspeaker and the listening room combination. These are either of the passive types, of…

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Phone Broadcaster Circuit

Engineeering Projects
circuit diagram of phone broadcaster

An interesting circuit design that is also used as a wireless telephone amplifier, is demonstrated below which has been proven very useful in prying on a telephone conversation and therefore is termed a phone broadcaster circuit. The more amazing or we can say a comforting fact about the phone broadcaster circuit design is that it draws the power essential to operate the circuit directly from the active telephone lines. Therefore, it avoids additional expenses in external battery and prevents the circuit from the extra bulkiness of other power supplies. Circuit…

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Water Level Indicator Circuit

Engineeering Projects
circuit diagram of digital water tank gauge

One of the most common circuits in the market is the water level indicator. But most of these circuits fault corrosion of metal electrodes due to electrolytic reaction. This fault can be minimized effectively by using alternating current instead of direct current supply. Here we design and verify a circuit called electrolysis proof water level indicator using a COMOS IC which has profitably exploited the normally unused property of CMOS devices. Other Water level indicators and controller circuits posted on bestengineeringprojects.com  Ultrasonic Water Level Meter Water Level Indicator Circuit using…

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Preamplifier for ceramic-pickup

Engineeering Projects
circuit diagram of preamplifier for ceramic pick up

The circuit posted here is of a preamplifier for ceramic pick-up having moderately high input impedance about 470Ω and voltage gain of more than 12. Circuit Description of Preamplifier for ceramic-pickup The circuit of a preamplifier for ceramic pickup is built around FETs because it has outstanding low-level characteristics including a high input impedance and low noise. These characteristics make the FET a natural choice at the input stage of a preamplifier for accepting signals from high-impedance transducers such as ceramic-pickup. Inputs from the ceramic microphones are given to the…

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Non-Destructive Power Supply Circuit

Engineeering Projects
circuit diagram of non destructive power supply

The power supply is the basic unit for any electronic circuit and it must be non-destructive. Various types of power supply circuits like stabilized power supply units, Digital control variable power supply units, self switching off power supply units, etc are available on bestengineeringprojects.com. Now, here is another circuit for smooth power supply in the section of power supply-based projects called a Non-destructive power supply circuit using voltage regulator IC 732. Working of the circuit non-destructive power supply-Circuit Most circuits are set to an adjustable “knee” from 2mA to 30mA.…

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Sound Operated Relay Using Transistors

Engineeering Projects
circuit diagram of sound operated relay

Various type of switching circuit like a touch-operated relay, light operated relay, heat operated relay is already posted in bestengineeringprojects.com. Now here is another simple electronic project in the series of switching circuits called sound-operated relays. Circuit Description of Sound Operated Relay using Transistors The circuit of sound operated relay is self-explanatory and is very easy to understand. This circuit is built around a 2-stage audio amplifier using PNP transistors. The sound sensor of the circuit sound-operated relay is done by 8Ω loudspeakers. The output of the loudspeaker is given…

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High-Gain Preamplifier Circuit Using Single Transistor

Engineeering Projects
circuit diagram of high gain preamplifier

The project posted here is of a high gain preamplifier circuit with a low input impedance of about 4 KΩ. It is capable of very high gain in the order of a few hundred if Rc is very greater than RL. Circuit Description of High Gain Preamplifier Circuit The circuit of the high gain preamplifier is built around a low-power NPN transistor T1 which is here configured in common emitter mode using self-bias or emitter bias. This biasing method is used because it produces excellent operating point stability. Resistor R1…

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Simple Preamplifier Circuit using Single Transistor

Engineeering Projects
circuit diagram of simple preamplifier using transistor

The project posted here is of simple preamplifier circuit and is the simplest possible. This circuit provides a voltage gain of about 3 to 30 and is dependent upon source and load impedance. The simple preamplifier circuit has low input impedance. Description of Simple Preamplifier Circuit The circuit of the simple preamplifier is designed using a single low power amplifier transistor and is configured in common emitter mode. The input signal is given to the base of transistor T1 through capacitor C1. Capacitor C1 is a coupling capacitor to couple…

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Listening Bug Using op-amp 741

Engineeering Projects
listening bug thumbnail

Here is a simple project called listening bug circuit using 741 using the most popular op-amp IC 741. This circuit can be used for spying because by using this circuit we can hear any conversation held in any other room or we can say using this circuit one can hear the conversation held in another room. This circuit can also be used for baby monitoring. Also, check our Listening Bug Circuit using op-amp LM386. Description of Listening Bug Circuit Using 741 The circuit of the listening bug shown in figure…

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