4-channel data telemetry system

Basic Description

Basic Idea for the the project is to transmit the data from one point to another, this transmission may be wireless or with wire, well wireless is more enhance technology than with-wire transmission so we adopted wireless transmitting and receiving data. This project transmits 4 types of data by different types of sensors. They include Temperature sensor, Fuel level Sensor, Pressure sensor and rpm sensor. These all sensors have analog output in the form of voltages so we have to convert it into digital data then we will able to transmit.

Why convert analog into digital data?

Well we converted analog data into digital data. Why? Because four different types of data are being transmitted trough one channel so multiplexing is required. Due to this we used a digital switch which multiplexed the four data and convert it into digital form one by one. Note: Transmitter range 12-15 feet

Data transmission

Block Diagram shows the data Transmission of the message signal by some modulation process.

Data Receiving

After receiving Data from receiver, it will be demodulate after the process of demodulation we will get the real data which we required and we want to transmit and we can easily display it. Note: Transmitter Works on 98 MHz

Function Block Diagram

Circuit Diagram

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Circuit Description

This is the circuit for the project Section A of the circuit is receiving signals from the four sensors, here we use an IC M4066 this is just an analog as well as digital switch which have three four input/outputs having a controlling signal pin which controls the data flow in the circuit. This controlling is made by the pins of microcontroller with ports 2.1-2.4.

As these all signals are analog signals, so we have to convert it into digital data by converter called Analog to Digital Converter ADC. For this purpose we used an IC ADC0804. this will convert the analog signal in to digital equivalent. The main thing is that Why we analog to digital converter??

Due to the fact that we have three sensors and we have to transmit these signals so multiplexing is required and this multiplexing is done in the digital signals thats the basic reason of using this analog into digital converter. The output of the digital 8 bit signal will go into the controllers port 1.0-1.7.

After entering data into microcontroller it will transmit by transmitter.

Well this is the end of section A of the circuit. Here another section of the circuit which is the transmission sections. Let explore this part of the circuit. To transmit some signal we have to modulate this signal to transmit it for far distance. Well the modulation circuit is built in the transmitter circuit. Here we use Frequency Modulation, the main aspect is that frequency modulation is easier to use can be transmit through a distance which we required, this is near about 2 Km. so in Radio Frequencies FM is widely use for the data transmission. This transmitter transmits the signal on 102 MHz.

The Output wave form is just like square wave not exactly. Well we can say that the wave form is just a square wave form. Here we cant describe the exactly wave form because oscilloscope is required for the purpose.

Data Flow Diagram

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Data Sheet

Calculations for downlink

1. Free space path loss at distance 2km is 78.285dB

2. Frequency 98 MHz

3. Effective Isotropic radiated Power is 9dB

4. Antenna gain is 10

5. radiated power is 0.8W

6. Carrier to noise ratio C/N = 159.35dB cant calculate satellite gain and additional atmospheric losses because we haven't much knowledge about it.