February 22, 2026
Description
For a while, I've been using Zigbee and Bluetooth temperature and humidity sensors around my house.
After many issues with Zigbee disconnecting and batteries running out 3 times a week. And since I've been constantly repairing Home Assistant sensors, I've decided to design the best smart home temperature and Humidity Sensor for myself.
I've designed a plug-in, temperature/humidity sensor that works over Wi-Fi, and it's all open source!
Fully plug-in design - no batteries needed.
Fully Open Source - All code is available using ESPHOME.
Automatically discovered and connected to Home Assistant.
Only 5Â components for the PCB.Â
PCBÂ
10 KΩ resistor x2 - Link
100nF capacitor - Link
ESP 32 - Affiliate Link
SHT40 - Link
3D Printed Enclosure.
Open the 3mf file as a project, that way you can see the mid print pause to add the magnets
Fully assembled version to purchase are aviaalbe here -Â Link
All files are available on my GitHub -Â Link
Assemble the PCB:
     Solder the capacitor, 2 resistors, the temperature sensor, and the esp as shown in the images.
Software:
Download the compiled bin file from GitHub, and go to the ESPhome installer.
Connect the PCB to your computer, press the connect button, and choose your esp in the pop-up window.
     Then press install and add the bin file. and wait for the installation to complete.
    If the ESP keeps disconnecting, press the reset button on the ESP and connect it to the computer simultaneously. That will ensure the esp is in pairing mode.
 Next, go to your phone, look for the Wi-Fi hotspot the ESP is transmitting, and connect to it.
 Enter the Wi-Fi credentials on the page that opens. If nothing opens, go to your browser and type 192.168.4.1
Next, you need to adopt the sensor into Home Assistant. Home Assistant should discover it automagically, and the sensor should appear in the integration page. (Check the video to see the software and the process.
Last, put the PCB inside the enclosure, and enjoy!
If you need to calibrate your sensor in the enclosure, these are my values:
                       Temperature:   -4.1       Humidity:    +11
AND that's it, you're done making the DIY Smart Home Temperature/Humidity Sensor For Home Assistant.
License:
Creative Commons — Attribution — Noncommercial — Share Alike