How does a Two Way Switch Work - Wiring Connection and Demonstration

One of the simple yet interesting connection diagrams that young engineers learn in their lab is the staircase lighting setup. Perhaps most of us might have already used it without paying much attention to how it works. Staircase lighting at home or at any other place, for that matter, is normally done with something called a two-way switch. 

Now, there are many different types of switches in the market, and a few of them can be directly used for a two-way connection without any special wiring connections. But in this tutorial, we will show you how to make a two-way switch wiring with normal household switches. A two-way switching connection means you can control electrical equipment, like a bulb, with two switches placed at different locations, generally used in staircases. 

A two-way switch can be operated from either switch independently, meaning whatever the position of the other switch (ON/OFF), you can control the light with the other switch. There are two methods of making a two-way switching connection: one is the 2-wire control, and the other is the 3-wire control. We have explained both methods below, and both methods are demonstrated in the video given at the end of this article.

Two Way Switch?

From Starting We are using the word Two Way switch. Some might know, some not. Let’s see that in brief. 
So, technically a two-way switch is known as Single Pole Double Through (SPDT) Switch. Below You can see Some of the Types available in the market.

 Some are used in DIY Projects and Some are Used in Electrical. The following concept is Applicable to all types of applications from Small DIY Projects to Complex Electrical Wiring Works.

Required Components for Two-Way Switch Connection Experiment 

• 2-way switches x 2

• Bulb x 1

• AC supply x 1

• Connecting wires

Connecting Two-Way Switch in Two Wire Configuration

This is the first method to make a 2-way switching connection, this is the old method. If you are going to install a new one, then go for three wire control methods.

As you see in the 2-way switch diagram below, you will find that the phase/live is connected with the common of the first 2-way switch. PIN1 & PIN2 of the first switch are connected with the PIN1 & PIN2 of the second switch respectively. One end of the bulb is connected with the Common Terminal of the second switch and another end of the Bulb is connected with the Neutral line of the AC power supply.

Note: In the 2-wire control method when switches are in an opposite state the light will be in OFF state as shown in the circuit below:

The condition of getting Output in ON condition is the same as the Ex-nor gate truth table which is given below:

 Connecting Two-Way Switch in Three-Wire Configuration

This is the new method to make a 2-way switch connection and it is slightly different from the two-wire control method. This method is commonly used nowadays as it is efficient than the Two-Wire control system.

As you can see in the Schematic Diagram of 2-way switch circuit below, the common of both the switches are short-circuited. PIN1 of both the switches are connected with the phase or live wire and PIN2 of both the switches are connected with the one end of the lamp. The other end of the Lamp is connected with the Neutral line of AC power supply.

Note: In the 3-wire control method when switches are in the same state the light will be in OFF state as shown in the circuit below:

The condition of getting Output in ON condition is the same as the Ex-or gate truth table which is given below:

Advantages and Disadvantages of these Configurations

Advantages:

Allows control of any appliance from two different areas, regardless of the distance between them. Ideal for locations like staircases, large rooms, and bedrooms where control from multiple points is beneficial. Reduces the need to walk across dark areas to turn lights on or off, enhancing safety.

Disadvantages:

-Increased Wiring: Requires a significant amount of wiring, which can be more complex and costly to install. Diagnosing and fixing issues can be more challenging due to the additional wiring and switch points.

Applications of Two-Way Switch:

• Staircases: For controlling lights from both the top and bottom of the stairs.

• Erroneous Tripping of Safety/Circuit Protection Equipment: Helps in resetting tripped circuits from different locations.

• Large Rooms with Multiple Entry/Exit Gates: Allows for convenient control of lighting or other equipment from different entrances.

• Controlling AC Appliances (like fans or lights): Can be controlled from two places, such as the entry and exit points of a room.

• Bedrooms: For controlling lights or fans from near the bed or while entering the room, providing convenience and flexibility.