Recently I bought an Arduino Uno to discover electronics. I am a computer science student, hence the programming part is not a problem, however, I lack some knowledge about electronics.
Now I want to do some simple home automation, mainly to control the lights in my house. I was thinking about adding an Arduino controlled relay (in the central electrical box of my house) for each light I want to control.
However, for each light in my house I have a switch. Suppose, I'd add Arduino controlled relays in series with the switch (as in the figure below):
The problem is that with the relays being in series, I can only switch on and off the light if the switch is closed. Hence, like above, the switch is open and my Arduino controlled relay will have no effect.
Now, suppose I'd add the Arduino controlled relays in parallel:
In parallel, we observe the inverse problem. If the switch is open, we are able to control the light using the Arduino controlled relay. However, if the switch is closed (like above), the current will flow through it anyway, i.e. the light will glow without the Arduino controlled relay having any effect.
How does one tackle this problem in home automation systems, without the need to rewire my entire house?
PS : Excuse me if the diagrams are wrong in some way. I absolutely have no electronics background.