Review of Zigbee temperature and humidity sensor Sonoff SNZB-02: work in Tuya Smart, integration into Home Assistant 2022.
In this review, we will continue to get acquainted with the budgetary ZIgbee series of sensors from Sonoff and the hero of this review will be a sensor that measures temperature and humidity in real time.
Buy Sonoff SNZB-02 Zigbee Temperature Humidity Sensor on Aliexpress
Parameters
- Model: Sonoff SNZB-02
- Protocol: Zigbee 3.0
- Operating temperature range: -10 +40 С
- Humidity range: 10 – 90%
- Battery: CR2450
- Size: 43x43x14
Supply
The sensor is supplied in a standard orange box for this series, the design is minimalist – the image and name of the sensor on the front side and a list of basic parameters on the back side.
The box actually contains the square-shaped sensor itself; only its corners can be attributed to light design delights. Sticker of double-sided tape for attaching it to the wall.
The complete instruction, although small, is multilingual, the English language is present, but the only useful information is how to put the sensor into pairing mode.
Appearance
As I said, the design of the sensor, as well as of this entire line of sensors, is quite specific. It does not leave the feeling that when making a blank for the body, the designer used an ax.
On the conditionally upper end there is a button, pressing which serves to exchange data with the zigbee coordinator, and holding it – to transfer the sensor to pairing mode.
On the opposite end there is a hole for air, which is necessary to measure its parameters. On the same side there is a small groove to snap off the back cover.
It shows the model number and type of battery used in the sensor – CR2450
The lid opens with a slight force, underneath is the battery compartment. To avoid unnecessary discharge, there is a safety insert under the battery that must be removed before use.
Unlike more common sensors of this type, for example from Mijia or Aqara where a more compact but less capacious CR2032 cell is used, this sensor has a CR2450 battery.
For correct alignment of the cover with the sensor – they are marked with symbols in the form of an arrow. They need to be installed opposite each other and the lid should be closed.
In comparison with the already mentioned sensors Mijia and Aqara – the hero of the review looks like a giant, although from the picture it may seem that it is not so big.
Tuya Smart
In this review, in terms of support for stock applications, I decided to focus only on Tuya Smart, because with Ewelink, in principle, everything is clear and this system does not have the same distribution as Tuya. Moreover, the support of Sonoff sensors by gateways and the Tuya Smart application is not explicit, it is not indicated anywhere in the documentation.
My test uses a wired Zigbee gateway for Tuya Smart from Moes. The connection process is similar to native devices – go to the gateway menu and click add a sub-device.
After that, hold down the button on the sensor until the LED, which will be visible from the front side, blinks three times. We are waiting until the application shows the detected sensor.
Next, we select the location for the sensor and, if necessary, we can change its name, this completes the connection process. Temperature and humidity data will be available in the sensor plug-in and in its line located in the general list of smart home devices.
The sensor plug-in has a measurement history that can be viewed in the context of the day, month and year for the entire time of its use. There is also an option to enable notifications – although I could not find where the parameters of these notifications are indicated.
Automation
In automations, this sensor can only work as a trigger and a condition, which is logical – since it only has a monitoring function. For this, three parameters are available – in addition to temperature and humidity, there is also a battery charge.
For each of them, greater, less, or equal conditions are available, based on the sensor specialization – usually greater or less conditions apply.
An example of classic automation that will turn on an outlet (for example, with a heating radiator) when the room temperature drops below 20 C.
Zigbee2mqtt
Let’s move on to the operation of the sensor in Home Assistant, I think that the most common integration option for this is zigbee2mqtt.
In the example, the sensor was connected to version 1.17.1, even before the big update to 1.18, the stick used is CC2652 on firmware dated February 11, 2021, for more information about integration and stick, see part 5 of my Home Assistant lessons, the link to the playlist is in the description …
We turn on the mode of connecting new devices, hold down the button on the sensor up to three light signals and the sensor appears in the general list of the system
The device has full support, like other battery-powered sensors – it is an end device, that is, it cannot send commands from other network participants through itself.
Integration gives 4 parameters – temperature, humidity, battery level and signal quality, the same parameters will be forwarded as objects in the Home Assistant
An interesting feature of this sensor is the refresh rate. This can be clearly seen in the MQTT Explorer – these screenshots show that the data is updated several times a minute. Moreover, this is more about humidity, the temperature changes less often – in this example, it has changed only once. On the one hand, this is good, on the other hand, it will definitely affect the discharge of the battery.
In the reporting zigbee2mqtt menu, you can see that the minimum reporting interval for temperature and humidity is set to 5 and 10 seconds respectively. The maximum also differs by half – 1800 and 3600, although despite this – the change in humidity occurs much more often.
I tried to increase the minimum interval to 3 minutes, but unfortunately this setting is not saved, I think that it is embedded in the logic of the sensor.
This is how the device page in Home Assistant looks like – four objects corresponding to four values in zigbee2mqtt
SLS gateway
Of course, I will not ignore another popular method – this is the SLS gateway, which, unlike the USB stick, is itself a stand-alone device, but interacts with Home Assistant via MQTT
The sensor connects without problems, by the way, I like the connection process on SLS more than in zigbee2mqtt – it is much clearer.
Otherwise, everything is the same, the end device, full support from the manufacturer and model to the sensor image in the interface.
Initially, the charge level is not visible in the properties of the sensor, but this is a feature of the SLS, the data appears as it is received. As soon as the sensor decides to transmit charge data, they will appear here too.
Similarly, these parameters are forwarded through the MQTT integration in the Home Assistant, the charge level object will appear simultaneously with the gateway.
Comparison
For comparison, I used the readings of the mijia sensor – during the entire test, the sensors lay as close to each other as possible, so it can be argued that the conditions were identical.
During the observation period – the temperature readings were always as close as possible, differing by no more than 0.3 degrees, as for the humidity – then the difference here is slightly more than about 2%, but remember that Sonoff sends updates much more often than mijia. The shape of the graphs – here the data for 36 hours is also generally identical – both sensors react to changes in the environment in the same way.
Conclusion
Summing up, the main advantage of this sensor can be called its budget, analogs cost one and a half to two times more. The conditional pluses include the frequency of transmission of changes – why to conditional, because this will most likely affect autonomy, I heard evidence that the battery lives in it for only a few months, but I cannot confirm it yet. The downside is the size and clumsy design, although this is a rather subjective assessment, and you can place this sensor in an inconspicuous place.
