Hello,
I would like to know the external temperature putting a thermometer in an open external space so it shows the exact external temperature.
Do you know a reliable sensor compatible with HA?
I would like to build an automation that, depending on external temperature in the early morning, would set my alarm at different time (if it’s not too could I could get my bike to get to work and I can wake up later).
Thank You for any help.
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That’s a cool automation idea
I have used a couple of different sensors outside but neither are actually weatherproof so need to be in a protected area (ie: under cover) which actually seems fine to me since they need to be out of direct sunlight to give a proper temp reading anyway.
Aeotec multisensors have temp. I used them under a patio for motion controlled lights.
Xiaomi plant sensors have temp. I have them in potted plants so I can keep on top of the moisture level.
Both of the above seem to give me a reaonsable (caparible with the temp esimated by weather forecast) value at my home location and work well with HA. Obviously these are not the primary function of these sensors and there are others out there but I know these work and perhaps you (like me) could also use the other functions of these devices.
I have one of these outside, but under the eaves of my roof, so its protected from rain.
Do you connect it via the Xiaomi gateway, or via something like ConBee ?
i use netatmo weather station with outdoor and indoor modules. There are also rain and wind modules available.
Just found this topic as need external sensor for myself.
I did try Xiaomi’s sensor outdoors (under the rain cover as well, so it’s not an issue) as I have many other Xiaomi devices at home.
But when it become a bit cold (lower than 5 Cels) it battery become flatten extremely quick.
I did change few of them when each last for max 3 days! and them gave up and start looking for something more reliable and maybe with different source of power e.g. AAA or even AA batteries
You will not get the “meteorological” outdoor temperature with any of these temp sensors or… any temp sensor at all without it being in at least a Stevenson screen.
What you will get is probably more what you are after, the effective ambient temperature. The temperature will spike high if direct sunlight falls on the probe and you will get sudden troughs when rain falls on it. However for your automation this is probably what you want.
I just use a Dallas One Wire probe, pre-bought sealed. The metal canister has rusted a little in the past 2 years but it still work fine. I sends the data using an ESP8266. You can find code to send MQTT temperatures for HA (including discovery stuff) in a dozen different places on the web. (Note the idea is the ESP8266 is inside, the probe lead is thin enough to make it out through the seal of a window easily.
One question you should consider - what technology are you currently using / plan to use?
There are solutions for all types, Zigbe, Z-wave, WiFi, and 433Mhz come to mind.
If you are not currently using some of these and don’t plan to, then adding them just for one sensor is probably not cost effective or convenient. In that case you would probably want to go with something that uses WiFi as I expect you have that technology in your house.
For myself, I use 433Mhz sensors. I have multiple Temp+Humidity sensors and also some door sensors that use 433Mhz and all run on AAA batteries (I have a collection of decent rechargeable). This is a very inexpensive solution ($3-$5 each), and batteries should last a long time as they don’t need constant connections.
This did require adding some hardware (a Software Defined Radia aka SRD) and an in-between program - RTL433 (there are others) to translate the messages. The hardware was $10, and the software runs on my server with HA. You could also use a hardware 433Mhz gateway that does both jobs at once.
I hope this helped a little - and didn’t just generate more questions 
.
Cheers!
DeadEnd
I opted to not use outdoor equipment and instead created a temperature sensor using open weathermap and have found it to be quite accurate and dependable for my area. I use it to switch between my heat pump and my oil fired boiler at above/below 35 degrees.
It shows up as…
sensor.owm_temperature
attribution: Data provided by OpenWeatherMap
unit_of_measurement: °F
friendly_name: OWM Temperature
My config yaml
sensor:
-
platform: yr
-
platform: openweathermap
api_key: MY_API_KEY
monitored_conditions:- temperature
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Did you try to connect Xiaomi sensor to 2 AA batteries? It will by also 3V and should work very long time.
No, I didn’t
Instead I just took ESP32 controller, flashed ESPHome on it and connected by wire BME280 sensor, so as PROS I do have stable measurements with even more accurate figures, as a CONS - I need to hoock it up to +5V (cheap USB charger in my case).
As another option did try to use “Xiaomi Mijia Bluetooth Temperature Smart Humidity Sensor”
Covered with a piece of plastic bottle to protect from rain