In this post we are reviewing the ESP-01 Wi-Fi Relay Module. It is one of the cheapest smart switches you can purchase currently for making smart home, internet of things, and other wireless do it ...

That is why you must use an external power supply (Vcc) that is between 7 to 12 volts to power up the Arduino board and the transistor + relay. The load uses its own power supply, for instance if you ...