In this quick Arduino tutorial ... to introduce a delay in your circuit. The variable “stayON” is used to delay() the program execution with the desired amount of time. In our case after the button is ...

In this project, we are going to build something very simple project, a temperature controlled relay that is used to turn on a dc fan. You can actually change the DC Fan to other electrical devices ...

but sometimes you get people like [Aart] who can’t resist to turn a stack of clackity-clack relays into a functional design, like in this case a clock (article in Dutch, Google Translate).