Micro ampere meter circuit using uA 741

admin July 30, 2008 4 Comments
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 with Parts list. Notes. Assemble the circuit on a good quality PCB or common board. Use a +9V/-9V dual power supply for powering the...
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Voltage follower circuit

admin July 28, 2008 3 Comments
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 and below this value.The standing DC voltage at pin 6 does not matter because the output is coupled to the next stage via a...
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Missing pulse detector circuit using NE555

jacky July 25, 2011 4 Comments
Description. An NE555 timer IC connected as shown here can detect a missing pulse or abnormally long period between two consecutive pulses in a train of pulses. Such circuits can be used to detect the intermittent firing of the spark plug of an automobile or to monitor the heart beat of a sick patient. The signal from the pick up transducer is shaped to form a negative going pulse and is applied to pin 2 of the IC which...
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555 Tester circuit

jacky February 28, 2010 6 Comments
Description. NE555 is an IC which is widely used in timers and control circuits. A circuit for independent testing this IC is given here. Here the NE555 is wired as an astable multivibrator. When the push button switch S1 is pressed the LEDs D1 & D2 will flash alternatively. That is when output is high D2 will glow & when output is low D3 will glow. The rate of flashing will depend on components R1,R2 & C1.   When...
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Sound pressure meter

admin April 7, 2010 3 Comments
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 on op-amp CA 3140 9 (IC1).The sound picked by the condenser mic will be amplified by the IC1 and rectified by the bridge D1...
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Field strength meter

admin May 8, 2008 3 Comments
Description. Here is a handy field strength meter that can be used to check the strength of AM radio signals.The circuit is a very useful for those who assemble radio transmitters(especially in the tuning of the final stage for maximum range). The circuit is essentially some sort of a AM receiver it self. The capacitor C3 and inductor L1 forms a tuned circuit to receive a particular frequency(the frequency of your transmitter).The diode D1 detects the signal and applies...
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Saw tooth wave generator using NE555

jacky February 1, 2012 8 Comments
Description. A simple sawtooth wave generator circuit for generating a saw tooth wave form using a NE555 IC is given below. The frequency of the wave form can be varied by using a POT. The capacitor C, resistor R and zener diode forms a constant current source for charging of the capacitor. When the voltage across capacitor reaches 2/3 Vcc the internal comparator inside 555 goes on and capacitor discharges. When the voltage across the capacitor goes below 1/3...
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Variable frequency oscillator

jacky March 8, 2012 1 Comment
Description. Here is a simple variable frequency circuit based on timer NE555. Here NE55 is wired as an astable multivibrator, whose output frequency can be varied by varying a potentiometer. This circuit is a must in the work bench of a electronic hobbyist. Frequencies ranging from several Hz to several KHz can be obtained using this circuit. For very low frequencies (few Hz) replace C with a higher value electrolytic capacitor. The low frequency oscillator schematic is shown below....
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Humidity tester

jacky March 7, 2012 4 Comments
Description. A variety of humidity tester circuits are available, but this  is a circuit which is as simple as possible. Using only a transistor, LED and few resistors, this circuit can be used to check the humidity level of materials like soil, paper etc. When the humidity in a substance increases the current conducted through  it also increases. This is the working principle. If there is required humidity, the current through R3 will be sufficient to produce a voltage...
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Remote control tester circuit

jacky January 21, 2014 43 Comments
Remote control tester Description. This is a simple remote controller tester circuit  based on infrared sensor IC TSOP 1738. When the IR waves fall on the sensor it output changes to low state.This makes the transistor Q1 ON and LED will blink according to the code contained in the signal. So for press of each button the LED blinks in different ways. This is a good indication of the working of remote.The diode D1drops 0.7 V to give the...
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