Wireless power is not an original idea, Nikola Tesla even experimented in it in the past!
Many products including phones, electric toothbrushes and even certain medical equipment are now wirelessly charged.
However, there is always space for improvement.
This post covers how to assemble a simple wireless power transmitter and receiver circuit using readily available components.
This will help you know the process of wireless charging.
What is a Wireless Power Transmission Circuit:
A wireless power transmission circuit is an electronic circuit which transfers electrical energy from a power source to a particular device without the using cables or other physical connections.
Techniques for electromagnetic fields to transfer electricity over short or long distances are the backbone of wireless power transmission.
Inductive coupling is one common technique for wireless power transmission
Transmitter Circuit Working:
Parts List:
| Type | Component | Quantity |
|---|---|---|
| Resistors | 1k 1/4 W | 1 |
| 10k 1/4 W | 1 | |
| 27k 1/4 W | 1 | |
| Capacitors | Ceramic 0.1µF | 1 |
| Electrolytic 47µF 25V | 1 | |
| Semiconductors | IC LM386 | 1 |
| Coil | As given in Diagram | 1 |
The output of the LM386 is a 1khz square pulse signal.
This signal is then sent to the copper coil starting an oscillation in the coils magnetic field at 1khz.
As the coils magnetic field starts to rotate, it produces a strong fluctuating magnetic field around it.
Receiver Circuit Working:
Parts List:
| Type | Component | Quantity |
|---|---|---|
| Capacitors | Electrolytic 100µF 25V | 2 |
| Semiconductors | Diode 1N4007 | 4 |
| IC 7805 | 1 | |
| Coil | As given in diagram | 1 |
An electromotive force (emf) is generated by the increased electromagnetic flux in the receiver coil and its amplitude changes with the number of windings and the gap between the coils.
By changing the alternating current (AC) into direct current (DC) the bridge rectifier corrects the potential difference created in the receiver coil.
A constant and regulated output voltage therefore is ensured by the positive voltage regulator 7805 which controls the rectified DC voltage.
To modify the output frequency range, experiment with the values of the timing resistor R1 and timing capacitor C1.
The circuit could be corrected to meet particular power transfer needs by modifying the transmitter and receiver coils.
Formulas:
1: The below mentioned formula are used to calculate the frequency of an RC oscillator circuit:
f = 1 / (2 * π * R1 * C1)
where,
- f represents the output frequency of the oscillator circuit in units of hertz Hz.
- π (pi) is a mathematical constant with a value of around 3.14159.
- R1 represents the resistance of resistor R1 in the circuit measured in ohms Ω.
- C1 represents the capacitance of capacitor C1 in the circuit measured in farads F.
How the formula works:
In an RC oscillator circuit a resistor R1 and a capacitor C1 are connected to create a feedback loop that generates a continuously oscillating voltage.
The formula provides the connection between the oscillation frequency and the values of the resistor and capacitor.
2: The formula below indicates the simple connection between the parameters regulating the induced electromotive force (EMF) in a transformer or coil setup.
Induced EMF ∝ Number of Windings, Distance between Coils
The meaning of the symbol ∝ is “proportional to.”
This indicates that the induced EMF and the product of the number of windings and the distance between the coils do not always have a linear relationship.
Induced EMF:
With the symbol ε (epsilon) it is the voltage that is induced in a conductor due to a fluctuating magnetic field.
It is the voltage generated in a transformers secondary coil when the magnetic field is modified by the current flowing through the primary coil.
Number of Windings N:
- In a coil this refers to the number of wire turns.
- It works with transformers primary and secondary coils.
Distance between Coils (d):
- This signifies the distance between the centers of the primary and secondary coils.
- With a shorter distance between the coils a greater magnetic field coupling is achieved.
How the formula works:
The electromagnetic induction idea that drives the working of a transformer.
A fluctuating magnetic field is generated when the main coils current changes.
The secondary coil is then cut by this magnetic field which causes Faradays Law of Induction to be activated.
How to Build:
To build a Simple Wireless Power Transmission Circuit follow the below mentioned steps:
- Place the IC LM386 as a square wave oscillator.
- Connect the Timing Resistor R1 and timing capacitor C1 to control the output frequency range.
- Apply a power supply of 5V to 12V to start the LM386 oscillator.
- The LM386 produces a 1khz Square pulse signal which is then transmitted to the coil.
- The coil starts oscillating at 1khz generating a strong fluctuating magnetic field.
- Join a bridge rectifier and an IC 7805 positive voltage regulator to the receiver coil.
- Electromagnetic flux is produced when the transmitter and receiving coils are put close to one another.
- The distance between the transmitter and receiver coils as well as the number of windings decide the induced electromotive forces (emf) amplitude.
- The positive voltage regulator controls the bridge rectifier which corrects the potential difference generated in the receiver coil.
Conclusion:
You can learn the basic principles of wireless energy transfer by building a wireless power transmission circuit which is an interacting DIY project.
One may look into further developments in this field and assist in the development of wireless power technology by having a basic knowledge of the parts, equations and construction details.
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