Simple Wireless Power Transmission Circuit

In this post we are going to construct a simple circuit which can glow an LED wirelessly with range of few inches from the transmitter.

We will see:

  • What is Wireless power Transmission.
  • Types of Wireless Power Transmission.
  • Circuit Diagram and Description.
  • Efficiency of Wireless Power transmission.
  • Is it Safe for Human Begins?
  • Advantage and Disadvantage of Wireless Power Transmission.

Are you looking forward to build a simplest wireless power transmission circuit for your school or college mini-project or even as a hobby project? Then you landed on the right page. You will learn everything about wireless power transmission technology and learn how to build one at your home.

What is Wireless power Transmission:

Let’s start with a simple question “what is a wireless power transmission?” is it electricity passing through thin air? Will it shock me? Is it safe for living beings? Is it safe for nearby electronic gadgets?

These are the question raised by many tech enthusiasts who are just exploring this concept. We will answer these questions in this article.

Wireless power is transmission means transmitting electricity without wires up to a certain distance. This practical process consists of:

  • Transmitter
  • Medium
  • Receiver

Transmitter:

The transmitter is where we apply electrical energy to transmit; the transmitted energy may be in the form of light or changing magnetic field or electromagnetic wave like microwave.

Here basically we are converting electrical energy to some other form of energy to transmit power.

Medium:

Medium is where the transmitted energy is passing through. The medium can be solid or vacuum or air. If you are familiar with smartphone charging wirelessly, the energy from the charging pad passes through solids like glass or plastic housing of charging pad and also passes through air to reach the phone.

Metallic medium is a big “NO” for wireless power medium (between transmitter and receiver) because it won’t let the power pass through and absorbed most energy and generate heat. This is applicable only for inductive based wireless power transmission.

Receiver:

The receiver is the one which receives the transmitted power and converts the light or changing magnetic field or electromagnetic wave back to electricity which we can use.

So the start and end product is electricity and the intermediate products are some other form of energy.

Types of Wireless Power transmission:

There are main three protocols for wireless power transmission, they are:

  • Inductive Coupling Power Transmission.
  • Laser Power Transmission.
  • Microwave Power Transmission.

Let’s explore them each.

Inductive Coupling Power Transmission:

In this project we are going to construct inductive based power transmission circuit and we will be digging deeper about this concept.

Inductive coupling power transfer is the most commercially used protocol; you can spot them on wireless smartphone charging, electric tooth brush, charging remote keys of luxury cars etc.

We can compare this protocol with ordinary transformer in which primary and secondary coils are electrically isolated and coupled by iron core of the transformer.

Inductive charging involves conversion of electricity into high frequency alternating magnetic field which is generated by coil of the transmitter. The receiver coil picks up the high frequency magnetic field and converts back to high frequency AC current and rectifies it.

The efficiency of the inductive power transfer depends on the “coupling factor”, the transmitting and receiving coil should resonate at same frequency.

The maximum efficiency of the system is achieved at its resonant frequency. The resonant frequency is determined by the capacitance and inductance of the tank circuit.

Resonant frequency is given by:

F = 1 /2 x pi x square root (L x C)

F is the frequency in Hz.

L is the inductance in Henry.

C is the capacitance in Farad.

Say your resonant frequency is 100 KHz; you should apply oscillating voltage at 100 KHz to the transmitting coil.  The receiving coil should also have identical resonating frequency and now you will achieve good efficiency and longer wireless transmission range.

You can learn about this concept much deeper in this video by GreatScott:

Laser Power Transmission:

In laser power transmission the start and end product is electrical energy and intermediate product is light. The transmitter converts electrical energy into light beam which is sharply focused to the receiver.

In laser power transmission, infra-red lasers are mostly used. The receiver consists of photo voltaic cells which are tuned to respond to the wavelength and frequency of the transmitted laser beam.

The advantage of this topology is that we can transmit power much to longer distance even several meters with least medium loss.

One such product is being developed and you can see how it works in this mind blowing video by LinusTechTips:

Microwave Power Transmission:

Microwave power transmission is much more complex in construction and most efficient wireless power transfer protocol. In this method the electrical energy is converted to microwave, yes the same frequency band at which your food is cooked in your oven.

But need not to worry it may not probably cook your body. Microwave spectrum ranges from 300MHz to 300GHz which includes your mobile phone’s communication frequency and even your Wi-Fi frequency.

The microwave power transmitter consists of microwave generator and wave guide for guiding the wave in a particular direction. The antenna can be micro strip patch or parabolic reflectors or slotted waveguide antenna.

Up to 95% efficiency can be achieved by using slotted waveguide antenna, which very impressive result compare to other two protocols which has efficiency around 5% to 40%.

The receiver antenna is also called “RECTENNA”. It is the combination of antenna and rectification; it directly converts the received microwaves to DC current.

You can witness wireless power transmission using microwave in this video:

That’s enough of theory! Let’s see how to construct one.

Circuit Diagram:

Wireless Power transmission Circuit
Wireless Power transmission Circuit

Description:

The circuit consists of very few components and can be easily built. The transmitter coil consists of 10 turns with center tap; please use thick electrical wires for coil. Use heat sink for BD139 NPN Transistor.

Pin Diagram of BD139 NPN Transistor:

The 4.7nF and the coil with 10 turns resemble as tank circuit which resonates at a particular frequency. The receiving coil also consists of 10 turns with same thickness and 4.7nF capacitor to match the resonance.

The diode IN4148 used as half wave rectifier, IN4148 is schottky diode which can efficiently rectify high frequency AC current. You can also use normal 1N4007 diode but you may see slight reduction in brightness of LED due to higher forward voltage drop.

Coil Construction:

The Receiving coil has 10 turns and 5 cm in diameter (or 10 turns with any diameter) but make sure that transmitting coil and receiving coil measures same diameter.

Transmitter coil:

Wind 2 coils of 5 turns and stack them one another and tape them and solder the center tap and your transmitter coil is ready.

You can definitely try experimenting changing the coil windings, capacitors and input voltage to improve the distance of power transmission.

Efficiency of wireless power transmission:

The efficiency of the proposed circuit is around 10% or less. You can calculate efficiency by measuring the power consumption at input and output.

Power = Volt x Current

Efficiency = (Output Power / Input Power) x 100%

Did you know why only low power gadgets like Smartphones and electric tooth brush are commercialized with wireless power and not laptops or electric cars? That because there is huge efficiency loss.

If everyone starts using wireless powered tech gadgets then it is not good for our planet. You have to apply 5 times or even 10 times the power to get things working. That’s why still wire powered devices rule the world.

We have seen a good efficiency with microwave power transmission but it has not commercialized yet or it won’t commercialize any time soon. This protocol cannot be used with smartphone or electric cars regardless of its good efficiency because high energy microwaves can raise health issues.

This lead us to another question is wireless power transmission is safe?

Is Wireless Power Transmission Safe?

Short answer is YES. Long answer…. keep reading on.

The safety of wireless power transmission depends on how powerful you transmission is and what protocol you use.

Commercial products like wireless smartphone charger are very much safe to use and passed several safety tests before arriving at market. We are not transmitting electricity through the air like Tesla coil sparking around the room; we are converting one form of energy to another form before transmitting.

Inductive chargers are safe and it won’t shock you if you place your finger between Tx and Rx coil.

Laser power transmission is new to consumer market and high power lasers are certainly dangerous but they will never use such high power lasers that cause harm to human beings or animals.

Microwave power transmission is several decades old concept as you saw on the video, but nobody should stand near a high energy transmitter or receiver or in between the transmission path for longer period.

But till date there is no documented health hazard due to wireless energy transmission.

Advantage of Wireless Power Transmission:

  • Convenience for charging gadgets.

Many companies are spending million and even billions of bucks just for one thing “convenience”. That’s the only main advantage of wireless power transfer.

Disadvantage:

  • Big efficiency loss.
  • Limited range.
  • Not eco-friendly due to huge energy loss.
  • Heath hazards yet to discover with various protocols.

If you have any further questions, please ask us in the comment you can anticipate a guaranteed reply from us.