Wood moisture meter with data transmission

1. Project Goal:

First Stage:

Develop an autonomous electronic device for measuring wood moisture with data transmission to Google Sheets. The device should operate in household conditions without connection to mains power for at least 48 hours. During simultaneous operation, approximately 20 identical devices will be used.

Second Stage:

    Add sensors:

• 2 pcs humidity sensors + data transmission to the table
• 1 air temperature sensor around the device + data transmission to the table
  
  We can combine stages 1 and 2

2. Main Functions:

2.1. Measuring Moisture

• Principle: resistance measurement between two metal probes immersed in wood.

• Power is supplied to the probes via a 0.1 sec pulse through a MOSFET to prevent electrolysis and corrosion.

• The value is displayed as a percentage (%) based on a calibration table.

• Calibration is performed using a reference hygrometer.

2.2. Calibration

• Resistance table → moisture updates via web interface or OTA.

3. Data Output:

• Display :

  • Device ID

  • Current moisture (%)

  • Connection status (Wi-Fi or GSM)

  • Last transmission time

4. Data Transmission to Google Sheets:

• Data is transmitted at controlled intervals (from 5 minutes to 24 hours).

• Network options:

  • Wi-Fi (dedicated access point configured for these devices, for easy connection of hygrometers to the network)

  • GSM module (SIM800L / SIM868) if Wi-Fi is unavailable

    • Preference is to build connection only via Wi-Fi (since usually 3-5 hygrometers will be used at one location)

• Transmission format:

  • Device ID

  • Moisture (%)

  • Timestamp

  • Battery level (optional)

5. Network Architecture:

• Group of several devices (up to 100)

• Each has a unique ID

• Direct transmission to Google Sheets

6. Power Supply and Autonomy:

• Li-ion battery 18650 / 3000 mAh or similar

• Charging via Type-C

• Autonomous operation at least 48 hours in the following mode:

  • Measurement once every 10 minutes

  • Data transmission once every 30 minutes

  • Sleep mode between cycles

• Support for deep-sleep mode

• Battery charge indicator

7. Operating Conditions:

• Household conditions: room temperature (10–35°C), relative humidity up to 70%

• Enclosure protection — IP40 or higher

• Installation indoors with wooden structures (walls, beams, floors, etc.)

9. Software:

• ESP32 Arduino Core

• Web interface (Wi-Fi setup, intervals, calibration)

• OTA firmware updates

• Serial port log file

• Ability to manually update calibration table

Initially, we will build a working prototype that measures humidity and transmits data, then develop a full device. I mainly expect the software part from you.

Write about the cost — we will discuss.

If you have ready or similar solutions, write — we will discuss.