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 ...

To solve the problem without sourcing a new switch, [Jean-Noel] built his own Arduino based Dahlander switch. This consists of three relays that select the wiring configuration for each speed mode.

After wiring up each outlet so it can be controlled independently, he set out designing a four port relay board. This was a pretty simple build – four 10 Amp relays and a few terminal blocks.