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--- en:iot-open:practical:hardware:taltech:arduino:scenarios:thermistor [2025/07/18 14:06] – ingmar05
+++ en:iot-open:practical:hardware:taltech:arduino:scenarios:thermistor [2025/09/02 14:38] (current) – raivo.sell
@@ Line 1: / Line 1: @@
+<pagebreak>
+====== Temperature Measurement Using Thermistor ======
+This scenario demonstrates how to measure temperature using a thermistor (temperature-sensitive resistor) connected to an Arduino Uno. The temperature is calculated using the Steinhart-Hart equation.
+===== Prerequisites =====
+  * Familiarize yourself with the Arduino hardware reference.
+  * Basic understanding of analog sensor readings and voltage dividers.
+  * Install LiquidCrystal library for LCD display.
+===== Hardware Connections =====
+^ Component   ^ Arduino Pin                         ^
+| Thermistor  | A5 (Analog)                         |
+| LCD         | RS=8, EN=9, D4=4, D5=5, D6=6, D7=7  |
+===== Task =====
+Measure temperature using a thermistor and display the results (ADC reading, voltage, resistance, and temperature in Celsius) on the LCD.
+===== Steps =====
+=== Step 1: Include Libraries ===
+<code c>
+#include <math.h>
+#include <LiquidCrystal.h>
+</code>
+=== Step 2: Initialize LCD ===
+Declare LCD pins and initialize:
+<code c>
+LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
+const int sensorPin = A5;
+</code>
+=== Step 3: Setup ===
+Set LCD dimensions and initial message:
+<code c>
+void setup() {
+  lcd.begin(16, 2);
+  lcd.print("Temperature");
+  delay(1000);
+}
+</code>
+=== Step 4: Main Loop ===
+Read sensor value, calculate temperature, and display on LCD:
+<code c>
+void loop() {
+  readThermistor(analogRead(sensorPin));
+  delay(1000);
+  lcd.clear();
+}
+void readThermistor(int RawADC) {
+  double Temp;
+  long Resistance;
+  // Calculate resistance
+  Resistance = ((10240000 / RawADC) - 10000);
+  // Display ADC and voltage
+  lcd.setCursor(0, 0);
+  lcd.print("AD=");
+  lcd.print(RawADC);
+  lcd.setCursor(8, 0);
+  lcd.print("U=");
+  lcd.print(((RawADC * 5.0) / 1024.0), 3);
+  // Display resistance
+  lcd.setCursor(0, 1);
+  lcd.print("R=");
+  lcd.print(Resistance);
+  // Calculate temperature (Steinhart-Hart)
+  Temp = log(Resistance);
+  Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp)) * Temp);
+  Temp = Temp - 273.15; // Convert Kelvin to Celsius
+  // Display temperature
+  lcd.setCursor(8, 1);
+  lcd.print("T=");
+  lcd.print(Temp);
+}
+</code>
+===== Validation =====
+LCD displays accurate ADC values, voltage readings, resistance, and temperature in Celsius. Typical room temperature should range between 19-24 °C.
+===== Troubleshooting =====
+If temperature readings are incorrect or unstable:
+  * Check wiring and verify analog input connection (A5).
+  * Verify the correct resistor value in the voltage divider.
+  * Ensure accurate Steinhart-Hart constants are used.