Easy Wireless LEDs

Yes ! That's right , this instructable will guide you to create your own wireless LED.

This instructable is inpired from : Wireless L E D by neelandan ! Thanks for this great instructable !

This version uses a more powerful high frequency switching transistor ( BD139 ) so that means now you've got great power and " with great power comes great responsibility " :D

*So use this device with great caution and DO NOT use it near any sensitive electronic device ( specially hard drives ) as it is capable of creating high frequency EMPs which could easily mess with your gadget ! While working with transformers take proper safety measures and use an insulated casing as there may be a potential threat of getting electrocuted. ( Instead use a power adapter or a battery ).

This project is pretty easy to make and can be used to demonstrate and study the principle of electromagnetic induction practically . The components are pretty easy to get

all you need is :

1. 2 x 2 turn coils

2. 33k resistor

3. a 100nf capacitor ( code : 104 )

4. 100 µH ( micro Henry ) Inductor

5. An LED ( red / orange / SMD red works best )

6. BD139 transistor ( or equivalent )

7. A bridge rectifier ( optional I've used 1n4148 diodes )

8. A perfboard ( 3x3 cm )

9. Wires , solder , power source ( 6-12 V ).

Gathering the Parts ->

1. Coils can be salvaged from old toroids

2. Transistor ( BD139 ) , Resistors ( 33k - orange // orange // orange ) and Capacitors ( 100nf - 104 ) are pretty common and can be bought from a local electronic hobby shop.

3. Inductors can be salvaged from old PCBs and can also be made by winding a coil around a ferrite core.

4. Make a mini bridge rectifier >> ( next step ).

Mini Bridge Rectifier

You'll need 4 x 1n4148 diodes.

1. Follow the schematic and join the four diodes one - by - one.

2. Twist the wires ( pay attention to the polarity of diodes black lines denote negative terminal ).

3. Solder them together.

4. Your bridge rectifier is ready !

*I've used a bridge rectifier because I'm taking power from an AC source ( 6 - 12V ) but you can skip it and just use a battery.

Soldering the Circuit

OSCILLATOR CIRCUIT :

1.Follow the schematics and solder the circuit as shown ( on a perfboard ) .

2. You can also assemble it on a breadboard ( I recommend you to first prototype the circuit on a breadboard and then solder the final circuit ).

3. Be careful while soldering the coil and try not to deform it. The shape needs to be perfectly circular and planar.

LED PART :

1. If you're using an SMD LED then solder a pair of leads to the solder pads on the led.

2. In case you're using a through-hole LED , just solder it's leads directly to the coil ( don't worry about the polarity ).

WORKING

This device basically works on the principle of mutual induction . The magnetic flux generated by the emitter coil gets linked to the secondary coil ( coil with LED ) due to this , EMF is induced in the coil.

According to the expression of induced EMF (rate of change of flux linked to the coil ) , the EMF induced in the secondary is directly proportional to the rate at which the current changes ( or switches ).

Also DC can't be directly induced using this method , this is because in DC , the current is constant throughout unlike AC current.

Commonly , the frequency of AC current that we get is 50-60 Hz which isn't enough to light up an LED using this process , so here comes the oscillator circuit which takes in power from a DC source and converts it into a high frequency switching current.

This is done by a high frequency power transistor ( BD139 ) which constantly switches , generating a high frequency switching current. This is then fed to the primary coil which converts this energy into a constantly changing magnetic field. This increases the frequency of the current and therefore the EMF induced in the secondary coil becomes enough to light up an LED.

You don't need to worry about the polarity of the LED because , the frequency of the current is so high that the human eye won't be able to identify the blinking effect ( due to persistence of vision ).