Master switch – Turn off the light with one button

You will no longer surprise anyone with a hotel automation system, where the light only turns on when you enter the room. Installation of a master switch in the form of a key card that is inserted into a special device addresses both energy saving and safety issues.

In recent years, the use of such master switches is also becoming increasingly popular in home and office appliance control systems. People often worry that they have forgotten to turn off a coffee maker or iron, or if a light or TV is on. And it’s not just about saving energy, it’s also about safety: the most common cause of house fires is failure to turn off household electrical appliances. The installation of a master switch will permanently solve this problem..

Master switch applications

The installation of a centralized control system for electric appliances is useful in a wide variety of environments:

• In apartments and private houses, it guarantees that all lights and household appliances have been turned off.
• In offices, stores and other businesses, it eases the work of the manager and ensures energy savings.
• At industrial facilities, it saves the time of employees responsible for closing up at the end of the working day.

Schematic diagram of the master switch

The simplest master switch circuit is a relay (contactor) installed in the distribution board. It is connected to an on-off (toggle) switch installed near the entrance door. When the switch is set to the OFF position, the relay opens only selected lines, and the power supply of high-priority consumers will not be disconnected.

Although this circuit is simple, it has a very significant drawback: setting the master switch to ON re-activates all electrical appliances that were previously turned off using the switch. There are many known cases when an iron that was turned off by a master switch was turned on by the same master switch upon returning home, which was only noticed later.

The answer to this is to use impulse relays instead of a contactor. Impulse relays with central control should be used instead of ordinary relays. One input of an impulse relay is connected to the room switch, and the other is connected to the switch at the exit.

Impulse relays with central control ensure that selected devices do not turn on when returning home, allowing you to turn them on locally. However, this also has drawbacks – such impulse relays are not rated for large currents, so they should be installed for each line separately (as the modern power supply units of electrical appliances have high inrush currents). And if you need several master switches (for example, separate group switches on each floor and one main switch at the exit), then the circuit gets much more complicated. An even more complicated control scenario is as follows: you need to turn on the light for a set time when activating the master switch (for example, turning on the front porch lights for a few minutes when leaving home to allow time to close the door and reach the exit from the yard). And the increased complexity of installation makes it considerably more expensive. And finally, additional space in the distribution board is needed (and you almost never have any free space).

Another way to implement a master switch is to use a programmable logic controller (PLC), with which you can expand the control functionality.

The high price is the main drawback associated with the use of a PLC as a master switch. Besides, you’ll need to install additional contactors as the PLC outputs are usually not designed for the connection of high-power loads.

Additional functionality of the master switch

Of course, it is convenient to turn the lights on or off using a central switch at the exit. But it is much better when the system can be controlled in a smart manner to provide additional functionality to wall switches. For example, to turn off unnecessary lights without getting out of bed or to set a delayed switch-off time for the extractor fan in the bathroom. You don’t need to install an expensive Smart Home system as all these control functions can be implemented using the ION CS-8 Central switch with built-in control scenarios.

You can see examples of such scenarios in our interactive online demonstration.

And finally, a useful tip: regardless of the centralized control option you choose, always install the central switch in a place where you cannot mistake it for a wall switch (for example, at a different height). You can also use special switches with a protective cover that prevent accidental activation.

More to read

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