Skip to main content

LiFi Internet Transmitter - USB Signal Transfer through LED

In this post we learn how to transmit Internet data through LiFi using a class D amplifier as the transmitter and an ordinary audio amplifier circuit as the receiver.

How Li-Fi Concept Works


If you are wondering how a LiFi concept could be used for transmitting USB data, this article will provide with all the details you required.

We know that a Li-Fi concept is used for transmitting  a digital data across a given premise  more efficiently than any other means invented so far, especially because the Li-Fi idea allows the user to transmit the data and additionally illuminate the area where it's been installed, so it's like getting two crucial benefits from a single unit.

Remember our age old film projector device? It's probably the oldest known method of using light for transmitting data (picture).

Although we always had other great means of transmitting wireless data such as Wi-Fi technology, RF circuits, etc, using light for this purpose was never imagined simply because lights have been always considered as low-tech units, and thus underestimated, until the day when Mr. Harald Hass discovered this hidden potential of lights (LEDs), and showed the world how LEDs could be actually used for transmitting data in a much efficient way than any other contemporary techniques.

In one of our earlier articles we learned through an example circuit regarding how to effectively transmit audio signal through a Li-Fi, in this article we'll go a little further and learn how to transmit an USB signal through Li-Fi.

Since LEDs are semiconductors devices these become perfectly compatible for handling digital data without any form of distortions. An LED will replicate and transmit the input content exactly as it was in the original source, and this property make LEDs extremely easy to configure for the intended purpose.

So far we have understood that Li-Fi is a method in which LED is used for transmitting a high frequency content within an enclosed room, which effectively transforms the LED into a wireless  transmitter as well as a light producing device.For example Li-Fi concept can be used for transmitting and receiving a music data by using an LED as the light source and also a wireless music transmitter.

However the biggest challenge is to use a Li-Fi circuit for transmitting Internet data using ordinary parts and without involving complex and difficult to get components or MCUs.

A USB connector basically consists of the following wiring details:



1) +5V
2) Ground
3) +D
4) -D

The +5V and ground are the supply out terminals which are normally used for powering the connected external device.

The +D, and -D are the data communication terminals which produces the complex differential signal across each other in a push-pull manner, meaning the +D is referenced to -D, while the -D signal is referenced to the +D terminals. This is what makes transmitting Internet through LED so confusing and complex.

This forced me to think of an alternative and more efficient design, that could actually transmit an USB internet data through LED Li-Fi circuit, without distorting the actual signal, and by employing ordinary components.

After some thinking I came up with the following circuits which hopefully would enable transmitting internet through LED light.

For the transmitter I decided to use a simple differential amplifier circuit module using IC BD5460, the following image shows the basic layout of this amplifier circuit.



I modified the design into the required Li-Fi transmitter circuit for making it compatible to internet signals, as shown below:



We can see how the differential  music input terminals are used for receiving the internet data, while the output is connected to an LED via a bridge rectifier.

Using a bridge rectifier appears to be a smart idea, otherwise it would be simply impossible to transmit the push-pull signals through a LED, since an LED would simply fail to differentiate between these two signals.

By using the bridge we have effectively enabled the LED to recognize both the halves of the USB signal and send it to the receiver without causing any distortions in the original content.

The Receiver Li-Fi Circuit


Now the next challenge for me was to ensure that the rectified pulsating internet data through the LED is correctly decoded back to the original differential form in the receiver section.

This looked difficult however the simulation could be quite easily accomplished by using a dual supply based power amplifier circuit, for example the 100 watt mosfet amplifier already published in this website efficiently fulfilled the intended purpose as shown below:



The BJTs and the mosfets can be any general propose rated to work with 12V/1amp supply. However if you want a powerful decoded output you could very well keep the original values for the devices and enjoy a powerful LiFi decoded inernet output.

UPDATE:

In the discussed concept we used a class D amplifier for the LiFi transmitter, however a class D amplifier essentially involves PWM for processing the input, which could be highly undesirable for an internet data to go through.

We do not want to distort or modify the complex Internet data in any manner, therefore a class D amplifier perhaps cannot be applied for an internet LiFi.

As per my assumption we don't need a classD amplifier rather only a BTL amplifier, which does not involve a PWM function, an example design can be witnessed below using the IC TDA7052.



Now this looks perfect, and seems like the Internet data would be transferred to the LED without going through any sort of artificial  transformation.

To start with we can go with this 1 watt amplifier circuit as the Li-Fi transmitter and use a 1 watt LED at the output. The idea will confirm whether the proposed Li-Fi transmitter really works or not.

If you have any further doubts regarding this simple yet seemingly working LiFi Internet transmitter circuit you can feel free to express them in the below given comment box.

Adding a Push Pull Stage


In the above diagram everything looks great and it seems the circuit is ready for transmitting the Li-F- data without any issues, however there seems to be a little flaw in the design.

What happens if there's no data at the input? The LED would simply shut down, and that's something totally  unacceptable in a Li-Fi concept. Therefore we must somehow make sure that the LED always remains illuminated regardless of the input variations or presence of an input data.

In order to satisfy this condition, we need to introduce a basic LI-FI BJT push pull stage, which was already discussed in our first Li-Fi article.

The following image shows how to do it:




The above design now looks to be a perfect Li-Fi internet transmitter circuit without any flaws.

Need Help? Please leave a comment, I'll get back soon with a reply!




Comments

  1. Sir my self sangeet grover B tech 3rd yr electronic engineer student. I want to make a lifi project regarding this I see some information about this project on your website. Can u help me to make this lifi project.

    ReplyDelete
  2. Hello Sangeet, if you have any specific questions, you can ask them here, i'll try to solve them...+

    ReplyDelete
  3. Hi, I'm looking for delay circuit which will be used with motion sensor to open gate. Motion sensor will human presence and will wait for 5-10 seconds to open gate. During this gate we will need to capture Human face & expressions. Can anyone help us on this?

    ReplyDelete
  4. motion sensing can be achieved using PIR

    https://homemade-circuits.com/search/?q=pir

    and delay using the following circuit

    https://homemade-circuits.com/2013/02/make-this-simple-delay-on-circuit.html

    ReplyDelete
  5. Thank you Sir.I believe in you.

    ReplyDelete
  6. sir ...good morning.... need a adapter circuit 220V AC to 9 V DC ...1500mA....if u already posted plz share the link.... transformer or with out transformer ......thank you

    ReplyDelete
  7. Soumen, you can try the following design

    https://homemade-circuits.com/2014/02/220v-smps-cell-phone-charger-circuit.html

    ReplyDelete
  8. Please sir do u make videos of your circuit implementation

    ReplyDelete
  9. Could you think of a way to go from manchester coding such as from a cat 5 cable to pwm to drive an led or led array

    ReplyDelete
  10. I am not too sure about it, will need to research the subject..

    ReplyDelete
  11. Good Afternoon Mr Swagatam,i have been able to simulate the project for audio transmission on proteus and the transmitter worked.
    Which other Electronic Design Simulator will you recommend i use apart from proteus before i implement it on breadboard and later conclude on the PCB layout.
    I am behind schedule on my final year project.
    Looking at focusing on the Internet Circuit,Please can you explain the transmitter and receiver circuit to me and its implemenatation.
    Look forward to your response

    ReplyDelete
  12. Hi Aroloye,

    Since so far I have entirely relied on my brain simulation for designing my circuits and have acquired 100% success, I have never required artificial simulators, therefore I cannot suggest much about them.

    the Li-Fi explanation has been already provided in the article, but if you have specific questions, you can ask them I'll try to solve them...

    ReplyDelete
  13. Hi,

    I am just curious to know shouldn't the Lifi Internet be bidirectional? Would the above single way would be enough to do Internet? I am confused!!!

    ReplyDelete
  14. bidirectional in what manner? I did not quite understand? Here we are only interested in transferring files from one source to other, for example just as we transfer files from a mobile to computer, the same may be done using light though the specified Tx/Rx units.

    ReplyDelete
  15. Hi,

    I meant Internet browsing where we send request to the server and then we get the information. How can it be done ?

    ReplyDelete
  16. In the above article only the USB port's communication has been discussed not the modem side, modem side could be a little more complex.

    ReplyDelete
  17. Oops. ok. I missed that.

    How do we do Bidirectional data transfer using single USB port?

    ReplyDelete
  18. Would this circuit transfer files from Mobile to PC? Apart from this circuit what to do in the mobile to send file? from File Manager then? How & what to select Destination?

    ReplyDelete
  19. As per my assumption, when the USB module LED light hits the sensor of the mobile module, the two counterparts should start communicating just as they would do with a direct connection.

    to have a bidirectional exchange the mobile side should also have its own Tx LED module separately installed, and the USB side with a Rx...

    The above basic set up explained above is for experimental purpose onlyt and recommended for basic applications such as listening to music from USB etc.

    ReplyDelete
  20. sir ,how can i get a USB cable connected to server, i mean connected to internet source.

    ReplyDelete
  21. milind, I am sorry the title is mistakenly mentioned as internet transmitter for the above article. The circuit is actually designed for handling USB data and not internet data.

    ReplyDelete
  22. ololo chukwuemeka brightJune 16, 2018 at 6:27 PM

    sir
    i am aware of the solar LiFi internet and i want to know if my 3 watts solar panel with the USB integrated can also be used as a photo detector to receive and transmit binary data for internet browsing kindly help out on this

    ReplyDelete
  23. Ololo, if the LED light is able to collect optimally on the solar panel, then it can be used

    ReplyDelete
  24. ololo chukwuemeka brightJuly 3, 2018 at 5:30 AM

    Sir
    Let's take it from the transmitter section
    I have made three LED panel lamps of 6 wattsw each with LED as a semiconductor ,when i plug this directly to light of the mains in my home and it beams isn't that some internet data streams from a VLC waiting to be converted at the receiver section?

    ReplyDelete
  25. ololo chukwuemeka brightJuly 3, 2018 at 6:38 AM

    Hello but u told me this set up covers LiFi internet transmitter and receiver why saying its just usb data in response to milinds ?

    ReplyDelete
  26. ololo chukwuemeka brightJuly 3, 2018 at 8:40 AM

    From the transmitter section let's see the receiver section
    Streams of Beam from my three 6 watts LED PANEL lamps emitted to fall on my 3watts solar panel with female USB port integrated into for output as my photodetector because emerging energy from the LED PANEL lamps has to be more than the energy on the cells of the solar panel in order to excite the molecules of the solar panel
    I now see the need for an amplifier circuit with usb female ports for input and output where i will be connecting the male to male usb chord from female output port of photodetector to female input port of amplifier
    The usb chord or usb to RJ 45 chord from the female output port of the amplifier is connected to the system giving the system binary bitrate internet
    The amplifier for my 3 watts photodetector is my problem now
    Kindly help a design for lifi internet receiver that best fit
    Or kindly suggest device with such amplifier i can use
    I intend creating such simulated amplifier with female usb input and output on the bread board and then on the printed circuit board
    Will this work
    HELP!!!!!!!!!!!!!!!!!!!!!!

    ReplyDelete
  27. In the above article I have only tried to explain a digital LiFi concept with two input signal, such as from a USB.
    It is recommended that you first understand all the details carefully, then make a sample design exactly as explained above.
    If you are successful, then you can try upgrading the above idea by adding more such units together to handle multiple inputs from a internet source.

    ReplyDelete
  28. ololo chukwuemeka brightJuly 5, 2018 at 5:22 AM

    Sir
    Thanks on the receipt of your mail
    From my last responce did i sound like i missunderstood u kindly meticulously go over my last mails and correct my flaws
    You dwelt lagely on the transmitter circuit i saw that and told u i already have three LiFi panel lamps of 6watts each for a transmitter section and lamps beams magnificently i hope that is OK for internet transmission
    I went on to talk about the receiver section where i will be using a solar panel of 3watts instead of silicon photodiodes or whatever to be used.
    My fear is the amplifier that should amplify and process currents from the solar panel into binary data to be received by desktop.
    So i thought of the usb plug circuit where u plug in the usb male mouth before pluging to light to charge ur phone.
    I opened it and saw it had a space for photodiode which was absent
    Then i also observed it had a female USB port where i can connect a male to male USB chord from 3 watts solar panel female USB port to it
    There is an amplifier circuit on the PCB of that USB plug correct me if i am wrong
    I think using that amplifier circuit with my solar panel embedded to it and then linking them with a USB hub to the desktop might give me an internet lifi dongle receiver for my desktop
    Help!!!!!!!!!!?

    ReplyDelete
  29. Ololo, Your approach seems to be OK and it makes sense, and the USB plug should be able to process things correctly as per the computer internal specifications.

    According to my understanding you should go ahead with this and let us know about the results.

    I would appreciate if you could share your schematic with us...

    ReplyDelete
  30. ololo chukwuemeka brightJuly 6, 2018 at 3:41 AM

    sir
    thanks on your response once again.
    you know the photo detector is of two types the PHOTOVOLTAIC which is anticlockwise and the other
    I think the PHOTOVOLTAIC is preferably used
    Do u think the usb plug's amplifier will be photovoltaic when i plug the male to male usb chord from the female part of the 3.5 watts solar panel to the female port of the usb plug after removing the circuit board of the usb plug and removing the wire that links the plug to direct current?
    sir are u saying if I beam my 18 watts streams of LED panel lights on the solar panel (photodetector) connected to the usb plug circuit that the usb plug circuit will amplify the voltage as seen from the solar panel to a voltage that will allow for internet transmission and received by the system for browsing free?
    Bearing in mind that this panel is connected to usb hub with 4 usb female ports inwhich i have pluged the solar panel extended male usb chord in one of the 4 usb hub's female ports with the USB charger plug's circuit as amplifier also connected to one of the 4 USB hub's port close to the port where i connected the solar panels usb extended chord
    Sir what will the configuration on the destop system be like for me to start streaming live internet videos
    is the amplifier responsible for the high bandwith or speed of the internet connection?
    how does the speed of the internet in bytes/s relate to this amplification?
    kindly respond in brief details as you travel through my words and lines so i can properly grab the worlflow ,logic and principle behind this because am scared my wild imaginations might not work
    THIS SOUNDS LIKE MAGIC TO MEEEEE
    HEHEHEEEE!
    HELP?!?!?!!!!!!!!!!!!!;!;!!;;;!!!!!!!!

    ReplyDelete
  31. Hi ololu,
    As I said earlier I have only tried to present a concept regarding how digital signals could be processed using a bridged amplifier circuit. The concept will need to be verified step wise by first making the above explained 2 input amplifier and then subsequently using more inputs for implementing an internet LiFi transfer.

    I do not have any advanced knowledge regarding this field at this moment

    ReplyDelete
  32. ololo chukwuemeka brightJuly 7, 2018 at 12:44 PM

    sir
    I am new to circuit board creation
    in trying to create a transimpedance amplifier for a lifi internet receiver,what kind of operational amplifier (op amp) or integrated circuit (IC) is best for this amplifier.
    Sir,does the arduino circuit board of a USB phone plug that goes to direct current have op amps in them?
    The transimpedance amplifier must have 2 female port first for an input 3.5watts solar panel which will act as a photodetector while the second female port will act as the output that leads to the desktop system
    sir,what is responsible for the creation of the internet bitrate as the amplified voltage enters the desktop system
    sir, is it possible to use 2 operational amplifier to have an optimal voltage output from the transimpedance
    Sir,can the op amp be refered to as a COMPARATOR?
    sir,what is the relationship between components in the transimpedance amplifier with the byte/seconds or kb/seconds or GB/seconds
    sir,do i need to integrate a java program into the transfer impedance amplifier for it to run in the desktop or is all that taken care of by java in desktop already
    sir,how is the internet from the lifi after receiving it into the desktop configured to work in the windows operating system
    if i have to integrate java or any program how do i go about it
    please be explicit in your detailed explanations in response to my quest
    HELP!!!!!!!!!!!!!

    ReplyDelete
  33. ololo chukwuemeka brightAugust 9, 2018 at 12:58 PM

    need detailed step by step help in making a lifi ethernet transceiver at home from scratch on an empty circuit board and how to configure it to browse the internet on desktop operating system I have the empty circuit board, op amps resistors and capacitors Help!!!!!!

    ReplyDelete
  34. ololo chukwuemeka brightAugust 22, 2018 at 4:16 PM

    sir
    kindly help me with detailed steps on how to create an optotransciever on an empty copper substrate board

    ReplyDelete

Post a Comment