Description. A preamplifier operating on a single supply and suitable for use with high impedance type crystal pickups is shown here.The circuit is basically a non-inverting AC amplifier in which the gain is dependent on the feedback resistor R4.The smaller is the R4,the lower will be the gain.The low frequency roll off characteristics are decided […]
An inverter is used to produce an un-interrupted 220V AC or 110V AC (depending on the line voltage of the particular country) supply to the device connected as the load at the output socket. The inverter gives constant AC voltage at its output socket when the AC mains power supply is not available. Let’s look
Description. A Schmitt trigger circuit shows two distinct signal input levels for turning the circuit ON and OFF. The difference between the Von and Voff voltages called hysteresis Schmitt triggers are useful in converting slowly rising waveforms into fast rising ones and in relay like application. The circuit shown here uses a 741 with positive
We have already discussed in detail about the basics on operational amplifier, its block diagram, symbol, different characteristics, and its circuit diagram (Refer:- Op Amps-Operational Amplifiers). In this post, we will be discussing about the 741 IC, one of the most popularly used op-amp IC. About the uA741 Op-amp IC The 741 IC was designed
Description. The micro ampere meter shown here is basically a DC millivolt meter.The circuit gives full scale deflection for 0.1V input.The current to be measured is passed through a known resistance R and the voltage drop across it is measured.Here the IC 1 uA 741 op-amp is wired as a non inverting amplifier. Circuit diagram
Square wave generator using uA741 opamp. uA 741 opamp IC. uA 741 is a very popular monolithic opamp IC that can be used for a lot of applications. The uA741 opamp was first introduced by Signetics and now a lot of manufacturers produce them. uA741 is commonly available in an 8 pin DIP plastic package
Description. An AC coupled unity gain gain voltage follower operating on a single supply is shown here.The voltage divider network of R1 and R2 provides a DC voltage equal to half the supply voltage to the non-inverting input of the 741.The output DC voltage therefore stands at half the supply voltage.The output signal swings above
Description. Just about any power transistor can be used in this megaphone.Its suitable for boats,playing fields etc.the transistors Q1 & Q2 are the HEP-230 type which are easily available in the market.The transistors are parallely connected to handle the required power and speaker matching.The microphone is a carbon type like that used in telephone hand
Description. When S2 is ON ,the circuit here operates as an astable multi vibrator and the LED is lit for about o.1sec,flasing every 1.5 seconds.Since the human reaction time is more than this,you cannot catch it once it is seen o,by pressing S1.If your sense of time interval is good,and you press S1 with in
Description. This voltage regulator circuit can deliver up to 3A at 12V output voltage. The circuit can be employed on occasions when a current of more that 3A is demanded for regulator. IC regulators of such high current rating are pretty hard to find. The transformer T1 steps down mains voltage, to 12rms & the
Description. This circuit is a compact timer circuit that will keep the headlights of your car ON for about 1.5 minutes and then turns it OFF.This circuit incorporated to your car will help you to access dark places with out the need to come back and turn OFF the head lights. When the push button
Description. This simple circuit that can be used to flash incandescent lamps up to 10W power rating.The circuit is ideal for making flashing beacons on automobiles and other applications like that.The circuit is nothing but an astable multi vibrator based on Q1&Q2 ( BC557&BD139).The capacitor C1 is the main timing element which determines the flashing
Description. This is a compact electronic siren circuit based on three transistors.This circuit is suitable for in corporating with other alarm or siren projects such as burglar alarms, automatic factory sirens etc or a simple push to on alarm. The electronic siren circuit given here  is based on a complementary transistor pair consisting of Q2
Description. Here is a simple water level alarm circuit using 555 timer that will produce an audible alarm when the water level reaches a preset level.The circuit can be powered of a 3V battery and is very handy to use. The circuit is based on an astable multivibrator wired around IC1 (NE 555).The operating frequency
Description. Here is a simple and effective circuit for driving florescent lamps from a 12 V supply.The circuit is nothing but consists of an oscillator, a MOSFET switch and a step-up transformer for driving the florescent lamp. The IC1 TLC 555 is wired as an astable multivibrator for producing the necessary oscillations.The MOSFET Q1 is
Description. This circuit will produce a visual as well as audible alert whenever the connection between the charger circuit and the battery being charged.What ever be the situation whether it be a loose contact or breakage the circuit will give you the alarm.Such a circuit can be very handy in the fail safe charging of the batteries
Description. Here is a simple charger circuit for charging SMF(sealed maintenance free ) batteries.The charger circuit being curernt and voltage regulated,can be safely used to charge SMF batteries of 1.2 AH rating.This circuit was actually designed in response to a request from a reader.With slight modifications you can use it for charging any sort of
Description. Here is a simple head phone amplifier circuit that can be used to drive your head phone if your music player doesn’t have enough power to drive your head phones.The circuit is straight forward and uses only three transistors. The transistor Q1 (BC 239) and associated components forms a pre amplifier.The transistor pairs Q2
Description. Here is a simple circuit that can be used to check the sound levels.The sound pressure meter is vey useful in setting up home theater systems , if you need to test the sound pressure of each channels on different positions in the room. The circuit is nothing but a non- inverting amplifier based
Description. This circuit given here can be housed in the box containing the speaker to form a handy microphone amplifier.The device can be used by teachers,guides,lecturers etc for speaking in a crowdy or noisy environment. The circuit is designed base on the audio power amplifier IC TDA 7052.The IC can deliver a maximum power output
Description. The contact less telephone ringer circuit can produce a ring as well as a visual indication when a call comes.The main advantage is that since there is no direct contact between the phone line and the circuit there is no chance for a loading or disturbance in the telephone line. When the telephone
Description. This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated. When a call is coming to the mobile phone, the transmitter inside it becomes activated. TheÂ
Description. This circuit can give a visual indication of the rate of air flow.It can be also used to check whether there is air flow in a given space. The filament of a incandescent bulb is the sensing part of the circuit.When there is no air flow the resistance of the filament will be low.When
Description. This circuit can be used to glow a bulb or turn a alarm when the phone rings.Using this circuit nuissence of telephone ring at night can be avoided. When the telephone rings the line voltage rises to 72 volts.At this time the LED in the opto-coupler glows and the transistor conducts. Due to this
 Description. Low power ( 3 to 30 MHz) transmitters constructed by hams are generally called QRP’s. For such transmitters a well tuned antenna is a must.If the impedance is not properly matched there will be a little or no output.But if properly matched there will be great results.A circuit for matching the antenna properly with
