Wemos and LM35 temperature sensor

In this example we will connect an LM35 temperature sensor to our Arduino

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1/4°C at room temperature and ±3/4°C over a full -55 to +150°C  temperature range

Here is a picture of the pins, its important to get these correct or you can damage the sensor

lm35-temperature-sensor-pinout

I purchased a small module, which looks like this. This was clearly labelled and helps avoid any mistakes with wiring, I also prefer using cables to modules rather than breadboards

lm35-module

Schematics and Parts

You will need

Wemos Mini
LM35 sensor or module
Hook up wire (dupont cables)

Very simple to connect Vcc is 3v3, Gnd is any Gnd and out goes to Wemos Mini A0, you can see this below

wemos-and-lm35_bb

Code

//initializes/defines the output pin of the LM35 temperature sensor
int outputpin= 0;
//this sets the ground pin to LOW and the input voltage pin to high
void setup()
{
Serial.begin(9600);
}
 
//main loop
void loop()
{
int rawvoltage= analogRead(outputpin);
float millivolts= (rawvoltage/1024.0) * 3300;
float celsius= millivolts/10;
Serial.print(celsius);
Serial.print(" degrees Celsius, ");
 
Serial.print((celsius * 9)/5 + 32);
Serial.println(" degrees Fahrenheit");
delay(1000);
 
}

 

Results

Here are the results via the serial monitor

25.14 degrees Celsius, 77.25 degrees Fahrenheit
25.14 degrees Celsius, 77.25 degrees Fahrenheit
25.46 degrees Celsius, 77.83 degrees Fahrenheit
26.43 degrees Celsius, 79.57 degrees Fahrenheit
27.71 degrees Celsius, 81.89 degrees Fahrenheit
28.36 degrees Celsius, 83.05 degrees Fahrenheit
29.00 degrees Celsius, 84.21 degrees Fahrenheit
29.33 degrees Celsius, 84.79 degrees Fahrenheit
29.33 degrees Celsius, 84.79 degrees Fahrenheit
29.00 degrees Celsius, 84.21 degrees Fahrenheit
28.68 degrees Celsius, 83.63 degrees Fahrenheit
28.36 degrees Celsius, 83.05 degrees Fahrenheit
28.36 degrees Celsius, 83.05 degrees Fahrenheit
28.04 degrees Celsius, 82.47 degrees Fahrenheit

 

Links

LM35 datasheet
5PCS LM35D Temperature Sensor TO92 Packing

1 comment to Wemos and LM35 temperature sensor

  • Ryan Albert M. Orozco

    Good day,

    We did what you did on this project, unfortunately we are having very low readings in temperature(Celsius).
    We are using Wemos d1 r2 v2.1.0. Hope you can help us.

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