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 like audio signals through LEDs.


  • BD139 Transistor
  • White LED
  • 10uF and 100uF capacitor
  • 50 ohm, 100 ohm and 1k ohm resistors
  • 10k ohm potentiometer
  • Breadboard with jumpers
  • 3.5mm earphone jack
  • Solar Cell
  • Alligator clips

Making The Transmitter:

Circuit Diagram

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 Pinout 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.

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 the Female Audio jack and connect it with wires to a solar Cell or LDR and plug the speaker.


Once the Transmitter and Receiver are made just connect the earphone Jack to any music player or 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 a digital signal and transmitted via light.

Now just place the solarcell 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 clearer sound. For a long distance transmission, use a laser.

Now that you have successfully transmitted audio, you can experiment with a 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 Instructable. 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.

Also, read an interesting article: what is Li-Fi?