1. The university of Lahore Department of computer Engineering Electric Network Analysis Project Tittle : Audio tone IR transmitter and receiver Group members : Salman Bhatti Ayesha Hameed Asma Pervaiz Subject instructor : Sir Ahmed Bilal

2. About the project
This idea of our project just came into our minds when  frequency based projects were discussed in our lab. This project has the most basic construction and ideology. Transmission of audio tone signal through infrared waves was the purpose and to achieve an output through a speaker . The input frequency will be the frequency at which we humans speak  or hear ranging from 1KHz to 10KHz in this case.
The Ir transmitter or led’s will send out the  signal, and a photo transistor will be able to detect the signal.

3. MATERIALS REQUIRED TRANSMITER SECTION:
Resistor 1kilo-ohm (2).
IR transmitter (2).
Transistor BC548 (1).
Connecting wires.
Bread board.
Function generator for supply.

4. MATERIALS REQUIRED RECIVER SECTION
9V dc battery (1).
photo transistor (1).
Transistor BC548 (2).
Electrolytic capacitor 1UF (1).
Resistors 10k ,1k.
8ohm speaker.
Connecting wires.
Bread board.

5. Simple IR Audio tone Link Circuit Design:
The IR audio link circuit is divided two parts, one is transmitter section and other is receiver section. The transmitter section works with a function generator supplying an offset voltage of 5.5Vdc and amplitude of 9Vpp  . Here the audio signal input is applied at the base of the transistor via 1k resistor. Here transistor is used to drive the IR diodes. The input audio signal is modulated to Infrared signals transmitted.

6. The transmitted Infrared signals are received by the photo transistor
The transmitted Infrared signals are received by the photo transistor.The transistors in the receiver circuit form a circuit, used to amplify the output signal of photo transistor. Now the output signal from circuit is able to drive the headphone or speaker. The capacitor  and  resistor together form a filter (High pass), used to reduce the interference from Infrared signals.
In this circuit to power the transmitter and receiver sections  9V PP3 DC batteries can be used. But to apply tone at frequency and to vary the frequency to hear the tone, a function generator is used .

7. Circuit diagram

8. Circuit Result This circuit will produce a tone with the help of function generator.