RemoteLight – step 1 – requirements and general architecture

Let’s start with our project: Remote light

Mission:
We want to build up a system to control, with a web interface, all the lights of our house, with a small impact in terms of user experience (everything should work as before) and in terms of cost.

Requirements:
– we want to be able to control from our PC/mobile device every single light of our home, if they are on or off and switch them on/off from our device.
– we do not want to change any wall switch in our home, we want to use the same in use in this moment
– we do not want to change any light inside our home. Any lump or bulb should be involved without changing them.
– for people not directly interested in home automation (like my wife) everything should work in the old plain way, the same user experience as usual. He should not even be able to understand something has changed behind the curtain.
– everything should work without Internet, no external dependencies
– in case the wifi in the home is down, everything should work as usual: when I operate on the wall switch, light should turn on or off without any problem. Obviously it will be impossible to control lights from your pc or mobile.
– if in the house we have 2 switches controlling a single light, this behavior must be replicated as is
– we do not want to use a close standard or a specific vendor line of products

Nothing special, any serious Home automation system provides this kind of features. Usually the cheap components, easy installation with no configuration, are not able to provide you there features, due to strong dependencies from external infrastructures.

How can we achieve these result?
The main idea is to have a small controller able to understand the status of our wall switches and to control the light.
In this example we will have 2 wall switches controlling a single light. A classical configuration presents in all houses with 2 diverters (divA and divB) and a light.

Now image you introduce a very small “controller” able to understand if one of the 2 switches changes the status (from on to off and vice versa) on one side, on the other side  is able to turn the light on or off through a small relay.
You achieve your target to use, through a complex controller, standard light bulbs (led or whatever) and the same wall switches as before.
What is missing is only a little of logic:
when one of the switch change its status, the controller has to invert the status of the light (from on to off, from off to on). Because this small controller is attached to our wifi, we can even ask directly to the controller the status of the light and change it. So the message the controller is able to understand is only “change the status of the light” and this can happen due to a wall switch changing its status or with a remote wifi command.

The relation between light and switches becomes only login, no physical direct connections among them.
This will allows you to have a single light controlled by 3-4-5 different switches placed around the room, readdy difficult to have with a normal electric circuit.

Because we are thinking about a very small controller, with limited capabilities (3-4 switch, 1-2 lights each) we can think to have one for room, so we can plan to have an application to coordinate all of them. If you want a single command to switch off all lights in your house before going out, you need this coordination.

Let’s see the controller we can use and how

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