Description. Here is the circuit diagram of an infrared intrusion detector. Whenever a trespasser cuts the invisible infrared beam an alarm sound will be raised. The arrangement consists of a receiver circuit and a transmitter circuit. The transmitter circuit is based on two TLC555 ICs (IC1 and IC2). The first 555 (IC1) is wired as […]
Description. This is one of the simplest stereo balance indicator circuit that you can have. The circuit will give a visual indication (using two LEDs) proportional to the difference in balance between the left and right channels of a stereo system. The circuit is based on a uA741 opamp IC. The IC compares the signals
Description. Here is the circuit diagram of a simple dynamic microphone amplifier using two transistors. The amplification factor of this circuit is around 150 and can handle signals from 50Hz to 100Khz.These features make it ideal for audio applications. The audio signal from the microphone is coupled to the base of Q1 via the capacitor
Description. This is a very excellent 40W power amplifier design using TDA2030 IC and two transistors. The circuit employs only few components and does not require a dual power supply. The input signal is coupled to the non inverting input of TDA2030 through the DC decoupling capacitor C5. The TDA 2030 performs the major part
Thermistors are of two types, NTC (negative temperature coefficient) and PTC (positive temperature coefficient types). As their name indicates the resistance of an NTC thermistor will decrease with temperature and the resistance of a PTC thermistor will increase with temperature. Both PTC as well as NTC thermistors can be roughly checked by using an analogue
This article shows you how to test a capacitor using analogue multimeter. Firstly short the capacitor leads for discharging it completely. Set the multimeter to high resistance mode. Connect the multimeter terminals to the capacitor leads. For electrolytic capacitors the positive terminal of multimeter must be connected to the positive lead of the capacitor and
LDR (light dependent resistance) can be very easily tested by using a digital multimeter. We all know that the resistance of an LDR varies according to the light falling on it. At bright light, the LDR resistance will be around 500Ohms and at darkness the resistance will be around 200K. For a proper diagnosis we
Description. Here is a low noise preamplifier design for dynamic microphones. The circuit is based on the uA739 IC from Fairchild Semiconductors. uA739 is a dual audio operational amplifier with high gain and excellent stability. Out of the two opamps available in the IC, only one is used here. The audio signals from the microphone
Description. This is the circuit of a based audio preamplifier which has very low noise. One FET and one BJT are used in this circuit. The audio signal to be amplified is coupled to the base of FET Q1 using capacitor C1 and resistor R3.Base of transistor Q2 is coupled to the drain terminal of
Practical power amplifier. Audio power amplifier is an amplifier which produces amplification of power between the input and output. Theoretically every audio amplifier produces some amount of power amplification, but in practical scenario every audio amplifier cannot be called a power amplifier. It is the amount of power amplification that makes an amplifier power amplifier
Description. This dual power supply is based on the L165 power operational amplifier from SGS-Thomson Micro electronics. The IC L165 can easily deliver up to 3.5A of current (internally limited). The IC is available in Pentawatt package and is very suitable for power supply applications like this. Here the L165 is wired as a voltage
Introduction To Power Amplifiers An amplifier system consists of signal pick-up transducer, followed by a small signal amplifier(s), a large signal amplifier and an output transducer. A transducer is used to convert one form of energy into another type. For example a microphone is used to convert acoustical energy into electrical energy. Conversely, a loudspeaker
Description. This jet engine sound generator circuit is based on the sound generator IC HT2844P from Holtek Semiconductors. This particular IC can make four sounds namely low speed sound of jet engine, high speed sound of jet engine, missile sound and machine gun sound. Each of these sounds can be activated by connecting the pins
Description. Here is a very simple three transistor audio amplifier circuit that can deliver 250mW to a 8Ohm speaker. Complementary transistors BC337 and BC227 (Q3 and Q2) are used as the output pair. Transistor Q1 (BC 547) acts as the preamplifier.POT R5 can be used as a volume control. Capacitor C1 decouples the DC from
Description. This 13V/5A power supply is based on the famous LM338 IC from the ST Microelectronics. The IC has time dependent current limiting, thermal regulation and is available in 3 lead transistor package. The IC can easily supply well over 5A at an output voltage range between 1.2V and 30V. In this circuit the output
Description. The circuit is nothing but two LEDs (D1 and D2), whose status are controlled by the temperature of the surroundings. The famous IC LM35 is used as the temperature sensor here. Output of LM35 increases by 10mV per degree rise in temperature. Output of LM35 is connected to the non inverting input of the
Description. This is a very simple cable TV amplifier using two transistors. This amplifier circuit is most suitable for cable TV systems using 75 Ohm coaxial cables and works fine up to 150MHz. Transistor T1 performs the job of amplification. Up to 20dB gain can be expected from the circuit.T2 is wired as an emitter
Description. Here is the circuit diagram of a 10W audio amplifier using the popular TDA2003 IC from SGS Thomson. The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage. The IC can be also operated from 12V and that makes it applicable in car audio systems. The useful features
Description. Here is the schematic of a very simple electronic thermostat using IC LM56. LM56 is a very accurate dual output low power thermostat from National Semiconductors.LM56 has various useful features like internal temperature sensor, two internal voltage comparators, internal voltage reference etc. Two stable temperature trip points (VT1 and VT2) are created by dividing
Description. Here is the circuit diagram of an FM transmitter using the IC UPC1651. UPC1651 is a wide band UHF Silicon MMIC amplifier. The IC has a broad frequency response to 1200MHz and power gain up to 19dB.The IC can be operated from 5V DC. The audio signals picked by the microphone are fed to
Description. Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles. The frequency of the flashing depends on the value of
Description. This is a very simple AM radio circuit using only two transistors. The coil L1 and variable capacitor C1 forms the tank circuit. Transistor Q1 does the job of demodulation. The demodulated signal will be available at the base of Q1.This audio signal is coupled to the base of Q2 for further amplification. The
Description. Many audio mixer circuits have been published here. But I think, this one is the simplest of them. This very simple audio mixer circuit uses only one transistor. The base emitter junction of the transistor is biased by the diodes D1 and D2.The signals to be mixed are directly coupled to the base of
Description. This powerful lamp flasher circuit is ideal for use in automobiles. The circuit is based on IC LM395 (also known as super transistor) which is a very powerful integrated monolithic power transistor with features such as thermal overload protection, current limiting etc. In fact this IC is almost indestructible.The IC can handle currents up
Description. Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1
