Is temperature sensor most used and most popular. In this article we are going to analyze the highlights of the LM35, a high-precision (and also very cheap) temperature measurement device that is widely used in electronics and automation applications.
This analog sensor, which measures the temperature in degrees centigrade or Celsius, operates within an operating voltage range ranging from 4 V to 25 V. In this post we are going to give a detailed description of the LM35, including the pinout, its operation, the protocol it uses and other details.
The LM35 integrated circuit was developed by the American company National Semiconductor in 1976. The gran ventaja What was provided at the time was that, due to the low input power of the converter, there is hardly any self-heating of the component, which is important from the point of view of measurement precision. Currently, it is widely used in projects developed on the popular open source electronics creation platform Arduino.
This temperature measuring device three terminals It offers an analog output voltage proportional to temperature, without the need for any external calibration circuit. These are some of its most frequent applications:
- Temperature measurements in a particular environment.
- Thermal shutdown function for a circuit or component in a specific project.
- Battery temperature measurement (as a way to protect against overheating).
LM35 Specifications
These are the basic technical aspects of LM35 temperature sensor:
- Temperature range from -55 °C to 150 °C.
- Output voltage with scale factor of 10 mV/°C. This means that the voltage increases by 10 mV for every degree increase in temperature. For example, 280 mV means 28°C.
- Calibration accuracy ±0,5°C at room temperature.*
- Required power supply from 4V to 25V.
- Current consumption: 60 µA.
(*) The degree of precision may vary depending on other factors such as power supply voltage or environmental conditions. On the other hand, self-heating hardly influences the measurement process.
LM35 Temperature Sensor Pinout
This is the PINOUT configuration of the LM35, which is made up of three pins (as shown in the image above):
- Vcc. input pin or Power Pin, connected to +5 V.
- Vout. Output pin, also called Output Pin. It must be connected with an analog pin of the microcontroller.
- Grounds. “Ground” pin (connected to 0 V or GND).
How it works
The LM35 sensor core contains a temperature sensitive element, which is generally made of silicon or some other solid material with similar characteristics. This element shows a linear change in its electrical properties in response to temperature variations.
The linear analog voltage output that is directly proportional to the temperature being measured, as we have already explained in the specifications section. Afterwards, there is calibration process, by which the relationship between the temperature and the corresponding output voltage is established. The stability of the supply voltage is what guarantees the accuracy of the readings.
The analog voltage output of the LM35 sensor can be connected without problems to microcontrollers, analog-digital converters and other types of electronic circuitss. It can be directly connected to the idea of converting analog voltage into a digital temperature reading. Data that is of great help for subsequent analysis and processing.
Advantages and disadvantages of using the LM35 sensor
Many and advantages of the use of the LM35 sensor, which is why it has become a widely used component with numerous applications. These are, in summary, the most notable ones:
- High accuracy.
- Linear output.
- Wide temperature range.
- Low energy consumption.
- Simple interface.
However, there are also some weak points that must be put on the table when using this sensor. Basically, there are two: its excessive sensitivity to noise, which can affect the precision of the measurements, and the fact that it does not offer a standard output.
Example of using LM35 with Arduino
Finally, we include a simple project that will help us better understand the operation of the LM35 sensor. The proyect consists in monitor temperature in Arduino virtual terminal. The components of this circuit are the following:
- Arduino as the main component that controls all functions.
- LM35 sensor for temperature detection and its conversion into an analog signal.
- Analog to Digital Converter (ADC).
The value of the temperature detected by the sensor is displayed on the serial terminal (or in the virtual terminal in case we are working with Proteus, one of the best options in terms of simulation of electrical circuits). Everything explained in these lines is well summarized and graphically explained in the image above.
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