0. Introduction

With the advancement of technology, smart homes have gradually become prevalent in many households. The various control methods and home automation features of smart homes have attracted numerous consumers. The product range of smart homes is quite extensive, ranging from large appliances like refrigerators, televisions, and solar heating systems to small devices like NFC tags and remote control buttons. Today, we will focus on one of the most common smart home devices – smart wall switches.

Before diving into smart wall switches, let’s first understand the two main categories of traditional wall switches. This knowledge will influence your selection of smart wall switches and prevent unnecessary losses caused by purchasing mistakes.

One of the categories is the “Neutral Wire Switch,” which requires a neutral wire for proper functioning. The other category is the “No Neutral Wire Required Switch” or “Single Live Wire Switch,” which, as the name suggests, does not need a neutral wire for installation and operation.

1. Understanding Single Live Wire Switch and Neutral Wire Switch

Common Issues with Traditional Wall Switches

Before the advent of “Smart Wall Switches,” there were no specific terms like “Neutral Wire Wall Switch” or “Single Wire Wall Switch.” The only distinction lies in how the “switch” is connected either to the live wire (fire wire) or the neutral wire. This connection determines the control of turning the light bulb on and off.

When the switch is connected to the neutral wire, it functions properly. However, due to the live wire carrying electricity and the neutral wire being non-electrified, when the switch is installed with the neutral wire, the light bulb will be directly connected to the live wire. This means that the light bulb remains electrified, regardless of whether it is turned on or off. When a person touches the glass part of the light bulb, there is no electrical conductivity, and it will not cause any harm. However, if a person touches the metal part of the bulb, an electric shock can occur. Refer to Figure 1 below for illustration.

(Comparison Between Connecting Switch to Neutral Wire and Live Wire)


Therefore, installing the “switch” on the neutral wire is very unsafe and non-standard.

As a result, the commonly seen “wall switch” in our homes must be connected to the live wire.

The most straightforward difference between the traditional No Neutral Required Switch (Single Wire Switch) and the Neutral Wire Switch lies in their wiring configurations.

As shown in the diagram:

The No Neutral Required Switch (Single Wire Switch) only has the live wire connected to the control line of the light.

On the other hand, the Neutral Wire Switch has both the live wire and the neutral wire connected to the control line of the light.
the difference between single wire switch and neutral wire switch

Utilize the sunrise or sunset time in your city as triggers. Additionally, you can set the trigger to occur at specific minutes before or after sunrise/sunset. Up to 30 minutes can be set.

2. Smart Wall Switches

The regular “wall switch” operates manually, allowing users to turn the light on or off by physically interacting with the switch. However, the reason why “smart switches” are considered intelligent is due to the integration of a “smart control module” within the switch. Once the switch is turned off, both the “light bulb” and the “remote control module” lose power simultaneously, resulting in the “smart control module” being unable to perform remote control functions.

To make a “switch” smart, it is essential to ensure an uninterrupted power supply to the “smart control module.” There are two methods to achieve this: the “Smart Neutral Wire Wall Switch” and the “Smart No Neutral Required Wall Switch.” Both of these methods ensure that the “smart control module” remains powered and functional for smart control capabilities.

The Principle of Smart Neutral Wire Wall Switch

In the Smart Neutral Wire Wall Switch, the live wire and the neutral wire are connected to the “Smart Control Module” on the smart wall switch, providing power supply as shown in the following diagram.
neutral wire connection

When the smart wall switch is in the OFF position, the “Smart Control Module” continues to receive power supply from the neutral wire (A) and live wire (B). However, since the light is not connected to the power supply, it remains off.

Conversely, when the smart wall switch is in the ON position, both the “Smart Control Module” and the light bulb receive power supply, causing the light to turn on.

Therefore, the Smart No Neutral Wall Switch ensures that the “Smart Control Module” remains powered, whether the light bulb is on or off. This allows the switch to maintain a continuous connection to the network, enabling control through various means like voice commands from a mobile phone.

The Principle of Smart No Neutral Wire Required Wall Switch
Inside the Smart No Neutral Wire Required Wall Switch, there is a built-in variable resistor used to control the current. This method is employed to supply power to the “Smart Control Module.” The wiring diagram for the Single Wire version of the switch is shown below:
single live wire connection

The “Smart No Neutral Wire Required Wall Switch” integrates a variable resistor in series with the light bulb. When the light bulb needs to be turned off, the variable resistor is adjusted to a high value, almost approaching an open circuit, but not entirely. There is still a tiny current flowing through the circuit, providing power to the “Smart Control Module.”

Due to the use of the variable resistor, the Smart No Neutral Wall Switch often has the following drawbacks:

  1. If the quality of the light bulb is poor, it may cause flickering after turning off the light.
  2. Power limitation – Most No Neutral Wire Required version smart wall switches can only handle devices up to 800 watts, whereas the Neutral Wire version can typically support devices up to 2500 watts.
  3. Higher cost – Due to different design requirements, the production cost of the Smart No Neutral Wall Switch is generally higher compared to the Neutral Wire version.

3. How to Choose

When selecting a smart wall switch, most of the choices involve direct replacement of the “existing switch.” Therefore, our primary task is to confirm whether there is a neutral wire in the wall switch’s junction box, as this will determine which version of the product we should choose. While inspecting the junction box, please ensure to turn off the power to avoid the risk of electric shock.

If you are in the renovation phase, I recommend leaving a neutral wire in the switch’s junction box during the renovation process. Having only a live wire will prevent you from using the version of the product that requires a neutral wire. If you later wish to use the neutral wire version of the smart product, rewiring will be a daunting task and will require a significant investment.

Therefore, whenever possible, if your home’s electrical wiring permits, it is advisable to install the “Smart Neutral Wall Switch,” as it offers safety, stability, and is more cost-effective.

4. SONOFF Wall Switches Recommendation

Smart Neutral Wire Switches

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