In this tutorial we are going to demonstrate how electricity can be transferred wirelessly over short distance without wires.
This demonstrate works on the principle of magnetic coupling, in which energy is transferred from the transmitter coil to the receiver coil when both coils are magnetically linked together. Magnetically linked together in this sense means that the reciever coil is linked by the varying magnetic field of the transmitter coil.
The varying magnetic field of the coil creates an induced electric current in the receiver due to the movement of electrons caused by the oscilating magnetic field.
Electronic components.
- 2N2222A NPN transistor
- Copper coils
- 9v battery
- Blue LED
- Connecting wires.
- 9v battery connector
- 27k ohms resistor.
How does it works?
The NPN BJT transistor(2N2222A) is used as a switch for turning on and off the DC power supply from the battery rapidly at a very high speed.
The wireless power system is divided into two parts, the transmitter and receiver.
1. Transmitter.
The transmitter is made of the oscilator and a center tapped coil.
Making the coil; an enameled copper wire is wound around a cylinder with 15-0-15 turns. This means that a 15 turn is made first and tapped out then another 15 turns is made again, totalling the transmitter's coil number of turns into 30 turns.
Circuit diagram of the transmitter.
Study the circuit diagram above, current flows from the positive terminal of the battery to the center of the coil and then half of the current flows through the coil to the base and other half of the current flows through the collector of the transistor. Current can only flow from the emitter of the transistor to the collector only when a link current is applied to the base. During the first cycle, the current flows from the emitter to the collector because current is made to flow through the base. When current flows through the base, because of the high current draw between the emitter and collector, no current flows the base, thus at during this time the transistor is in the off mode. The switches on and off rapidly using this effect and oscillating or varying magnetic field is created at the transmitter coil.
A 27k ohms resistor is added to the transistor's base to increase the sensitivity and preventing it from getting hot.
2. Receiver.
The receiver coil is made of 30 turns of enameled copper wire just the same diameter as the transmitter coil. It is connected directly to an LED. The light emitting diode turns on because it is a diode, so it rectifies the alternating current induced into the reciever coil and at the same time it lights up.
To power other electronic components like motors, a rectifing diode need to be connected in series with the coil. Mostly 1N4007 is commonly used.
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DIY