ESP32 - LM35 Temperature Sensor

This tutorial instructs you how to use ESP32 to read temperature value from LM35 temperature sensor, and print it to Serial Monitor.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	Micro USB Cable
1	×	LM35 Temperature Sensor
1	×	(Optional) 5V Power Adapter
1	×	(Optional) DC Power Jack
1	×	(Optional) ESP32 Screw Terminal Adapter

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Introduction to LM35 Temperature Sensor

LM35 Temperature Sensor Pinout

LM35 temperature sensor has three pins:

VCC pin: connect this pin to VCC (5V)
GND pin: connect this pin to GND (0V)
OUT pin: This pin outputs voltage in proportion to the temperature value.

How LM35 Temperature Sensor Works

The LM35 sensor outputs the voltage in linearly proportion to the Celsius temperature. The output scale factor of the LM35 is 10 mV/°C. By measuring the voltage on the LM32's OUT pin, we can calculate the temperature value.

Wiring Diagram between LM35 Temperature Sensor and ESP32

The wiring diagram with power supply from USB cable

ESP32 LM35 temperature sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

The wiring diagram with power supply from 5v adapter

This image is created using Fritzing. Click to enlarge image

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-lm35-temperature-sensor */ #define ADC_VREF_mV 3300.0 // in millivolt #define ADC_RESOLUTION 4096.0 #define PIN_LM35 36 // ESP32 pin GIOP36 (ADC0) connected to LM35 void setup() { Serial.begin(9600); } void loop() { // read the ADC value from the temperature sensor int adcVal = analogRead(PIN_LM35); // convert the ADC value to voltage in millivolt float milliVolt = adcVal * (ADC_VREF_mV / ADC_RESOLUTION); // convert the voltage to the temperature in °C float tempC = milliVolt / 10; // convert the °C to °F float tempF = tempC * 9 / 5 + 32; // print the temperature in the Serial Monitor: Serial.print("Temperature: "); Serial.print(tempC); // print the temperature in °C Serial.print("°C"); Serial.print(" ~ "); // separator between °C and °F Serial.print(tempF); // print the temperature in °F Serial.println("°F"); delay(500); }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Make the sensor colder or hotter. For example, putting the sensor near an ice cup
See the result on Serial Monitor. It looks like the below:

COM6

Send

Temperature: 26.31°C ~ 79.36°F Temperature: 26.44°C ~ 79.59°F Temperature: 26.50°C ~ 79.70°F Temperature: 26.56°C ~ 79.81°F Temperature: 27.06°C ~ 80.71°F Temperature: 27.75°C ~ 81.95°F Temperature: 28.37°C ~ 83.07°F Temperature: 29.00°C ~ 84.20°F Temperature: 29.56°C ~ 85.21°F Temperature: 30.00°C ~ 86.00°F Temperature: 30.31°C ~ 86.56°F Temperature: 30.62°C ~ 87.12°F Temperature: 30.87°C ~ 87.57°F

Autoscroll Show timestamp

Clear output

9600 baud

Newline

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