I have 13 ESp32's in various locations around my property. Spaces like crawl spaces, attics, out in the middle of the backyard.
The ESP32's exchange data though a RPi running MQTT Broker. Node Red can be used as a control center, I wrote a Python program that runs on the RPI as a control center.
The RPi sends and retrieves data from my web site as well.
I have a Pi 3 doing this job for a single station indoors. It's massive overkill, power hungry and expensive compared to the alternatives. I'm only using it because the Uno it replaced had an obsolete WiFi stack and can't talk to my network any more because the best security it could handle was WEP.
@SteveMann uses Wemos D1 minis in his home automation setup - lots of them. There's also various other ESPXX options as @Idahowalker is using.
If you can verify that WiFi can reach the remoter areas you want to monitor, that's probably your best option.
As of ESP8266WiFi library Version 2.5.0, WPA is is the default mode. The solution is to get a better router, or add WiFi.enableInsecureWEP();
I don't know if this would work in the Uno WiFi library, but ...
Thanks. The folks that built my WiFi board and associated libraries are long out of business, so I'm resigned to the fact that that board is now e-waste. As to WEP, just say no!
I had the same project. I started with ESP8266 as WiFi modules but that prevented me from installing a couple of them outdoors unless I invest on a solar panel/battery/controller etc. So I decided to build a simple and flexible custom PCB that runs off a CR2032 or CR123A.
This nicely fits the 83mm x 58mm x 35mm project boxes you get off eBay
It can take an AHT10/21 (temp and humidity sensor), BH1750 (lux sensor), and APDS99XX (color or gesture sensor, for future touch switch application I have in mind). I also have it so I can use different wireless modules (NRF24, RFM70, or the 433 MHz modules).
The ESPs are okay but they don't last very long on battery (even when implementing deep sleep as WIFI connection takes at least 5 seconds to come up). The NRFs takes literally a few millisecond from deep sleep to transmission end and only consume 15ma give or take (ESP transmission goes well over the hundreds of ma)
Should I use Raspberry Pi or Arduino for the sensors? Price, temperature, power input (battery/power outlet), etc. (Raspberri is way overpowered for this and consumes lots of power and not cheap)
Should I use WiFi, Bluetooth or radio or something else to send the data from the sensors to the server? (Wifi gets you direct access to the server, anything else, you would have to have a dedicated radio gateway that listens to your sensor node and packages the data towards your server via UDP/TCP)
Can I use a battery for the sensor? Can I wake up the WiFi/Bluetooth/radio module so it isn't constantly connected? (WiFi is not suitable for battery power)
Should I put the sensors in some sort of container because of fire hazard? (Not really when using basic batteries, some 18650 types can dump lots of Amp so they can cause fires when short circuited)
The Raspberry Pi documentation states that the LAN module can only operate in zero Celsius or above, so then I should use Arduino for cold places? (the MCUs can generally go below zero but some sensors would fail)
I am also facing the same problem in my house. Many sensors to monitor temperature/humidity distributed over large space. Some sensors are with critical importance as they should monitor temperature reliably with their readings included into zone heating system.
Some sensors are WiFi (Sonoff devices with Tasmota firmware), but most of them are wireless 433 MHz. Home Assistant is running on RPi4. Those cheap 433 MHz devices are not reliable enough, and signal coverage is an issue. I retired a RFXTRX transiver in favour of my custom solution.
Alerting is not a problem in HA if a NodeRed add on is used.
