It’s surprisingly hard to find reliable and reasonably priced temperature/humidity sensors for Home Assistant. I want to monitor temperature and humidity in crawl space, garage, attic, RV etc. and alert if there’s a problem. Below are my experiences and thoughts about a few alternatives. Does anyone have recommendations for other things to try?
Note: I’m using a HUSBZB-1 USB stick for Z-Wave and Zigbee connectivity with Home Assistant.
I have a few Xiaomi/Aqara WSDCGQ11LM sensors, which are a nice form factor, look great, and are priced well. However, even though they pair easily at first, they tend to disconnect and not recover their connections, leading to lots of frustrating troubleshooting. I bought them at Aliexpress a few years ago. What are the chances I’d have better luck with newer ones?
Aeotec Multisensor 6 works great, but $60 USD is very expensive when you just care about temperature.
Aeotec TriSensor is also good, a little cheaper ($45), but lacks the humidity sensor.
Zooz 4-in-1 sensor looks like a good device at a fair price ($40). I haven’t tried it yet, but it looks a bit ugly and bulky if you don’t need the motion sensor capability.
Wifi-based retail alternatives seem to be basically non-existent. Building something based on a microcontroller is possible, but lots of work, and probably won’t look too great.
433 MHz devices would probably work fine for my purposes, if I could figure out specific good sensors, a good receiver for Home Assistant, and how to integrate it. It’s been surprisingly hard to find comprehensive info about this.
I use a few Aqara sensors, but I switch to Wifi-based sensors now. I use ESP8266 (Wemos D1 mini) with BME280 sensors. I have good experience up to now.
The price is very low (about $4 if you have an old USB charger) and the work is not that much. Flashing the ESP with tasmota and configuring it is a task of 5 minutes. Soldering 4-5 cables from ESP to the sensor - depends on how often you do that. I would say another 5 minutes.
“won’t look too great” - yes, that might be true But maybe you can stuff it in a nice case or into a “decoration item” or something…
As for a Wifi-based retail alternative I am using a few Sonoff TH10 with Sensor Si7021 purely as temperature and humidity sensors. They work very reliable with HA and you get them for a reasonable price: https://www.itead.cc/sonoff-th.html
I ordered some BME280 breakout boards from aliexpress for about $2 each. Of course this is not an original Bosch sensor (I think they cost $10-20 if you find an original one). But I had 4 of them next to each other and the max. difference was 2% in humidity. And it was very stable, that means I can add an offset for calibration (in HA).
I said $4 per sensor, as you also need an ESP8266 (in may case a D1 mini for another $2).
If you want to order the same, use the 3.3V variant as the BME280 needs 3.3V. The 5V board use a voltage converter which produces a little heat and can offset the temperature measurement.
FWIW the Xiaomi sensors work perfectly fine for me, haven’t lost connection to any of them in the last year. But it dependa om how many other zigbee devices you have and how many are mains powered, the distance etc.
Since I use ZHA, the aqara sensors also work stable here. But they need a pretty long time until they update and deliver a stable value (sometimes 1 or 2 hours). This value is about 5% higher than the 4 values of the BME280 (but only tested with one aqara sensor).
For me, the main reason against them is the response time. I want to use it for controlling air dryers in 2 rooms. But if you have low change rates, I also think they are a good choice.
That’s not the bahaviour I see, mine update immediately when there’s a change of more than x%/x° (don’t know the exact values). For example when I take a shower it detects it in a few seconds.
Regarding aqara sensors, I have many - 3 temp/humidity, 15+ motion, water, vibration. I too originally had issues with them disconnecting. A real pain. The solution to my issue was dealing with the frequency overlap between 2.4Ghz wifi and zigbee. Been going for 1.5 years no, no disconnect ever. See:
Yeah, I should try this some time. Would be a neat project to do together with the kids, I guess. It’s strange to me that this isn’t a commercially sold package (that I have found, anyway). Also, that I haven’t found any elegant solutions for combining the power supply with the microcontroller into one neat box. Would be awesome to be able to buy that on ebay.
Interesting. When I put them in our small RV and they couldn’t even keep a connection directly to the RPi with the Zigbee stick ~6ft away is when I gave up.
I have 11 Digoo DG-R8H (9 in use, 2 spare), used with rflink
pro : long battery life ( 2AAA, the one outside is still OK after 1 1/2 year), accurate, feedback every minute
con: no display, 433 Mhz
I have 2 Xiaomi WSDCGQ11LM, used with zigbee2mqtt
pro : long battery life, zigbee
con: does not like to change route, only updates when certain % change, no display
I have 2 blitzwolf bw-is4, used with zigbee2mqtt
pro : long battery life, zigbee, nice display
con: only updates when certain % change
I have 4 Xiaomi LYWSD03MMC, used with an esp32 flashed with openmqttgateway
pro : nice display, updates every minute
con: bleutooth, you have to flash alternate firmware if you want long battery life, you need a esp32 to convert the bluetooth to wifi.
I have 1 DHT11 connected to an esp32cam, esphome
pro: none
con: very inaccurate.
But maybe you can stuff it in a nice case or into a “decoration item” or something… 
Thanks for all the details!