Wall Switches

The main philosophy behind the automation in our home, is to provide a simple and intuitive user experience. This means that the automation must be intelligent and supportive and not intrusive or disruptive. For most of the time the automated elements should just work in the background, requiring no manual intervention and no need to expose a physical interface to the users of our home. The automation system should also learn and adapt to the changing environment both inside and outside of the home.

In this respect, our approach to automation differs from the mainstream practices of adding complex display panels and banks of switches on the walls. Our view is that if you require an iPad and application to control things in your home, then the automation has become a core feature of your home and is no longer simply a tool to improve the quality and efficiency of it.

There will be occasions where some manual control is required though. When this situation does occur, the controls and interface provided need to be intuitive to both familiar and unfamiliar users. Actions taken by users in our home must result in changes that are predictable and timely and they must not be ignored or undone.

This means that the traditional manual interfaces such as wall switches need to be provided for both family and visitors and they must work in the expected way. Our automation layer will sit above this traditional manual control and intelligently automates aspects of our home, such that manual control is minimised and typically not required at all.

To implement this manual control layer, we plan to use standard (off-the-shelf) wall switches to provide the main user interface to lighting, curtains, blinds, etc. Whilst the appearance, function and results are consistent, the underlying technology works in a different way to the switches found on the walls of your typical home, as this section will now explain.

MK Switches

MK Grid Plus switches
In our next home, we plan to standardise on MK Logic Plus and Grid Plus switches. The reasons for this are:
  • They are an attractive range of switches in white, with a wide range of switch types and configurations. They are availabl as 1,2,3 and 4 gang layout.
  • The switch modules can be used with both mains voltages and low voltages, such as 12Vdc.
  • Momentary action switches, on/off switches and on/off/on switches are available.
  • Although they have metal mounting 'grid plates' they are quite transparent to wireless transmissions.
  • They can be mounted vertically (for lighting) or horizontally (for curtains, etc.).

Switch Plates

MK K3231 face plate
This system of switches uses range of white face plates and these are available in four formats, to accept 1, 2, 3 or 4 switches.

Grids Frames

MK K3701 single grid
A metal 'grid' is used to attach the switches to the face plates.

Switch Modules

MK K4900 momentary switch
The main switch we plan to use in out home is the K4900. This is a two-way momentary switch with the central position being off. In vertical orientation it can be used in up and down format to control lighting brightness (an on/off) or blinds. when mounted horizontally, it can be used to control curtains open and closing. This assumes the (single) faceplate is rotated at 90º and that the wall box has been fitted to accomodate this change of orientation.

Completed switch

The parts all constructed into a usable switch. One thing to note is that although these switches are rated to main voltages (240V ac), we are only planning to use them with 12V dc signals at very low current. These switches are basically used as input devices to lighting and curtain controllers, etc. These are covered in more detail in the projects section.

Switch Wiring

The advantage of a momentary switch is that it can be used to drive both binary functions and variable ones. We have configured the switches to work with a 12V pulse generator circuit, which operates whilst the switch is depressed. The pulse generator circuit consumes zero power when not in use. A single pulse is enough to activate a binary device (acting as a flipflop). A pulse train can be sent to ramp a counter up or down, with the counter driving a variable device, such as a lamp dimming circuit.

It should be noted that the pulse generator circuit is shown below but, it is not required when switching a device with a binary state, such as on/off lighting and curtains. The wall plate switch contacts can be used directly to provide the required momentary pulse. Because there are two input lines, we don't need to worry about contact bounce either.

Switch configuration

Two optically isolated input lines also provide connection to the Home Control System (HCS). These don't really need to be optically isolated but this approach has been added as a precaution.

Note that there is no feedback path shown above from the switch to the Home Control System (HCS) but, in our implementation the monitoring of switch operation can captured if required.

Pulse Generator

This is a very simply circuit (details to follow soon), which simply outputs a pulse train when power is applied. The frequency is set to enable the counters used in our electronic dimmer circuits to go from off to full brightness in approximately 2 seconds.

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