Semiconductor Temperature Sensors

Semiconductor Temperature Sensor

Semiconductor temperature sensors are devices that use the properties of semiconductor materials to measure temperature. These sensors provide highly accurate readings over a wide temperature range and are commonly used in many electronics and industrial applications. Semiconductor temperature sensors are often more linear in response compared to thermistors and typically offer digital or analog outputs.

Types of Semiconductor Temperature Sensors:

1. Analog Temperature Sensors:

Provide a voltage output proportional to temperature.

Examples: LM35, TMP36.

2. Digital Temperature Sensors:

Communicate temperature data using digital protocols like I²C, SPI, or 1-Wire.

Examples: DS18B20, TMP102.

Key Features:

Linear output: Semiconductor temperature sensors often provide a linear relationship between temperature and output voltage (in analog sensors).

High accuracy: They are precise and can achieve accuracy levels within ±0.5°C for certain ranges.

Simple interface: Analog sensors are easy to connect, while digital sensors often use simple communication protocols.

Low cost: Affordable for many consumer and industrial applications.

Example Semiconductor Sensors:

1. Analog Sensors (e.g., LM35 and TMP36)

LM35: Output voltage is directly proportional to temperature in degrees Celsius. For every 1°C increase, the output voltage increases by 10mV.

TMP36: Similar to the LM35, but can measure negative temperatures. It outputs 500mV at 0°C, and the output increases by 10mV/°C.

Key Characteristics:

Temperature range: Typically -55°C to 150°C for LM35 and -40°C to 125°C for TMP36.

Output voltage: Linear relationship between temperature and output voltage.

2. Digital Sensors (e.g., DS18B20, TMP102)

DS18B20: A popular digital temperature sensor that uses the 1-Wire protocol, capable of measuring temperatures from -55°C to +125°C with an accuracy of ±0.5°C.

TMP102: A high-precision digital sensor that communicates over I²C, with a temperature range of -40°C to 125°C and an accuracy of ±0.5°C.

Using a Semiconductor Temperature Sensor with Arduino:

Example 1: LM35 (Analog Temperature Sensor)

The LM35 is one of the most commonly used analog temperature sensors. Its output is in the form of a voltage proportional to the temperature in °C.

Components Required:

Arduino board (e.g., Uno)

LM35 sensor

Jumper wires

Breadboard (optional)

Wiring the LM35:

VCC: Connect to the 5V pin of the Arduino.

GND: Connect to GND on the Arduino.

Output: Connect to an analog input pin on the Arduino (e.g., A0).

Arduino Code:

const int sensorPin = A0;  // Analog pin for LM35 sensor

void setup() {

  Serial.begin(9600);  // Start serial communication

}

void loop() {

  int sensorValue = analogRead(sensorPin);  // Read the analog value

  float voltage = sensorValue * (5.0 / 1023.0);  // Convert analog value to voltage

  float temperatureC = voltage * 100;  // Convert voltage to temperature (Celsius)

  Serial.print("Temperature: ");

  Serial.print(temperatureC);

  Serial.println(" °C");

  

  delay(1000);  // 1 second delay between readings

}

Explanation:

Analog Read: The Arduino reads the analog voltage from the LM35.

Voltage Conversion: The analog reading is converted to voltage by multiplying it by the reference voltage (5V) divided by the ADC resolution (1023).

Temperature Calculation: The voltage is then converted to temperature, where each 10mV corresponds to 1°C.

Example 2: DS18B20 (Digital Temperature Sensor)

The DS18B20 is a digital temperature sensor that communicates over the 1-Wire protocol, meaning you only need one data wire for communication.

Components Required:

Arduino board (e.g., Uno)

DS18B20 sensor

4.7kΩ pull-up resistor

Jumper wires

Breadboard (optional)

Wiring the DS18B20:

VCC: Connect to 5V or 3.3V.

GND: Connect to GND.

DQ (Data pin): Connect to a digital pin on the Arduino (e.g., D2) with a 4.7kΩ pull-up resistor between the DQ pin and VCC.

Arduino Code:

1. Install the OneWire and DallasTemperature libraries in the Arduino IDE.

2. Use the following code to read temperature:

#include <OneWire.h>

#include <DallasTemperature.h>

const int oneWireBus = 2;  // Data pin for DS18B20

// Setup a oneWire instance to communicate with the DS18B20

OneWire oneWire(oneWireBus);

// Pass the oneWire reference to DallasTemperature library

DallasTemperature sensors(&oneWire);

void setup() {

  Serial.begin(9600);

  sensors.begin();  // Start the DS18B20 sensor

}

void loop() {

  sensors.requestTemperatures();  // Request temperature from sensor

  float temperatureC = sensors.getTempCByIndex(0);  // Get temperature in Celsius

  Serial.print("Temperature: ");

  Serial.print(temperatureC);

  Serial.println(" °C");

  delay(1000);  // 1 second delay between readings

}

Explanation:

OneWire: The sensor communicates using the 1-Wire protocol, so the OneWire library handles communication.

DallasTemperature: This library makes it easy to get temperature readings from DS18B20 sensors.

Temperature Measurement: The sensor reads the temperature in degrees Celsius and sends it to the Serial Monitor.

Applications of Semiconductor Temperature Sensors:

Consumer electronics: For monitoring temperatures in laptops, smartphones, and power supplies.

Medical devices: Such as digital thermometers or patient monitoring systems.

Automotive industry: For engine and battery temperature monitoring.

HVAC systems: For controlling and monitoring heating and cooling systems.

Advantages:

High accuracy: Provides accurate readings in the specified temperature range.

Linear output: Especially useful for analog sensors like the LM35 and TMP36.

Easy to interface: Both analog and digital sensors are easy to interface with microcontrollers like Arduino.

Limitations:

Limited temperature range: Generally used for moderate temperature ranges compared to thermocouples.

Requires proper calibration: Especially if being used in critical applications.

These semiconductor sensors are reliable, affordable, and easy to use in a wide variety of temperature-sensing applications.