Simple Li-Fi Transmitter Receiver Circuit

Think internet is like a light and not a radio wave.

Simple Li-Fi Transmitter Receiver Circuit do the same thing like that.

This article tell how to make simple Li-Fi system to send and get data using light.

Transmitter uses bright LED and normal transistor to send signal.

Receiver catch signal with light sensor like solar cell and make signal strong so we can hear from speaker.

This project is easy to understand and how Li-Fi work but it does not replace Wi-Fi.

Transmitter Working:

Parts List:

2N2222 transistor is used like common emitter amplifier.

Two resistors R1 and R2 make voltage divider at base which is called VBias.

When audio connects in transmitter it changes transistor output.

This change make 1 watt LED light blink same like audio signal.

Capacitors on transistor base help keep audio clear and they stop DC from going through.

If we use higher voltage like 12V and put resistor with LED to control current then it works right.

Formulas and Calculation for Transmitter Working:

This formula below shows how to find base voltage (VBias) in voltage divider circuit for transistor:

VBias = R2 / (R1 + R2) × VSupply

here,

• VBias is voltage at transistor base and we want to find this.
• R1 and R2 are resistors used in divider.
• VSupply is the main voltage for circuit.

Formula uses voltage divider rule and it tells voltage across R2 which goes to transistor base.

Transmitter Construction:

• To make transmitter use 2N2222 transistor and set it like common emitter amplifier.
• LED light become bright or dim with audio signal which changes same like sound.
• Put capacitors at transistor base because they block DC and keep audio clean.
• If using high voltage like 12V then add one resistor with LED to limit current.
• We can give audio from MP3 player, phone or microphone with preamp.

Receiver Working:

Parts List:

Receiver use solar cell and 2.2μF capacitor in series.

Solar cell give voltage that change with light which is sensitive to light around.

This changing voltage goes to amplifier like LM386 or other similar type.

Amplifier is very sensitive so it can catch weak audio signal.

Then sound is louder and goes to speaker so we hear it clearly.

How to Make Receiver:

• Use 6V solar cell and 3V also okay with 2.2μF capacitor in series and connect with amplifier.
• Amplifier can be any good one that has high sensitivity.
• Test the circuit in dark room with no lights nearby to work better.

Formulas:

Audio amplifier can use one transistor and one transformer.

Below is formula:

Impedance Ratio = (Np / Ns)²

here,

• Np is the number of turns in primary coil
• Ns is the number of turns in secondary coil

Note:

To make good audio amplifier use correct parts and build it carefully.

For better sound use multistage amplifier circuit with more than one amplifier stage.

Overall Circuit Operation:

This circuit can work in low light and does not get much problem from electric lights because of how it is made.

LED may flicker a little which human eye cant see it.

Even if we do not see it LED brightness changes when audio goes in transmitter.

Solar cell in receiver catches small voltage changes and then amplifier make sound from it.

To test turn on both transmitter and receiver and give audio to transmitter and change the volume.

Speaker on receiver should give clear sound.

We can build simple Li-Fi circuit for wireless sound if we learn and follow these steps.

Steps:

• Make transmitter and receiver circuits one by one.
• Connect 1 watt LED in parallel with solar cell.
• Power both circuits and adjust transmitter volume.
• Give audio input to transmitter.
• In dark room listen if speaker is ON and receiver gives clear sound.
• Try using photodiode and change amplifier to LM386 circuit.
• Circuit will still work good and we must try different parts too.

Important Notes:

LED may flash a little and this mean something is not working right.

When audio is given LED brightness changes to a very small which eyes wont see it.

If no audio then LED stays always ON and this is because input capacitor blocks DC signal.

Solar cell can feel small voltage changes but ignore steady DC.

Capacitor helps send only the audio signal.

Use sensitive amplifier to make circuit work better.

Conclusion:

We can build Simple Li-Fi Transmitter Receiver Circuit and receiver by following these steps.

It gives new way to send sound in places with low light.

Try different parts to get best result for your need.

References:

System architecture of Li-Fi transmitter and receiver.

Li-Fi