You can light an LED without a battery! It is funny to see that, the LED is glowing without power from a battery. The trick is Wireless electricity that is lighting the LED through the mechanism of Induction. Many projects are available in You tube and selected one simple project for you. The step wise procedure is explained here. You can learn some theory along with this. Make it and enjoy.
You need the following components
1. 26 SWG Enamelled Copper wire – 2 Meters.
You can take any copper wire between 24 SWG (Standard Wire Gauge) to 36 SWG. Also you can take the single core hook up wire used in projects. Type of wire is not a problem. Use any type.
2. 1K Resistor – 1
3. Transistor 2N 3904
4. 5 mm RED transparent LED
5. 9V Battery Snap
6. 9V Battery
Let us start to make the Project
The circuit has two sections – A Transmitter and a Receiver. We need two coils for these sections.
Take a piece of 1 inch PVC pipe or a bottle or any cylindrical object to wind the coil. First make the Receiver coil to connect the LED. Wind 30 turns of wire around the PVC pipe. Slowly remove the coil without unfolding the winding. Twist the free ends of the wires around the coil to make the winding intact. You can also use Cello tape for this.
See the finished coil
Now remove the insulation from the tip of the free ends of coil using a knife. Tin it using solder. Solder the Anode and Cathode of the LED to the wires. Polarity of LED is not a problem. You can connect either way round.
Now make the Transmitter coil
This coil is similar to the Receiver coil already made but has a Centre tap. First wind 14 turns around the PCV pipe (or bottle). Then make a Centre tap by extending the wire to 2 inches. Fold it and wind the remaining 15 windings.
Now the Transmitter coil has three leads. A Start lead, a Centre tap and the End lead. Twist some portion of the leads around the coil to prevent the unfolding of windings. You can also use Cello tape for this.
See the finished coils.
The main part of the Transmitter circuit is the NPN transistor 2N 3904 which is a high gain RF transistor. Connect one lead of the Transmitter coil to the Collector of transistor. Connect the other end of coil to 1K resistor. Then connect the other end of 1K resistor to the base of the transistor. Remove the insulation from the tip of the Centre tap and connect it to the positive wire of the battery snap. Connect the negative wire of battery snap to the emitter of the Transistor. The Transmitter circuit is ready
Let us see how it works
The Transmitter circuit is powered by the 9V battery. The High gain RF transistor 2N 3904 and the coil works likes an Oscillator. This oscillation causes the generation of an Electromagnetic field around the Transmitter coil. Depending on the power supply and the turns of coil , the strength of EM field varies. In the given circuit, you will get more than 1 inch range. The Receiver circuit also has the similar coil with the connected LED. When the Receiver coil comes close to the Transmitter coil, the EM field from the Transmitter coil induces current in the Receiver coil. This current is strong enough to light the LED. The LED itself acts as a rectifier, so it Lights just like connecting to a battery.You can use any high gain transistor like 2N2222 instead of 2N 3904.
The Wireless electricity thus generated in the Receiver coil will have around 9 V similar to the supply voltage to the Transmitter circuit. To check the voltage induced in the Receiver coil, we have to use a IN4007 diode for rectification. Remove LED and connect the Anode of IN4007 diode to one end of coil and connect its Cathode to the Red probe of Multimeter. Connect the Black probe of the Multimeter to the other end of coil. Bring the Transmitter coil close to the Receiver coil. You can see the voltage level in the Multimeter. It increases to 9 Volt when both the coils are close together. The coil also has sufficient current around 50 mA even to light a White LED. See image
No direct line –o – sight between the two coils is necessary. You can enclose the Transmitter circuit inside a plastic box or a wooden box. Just place the Receiver circuit over the box. LED will light. The emf passes through, plastic, wood, paper cloth etc to light the LED. See the images below.
The finished Project. You can show it your friends
It works in 1.5V Pen cell also but the brightness of LED will be less.