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Designing a Temperature Warning Device System using Thermistors

This project focuses on designing and simulating a temperature warning device system utilizing thermistors, a type of semiconducting material that changes electrical resistance with temperature variations. The system aims to trigger an alarm when the temperature reaches a specific level, offering practical applications like greenhouse temperature monitoring or fire detection. The report discusses the importance of temperature measurement in industrial settings, introduces the role of sensors and transducers, and provides a detailed circuit diagram for the alarm system operation. The project successfully demonstrates a reliable temperature controller with a variable resistor and cold junction compensation circuit.

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Designing a Temperature Warning Device System using Thermistors

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  1. By Saleh Braki Alrashedi ID:291103609 Under supervision of Dr. Abdu Idris

  2. Abstract The triggering of this device depends on the action of a thermistor . This is a bar, disc or bread of semiconducting material with the special property that its electrical resistance decreases appreciably as its temperature increases. The variation of its resistance is used to trigger a circuit to switch on an alarm device whenever the temperature exceeds a given level. We can arrange for the alarm to be set off when the green house becomes overheated, or when a house catches fire. The circuit can be modified to operate in a reverse manner, so that the alarm is triggered when the temperature falls below a given level, making it useful as s frost detector.

  3. Objective of the project The objective of the project is to design and simulate a temperature warning device system using the Proteus software .

  4. Introduction Temperature measurement in today’s industrial environment encompasses a wide variety of needs and applications. To meet this wide array of needs the process controls industry has developed a large number of sensors and devices to handle this demand. In this experiment you will have an opportunity to understand the concepts and uses of many of the common transducers, and actually run an experiment using a selection of these devices. Temperature is a very critical and widely measured variable for most mechanical engineers. Many processes must have either a monitored or controlled temperature. This can range from the simple monitoring of the water temperature of an engine or load device, or as complex as the temperature of a weld in a laser welding application. More difficult measurements such as the temperature of smoke stack gas from a power generating station or blast furnace or the exhaust gas of a rocket may be need to be monitored. Much more common are the temperatures of fluids in processes or process support applications, or the temperature of solid objects such as metal plates, bearings and shafts in a piece of machinery.

  5. Certification Certified that the contents and form of research report entitled “Design and Simulation of a Temperature- Operated Alarm System ”submitted by Salih B. have been satisfactory for the Partial Fulfillment of the Requirements for the Degree of Science in Science, The Majmmah University.

  6. Figure 1: Example of an industrial control relay commonly used on movable spans

  7. Relay and Contactor Unit The connection of the relay and contactor circuit is shown in Fig.2

  8. Alarm system operation When the switch is ON then a certain voltage is generated from the variable resistor to the base of the transistor, a certain collector current accordingly is generated and applied to the relay. The light emitting dide gives light and at the same time the relay energizes and switches on the siren circuit to produce loud sound of a fire brigade siren. V2 R2 560 110V RL1 12V C1 470u D1 1N4148 D2 LED-RED BUZ1 V1 15V BUZZER L2 50V R1 10 RV1 Q1 BC548 R6 10k +0.55 mA 43% C2 470u +6.32 1K Volts

  9. CONCLUSIONS A simple simulated reliable temperature controller was designed and tested successfully. Variable resistor is was used instead of the temperature sensor Cold junction compensation circuit is provided

  10. THANK YOU

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