The final project for my Circuits II class. Our task was to come up with a project that could be done as a if it were a lab exercise. We could use any equipment within the lab and would write up the process as if it were an exercise received from the professor.

Wireless electricity always interested me. Being able to connect a device for power without any wires makes the whole process seem like something from a sci-fi film. To keep our project simple, we decide to power just an LED and measure the power transferred to understand the efficiency of wireless vs wired.

The Setup

The RLC circuit used for our setup

The circuit ended up being very simple. When applying AC power to an inductor, it creates a magnetic field that another inductor can be placed inside of to harness the power. We created custom inductors by winding magnetic wire around a cylindrical object. We then calculated the harmonic frequency for these inductors and applied an AC voltage at this frequency to one of the inductors. We were able to transfer electricity using this method, however, the amount received as only a fraction of the original amount sent.

We were able to improve the efficiency by also connecting a capacitor and resistor in series with the inductor. A new harmonic frequency was calculated for the inductor and capacitor. We saw great improvements in the amount of power transferred depending on how far apart the inductors were from one another. When placed extremely close together, we measured nearly 100% power transfer.

The Results

We received a lot of compliments from classmates for this project. I wasn’t the only engineer curious about wireless electricity and it makes for a fun way to learn about mutual inductance. Our professor’s specialty was in magnetic fields so he also enjoyed getting a chance to play with the circuit.

Our original lab report can be found here. A video can be seen below of our professor taking a look at the circuit. The additional wires on the receiving inductor were coming from the oscilloscope to measure the received power.

Wireless circuit in action