How to Build a Wireless Powered LED with Arduino

Last weekend, I decided to create my first “Wireless Power” project. I wanted to make it as simple as possible, with materials and components I already had lying around, and this is the result:

In this post, I am going to share with you the details so you will be able to quickly build your own wireless-powered LED project.

The Ingredients

You can get all the ingredients from Sparkfun, links included below:

1. Arduino Uno (or a compatible board)
2. Two spools of Hookup Wire. I used Red and Black, $2.50 each
3. An N-Channel MOSFET transistor, $0.95
4. A LED you will power wirelessly, $0.35

You may also want to get a Solderless Breadboard, which makes it easier to connect everything.

Let’s Build It!

First, locate and expose both ends of each of the hookup wire spools:

We will use these spools as our coils.

Then, connect the circuit, as shown below. You can either solder the components or use a Solderless Breadboard. You can also cut some of the hook-up wire from one of the spools and use it for connecting the components, if you need.

The stripped hook-up wire spools are represented by the red coil in this drawing. I found that it works best when you put one on the top of the other.

Finally, connect the Arduino to your computer, fire up the Arduino IDE, and paste the following simple program into it:

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delayMicroseconds(1);
  digitalWrite(LED_BUILTIN, LOW);
  delayMicroseconds(1);
}

Upload and run your program to the Arduino. You should see your red led lighting up!

If the Red led is faint or does not light up at all, do the following:

1. Check your connections, make sure there are no loose connections.
2. Turn one of the coils upside down. Coil polarity seems to have a great affect on the result.
3. Try different parameter values for delayMicroseconds(), such as 5, 10, 50, 100, etc.

So how does this circuit work?

The Arduino code generates a high-frequency alternating current (I measured around 76KHZ). This current is fed into the MOSFET transistor, which serves as a gate — it opens and closes the circuit many times per second, thus producing quick bursts of current into the first coil.

These changes in the current inside the first coil produce a magnetic field according to Lenz’s Law, which then induces a current inside the second coil. This phenomenon is called Electromagnetic Induction, and is also the magic behind Power Transformers.

Finally, we feed the current from the second coil into the LED, which, in turn, transforms it into light.

Final Thoughts

This project is a simple introduction to Electromagnetic Induction, and helps to wrap your head around the basics of wireless power transmission. The idea behind this post is to give you a very simple starting point, and hopefully inspire you to build your own wireless power circuit.

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