The LM35 temperature sensor and red led are powered with 5V from the Arduino board. How does the circuit works? As you can see in the sketch on the first line I included the LiquidCrystal library ...

The hardware is consists of an Arduino microcontroller (here an Arduino Uno R3) and a pre-wired soil moisture sensor module. The soil moisture sensor module , built around the LM393 comparator, gives ...

As you can see from that sketch and the circuit diagram, the LED is connected to the digital pin 13 of the Arduino. Once you verify (compile) the sketch and upload it to the Arduino board, you should ...