Temperature Sensor tutorial for LM35 (LM35DZ), LM335 and LM34

In this section we’ll walk through creating a Temperature Sensor using ESP32, ESP8266 and then view the temperature via Alexa, Google Home or SmartThings.

Prerequisites :

  1. ESP32, ESP8266 x 1.
  2. LM35, LM335 and LM34 x 1.
  3. Jumper Wires.

Quick introduction to Temperature Sensor

The LM35/LM34 temperature sensors are a linear integrated circuit temperature sensor that works by measuring the voltage drop between the base and emitter of a diode-connected transistor. The voltage drop between the base and emitter of a diode-connected transistor decreases at a known rate as the temperature increases.

Wiring for LM35 or LM34 with ESP8266

Sinric Pro LM35 or LM34 wiring

Wiring for LM335 with ESP8266

Sinric Pro LM335 wiring

Pull-up via 2.2k Ohm resistor

ESP32 36 (ADC0)
ESP8266 A0 (ADC0)

Let’s verify that temperature is wired correctly and working.

Step 1 : Create a new device in Sinric Pro

Sinric Pro create device alexa

Sinric Pro temperature sensor device notifications

You can set the threshold here to receive a push notification via the Sinric Pro app when the temperature goes below or above a certain temperature. Use the Retrigger Time to set the delay between notifications.

Sinric Pro copy device id

Step 2 : Connect to Sinric Pro

Step 2.1 Install Sinric Pro Library

Sinric Pro install SinricPro library

You can generate the code using Zero Code feature or write it by your self. If you do not have programming experice, we recommend to use Zero Code feature in the Portal to generate the code, download and flash.

2.2 Complete Code

Now you should be able to view the temperature via Sinric Pro App

Sinric Pro App Temperature Sensor

Please note that Google Home App shows the temperature sensor as a Thermostat due to Google Home limitations.


  1. Please refer to our Troubleshooting page for more details.

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