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!

智慧家庭中師系統、網關、裝置關係圖

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.
  • Except for Home Assistant which is a local central system, other common central systems are cloud central systems. Although they all say that they can be controlled locally, they all use synchronization to synchronize settings, records, etc. to the cloud. If you want to have a deeper understanding of the central system, you can refer to:

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


WiFi device ↔️ Brand Center (Cloud base)

智慧家庭裝置、品牌中樞、整合中樞關係圖

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:

智慧家庭 WiFi 裝置 Cloud base 通訊流程示意

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!

智慧家庭 Zigbee 裝置、網關與中樞系統關係圖

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 don’t need to buy gateways that come with each brand! And perfect implementation of local control greatly reduces latency. Here is the integrated tutorial:

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:

蛋殼居智慧家庭架構圖
  • 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 to use local control as much as possible: If your home is a pure Apple environment, then congratulations, Apple Homekit may be your most convenient choice; if you are like me, your family members use iOS/Android mixedly, and you want to have a beautiful floor plan control (how beautiful is it?Watch 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~

9 COMMENTS

  1. I would like to ask if you have used VIZO Zigbee situational single button?
    If so, can the Vizo smart switch that is also connected to Z2M be operated in Z2M?

  2. Daikin should be able to use Zhurui's controller. It has HomeKit certification. Can it be added to HA?

  3. Hi Neil,
    What is the so-called local control (Zigbee device ↔️ gateway ↔️ HA)
    Does it mean that after using HA as a central control, you can connect to the local HA web page through the device without going to the external network? (Can it still be used even if the external network is down?)
    I saw that the 99% products on the market are all Chinese brands, so I am worried about security concerns.
    Can this doubt be eliminated if HA + Zigbee2MQTT is used?
    If your secondary central system needs to go through the brand cloud hub first, it means it also needs to go to the Cloud first, right?

    Thanks!

    • Hi TK,
      If the Zigbee device uses Z2M or ZHA, it can locally access HA for control, and it will not go to the external network.
      The secondary system part in my picture is indeed controlled by the cloud and then connected back to HA. This is a bit helpless. Some brand devices cannot be used purely local.

  4. Hi Neil, I am planning to install smart devices in my new home, mainly in lighting, curtains, and opening and closing doors. In addition to automating the opening and closing of doors, I also want to use Google Nest Hub to control these devices with voice. For a newbie, I Can I directly purchase the aqara m3 gateway to use as a central system and control all smart devices through this gateway? Or do we need to build an HA system? Thanks!

    • Hi Eric,
      Aqara Yes, you can use Aqara gateway to connect all smart devices, and then connect it to Google Home and you can use Nest Hub for voice control. However, because they are all cloud services, there will be privacy and delay issues, but it can be done. You can try it for a while first and then consider whether to switch to HA.

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  • Jerry 2025/04/14Thank you very much Neil for your selfless sharing. The websites you provided are of great help to me. I will save it first and digest it slowly^^ I also look forward to Neil's industry news and teaching articles in the futureHome Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Neil 2025/04/13Hi Jerry, I usually get information about HA from these places: Website: – Home Assistant official Release notes – Automata – Home Automation Community – Weijia Home Intelligence FB Group: – Taiwan Home Assistant enthusiasts exchange – Home Assistant YouTube channel: – Smart Home Solver – Everything Smart Home – Home Assistant Programming language: Strictly speaking, YAML is not really a programming language (let me make this clear in case some people mind 🤣), but if we include these data formats or style languages that “look like” programming languages, and sort them by depth of use in HA (the deeper the bottom, the deeper the bottom): – YAML (data format): a language for configuration files used in many places in the HA environment. – CSS (style language): used to adjust the interface style (font size, color, image, position, etc.). – JSON (data format): If you use Node-RED, you will probably come across it. – Jinja2 (Python template syntax): You may encounter it when you explore automation or Dashboard in depth. ※ But in fact, even if HA does not know the above, it can still make a smart home complete. You don’t have to put so much pressure on yourself, but if you are interested, it is also good to know more. It is actually difficult to generalize about the support of devices. Now, even if the home appliances themselves do not support it, there are still many different ways to connect traditional home appliances to HA. In addition, cases like Haier do require in-depth research. What I usually do is to crawl a lot of information on the Internet, and usually find attempts made by others. It just so happens that when I was looking up other information recently, I saw someone sharing how Haier water heaters were connected to HA. But it is indeed like what you said, if you get involved for a while, you will understand these details more and more. 🤣Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Jerry 2025/04/10Hello Neil: After observing for 1 or 2 days, everything seems to be normal. Maybe it’s because the system was not stable during the initial setup period!? The more I play, the deeper I feel. I also find that I still have many shortcomings. I wonder if Neil can share and teach everyone how to fish? For example, recommend good websites, forums, FB groups, youtube videos, or give some guidance. In addition to the YAML language, would it be helpful to know some CSS syntax? Do I need to know other languages? I can even start a new teaching direction. When I see non-big-name products that claim to support APP (such as products from mainland China), I can teach everyone how to identify whether they can be connected to HA and how to ask customer service? Where can I see supported articles or platforms? This kind of experience sharing, I think, will be very helpful to everyone. I am currently looking to buy a heat pump water heater from Haier. Haier is a big manufacturer in the world and has its own APP. I have also found Haier's kit from HACS, but it does not seem to support heat pump water heaters. Does that mean it cannot be connected to HA? Or is there any channel to check it? There are also many flat panel lights and fan function lamps on the other side of the strait, which also claim to support APP connection, but they are all small manufacturers and it is difficult to tell whether they can be connected to HA. These are the problems I am facing now. If the home appliances I buy are different from what Neil shared, I don’t know where to start. Maybe I'm still too inexperienced. If I play for a few more months, maybe the above problems won't be a problem anymore, haha^^Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Neil 2025/04/09Hi Jerry, I tested it myself and it was fine, but please note that because it is controlled through the cloud, there is an extra layer of brand mediation, so it is not suitable for fast switching. I tested it myself and it took about 1 second to complete the synchronization after clicking. Remember to put the entity in entities, otherwise the status display may have problemsHome Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Jerry 2025/04/07Thanks Neil for clarifying this. I tested it later and found that when using the "button panel" to control the switch of the Electrolux air conditioner (the same model as Neil), the device will respond to turning on or off in about 1 second, but the "status icon" for turning on is much slower, and it takes about 30 seconds. The "status icon" for turning off is normal, and the "status icons" of other negative ion switches and the "status icons" of the monitoring light switch are also normal, which made me think there was a problem with the synchronization. I'll test it again, maybe it's caused by the wrong setting.Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Neil 2025/04/07Hi Jerry, 1. This method is through cloud integration, which is actually using HA to call Xiaomi/Electrolux to control the device. 2. It is not normal. If this happens, you may need to check whether the entity you display on the floor plan can truly represent the status of the device. If not, you may need to try other entities of the same device.Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Jerry 2025/04/07The problem is solved. Thanks again to Neil for his help^^ I have two more questions about concepts. Neil, do I have any misunderstandings? 1. I connected Xiaomi and Electrolux devices to HA through HACS. Is it still connected through WiFi? Before connecting, you need to obtain API key and Access Token from the official. This means that the communication between HA and the device still needs to go through the official. It’s just that the official APP can be replaced and all integrated into the HA APP for control? 2. After testing, when controlling the device through physical operation or the original official APP, the HA app cannot know the status of the device synchronously, but it can know the opposite. Is this normal? For example, the Xiaomi electric fan at home was turned on by someone physically before going out, but when the person is outside, he cannot know through the HA app that the device was forgotten to be turned off. He has to connect to the Xiaomi app to know!?Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
  • Ghost 2025/04/07Xiaomi Home currently does not support Taiwan. For now, you can only use Xiaomi Miot Auto. As for Xiaomi Cloud Map Extractor, I currently have a 2FA problem. There seems to be no simple solution. I haven’t tried it successfully yet.Home Assistant must-install HACS plug-in installation steps detailed explanation – Home Assistant step-by-step tutorial EP 17
  • Neil 2025/04/07Jerry, it seems that the click action cannot penetrate the part where the picture changes because of the overlapping pictures. Try adding pointer-events: none to the style.Home Assistant Floor plan A new experience in smart home control with visual floor plan! – Home Assistant step-by-step tutorial EP 6
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