# Transmitter circuit diagram for fiber optic

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##### Newbie level 6
Hello Dear friends
My final project is PC to PC communicate over fiber optic
I saw this circuit from Indian student but unfortunately he didn't write IC's pin numbers.
I tried 5 hours to run this circuit but I can’t..!
there are many problems.
this is his project's report https://www.docstoc.com/docs/29154281/PC-TO-PC-FIBER-OPTIC-COMMUNICATION

1- Why he connected pin 1,2 and 3 together?
2- Why he connected pin 4 and 5 together also?
3- Can anyone please write on the MAX232 pin's numbers?
4- Why he didn't use pin 3 like a transmitter and pin 2 like a receiver? As I see in data sheet of MAX232 and serial port!!
5- The important question: How can I know that the circuit is running well?

Please is there any different has a circuit like this? And it's work 100% !
I should to submit my final proposal after 2 weeks and still I'm in a problem..!
Or Can anyone try to help me I draw this circuit on Multism 10 and if there is anyone wants it to correct it I will upload it for him
This is the circuit ( in the attachment ) and I worte What I know on the IC ..!

best regards to you and Thanks thanks for this forum.

#### IanP

Try this "modified" version ..

Rgds,
IanP

Points: 2

##### Newbie level 6
Hello,
Dear thank u
but it still not working
I uploaded the circuit for u, can u do it and correct it? please

Multisim 10

##### Newbie level 6
Hello Dear
I have changed manythings u and only 3 LEDS are ON

can u check my circuit please? I think I must change resisters value.
and give me some info how can I know if it's work or not? please
I don't understand what Indian sudent wrote.
he wrote:
Data signals transmitted through pin3 of 9-pin ‘D’ connector of RS-
232 COM port are sent to pin8 of MAX232 and it convertes these RS-
232 compatible levels of +9V or -9V to 0/5 volt TTL levels as given in
table.
The output of MAX232 drives the pnp transistor through a bias
resistor of 1k ohm, to switch on “IR LEDS” and also visible LED. Here
actually when the output of MAX232 is 0V at that time the pnp
transistor will be conduct and the IRLED as well visible LED will glow.
And when the output of MAX232 is 5V at that time the pnp transistor
will not conduct it is in cut-off region. So, at that time the IRLED as
well the visible LED will not glow.
We can use laser diodes and LEDs for the transmitter. Both have their
also cheap, so we will be using a LED.
There are several different schemes for carrying out the modulation
function. These are respectively: Intensity Modulation, Frequency
Shift Keying, Phase Shift Keying and Polarization Modulation. Within
the context of a premise fiber optic data link the only one really
employed is Intensity Modulation.
It must be noted that one reason for the popularity of Intensity
Modulation is its suitability for operation with LED's. An LED can only
produce incoherent optical power. Since Intensity Modulation does not
require coherence it can be used with an LED.

Do u know what does it mean?

#### IanP

If you use IR diodes as transmitters you have to use IR transistor as a receiver ..
(on your drawing LED4 is marked as standard LED)

Signal from IR receiver has to be converted to TTL/CMOS levels - if you want to transmi it further via MAX232 .. see attached pictures ..

Rgds,
IanP

Points: 2

##### Newbie level 6
I don't know what I must to say
Thanks alot Sir
May the God help u and bless u

I'm going to check it now
Regards,

##### Newbie level 6
Hello,
Is it important to connect Microcontroller to MAX232?
beacuse I want to write a program to send and receive files.

#### FvM

##### Super Moderator
Staff member
If you use IR diodes as transmitters you have to use IR transistor as a receiver
I'm not aware of a silicon based optical sensor, that is not sensitive to the radiation of IR LEDs (either 880 or 950 nm).
Any standard silicon photodiode or transistor has the maximum sensitivity in this range. Even "IR supressed" photodiodes have
still a sufficient sensitivity at 950 nm.

#### IanP

Is it important to connect Microcontroller to MAX232?
beacuse I want to write a program to send and receive files.

That depends where do you want to send files to ..
If it is PC’s serial port you need a level translator and MAX232 is a good candidate for the job ..

Rgds,
IanP

#### vijayparmar

##### Newbie level 4
any one have perfect fiber optic tx and rx ckts

#### vijayparmar

##### Newbie level 4
Hello Dear friends
My final project is PC to PC communicate over fiber optic
I saw this circuit from Indian student but unfortunately he didn't write IC's pin numbers.
I tried 5 hours to run this circuit but I can’t..!
there are many problems.
this is his project's report https://www.docstoc.com/docs/29154281/PC-TO-PC-FIBER-OPTIC-COMMUNICATION

1- Why he connected pin 1,2 and 3 together?
2- Why he connected pin 4 and 5 together also?
3- Can anyone please write on the MAX232 pin's numbers?
4- Why he didn't use pin 3 like a transmitter and pin 2 like a receiver? As I see in data sheet of MAX232 and serial port!!
5- The important question: How can I know that the circuit is running well?

Please is there any different has a circuit like this? And it's work 100% !
I should to submit my final proposal after 2 weeks and still I'm in a problem..!
Or Can anyone try to help me I draw this circuit on Multism 10 and if there is anyone wants it to correct it I will upload it for him
This is the circuit ( in the attachment ) and I worte What I know on the IC ..!

best regards to you and Thanks thanks for this forum.

plz see this link and also see db 9pin serial port diagram

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