For those of you that don’t know, I’ve been testing cheap Zigbee temperature and humidity sensors with a screen from AliExpress for past 2 months or so. You can check out their individual reviews from the list bellow:
- Tuya Zigbee Climate Sensor ZL02-ZX Review
- Tuya Climate Sensor and Alarm Clock JM-TRH-ZGB-V1
- Neo Zigbee LCD Climate Sensor NAS-TH02B2
- Zigbee Temperature & Humidity Sensor with a Screen SZ-T04
- Sonoff Temperature and Humidity SNZB-02D Review
- Moes Temperature & Humidity Sensor ZSS-KB-TH
- Tuya Backlit LCD Climate Sensor with Clock ZTH08
- Tuya Blue Climate Sensor and Clock YHZBTHP-1 Review
This is the last device that fits these criteria, white labelled Tuya ZG-227ZL. If you dig around AliExpress frequently, you will most likely recognize it by the baby face emoji comfort indicator on it’s display.
I got this climate sensor on AliExpress for $9 after some coins discount and it’s also available on Amazon. There is a non smart version of this device too, as well Wi-Fi although I suggest you stay away from it as it’s Tuya Cloud dependent.
In the upcoming month, I will write a detailed article summarizing my findings about these devices and organize it in tables to make it easy for comparison. Each and every one of these was benchmarked against a calibrated Xiaomi BLE Sensor model LYWSD02, which will also be included in the article.
- Model: ZG-227ZL
- Zigbee Manufacturer: _TZE200_znbl8dj5
- Communication Protocol: ZigBee 3.0
- Temperature Range: -10°C~55°C
- Temperature Accuracy: ±0.3°C
- Humidity Range: 0%—99%RH
- Humidity Accuracy: ±3%RH
- Working Voltage: DC3V
- Battery: CR2032
- Dimensions: 40x40x13mm
The Tuya ZG-227ZL comes packaged is cute little box containing the sensor, a mounting bracket, a sticker and a user manual. There were no batteries included, the seller claims they cause shipping problems and limitations for them so you will have to supply it yourself.
My first positive impression of this sensor are the contents of the screen. Everything is super crisps and clear, the numbers are bolded and easy to see from a distance even though the sensor is really small. Viewing angles are great, there are no significant distortions when looking at the device from an angle.
On the backside, there is a small hole for air circulation to easily reach the temperature and humidity sensor. The pairing button is also placed on the back cap for easy access, you need to hold it until the baby face starts blinking to indicate pairing mode.
The device is powered by a CR2032 single cell button battery, which you can get dirt cheap from AliExpress or Amazon. If you are a smart home tinkerer you should already have these laying around in your home.
Opening up the device requires only a small screwdriver and you can get to the main PCB and LCD screen. It’s a completely black PCB board, very atypical for Tuya branded devices. This is usually a trademark of Aqara devices, almost all of their smart gadgets have a clean, black PCB.
Zooming into the components of the PCB, I discovered this device uses the AHT20 Sensor [Datasheet] manufactured by a company called Aosong Electronic from Guangzhou, China. This sensor is also found in the Tuya ZL02-ZX and Tuya JM-TRH-ZGB-V1 climate sensors. Adafruit sells a rebrand of this sensor too.
Zigbee communication is enabled by a Telink TLSR8258 [Datasheet], which is a BLE + Zigbee IEEE802.15.4 multi-standard wireless SoC. This module was also used in the ZL02-ZX and these awesome cheap kitchen puck lights.
Home Assistant Integration
This Tuya ZG227-ZL Climate Sensor is supported in Home Assistant through ZHA and Zigbee2MQTT. To pair it, press and hold the button for around 5 seconds until the emoji starts blinking on the screen.
Once paired in Zigbee2MQTT, it is correctly identified as an EndDevice with model ZG-227ZL and manufacturer _TZE200_znbl8dj5. The device does not use recycled external converters, it has it’s own integrated in Zigbee2MQTT. It exposes the following entities in Home Assistant:
The temperature unit can also be changed from Zigbee2MQTT, although you can do that by single pressing the pairing button on the back too.
Unlike other sensors similar to this one, calibration in the Exposes tab of Zigbee2MQTT also changes the value on the screen of the device. This is a built in cluster which offsets the value on the device itself, and not just in Z2M/Home Assistant.
If you are having issues trying to calibrate, set the desired offset in both the Exposes tab and Settings (Specific) tab of Zigbee2MQTT. Make sure you wake up the device before sending the payload, as these types of sensors are usually sleeping.
The device is also supported in ZHA, with a custom quirk being applied automatically labelled tuya.ts0601_sensor.TuyaTempHumiditySensor_Square. It exposes the temperature, humidity and battery readings to Home Assistant.
Like all other climate sensors, the Tuya ZG227-ZL was benchmarked against a calibrated Xiaomi BLE LYWSD02 sensor placed on a shelf in my living room. Measurements are charted with the awesome History Explorer Card in Home Assistant.
About the Comfort Indicator
The emoji comfort indicator on the display, which is just a cute little baby face with different expressions is reliant on the humidity reading of the device and not the temperature. Here’s image explaining how it works:
Whenever the reported value is withing the predefined range, the emoji face changes to indicate the comfort level. It’s viewable from a distance too, I would say at about 3 meters max.
The temperature reading of the ZG227-ZL closely matched my Xiaomi LYWSD02 sensor. There were times when the reading did not have an offset at all compared to the Xiaomi sensor. Calculating the mean value out of the readings, I got an average offset of 0.4% which is more accurate than most.
Like I’ve explained many times before, the Xiaomi is a BLE sensor which is much noisier than any Zigbee sensors I’ve tested, hence the choppy chart in Home Assistant.
Humidity reported by the ZG227-ZL was inaccurate compared to the Xiaomi LYWSD02 sensor with an average offset of about 4.5%. Calibration was needed here, bumping up the value a little.
There was also a spike in one instance that reported a 9% higher humidity and than dropped immediately. This is possibly a fluke because going back one week I did not notice any other reading spikes or anomalies.
Even though it reports immediately when there is a temperature drop/increase, I’ve found the reporting interval to be very inconsistent. Usually, it would push it’s payload inside 30 minutes regardless of temp or humidity changes. Here’s what I found to be true:
- Report immediately when there is a significant temperature change (≥0.5°C) from it’s last payload
- Report every 15-30minutes regardless of state change (inconsistent)
There were instances where it would not push a payload at all for hours, and just report whenever it feels like it. Other times it would report 4 times in 10 minutes, with the value of the temperature/humidity staying about the same.
I could not find any patterns in the reporting interval, it feels very random. Whether or not this is important is up to you to decide, but it’s definitely something to keep in mind when considering this device.
Pricing and Availability
The Tuya ZG227-ZL is available on both AliExpress and Amazon for a very attractive price (~$10). Here are some links and listing, including my seller (1st link):
I have mixed feelings about the Tuya ZG-227ZL Temperature and Humidity sensor, so here’s my summarized experience with the device:
The temperature accuracy is great, it closely mirrored my calibrated LYWSD02 sensor. Humidity required setting a small offset, although I could live without it. Calibration reflects the changes on the screen too, which is great.
The screen itself is what impressed me the most, it’s very clear and viewable from all angles, great for an LCD. The device is rather small though, so don’t expect to see the information shown from way across the room.
The reporting interval is a major drawback of this model, it’s very inconsistent in my tests reporting totally random. It does push a payload when there is a temp change of ±0.5°C though, so it’s not totally useless.
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