Introduction

A thermistor is a type of resistor whose resistance varies significantly with temperature, A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiter, temperature sensors (NTC type typically), self-resetting over current protectors, and self-regulating heating elements.

Thermistors differ from resistance temperature detectors (RTDs) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a greater precision within a limited temperature range, typically −90 °C to 130 °C (1).

Components

- 1 Uno board
- 1 USB data cable
- 1 Breadboard
- 1 Thermistor
- Several jumper wires
- 1 Potentiometer (50KΩ)
- 1 Resister (10KΩ)
- 1 LCD16x02

Experimental Principle

The resistance of the thermistor varies significantly with ambient temperature. It can detect

Surrounding temperature changes in real time, this change in the resistance is Send to the analog I/O port of Uno board since it is an analog signal, in fact, we are reading the change in the thermistor voltage which indicates the change in the resistance value and the resistance value indicates the change in the ambient temperature, Next we only need to convert sensor’s output to Celsius and Fahrenheit temperature by simple programming then displaying it on the LCD16x02.

Experimental Procedures

Step 1: Connect circuit as shown in Fig1. The corresponding schematic is shown in Fig2. (Schematic is generated by EAGLE)
Step 2: Program the Arduino (download program from documents).
Step 3: Compile the program.
Step 4: Burn the program into Uno board.

Now, you can see current temperature displayed on LCD both in Celsius and Fahrenheit degrees.

circuit connection

Fig1: the connection of the thermistor

eagle schematic

Fig2: the schematic

Experimental summary

In this lesson we are dealing with a new component, that is LCD display, it is useful to monitor the circuit status for the applications that are not connected to the PC, sometimes you may feel blind in the absence of the display means.

We are also relying more on the code this time to convert the resistance change into the corresponding temperature value. It good to depend on the code more often than depending on the hardware.

Documents:

1-Arduino progrme (code)
2-Eagle file
3-Arduino LCD library

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1-https://en.wikipedia.org/wiki/Thermistor