Lifi

EcDarkSky · August 9, 2016

Hi guys,

So i have to do prepare a big school project based on lifi. I was actually asking myself if it can work.

So if i take a ethernet câble and every single wire (8) is connected to a light emitter (each one have different wave lenght). So when one of the wire in the ethernet cable is having electricity the led i going on on. So the principe is on and off. At the other end i've got some light sensors (8 for every single wire) that send turn on and off when the led turn on and off. Then i send back the signal in a ethernet cable and plug it in any device. I hope you underdtood what i mean.

Thanks for saying if it works and if not why

Thanks for answer

Silverwolf_7 · August 9, 2016

My first thought is that ethernet may not provide enough voltage or current to power an led. Some sort of amplifier circuit would probably be needed to ensure a reliable connection. Secondly ethernet and most data connections are a two way street, data is uploaded and downloaded so there would need to be some sort of reciever and transmitter on both ends of the cable. (I'm not sure if all 8 wires are used for transmission and reception but its a safe bet that some play double duty) Both of these problems can be solved with a transciever that the ethernet cable is plugged into on either end. This diagram from http://purelifi.com/lifi-products/li-1st/ illustrates where the transciever would be placed in the system.

Digital data transmission is difficult to reliably replicate with a diy solution. As this is a school project and it seems that you need a working example or something that illustates how the theory behind the system works. I came across a similar project awhile ago from Make Magazine, that involved transmitting audio across a room with a laser. It operates on the same principle but is analog as opposed to digital. Here's the links to the project article and a video by Kipkay on how to put it together.

Make: Magazine Article:

http://www.make-digital.com/make/vol16/?folio=67&pg=69#pg69

mariushm · August 10, 2016

Maybe if you configure the ethernet card to 10 mbps and half duplex, you may be able to do build something fast enough to catch all the bits and process things fast enough to do conversion to optical output. Half duplex will make everything easier.

You'll need fast analogue to digital converters at the receiver end where sensors catch light and convert it to a varying voltage, that varying voltage would need to be converted to 0 and 1 and so on.. it's not an easy project.

It would be easier to just use a ready made ethernet chip with SPI port or parallel port ... basically chip hides away all the ethernet conversion, sending and receiving and just puts the bytes on a port , a protocol specific to micro controllers, then the microcontroller...probably some ARM based or PIC32 running at high enough frequency can read that data and convert it to laser pulses or plain light pulses and send it through air to the other device that would just convert the analogue data from the optical sensors into bytes and push the data to another ethernet chip....