Author name: john

Testing Components

How to test an SCR

Testing SCR using a multimeter. A multimeter can be used to test SCRs quite effectively. The first procedure is to check the diode action between the gate and cathode terminals of the SCR. This test is just like what you have done in the case of testing a silicon diode (see testing a silicon diode). […]

Testing Components

How to test a triac.

Testing triac using a multimeter. A multimeter can be used to test the health of a triac. First put the multimeter selector switch in a high resistance mode (say 100K), then connect the positive lead of multimeter to the MT1 terminal of triac and negative lead to the MT2 terminal of triac (there is no

Testing Components

How to test a diode

Diodes are one of the components that can be tested very easily.Ordinary diodes as wells as Zener diodes can be checked by using a multimeter. While testing a diode the forward conducting mode and reverse blocking mode has to be tested separately. Testing ordinary diode using a digital multimeter. To check an ordinary silicon diode

Light Related

LED ramping circuit.

Description. In this circuit the intensity of LED will vary in a ramping fashion. The circuit consists of three ICs: Two 555 timer ICs and one LM393 op-amp. IC1 and IC2 are wired as oscillators to produce 10 KHz and 1 Hz frequencies respectively.These two frequencies are given to the inputs of the op-amp LM393.LM393

Sensor Circuits, Temperature Related

Zero degree Celsius alarm

Description. This simple circuit will produce an alarm whenever the temperature falls below zero degree. A thermistor is used here to sense temperature. The op-amp LM7215 is used to compare the reference voltage and voltage from the thermistor network. Reference voltage is given to the non inverting input (pin3) of the IC and voltage from

Battery Circuits

Battery charging indicator circuit

Description. This simple circuit can be used to monitor whether a battery is charging or not. The voltage comparator IC LM393 is the heart of this circuit. The LED D1 will remain ON whenever there is at least 25 milli ampere current flowing to the battery. This particular circuit is designed for a 12V battery

Power Supplies

1.3V Power supply

Description. This 1.3V power supply can be used as replacement for the 1.3V Mercury Cell in any circuit. When the input 5V is given to the circuit, the  voltage drop across  zener diode D1 will be around 2V.The diode D2 will drop a 0.7 V from the 2V volt and the remaining 1.3V will be

Power Supplies

Soft start power supply using L200

Description. Here is the circuit diagram of a simple soft start power supply using the well known IC L200.The L200 is a monolithic IC that can be used for voltage and current regulation. The built-in features such as thermal shut down, over current protection and input over voltage protection makes this IC nearly indestructible. When

Power Supplies

Soft start Power supply circuit.

Description. Here is the circuit diagram of a simple soft start power supply using the well known voltage regulator IC LM317.Here the IC is wired in soft start mode in which the output of the IC gradually increases to the desired output voltage .When the input voltage is given to the IC , the capacitor

UPS

Simple UPS

Description. This is the circuit diagram of a simple UPS that can deliver 12V unregulated and 5V regulated DC. The transformer T1 steps down the mains voltage to 12V AC and then the bridge B1 rectifies it. The rectified signal is smoothed by the capacitor C1.When the mains supply is available the battery will be

Power Supplies

12V 15A voltage regulator

Description. Here is the circuit diagram of a powerful 12V regulator that can deliver up to 15 A of current.The common voltage regulator IC 7812(IC1) is used to keep the voltage at steady 12V and three TIP 2599 power transistors in parallel are wired in series pass mode to boost the output current. The 7812

Audio Circuits

3 Input mic mixer circuit

Description. Here is a simple 3 input mic mixer circuit using the popular uA 741 ICs. Four 741s are used here.IC1, IC2, IC3 are used as preamplifiers. They produce a gain of around 40 decibel to the individual input signals. The IC4 is wired as a summing amplifier to add the signals from three preamplifiers.IC4

Audio Circuits

Two transistor tone controller

Description. Here is the circuit diagram of a simple two transistor tone controller circuit. This circuit is based on the famous Baxandal tone control design. The transistor Q1 is wired an emitter follower to provide sufficient current gain and input impedance. The second transistor is used to voltage amplify the signal in. The network of

Equipment Reviews

Equus 3320 Auto-Ranging Digital Multimeter

Every electronic maniac needs a Multimeter, which’s his basic tool. From the plenty of multimeters available in the market, how to choose the BEST one? I thought of reccomending the one I use for my readers. I have been using Equus 3320 Auto-Ranging Digital Multimeter for a year or so and I must say I

Audio Circuits

2X15 Watt stereo amplifier using TDA4935

Description. TDA4935 is bipolar stereo amplifier IC that can be wired as a 2X15W stereo amplifier or a 30W mono BTL amplifier. The IC also features built in circuitry for over load protection and over temperature shut down. Here the IC is wired in stereo mode in order to deliver 15W power on each speaker.

Radio Circuits

Single transistor radio

Description. Here is the circuit diagram of a simple radio that uses one transistor and few other passive components.The C6 and L1 forms a tank circuit which picks up the signal from your desired radio station.Diode D1, capacitor C2 and resistor R1 does the detection of the picked signal.The detected signal is coupled to the

Battery Circuits

Flashing battery monitor

Description. Here is a simple circuit in which an LED will continue flashing as long as the voltage of the battery to be monitored is above the set level.The transistors Q1 and Q2 are wired as a complementary astable multivibrator.The circuit can operate from a voltage range from 6V to 12V. The voltage level at

Lighting Circuits, Power Supplies

Delayed ON LED

Description. Here is very simple circuit in which the LED becomes ON only after a preset time the power supply is switched ON. When the power supply is switched on the transistor will be OFF. The capacitor now charges via the preset R3 and when the voltage across C1 is sufficient, the transistor switches ON

Radio Circuits

AM receiver circuit

Description. Here is a low cost AM receiver circuit that can be tuned from around 550 to 1100 KHz. Three transistors are used in this project. The transistors Q1 and Q2 are wired as a compound transistor pair in which Q1 is an emitter follower and Q2 is a common emitter amplifier. The emitter follower

Audio Circuits

Stereo line driver circuit

Description. This is the circuit diagram of a low cost stereo line driver is given here. The circuit consists of only two transistors and few passive components. Each BC 109C transistor is wired as an emitter follower for driving each channel. The voltage gain of the emitter follower is unity, but it has a high

Battery Circuits, Lighting Circuits

Battery operated mini night lamp

Description. This is the circuit of a low power LED night lamp that will automatically switch OFF at day time. The CMOS timer IC TS555CN is wired as a square wave generator operating at around 5Hz.The output voltage from the IC1 is doubled using the combination of capacitor C2 and diode D2 in order to

Audio Circuits, Transmitters

Audio monitoring system

Description. Here is the circuit schematic of a simple audio surveillance system in which the transmitter will pickup sound from one location and the receiver at other location will reproduce it. The receiver and transmitter are connected by only one set of wire. Here both power supply and transmitted signal share the same wire. The

Radio Transmitters

Medium power FM transmitter circuit

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Automotive Circuits, Battery Circuits

3 LED battery monitor circuit

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