There is one more dilemma that we have to solve in order to have complete control over the electronic appliance. If we create a digital ON and OFF switch that when set to ON sends a turn ON signal to the relay, the problem is that if the physical switch is already ON, the ON signal of the digital switch will end up actually turning OFF the appliance.

"If the appliance is already ON, why would I send a turn ON signal?" Okay, think about this. Both the switch and the relay are ON, but the bulb would actually be off if you look at the two-way switch and the relay image previously shown. Now, if you want to turn ON the bulb through the relay, you actually have to send an OFF signal.

Pretty confusing, isn't it? To solve this, we will use a flag or a status variable that stores the current state of the relay. This will help us solve logical issues such as the one stated before.

Make sure your router is working as expected. Then, plug in the Arduino into the USB port...