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A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors.

The word thermistor is a Portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self resetting over current protectors and self regulating heating elements. Thermistors can be classified into two types depending on the sign it bears. If it is positive, the resistance increases with increasing temperature and the device is called a positive temperature coefficient PTC thermistor or posistor.

If it is negative, the resistance decreases with increasing temperature and the device is called a negative temperature coefficient NTC thermistor.

Resistors that are not thermistors are designed to have a temperature sensitivity which is as close to zero as possible so that their resistance remains nearly constant over a wide temperature range. Instead of the temperature coefficient K, sometimes the temperature coefficient of resistance is used alpha sub.


The most recent advancement in technology has really given birth to different development in the fields of electronics engineering. Provisions have been made by technologist who covers a wide range of humans environment giving solution to humans problem.

In recent time, heat control has been unstable in the world which has really affected some heat level sensitive equipment’s. Most equipment was found to malfunction under high temperature in this case, high heat.

Heat/temperature level sensitive equipment aside, humans was as well found to behave abnormally under high temperature/heat at times. These findings necessitated the research of this project work where a thermistor is used to regulate the heat level/content of a room.

The first thermistor was discovered in 1833 by Michael Faraday who reported on the semiconducting behavior of silver sulfide.

Faraday noticed that the resistance of silver sulfide decreases dramatically as temperature increases. Because early thermistors were difficult to produce and applications for technology were limited, commercial production of thermistors did not begin until in the 1930s.

The thermistor was invented by Samuel Ruben in 1930.


The following problems necessitated the research of this project work.

1. High cost of using other methods of heating in a room.

2. Lack of means of heat regulation in houses located around the tropical rain forest.

3. The high rate of searching for adequate means of heating a room or regulating the temperature in a room.

4. Ignorance of thermistor and its applications among engineering students.


The purpose of this study is aimed at constructing a thermistor controlled room heater. It was prompted by a quest to produce/construct a comparatively cheap room heating element or gadget that can work as perfectly as other heating vent sold in the market today.


Having researched the problems faced by the electronic engineers in their collective attempts to produce a heating vent for room, the following therefore constitutes the objective of this study.

I. To produce a thermistor controlled heater for rooms which can be purchased by everyone at a comparatively cheap price.

II. To minimize the high rate of searching for adequate means of heating a room or regulating the temperature of a room.

III. To help create awareness among engineering students of the existence of a thermistor which can be used to regulate heat/temperature in a room.


The thermistor controlled room heater should be able to control the heating of the room in which it is installed. It can also be used to control the temperature of tropical aquariums; chemical processes etc. as long as their requirement can be classified by a two degree tolerance. The thermistor room controlled heater constructed here is not good enough for colour photographic works especially slide developing. To undertake such task, the need for real PI or PID controls is required PID is a new model of thermistors.


The focal point of this work is to construct a thermistor control room heater, highlighting its objectives and operational characteristics.

The gadget constructed here has only been confirmed to work adequately in a compatible single room or office.

Its application in a larger room, office or warehouse is slightly beyond the scope of this study.


The following forms the limitations of the study;

1. FINANCIAL CONSTRAINT: Sourcing for more information from diverse sources was limited to do, lack of enough money to extract information through more sources available in the Nigeria as a whole.

2. ORGANIZATIONAL POLICIES: The policies guiding the organization in which the research was carried out upon are restricted to give certain organizational file to keep as a secret from the public who have no direct contribution to the well being of the organization.

3. MATERIAL FACTOR: The materials required for the construction of a thermistor control room heater are limited because of this, alternative materials was used which may result in the constructed work not performing as was expected.


1. PNP TRANSISTOR: This is an electronic component used as a switch to ON or OFF the power supply of a system which can be AC or DC.

2. CAPACITOR: This is a device that is used to store energy.

3. RESISTOR: This is a component that provides opposition to the flow of electric current in a circuit.

4. ALTERNATING CURRENT: This is the flow of current in a circuit in a sinusoidal pattern.

5. TRIAC: This is a three terminal semiconductor device for controlling current. It is an ideal device to use for AC switching application because it can control the current flow over both halves of an alternating cycle.

6. THERMISTOR: A thermistor is a type of resistor whose resistance varies significantly with temperature.

7. NTC THERMISTOR: This is a type of thermistor in which the resistance decreases with an increase in temperature.

8. PTC THERMISTOR POSISTOR: This is a type of thermistor in which the resistance increases with an increase in temperature.

9. CONDUCTOR: This is a material that allows the easy passage of current through them.

10. UNIT: This is defined as a particular section of a circuit with a specified function.

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