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?

4 channel data telemetry system

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

4 channel data telemetry system

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

Data Receiving

4 channel data telemetry system

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

4 channel data telemetry system

Circuit Diagram
4 channel data telemetry system

4 channel data telemetry system

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.

4 channel data telemetry system

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??

4 channel data telemetry system

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.

4 channel data telemetry system

Data Flow Diagram
4 channel data telemetry system

Data Sheet
4 channel data telemetry system

Calculations for downlink

Free space path loss at distance 2km is 78.285dB

Frequency 98 MHz

Effective Isotropic radiated Power is 9dB

Antenna gain is 10

radiated power is 0.8W

Carrier to noise ratio C/N = 159.35dB cant calculate satellite
gain and additional atmospheric losses because we haven`t much
knowledge about it.


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