A picture will help you understand the relationship between smart home devices and central systems. What is the gateway? When is a gateway needed? Taking Zigbee and WiFi devices as an example – Smart Home EP 2

If you are just starting to build a smart home, you will definitely encounter this problem soon: "gateway".
What is a gateway (Hub)? What does it have to do with the central system? Why do some devices require a gateway and some don't?
Today I will use a picture to help you understand the relationship between devices, gateways, and central systems! Pictured above!

What are the respective roles of devices, gateways, and central systems in smart home architecture?

There are many devices on the market that have multiple roles. First, understand the roles of devices, gateways, and central systems so that you don’t buy them randomly:

device

• Role: The role of hands/legs and soldiers. The main tasks are to receive instructions and report status.
• Typical ones include: smart light bulbs, smart switches, smart sockets, sensors, etc.
• Atypical (composite roles) include:
  • Google Nest Hub: speaker device + gateway (Hub).
  • Apple HomePod, Apple TV: speaker/TV + gateway (Hub) + central system.
  • Smart screen (LG StanbyMe): screen device + gateway (Hub).

gateway

• Role: Messenger, translator, intermediary communicator between the central system and the device, receiving and summarizing the status of the "device", forwarding instructions from the central system, reporting the status of each device to the "central system", and receiving instructions for each device. instruction.
• Typical ones include: Aqara gateway, SmartThing gateway... and other pure gateways.

central system

• Role: Brain, collects information from each device, calculates and determines what reaction to take, and issues instructions to each device.
• Typical ones include: Apple Homekit, Google Home, Amazon Alexa, Home Assistant...etc.
• Supplementary explanation: They are both smart speakers/TVs. Why are Apple HomePod and Apple TV considered "home hubs", while Google Nest Hub is only considered a Hub? The reason is that Apple HomePod and Apple TV can perform local control of connected devices (this is a bit complicated, so I won’t go into it here), but the way Homekit implements local control is different from Home Assistant, which is another story. Already…

Next, we will break down and introduce each link! Let's get started!

WiFi device ↔️ Brand Center (Cloud base)

WiFi devices can be said to be the smart devices with the lowest entry barrier, but my personal suggestion is to reduce the number of smart devices controlled by WiFi as much as possible. After reading this article, you will know why.

Smart devices controlled through WiFi, like mobile phones and computers, need to be connected to the router at home through WiFi. Through the router, they are connected to the Internet and the brand center in the cloud for two-way communication. The brand center and the integrated center system communicate with each other through the Internet. Communication (Seeing this, you may be wondering what is the difference between "brand central system" and "integration central system"? This islater(will explain), every network connection communication will have a delay. Taking "turn on the air conditioner" as an example, the current configuration in my home, the device using this path will have a delay of about 3 seconds during operation. The command to go The path is roughly as shown below:

Devices that take this path will have two shortcomings:

1. Network latency (commonly known as lag): Because communication is through the Internet and cloud services, there will inevitably be delays. Normally, you will not feel the delay when using 3C products, but the delay will be particularly obvious in a smart home environment. Just imagine You pressed the switch but it took 3 seconds for the light bulb to turn on. Isn't it uncomfortable enough? This is why local control is so important for smart homes.
2. Limitation on the number of simultaneous connections that a WiFi router can carry: Chunghwa Telecom’s Little Turtle is reported to be able to connect to 16 devices at the same time. Of course, the number of simultaneous connections that different levels of routers can carry will vary (this is the power of money~ 💰💰), but At the same time, more connections will affect the connection speed to some extent, so it is recommended to reduce the number of smart home devices using WiFi protocols as much as possible if possible.

Zigbee device ↔️ Gateway ↔️ Central system (Cloud / Local)

If you understand this section, it will save you a lot of unnecessary steps and money in the process of building a smart home. Keep reading!

Zigbee device

Here we take a Zigbee device as an example, but most devices that require a gateway have similar principles.

Zigbee devices report device status in real time through the Zigbee protocol and gateway, and receive commands from the gateway.

gateway

The gateway is between the device and the central system, playing the role of intermediary and translator. Generally speaking, each brand will launch its own gateway, such as Aqara, Vizo... And these gateways usually only support devices of the same brand, and such brands have their own The gateway usually also needs to communicate with the brand's cloud central system through the Internet. This cloud base model also has latency problems.

If you, like me, use Home Assistant as the integrated central system and Zigbee as the main device communication solution, then I recommend giving priority to the Zigbee2MQTT gateway, which can connect to almost all Zigbee devices (Full support list), from now on you no longer need to buy the gateways that come with each brand! And the perfect implementation of local control greatly reduces latency.

central system

There may be multiple central systems in a smart home architecture, which are divided into "primary" and "secondary" according to different roles. Take the configuration of my home as an example:

• The "main central system" refers to the center used to gather the control of all devices in the home. I chose Home Assistant, which is responsible for all scene settings and automated judgments. It is recommended to choose a central system that can be connected to devices from across brands. Common choices There are: Home Assistant, Apple Homekit, Google Home.
• "Secondary central system" refers to a central system that only integrates some devices for a specific purpose, such as Aqara, Mijia, Lutron, SmartThings, Electrolux, Daikin (Daikin), and I use it to integrate devices that cannot directly access Home Assistant. .

Take away

1. The smart home architecture should be as simple as possible: This includes the choice of central system and device communication protocols. The simpler the architecture, the easier it will be to maintain in the future.
2. Try your best to use local control: If your home is a pure Apple environment, congratulations, Apple Homekit may be your most trouble-free choice; if you are like me, your family members use iOS/Android mixedly, and you want beautiful floor plan control ( How beautiful it isWatch EP 0), then I sincerely recommend Home Assistant, which will definitely give you a sense of accomplishment.

After reading this, you also want to make your own floor plan control? Take a look at my teaching~