LM 35- A verstile temperarture monitor
LM35 is a precision integrated circuit temperature sensor that can measure temperature with an accuracy of ±0.5°C at a range of -55°C to 150°C. It was developed by National Semiconductor Corporation, now a part of Texas Instruments, and has become a popular choice for temperature sensing applications in electronic circuits.
The LM35 is easy to use because it does not require any external calibration or trimming. It is also linear in its output response to temperature changes, making it ideal for temperature measurement applications in many different fields, such as HVAC systems, automotive systems, and medical devices.
The LM35 temperature sensor produces an output voltage that is proportional to the temperature it senses. Specifically, the output voltage of the LM35 increases by 10 millivolts per degree Celsius increase in temperature.
For example, if the LM35 is operating at a temperature of 25 degrees Celsius, its output voltage will be 250 millivolts (0.25 volts). If the temperature increases to 30 degrees Celsius, the output voltage will increase to 300 millivolts (0.3 volts), and if the temperature decreases to 20 degrees Celsius, the output voltage will decrease to 200 millivolts (0.2 volts).
This linear relationship between temperature and voltage output makes the LM35 sensor very useful in applications where precise temperature measurement is required, such as in electronic circuits and temperature control systems. Additionally, because the LM35 sensor does not require any external calibration or trimming, it is easy to use and provides accurate temperature measurements without requiring complex circuitry.
In this circuit, the LM35 temperature sensor is connected to a 5V voltage supply and ground. The output voltage of the LM35 is then measured relative to ground, and this voltage can be converted to a temperature reading using a simple formula:
Temperature (in Celsius) = (LM35 output voltage in millivolts) / 10
For example, if the LM35 output voltage is measured to be 250 millivolts, the temperature reading would be:
Temperature = 250 / 10 = 25 degrees Celsius
Note that this circuit is a very basic example and may not be suitable for all applications. In practice, more complex circuits may be required to amplify or condition the output voltage of the LM35, or to compensate for temperature drift or other sources of error.
Here’s an example Arduino code that reads the temperature from an LM35 sensor and displays it on a 16x2 LCD:
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // initialize the LCD pins
int lm35_pin = A0; // analog input pin for LM35
float temp; // temperature variable
void setup() {
lcd.begin(16, 2); // initialize the LCD
}
void loop() {
// read the LM35 sensor and convert the output voltage to temperature
int lm35_reading = analogRead(lm35_pin);
temp = (lm35_reading / 1024.0) * 500.0;
// display the temperature on the LCD
lcd.setCursor(0, 0);
lcd.print("Temperature:");
lcd.setCursor(0, 1);
lcd.print(temp);
lcd.print(" C");
delay(1000); // wait for 1 second before taking another reading
}
In this code, we first initialize the LCD pins and the analog input pin for the LM35 sensor. Then, in the loop() function, we read the voltage output from the LM35 sensor using the analogRead() function, convert it to a temperature reading using the formula temp = (lm35_reading / 1024.0) * 500.0, and display the temperature on the LCD using the lcd.print() function.
Note that the delay() function is used to wait for 1 second before taking another reading. This is to avoid taking too many readings too quickly and potentially causing the LM35 sensor to heat up and produce inaccurate readings.
The LM35 temperature sensor can be used in many different ways in industry, depending on the specific application. Here are a few examples:
· HVAC systems: In heating, ventilation, and air conditioning (HVAC) systems, the LM35 can be used to measure the temperature of air or water in pipes, ducts, or rooms. This information can be used to control the heating and cooling systems to maintain a comfortable temperature for occupants.
· Food processing: In the food industry, the LM35 can be used to monitor the temperature of food during storage, processing, and transportation. This is critical to ensure that food is stored and cooked at the correct temperatures to prevent bacterial growth and ensure food safety.
· Automotive systems: In automotive systems, the LM35 can be used to measure the temperature of engine coolant, transmission fluid, and other fluids. This information can be used to control the cooling systems and prevent overheating.
· Medical devices: In medical devices, the LM35 can be used to measure body temperature, as well as the temperature of blood, IV fluids, and other medical fluids. This information can be used to monitor the health and wellbeing of patients and ensure that medical treatments are being delivered at the correct temperature.
· Industrial process control: In industrial processes, the LM35 can be used to measure the temperature of fluids, gases, and solids in various stages of manufacturing and processing. This information can be used to control process parameters and ensure that products are being manufactured to the correct specifications.
Overall, the LM35 is a versatile and reliable temperature sensor that can be used in a wide range of industrial applications where precise temperature measurement is required.
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