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Gsm Based Temperature Measurement System Computer Science Essay

Short bursts of data once restricted to fixed LANs and WANs are now being delivered to mobile devices to boost productivity and improve customer service. Wireless Short Message Service (SMS), is the vehicle for this communication. SMS messaging has been one of the success stories of the mobile phone industry over the past three years.

Now a days it has become a major concern in monitoring the real time temperature for a remote area particularly in controlling the switch which is temperature controlled.

The real time temperature controlled switches are used to control some devices depending on the predefined temperature. The current temperature of the place is endlessly monitored by the microcontroller through the temperature sensor. If the current temperature of the place exceeds the stored value then the microcontroller will send the signal to relay. As the relay operates the status is displayed on the LCD as well as it is sending an SMS message to the authorized person using GSM module. The status of that place is monitored. If the user wants to monitor at a particular time he can send an SMS to the system by circulation user ID then the system will read this SMS and sends the status of the place.

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Temperature is a Physical parameter which is converted into an electrical parameter by a device called Temperature Transducer. Transducer is also referred to as a sensor.

The commonly used transducer produces an output voltage, current, capacitance and resistance. However we need to convert these signals to voltage in order to send an input to an A-D converter. This conversion is commonly called signal conditioning. Signal conditioning can be a current to voltage conversion or signal amplification.

Transducer is a device that converts one type of energy. Its commonly implies use as a detector.

For example, the output of thermistor is change in resistance with change in temperature. The change in resistance must be signal conditioned into voltage in order to use an ADC.

The most important parameter of an ADC is resolution. The higher resolution ADC provides a smaller step size, where step size is the smallest change that can be discerned by an ADC. In addition to resolution, conversion time is another major factor in judging an ADC. Conversion time is defined as the time taken by an ADC to convert the analog signal to a digital signal.

The ADC chips are either parallel or serial ADC. In parallel ADC, we have 8 or more pins dedicated to bringing out the binary data, but in serial ADC we have only one pin for data out.

Microcontroller is the central component which reads data (temperature) from ADC and from the keypad switches display the temperature and necessary on LCD (Liquid Crystal Display) and controls the Relay.

In order to do all the activities a program (sequence of instruction) must be written for the microcontroller. This program is called firmware. In order to execute the program, Microcontroller requires basic configuration like 5V regulated power supply, clock, and reset circuit.

16*2 (2 line of 16 character) LCD is used for displaying temperature and relay status. It provides easy user interface. It needs to initialize before displaying data. This initialization is done by Microcontroller.

Relay is used to control external device. (Cooler/heater) Since microcontroller does not provide sufficient current, hence relay driver is required.

Keypad switches are used to change the threshold values and see the maximum and minimum temperature.

Semen's GSM/GPRS Smart Modem is a multi-functional, ready to use, rugged unit that can be embedded or plugged into any application. The Smart Modem can be controlled and customized to various levels by using the standard AT commands. The modem is fully type-approved, it can speed up the operational time with full range of Voice, Data, Fax and Short Messages (Point to Point and Cell Broadcast), the modem also supports GPRS (Class 2*) for spontaneous data transfer.

Sampling Rates:

Resistance thermometers, also called resistance temperature detectors or resistive thermal devices (RTDs), that is exploit the predictable change in electrical signal. Some materials with only changing for temperature. As they are almost invariably made of platinum, they are often called platinum resistance thermometers (PRTs). It is slowly reduce the thermocouples in many industrial applications below 600 °C, due to higher accuracy and repeatability.

It is a basically temperature sensitive resistor.

Choice of scheduling algorithms:

The method of scheduling offset compensation for an IR imaging system to maintain good image quality. The method includes a scheduling for automatic offset compensation. The scheduling algorithm automatically adjusts periods between offset compensation based on the focal plane array (FPA) pixel levels. As a result, the periods are adjusted both camera is stable and when the camera is undergoing an internal thermal change.

Vital role of GSM modem:

GSM is one of the latest mobile technologies used to smart MODEM which can easily interfaced to embedded microcontrollers. Now everything is going to be automated using this technology, using these technology we can access the devices slightly. Using GSM and GPS now we can identify the people, vehicles etc in any where of the world.

Microcontroller and IC's requires 5V regulated power supply, which is obtained from 230V AC by using step down transformer , rectifier, filter and regulators.




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Tools for schematic design:



ATMEL 89C51 controller,

ADC 0804,




PCB for microcontroller unit, Reset switches, resistors etc,


Crystal 11.0592 MHz

Working Principle:

When the power is applied to microcontroller, it initializes GSM MODEM, LCD, ADC0804 and Relay Driver. Then it reads the temperature from ADC 0804 and transmits to GSM. Simultaneously it compared the temperature with Threshold values (a High and Low Threshold). If it crosses the threshold values will be activated.

The threshold values can be changed by Entering into Settings Mode (by pressing INC and then DEC buttons). The highest and lowest temperature over a period can be viewed by pressing Settings Button.

Micro controller:

Atmel AT89C51 is an 8051-based Fully Static 24MHz CMOS controller

With 32 I/O Lines, 2 Timers/Counters, 6 Interrupts/2 Priority Levels, UART, Three-Level Program Memory Lock, 4K Bytes Flash Memory, 128 Bytes On-chip RAM.

Choice of ADC:









Obsolete Versions


 Compatible with 80p µP derivatives-no interfacing logic needed - access time - 135 ns pa

ï‚· Easy interface to all microprocessors, or operates "stand alone".

ï‚· Differential Analog voltage input.

ï‚· Logic inputs and outputs meet both MOS and TTL voltage level specifications

ï‚· Works with 2.5V (LM336) voltage reference

ï‚· On-chip clock generator

ï‚· 0V to 5V analog input voltage range with single 5V supply

ï‚· No zero adjust required

ï‚· 0.3[Prime] standard width 20-pin DIP package

ï‚· 20-pin molded chip carrier or small outline package

ï‚· Operates ratiometrically or with 5 VDC, 2.5 VDC, or analog span adjust.


The ADC0801, ADC0802, ADC0803, ADC0804 and ADC0805 are CMOS 8-bit successive approximation A/D converters that use differential potentiMetric ladder-similar to the 256R products. These converters are designed to allow operation with the NSC800 and INS8080A derivative control bus with TRI-STATE output latches directly driving the data bus. These A/Ds appear like memory locations or I/O ports to the microprocessor and no interfacing logic is needed.

Differen Analog Voltage inputs allow increasing the common-mode rejection and offsetting the analog zero input voltage value. In addition, the voltage reference input can be adjusted to allow encoding any smaller analog voltage span to the full 8 bits of resolution.

Key Specification:


8 bits

Total error

±¼ LSB, ±½ LSB and ±1 LSB

Conversion time

100 µs

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