1.
Overview of LM35 :-
The LM35 is an integrated circuit (IC) temperature sensor that provides a linear
analog output proportional to the temperature in degrees Celsius (°C). Its main
features include:
High accuracy and low power consumption.
A simple three-pin configuration.
Calibration directly in Celsius, with a 10 mV per °C linear output scale
factor.
2. Features of LM35 :-
Accuracy: Typical accuracy of ±0.5°C at room temperature.
Temperature Range: The LM35 can measure temperatures in a range of
-55°C to +150°C.
Output Voltage: For every 1°C increase in temperature, the output
voltage increases by 10 mV.
Low Self-Heating: It consumes very low power, typically around 60 µA,
which minimizes self-heating.
Wide Power Supply Range: Operates from 4 to 30 volts.
3. Diagram of LM35 :-
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4. Block Diagram of LM35 :-
5. Pin Configuration : -
The LM35 has three pins:
Vcc (Pin 1): Power supply input (4V to 30V).
Vout (Pin 2): Analog output voltage, which is proportional to the
temperature.
GND (Pin 3): Ground.
6. Working Principle :-
The LM35 is a semiconductor-based temperature sensor. Inside, it uses a transistor-based
design where temperature changes cause variations in voltage across a diode junction. This
voltage is then amplified and output as an analog voltage signal.
The output voltage (VoutV_{out}Vout) directly corresponds to temperature. For example:
At 0°C, VoutV_{out}Vout = 0 mV
At 25°C, VoutV_{out}Vout = 250 mV
At 100°C, VoutV_{out}Vout = 1,000 mV
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This simple voltage-temperature relationship makes it easy to interpret the temperature
without complex calculations.
7. Calculating Temperature from Output Voltage :-
To calculate the temperature, you can use the formula:
For example, if the output is 300 mV, the temperature is:
8. Applications of LM35 :-
Weather Stations: For measuring ambient temperature.
HVAC Systems: To monitor temperature in heating, ventilation, and air
conditioning systems.
Industrial Automation: For temperature regulation in industrial
machines.
Home Automation Systems: Common in smart thermostats and
temperature monitoring devices.
Microcontroller Projects: Used with Arduino, Raspberry Pi, and other
microcontrollers for temperature-related applications.
9. Advantages of LM35 :-
Calibrated Output in °C: Eliminates the need for additional calculations
or conversions.
Easy to Interface: Its three-pin design and analog output simplify
integration with other systems.
High Accuracy: Reliable in environments with fluctuating temperatures.
Low Cost: Affordable and widely available, making it popular for DIY
electronics projects.
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10. Limitations of LM35 :-
Limited Temperature Range: It may not be suitable for extremely high
or low temperatures.
Analog Output: Requires an ADC (Analog-to-Digital Converter) if used
with digital-only devices like some microcontrollers.
Environmental Limitations: Susceptible to damage in harsh
environments unless properly shielded.
