The lighting system of a house or apartment should be designed in such a way that you do not have to wander in the dark for a long time to turn on or off the light. One option is to equip the system with automatic motion or presence sensors. With their help, the light will turn on as soon as you enter the room. But not everyone likes this kind of automation. A more familiar way is to install switches near each entrance to a room or hallway.
If there are only two inputs (for example, an entrance and an exit in a long corridor), then the problem is solved simply: a pair of special switches, called bidirectional switches, are mounted near each of them. They work great — but only when exactly two control points are required.
What if you need more? Say, in a living room with three doorways, near each of which you need to mount a switch.
In such a situation, it is advisable to use the so-called impulse relay. The relay looks like a modular circuit breaker and is installed in the same way — in a shield, on a DIN rail. It has several switching connectors, on one side a circuit with lighting devices is connected to one, and a circuit with switches (push-buttons) is connected to the other. Control pulses are applied to the relays from devices: a short press on the button, and the load turns on, when touched again, it turns off. (This way you can turn on and off the light in the living room from any input.) The number of pushbutton switches connected to the relay is unlimited. The elements of the switch circuit are interconnected by a two-wire cable of small cross section (twisted pair).
Like almost any electrical equipment, impulse relays differ in maximum rated current (usually household ones are rated at 16 A) and supply voltage (12, 24 and 230 V). In addition to standard relays, low-noise ones are produced that do not emit characteristic clicks when switching. We also note relays with a disconnection delay (from 5 to 60 minutes), disconnecting the load after a set delay time. They are usually used to automatically turn off the light (in stairwells, outdoors, etc.) or ventilation, for example, in bathrooms.
This design has many advantages. It is quite simple to install and does not require the use of expensive cables. As for the cost of the relay, today modules from Legrand, ABB, Schneider Electric or similar manufacturers can be purchased for 20–30$.
In addition, when using impulse relays and illuminated pushbuttons, LED lamps do not flicker in the off position, which is typical for conventional illuminated switches. The disadvantages of the system include a limited number of design options for the switch-button. Some difficulties also arise when using a large number (more than five pieces) of switches with built-in lighting, so the impulse relay is supplemented with the so-called compensation module. It prevents false tripping of the relay.
If the electrical panel in the house is located next to the rest rooms, it is better to use low-noise impulse relays that will not disturb the peace of your family members