DIY Smart Temperature Sensor with 18650 Battery: My Experience and Tips

General
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I’ve been experimenting with creating a low-temperature smart sensor using a regular SmartThings multi-sensor and a 18650 Li battery. After months of testing, I wanted to share my findings and tips for anyone looking to DIY their own solution.

What You Need

  • A SmartThings multi-sensor
  • A 18650 Li battery and holder
  • A 3V step-down converter
  • A 15EDGRK-3.81mm 3p plug
  • A twisted dual Ethernet cable
  • Soldering tools

Setup Process

  1. Modify the Sensor: Drill a small hole in the SmartThings sensor and solder the Ethernet cable to connect the battery holder and step-down converter.
  2. Battery Management: The 18650 battery provides a stable voltage of around 3.8V, which is safer for the sensor compared to the original CR2450 battery. I tested this in extreme temperatures (-18°C) and found the battery life to be excellent, with only a 0.15V drop over three months.
  3. Cable Length: I used a 2m Ethernet cable, but longer cables should work without significant voltage drop.

Cost-Effective Solution

This setup is incredibly affordable, with most components available for under $10 on AliExpress. Here are some of the parts I used:

Results

This DIY sensor has been a game-changer for monitoring temperatures in extreme environments. The battery life is impressive, and the sensor remains reliable even in freezing conditions. The only caveat is avoiding direct exposure to extreme cold, as the battery performs best when kept at room temperature.

Tips for Success

  • Soldering Precision: Take your time with soldering to ensure a secure connection.
  • Battery Placement: Keep the battery away from extreme temperatures using a longer cable.
  • Regular Checks: While the battery life is long, it’s a good idea to check the voltage every few months, especially in harsh environments.

If you’re looking to extend the functionality of your SmartThings sensors or need a reliable low-temperature solution, I highly recommend giving this DIY project a try. It’s a fun way to save money and customize your smart home setup!

Cheers to all the DIY enthusiasts out there! :rocket: