DO NOT connect in any ways the main power supply that drive the LOAD to the arduino and transistor circuitry! Turn OFF the relay with delay You can use this code example to introduce a delay in your ...

Solution 1 Connect the GND of the battery to the GND of arduino – common GND. If you are using a 5V relay instead of 12V relay, you only have to connect the arduino GND. I am using a 12V relay. So the ...

Looking for practical Arduino projects? This guide shows how to control a relay from your smartphone using an Arduino Uno — ...