17-11-2012, 06:26 PM
simple application of concepts of data communication
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INTRODUCTION
This project is a simple application of concepts of data communication, where the data is in audio form. It is a very easy and subtle example of wireless transmission system. By using this project audio musical notes can be generated and heard up to a distance of 10 meters.
The circuit can be divided into two parts:
1. IR music transmitter
2. Receiver.
Transmitter:
The IR music transmitter works off a 9V battery. The transmitter uses popular melody generator IC UM66 that can continuously generate musical tones. The output of this music melody generator is fed to the IR driver stage to get the maximum range.
Receiver:
The IR receiver also works off a 9V battery. The IR music receiver uses popular op-amp IC μA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 and some discrete components.
Melody Generator IC UM66:
The M66T series is a CMOS LSI designed melody generator IC for use in telephones and toys application. It has an on-chip ROM programmed for musical performance. Produced by CMOS technology, the device results in very low power consumption. And with built-in RC oscillator, a compact melody module can be constructed with only a few additional components.
IR Driver Stage:
This stage consists of 2 transistors. The first is a low noise transistor- BC 547. The second is the general purpose power transistor of P N P configuration – TLSK 100B. These two transistors constitute the driver stage and amplify the melody signal from IC UM66 for transmission.
IR LEDs:
An LED is connected in the Transmitter section. This LED flickers according to the musical tones generated by UM66 IC, indicating modulation. Two IR LEDs are connected in series. For maximum sound transmission these should be oriented towards IR photo diode.
Audio-frequency amplifier IC LM386:
The output of IC μA741 is fed to IC LM386 via capacitor C5 and potentiometer. The melody produced is heard through the receiver’s loudspeaker. Potentiometer VR2 is used to control the volume of loudspeaker (8-ohm, 1W). Switching off the power supply stops melody generation. The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value up to 200. The inputs are ground referenced while the output is automatically biased to one half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.