Can anyone recommend a good temperature and humidity sensor that is not battery powered?
I don’t mind paying quite a bit extra, as reliability and the convenience of not having to change batteries is more important to me. I need relatively frequent updates and I intend to use the sensors to trigger ventilation.
Design also matters - ideally I’d like a small case that fits a EU plug directly without a cable from a phone charger or similar.
(If I only need to change batteries every year and can get updates every minute I might also consider it)
If ventilation is your main concern you might want to look into the Qingping Air Monitor Lite, as it also measures CO2, PM2.5 and PM10 air pollution, but it does connect with a USB-C cable to a USB charger does look great though, in my opinion; I have two here.
Otherwise there are a ton of CR2032 driven temperature and humidity sensors around, Bluetooth, Zigbee … and they usually all last a year and more on one battery. Like the Inkbird TH1, Aqara temperature sensor …
Agree with the CR2032 driven Zigbee devices, more than a year on a battery easily and they update when the temp/humidity/pressure changes so you don’t lose anything - if it is 20 degrees for 3 hours, you get that and then the change later - doesn’t mess with graphs etc.
Also if you think they are slow, just blow on them and watch the instant report.
If you don’t find anything readymade, you can easily build one yourself. All you need is a BME280. They are sold on little boards and provide you with tempereature, humidity and even air pressure.
Couple this with a small ESP board like a Wemos D1 mini and a 5v micro USB wall wart.
Flash the board with ESPHome and put everything in a project box or something 3d printed. Just make sure, the actual BMP sensor can “breathe” the outside air.
I’ve been using 10 of these Xiaomi LYWSD03MMC with the custom firmware available (easy to install) and 2 of the Aranet4 around houses for 3+ years now. IMHO BLE bluetooth low energy is the choice for useful reading update rates, long battery life and low cost. You can place them anywhere, not tied to an outlet, no cords and you get local display. I use the Govee units cited below inside refrigerator and freezers, with same update frequency and multi-year battery life.
Xiaomi LYWSD03MMC, at a device cost of USD 3 each and a CR2032 battery life of 2+ years, they are pretty hard to beat. The Aranet4’s are great as well, but pricy, however I got them for CO2 monitoring. And that has found to be interesting.
I have never found a zigbee temperature/humidity device that yields reading at the frequency that is useful for home automation and gives confidence the device in still online, and I have drawer full of them… Sorry, but I don’t want to go around blowing on sensors to know if they are functioning. I think getting a communication from a sensor several times a minute is the rate that makes it useful in home automation. The BLE devices deliver this with years of battery life.
Wow. Thanks for the many great recommendations guys. I did contemplate building my own, but got a bit stuck on how to power it from mains without a USB adapter.
From the sound of it, I may try out one of the battery powered devices first.
I know you basically closed the topic with your last reply.
I you feel comfortable to work with mains circuits, there are small switching power supplies providing 3,3v or 5v directly from mains. That could be an alternative to a usb wall wart. However you would be working with mains voltage and you should know what you are doing otherwise it could be rather dangerous.
I have built my water meter with such a power supply. works great.
Zigbee vs. Bluetooth, both low power consumption.
CO2 measuring is interesting. Carbon monoxide from engine (ICE) cars seems worthwhile too due to the poisonous micro particles.
Yes, CO is in important one to monitor as well as Radon if you are in an area under that specter. I went with the Google Nest devices for smoke and CO a while back, even though they do not integrate very well with Home Assistant, they seemed to have a very good proactive automatic testing and have proven very reliable. I added some secondary Zigbee based CO sensors just so I could get a 2nd input and one that I could monitor CO levels over time in Home Assistant.
does look great though, in my opinion; I have two here.