Simple Li-Fi Circuit Using Transistor
In this post we are going to construct a very interesting project and this technology is just emerging in consumer electronics , here you will get hands on experience from this project.
You will be able to make your first fully functional analog audio Li-Fi circuit which can stream good quality music from your phone/mp3 player to speakers at home and you will be surprised how simple a Li-Fi system can get and you no need a million dollar laboratory to construct one, even a beginner in electronics can make this project with ease.
We will see:
- What is Li-Fi or Light Fidelity is?
- Is Li-Fi better than Radio Communication?
- Circuit Diagram of Li-Fi .
- Description of Li-Fi.
- Quick Video Demo of the Li-Fi setup.
Illustration of successful Li-Fi Transmission:
What is Li-Fi or Light fidelity?
Let’s clearly understand what exactly Li-Fi technology is before going in to circuit diagram.
Li-Fi stands for Light Fidelity, which uses visible light as medium for data transmission. The Li-Fi system consists of normal LED light bulbs and modulating circuits.
The idea of Li-Fi is to use existing light infrastructure to transmit data to our computer, Smartphones, tablets etc. This will eliminate some of the main limitations and disadvantages of traditional radio communication, such as Wi-Fi system that we use at home or office.
Li-Fi utilizes LED light bulbs which are connected to a modulating circuit which will convert incoming data stream into rapidly flashing light. We human begins can’t perceive the high frequency flashing light but we will perceive a steady room lighting without any flicker.
The receiver circuit can capture the high frequency flashing of LED and decodes it into understandable data stream for your computer or smartphone.
Now you would have got a basic idea what Li-Fi is all about.
Circuit Diagram for Li-Fi Transmitter:
NOTE: The above circuit diagram is copyright protected, the visitors/readers are NOT permitted to republish anywhere in any form. You can build this circuit for your personal purpose only.
The circuit is very simple; it consists of 3 transistors, couple of resistors, 3 electrolytic capacitors, one variable resistor and one 1 watt LED. The Whole circuit is configured in common emitter mode amplifier.
The three BC337 are connected parallel, that is base to base terminal, collector to collector terminal and emitter to emitter terminal.
There are two 1000uF input capacitors which allows only AC signal to enter the Li-Fi circuit and also prevents from 9V entering to your audio source/phone from the circuit.
If your audio source doesn’t have left or right channels, just connect ground to ground and connect the audio source to any one of the capacitor.
The 100 kilo ohm variable resistor is used for adjusting the LED brightness. The 1 Watt LED is used for transmitting the audio signal and light.
You should have been surprised by the simplicity of this Li-Fi circuit by now.
The receiver circuit is even simpler; make sure that you use a good sensitivity amplifier.
The 3V to 6V solar cell can be used as light sensor, you can use a good USB computer speaker to receive audio or you can use any amplifier with good sensitivity.
You should be getting very good sound quality and the LED should stay solid ON regardless of the audio input and LED should not flicker while transmitting signal.
How this Li-Fi Circuit works?
The Li-Fi circuit serves two purposes:
- Room Lighting.
- Data transfer.
While designing a Li-Fi circuit one must keep these two requirements in mind. Now consider the first requirement which is room lighting.
The circuit must provide a steady lighting and must not flicker due to data transfer or the flicker rate must above our eyes persistence of vision while transferring data. The circuit proposed here has negligible flicker and always produce a steady brightness regardless of data transfer and still manage to transfer analog and digital data.
You might wondering how can we transfer data without change in brightness? Actually there is very very small change in brightness of the LED. The difference between maximum and minimum brightness of the LED is not perceivable to human eye because the difference is extremely small. The difference in the brightness can be detected by a solar cell easily, this can be witnessed by hooking a oscilloscope across its terminals and we can see the waveform peaks few millivolts.
The millivolts peaks from solar cell must be amplified adequately using a USB computer speaker or any other good sensitive amplifier so that it can drive a speaker. To keep the circuit simple as possible (to avoid multistage) of the transmitter, we have connected three low power transistor in parallel so that it can drive 1 watt LED with adequate current.
The 4.7K and 1 K resistors provide necessary DC biasing for the three transistors which will put the transistors in active mode where the transistors acts as amplifier.
If we over bias the circuit with lower resistor values, it will put the transistor in saturation mode where the transistor fully ON and does not respond to the input. If we under bias the transistors it will go to cut-off mode where output current will be too low to drive the LED ON.
We can spot the 4.7K resistor is connected in series with 100k variable resistor, this is to adjust the quiescent current of the amplifier (transmitter) thus adjusting the brightness of the LED.
Quiescent current: Quiescent current is the current consumed when the circuit performing not work.
The quiescent current in the circuit is the reason why the LED stays ON regardless of the audio input. We have used the quiescent current to our advantage to glow the LED.
That concludes the working of this circuit.
- 3 x BC337 NPN Transistor
- 1 x 4.7K resistor
- 1 x 1K resistor
- 3 x 1000uF/25V electrolytic capacitor
- 1 x 1 Watt LED
- 1 x 100K Variable Resistor
- 1 x switch
- 1x 3V to 6V Solar cell
Below are the important points to be noted if you are doing a PPT / presentation in your college / school or just curious about Li-Fi technology.
Is Li-Fi better than Radio Communication?
In this section we will understand some of the limitations with traditional radio communication such as Wi-Fi and how Li-Fi will be a good replacement.
The Limitations/disadvantage of Radio communication are:
- Radio Waves have Limited Bandwidth.
- Cannot be used in some restricted areas.
- Health Hazards.
Let’s explore each of them.
1) Radio waves have limited bandwidth:
Radio frequencies range from 3 KHz to 300 GHz. The radio frequencies are classified into many categories like Low frequency, Medium Frequency, High frequency, Ultra High Frequency, Extremely High frequency etc. Each of them is allocated for specific applications.
For example FM radio signal is allocated from 88 MHz to 108 MHz and AM stations from 535 KHz to 1905 KHz.
Due to increasing of wireless devices per person and emerging of internet of things (IoT) devices, allocating the radio frequencies is getting tighter day by day and licensing the radio spectrum costs enormous.
We have something called ISM band which stands for Industrial Medical and Scientific band, the devices operating at this frequency don’t need be licensed by the users. The best example is your Wi-Fi router; it operates at 2.4 GHz and also 5 GHz.
Do you feel that your Wi-Fi internet is slow at times? If yes, then you are probably living in an apartment with many of your neighbor using Wi-Fi.
Wi-Fi routers mostly operate at 2.4 GHz range and some high end routers operate at 5 GHz. Due to the interference of many Wi-Fi signals from you and your neighbour’s router, the data transmission gets slow down than your wired connection.
Due to this congestion router manufactures are introducing 5 GHz band to avoid such Wi-Fi congestions, but with 5 GHz you will get shorter range, yet this is not a full solution for our future needs.
2) Restriction of Radio waves:
Radio waves are restricted in many areas such as hospitals, operation theatres, airplanes, research facilities etc.
You cannot always enjoy Wi-Fi internet in a hospital or in an airplane or in a place where the radio communications are restricted, because there could be interference with sensitive hospital equipments, which treats valuable patient’s life or very expensive experiment and interference of radio waves could alter the results.
So not everywhere radio communications are permitted.
Guess what is the worst thing can occur to your wireless internet, is it disconnection of your internet? No, it is your network getting hacked by someone else!
Wi-Fi can penetrate through walls and surround you area, you may say that my Wi-Fi is secured with a password but, a skilled black hat can break in to your network without any notice, and many of you are not good at setting a strong password for you router.
4) Health Hazard:
High energetic radio waves are suspected to cause health issues; there are some people who complained that they are affected from high energetic radio waves.
But there is no documented evidence to support the statement that radio wave causes cancer. May be science yet to discover the health hazards on human begin and animals and even plants.
Now, let’s see how Li-Fi can overcome these limitations:
1) No Bandwidth Limitations and Interference:
The Li-Fi has bandwidth at least 1000 times greater the radio waves; this can handle the future internet needs with ease.
No interference with neighbour’s internet connection as your internet will not go beyond your room and neither other’s internet will enter you room.
Very high data transfer speed compare to Wi-Fi, researcher calculated theoretical maximum data transfer speed of 224 Gb/s isn’t that mind blowing?
So, now you have very high speed data connection without any interference.
2) You can access Internet anywhere:
Radio communications are restricted in some area, guess what is not restricted? Visible light!
Now we can restore the access to internet in airplane or in hospital or in research facility without worrying about radio transmission interference.
3) Security is enhanced:
Now the internet will not go beyond your room as the light from your room will not leak like Wi-Fi and black hats will have tougher time to hack your network.
To access the network the black hat must be physically present on your room and you know what to do next if such unknown person present in your room.
4) Reduced Health Hazards:
We are using visible light since discovery of fire; visible light spectrum has little to no health hazard. LEDs don’t contain any mercury or other toxic chemicals present in like CFLs, which also emits small amount of ultraviolet rays, and yet CFLs don’t cause health hazards, so we can say that LEDs are one of the safest light sources available.
In conclusion we can say that Li-Fi is superior to traditional radio based communication, but Li-Fi may not be without its limitations or disadvantages which may be yet to discover.
Video demonstrating Li-Fi circuit: Watch it full screen.
If you have any questions reading this project, feel free to express in the comment section you can anticipate a guaranteed reply from us.
43 thoughts on “Simple Li-Fi Circuit Using Transistor”
Kindly help me with detailed steps on how to create the lifi internet transmitter and receiver and how to configure it to browse on the desktop
Hi ololo chukwuemeka bright,
Thank you for your concern.
According to your requirements, we need army of hardware and software developers to accomplish this from scratch.
It may not be as easy as transmitting audio.
But anyway if we could accomplish we will definitely post it.
IS ANYTHING IMPOSSIBLE?
ARE THESE ARMIES NOT IN THE MARKET I SHALL RECRUIT EM IF THEY AINT ENLISTED YET !
It is not impossible, there are successful internet transmission using Li-Fi but, the circuit and software are proprietary of that company and they are not open source.
You can hire a team for your company, but you should bare the huge cost and the legal stuff like certifications etc that come with.
Sir,,,,how can I understand that where to where you soldered?
You can solder in your own way, only thing you need to take care is the circuit diagram.
Hi.. Can you please briefly explain how this transformation happens – from sound to light??
we will update the post on how it work with in-depth detail.
i want to know how to send an image file using lifi
We will try to accomplish that in near future.
Sir what kind of TIA is best for LiFi internet receiver is it the inverting or non inverting
Moreso how do i create a high speed TIA
I am sorry, I not sure what is TIA.
Is it possible to have Ethernet port,USB female port,ADC,DAC,TIA,PHOTODIODE/LASER INFRA RED LIGHT that sends the uplink received by the PHOTODIODE which receives the downlink ON ONE VECRO BOARD OR BREAD BOARD?
Please am trying to CREATE a LiFi internet Receiver circuit HELP ON ALL I NEED TO DO TO ACHIEVE THIS
sir you misunderstood me am not about the audio data transmission am about the lifi internet data transmission and receiver
i am a CHEMICAL AND POLYMER ENGINEER WITH MAD ENGINEERING DREAMS
I NEED TO CROSS THIS PHASE OF MY DREAM HELP!!!!
kindly help me with detailed steps on how to create an optotransciever on an empty copper substrate board
Hi ololo chukwuemeka
I am sorry, we don’t have enough expertise to do your request, you need a full fledged lab for fabricating the opto-transceiver.
If you have any further questions feel free to ask.
TIA– This simply means Transimpedance Amplifier
i want to know ur project fabricated in the lab
This project was build at my home no special labs etc.
I want to know what amplifier did you use?
You can use any audio amplifier which has good sensitivity.
Can you name me a component that can take place instead of building a whole audio amplifier please
You can use a USB computer/laptop speaker and connect the audio jack to a small solar panel and max out the volume.
congratulations for your nice project! One question: why are you using 3 transistors instead of just one larger?
hi Fabio, thanks!
Yes, you can use single medium power transistor, but the problem is we have to input a larger amplitude signal, so we need a per-amplifier which will complicate the circuit.
thanks for this information about li fi
i want to ask if i will transmit any data instead of audio ?and how?
You can transmit data in digital and analog forms with this circuit.
Sir actually can you give us a detail cunstuction about this because my circuit is not working properly please sir
Thank you sir
There are enough construction details in the post.
Can you tell us what is your exact problem like: LED is flickering, LED did not lit up etc… we will solve it…
This is a fully tested circuit it should work flawlessly if you follow the circuit diagram correctly.
Why are the transistors connected in parallel???
To increase the power, so that it can provide enough current for 1 watt LED.
Can you post a detailed explanation on how the circuit works???
Yes, I will update it soon.
Looking forward to it …….thanks!
Hi, I have updated the explanation, please let me know whether the explanation is adequate or any further explanation is need to be added.
Can i have use Li fi circuit for my YouTube chnl. ? without copyright free? All tutorial use for Education purpose . I need permission ….
Thank you for contacting us.
Unfortunately we cannot allow republishing this lifi circuit anywhere or even modify, let me explain this.
The design you see is a first Li-Fi circuit on internet which can actually transmit voice (Even though I am not the first one to invert Li-Fi).
Some people already infringed copyrights, which is affected our traffic and we cannot allow this anymore.
Those who infringed, we are taking action on them.
If you want to buy rights for this circuit you can contact us here: email@example.com
We will reply to you.
Thank you for contacting us with your query.
I performed this li fi without transistors and capacitors but after some days it stoped working tell me why
You question is incomplete, please elaborate it.
Can you explain in detail on how the input is given from mobile through an audio jack.
Could you please rephrase your question, we can hardly understand.
Can I use a IR SENSOR instead of Solar Cell in receiving side