Easy Wireless LEDs





Introduction: Easy Wireless LEDs

About: Greetings ! I'm Tanay, a hobbyist interested in making robots and sharing stuff. I hope that my instructables help you in solving your problems Happy Tinkering ! Note : Sorry for the inconvenience but I won...

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 ).

Step 1: 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 ).

Step 2: 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.

Step 3: Soldering the 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.


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 ).


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 ).



1. Hook up the oscillator to a DC power source ( 6- 12V depending on your transistor ).

2. Place the driver coil on a flat steady surface.

3. Hold the led coil such that both the coils are in parallel planes.

4. Bring the LED coil close to the oscillator coil ( do not bring it in contact ).

5. The transistor may heat up a bit , but that's fine !

5. Success !


1. Check the solder-joints.

2. Avoid touching any loose contacts on the oscillator board.

3. Make sure that the coils are circular and not deformed.

4. Hold the coils at an optimum distance.

5. If the coils are a bit tilted then the LED wouldn't glow so brightly.

Suggestions and corrections are welcome ! Feel free to ask your questions about this i'ble !

Remix Contest

Third Prize in the
Remix Contest

2 People Made This Project!


  • Oil Contest

    Oil Contest
  • Water Contest

    Water Contest
  • Clocks Contest

    Clocks Contest

94 Discussions


7 months ago

I try to make it, but can only get et to sving at 1Hz :s

2 replies

Here it is the resoult :)


It is working now :)
I used wrong compones.


1 year ago

no resonance

Can I use 32AWG enameled copper wire for it? Please reply quickly I really need help

1 reply

32 gauge is pretty thin for this project, the coils will deform easily if you use a low gauge wire. Though it should work just fine if you build something to support the coils in the desired shape.

It seems that the inductor that you've got is a common mode choke ( i.e couple of two discrete 100µH inductors with a common core ). Try using your DMM to check the resistance or continuity between every combination of two pins. At some point you'll get a certain amount of resistance and at some point you won't get any continuity. If the case is true then the pins which show some resistance are to be used as an inductor. The other two pins can be left open. This schematic should help :


Hey, Akasi here again. I have built your circuit exactly as you said, except I used a breadboard and a 9v battery. I cannot get it to work! Please look at these images and tell me if there is something wrong!!! I need your help ASAP! Here are the pictures. The second-last picture is my receiving coil, and the last picture is what my DMM shows when I hook it up. Please reply!!! Thank you so much!

7 replies

Okay , so it seems that you've got the circuit all right. Did you check all the connections with your DMM's continuity tester ? specially the coil joints ?

Also make sure that your transistor BD139 is in working condition ( just by making a simple switch with an LED ).

Be sure to use a coil made up of a thicker wire ( smaller gauge number ) and that it has 1~2 turns ( both the coils should be identical ).

Have you tested this circuit with an LED ? Because the DMM isn't capable of measuring such high frequencies ( not more than a few hundred Hertz ). So either you may hook the receiver coil to a bridge rectifier and then filter it using a 10uF - 100 uF capacitor.

Why can't the number of turns be more than 1-2? I was planning to put 10 turns in both coils, and test out what happens when we change the diameter and turns of the transmitting coil. Why does the gauge of the coil have to be low? What gauge do you recommend?

Because, as you increase the turns, the resistance also increases. We need to keep the turns minimum ( though 10 turns should probably work fine ) and a lower gauge wire is to ensure that the structure stays in shape ( when you're making the coils manually ).

The most important thing is that, did you test it using an LED before hooking the rec. coil to the DMM ? and is the transistor working fine ?

Yes,I did use the LED, and it didn't work. I tested the transistor using a switch circuit and it works fine.

Good news! It works!!!!! Thank you so much! At this time, I cannot send photos, but I will once I record some data. I used 22 AWG wire, made 2 turns, stripped the wire well, and plugged it into the circuit, and it works!! Once again, thank you. I am eternally grateful towards you.

Keep making projects like this. I chose your project over everyone else's as you made it simple and explained how to make it throughly! You definitely have my vote!

Great job ! I'm glad to hear that ! :)

Thanks for the appreciation and support ! :)