Transmit Sound Through Light

In this project I will show you how you can transmit data signals from one place to another through Light. Sending data over light isn't a new concept but recently it gained a lot of attention after the introduction of LiFi. In this tutorial we will transmit simple data (Audio) through LED / Laser.

So lets get started....

Step 1: GATHERING COMPONENTS :-

All the components can be found at UTSource.net

• LED or Laser.Switch. (Amazon Link)
• 10k Ohm Potentiometer.
• Earphone Jack.Breadboard
• BD139 Transistor. (Any NPN transistor will work. 2N2222 can be used) (Amazon Link)
• 10uF capacitor. (Amazon Link)
• 100uF capacitor (Amazon Link)
• Two 1k Ohm resistor. (Amazon Link)
• 50 and 100 Ohm resistors each.
• Arduino (Optional. If you want to experiment with different data.)

PartsFor Receiver:-

NOTE :-If you have computer speakers you don't need to make a Receiver.But you will need Solar cell or LDR to receiver Light signals.

Two BC547 /2N2222 transistors. LDR or solar Cell

• 1k and 10k Ohm Resistors each.
• 1uf Capacitor.
• Speaker.

I have provided Links to the components but you can buy these from local electronic's store.

Step 2: MAKING THE TRANSMITTER :-

The setup is simple. Just follow the circuit diagram I have provided. For a reference check the Breadboard Layout. Here I have used BD139 transistor but you can use any general purpose NPN transistor, just take note of the Pin out diagram of it. Also power the circuit with 5v - 7v depending on what you are using ( Laser or single LED).

Once the circuit is ready. Power it up and see if the light glows. If it does, then turn the potentiometer to check if the intensity of light changes. If it does, Everything is fine and you can proceed to the next step.

If it does not work check the connections and polarity of the transistor.

Step 3: MAKING THE RECEIVER :-

Just in case you don't have a Computer speaker or you just want to make this full "DIY Project", You can follow the circuit given above to make a simple audio-amp.

If you have a computer speaker things are pretty simple in this step. just use a Female Audio jack and connect it with two wires to a solar Cell or LDR and plug the speaker. that's all here.

Step 4: HOW TO USE IT ???

Once the Transmitter and Receiver are made just connect the earphone Jack to any music player or a mobile phone and play a song. Adjust the Potentiometer to dim the LED, You will notice it flickering. If it doesn't recheck the connections and try again. When it flickers it means the sound is been converted to digital signal and transmitted via light.

Now just place the solar cell or LDR near the LED and you will hear the music being played on the speakers. Adjust the brightness of the LED to get a more clearer sound. For long distance transmission use a laser.

Now that you have successfully transmitted audio, You can experiment with different type of data using Arduino. To connect it to an arduino just connect the GND pin of arduino to Ground and Input pin of capacitor to any Digital pin of arduino and set the pin to transmit data. But to decode these signals of arduino you will need another Arduino at receiving end. But that's for another tutorial. Till then try this and experiment more...

I hope the instructions are easy to understand. If you have any questions feel free to ask in the comments.