Here it is demonstrated how one can build VCO(Voltage Controlled Oscillator) using 555 Timer an explains how it works. 555 Timer is a popular timer IC that can be used to build many electronics circuit application such as FSK(Frequency Shift Keying) modulator, oscillator, pulse generator, schmitt trigger etc. The 555 timer mainly operates as astable and monostable mode. The VCO is an application example of 555 timer operating in astable mode. Voltage Controlled Oscillator(VCO) is an electronics circuit which produces varying frequency due to varying amplitude. In other words when varying volta ..read more

Toroid RF transformer is often used for impedance matching in RF circuits. That is match the source and load impedance. In this tutorial we explain the process of making RF transformer for impedance matching with detailed calculation for constructing toroid RF transformer. This involves calculating the primary and secondary number of windings, calculating inductances at the primary or secondary, and choosing toroid core size. To build the toroid RF transformer we need the number of turns for the primary and secondary and select a toroid core. For calculating the number of turns we need to kno ..read more

 Here a class B audio power amplifier with 2N3904 and 2N3906 transistors is presented and its working principle explained. 2N3904 is NPN BJT and 2N3906 is PNP BJT which is used at the output stage of the audio amplifier. These transistors are readily available and with some other passive components found in junkbox this audio amplifier can be build in no time. Usually audio amplifier op-amp IC such as LM386 audio amplifier ICare used but sometimes you may not have such IC(Integrated Circuit) and you may want to build one with discrete components and here is one way you can build one. The ..read more

 Here it is shown how you can make your own FM transmitter. The circuit schematic and PCB(Printed Circuit Board) layout is created in Proteus professional software. 3D view of the expected FM transmitter is also generated to get view of how the FM transmitter looks like in the end.  The FM transmitter is made up basically of pre-amplifier and oscillator circuit. Two general purpose transistor BC547 is used for the pre-amplifer and the oscillator circuit. Besides these two transistor other passive components are used which are listed below. It is also shown how to make the coil needed ..read more

 Here it is shown how to build a simple single transistor FM Transmitter. The transistor used is 2N3904 general purpose transistor. Other than this single transistor we need just few passive components and battery. The following shows the FM transistor build with one transistor.   The corresponding schematic diagram is shown below.   In the above circuit diagram, the audio is enters the FM transmitter via the electret condenser labelled MIC1. The resistor R1 provides the voltage required for the electret microphone to operate. The audio from the microphone transducer into the ba ..read more

 In this tutorial it is demonstrated how to send humidity and temperature sensor data wirelessly using 434MHz wireless module. The temperature and humidity data is displayed on LCD and also printed on the PC serial monitor. This can be useful to monitor remotely environment humidity and temperature inside or outside the house. Monitoring humidity and temperature inside home can be useful since high humidity can effect health and if there is temperature is too hot one can automate to turn on FAN using DC motor. Also humidity and temperature of garden plants outside and inside can be benefi ..read more

  In this article it shown how to make a DIY(Do It Yourself) adjustable voltage lead acid battery charger. You may have lead acid battery of different voltages lying in your home and you want charge those batteries. These different voltage lead acid battery requires different voltage charger. So here adjustable AC-DC voltage adaptor is used with some few passive component to build the charger. The parts required are: - Adjustable AC-DC Voltage Adaptor - 330Ohm Resistor - LED - 1N4007 Diode - Aligator clips - Some wires The following picture shows the build Adjustable Voltage Lead Acid Bat ..read more

In this tutorial you will learn how do you check input and output voltage of a transformer with multimeter and oscilloscope. Transformers are major electrical part in electronics and electrical field of engineering. Sometimes you have a transformer and you might not know the rating of the transformer. You might not know which is primary and secondary side, the input and output voltage of the transformer. Here multiple solution is provided and demonstrated on how you can check the input and output voltage of a unknown transformer. Check Transformer with Multimeter First we should know which is ..read more

Here a circuit to control DC motor speed using MOSFET and Potentiometer is demonstrated. The MOSFET used is CEP7030L which is N-Channel Enhancement Mode Field Effect Transistor(MOSFET). This MOSFET transistor can be salvaged from old PC power supply units(PSU) as was done in this demonstration. Using such power MOSFET we can apply high voltage to the DC motor without heating the power MOSFET. Here the DC motor has voltage rating of 12V. The potentiometer is a 10KOhm potentiometer. An additional resistor of 1MOhm is also used.  Watch the following video to see how the DC motor speed contro ..read more

 Here a simple DC motor construction and operation is explained. The DC motor is easy to build with just few parts. Required parts are some magnets, here neodymium magnets are used, some conducting wires and power supply like 9V battery or power from bench power supply. Optional parts includes wood floor and nails for supporting the coil rotation above the magnet. Watch the following video to know how the motor works.  The following picture shows the simple DC motor.  The following show the Circuit diagram of the simple DIY DC Motor. The conducting coil that was used in this ..read more