What is Thermistor : Basics on Thermistor Using Arduino Project

In 1833, Michael Faraday discovered the first NTC thermistor. In high school, you were taught metal couple get bent with temperature. That thing is more old. Here is Basic Theory and Practical Basic Example on Thermistor Using Arduino Project With Circuit Diagram and Code. What is Thermistor? Thermistor is a basic electronic component like LDR, it is also a type of resistor whose resistance is dependent on temperature. In NTC thermistors, the resistance decreases with temperature rise. In PTC thermistors, the resistance increases with temperature rise.

 

What is Thermistor?

 

A thermistor’s operation is based on the variation in the resistivity of a semiconductor with temperature. The term thermistor comes from Thermally Sensitive Resistor. There are two types of thermistor:

NTC (Negative Temperature Coefficient) – negative temperature coefficient
PTC (Positive Temperature Coefficient) – positive temperature coefficient (also called posistor ).

When the temperature increases, the PTC type increases its resistance and the NTC decreases it. It is NTC Thermistors which are commonly seen.

The operation is based on the variation of the resistance of the semiconductor due to the change of the ambient temperature. For NTC thermistors, increasing the temperature will increase the concentration of carriers, so the resistance will be lower, hence the coefficient is negative. For PTC thermistors, in the case of a semiconductor with a very intense doping, it will acquire metallic properties, taking a positive coefficient in a limited temperature range. Usually, thermistors are manufactured from semiconductor oxides, such as ferric oxide, nickel oxide, or cobalt oxide. However, unlike RTD sensors, the variation of resistance with temperature is not linear. For an NTC thermistor, the characteristic is hyperbolic. For small increases in temperature, large increases in resistance will occur.

So, for real temperature measurement, DHT 11 like sensors are more sensitive.

NTC thermistors can be used in series with a circuit as an inrush current limiter. PTC thermistors can be used in series to protect against overcurrent like in resettable fuses. These are their actual usage.

 

Basics on Thermistor Using Arduino Project

 

If you are seeking for Thermistor Using Arduino Project, then you are probably seeking using thermistor as temperature sensor with Arduino. NTC thermistors like 102 NTC thermistor commonly sold and used. Michael Faraday not thought of Arduino! The circuit diagram and code is like any similar basic electronic component, like LDR. Thermistor is better to say HEAT DETECTOR than temperature detector. Of course we can use thermistor in complex Arduino projects as “safety valve”, like in real life.

Our example is for using it with Arduino to watch the serial monitor of Arduino IDE. We have to use a 10K resistor with 102 NTC thermistor as voltage divider, like we used in LDR projects :

This is example code :

Thermistor can be used in Arduino project to create an unit for refrigerator which will send text message or message via WiFi dipped inside a fluid – like to be ice-cream (wrapped inside plastic sheet). If temperature is minus 4 degrees for 1 hour then ready like logic. Because thermistor unlike DTH 11 will not die in such torture.