I recently faced an interesting challenge that I wanted to share with the community. I wanted to create a simple contact sensor to monitor my furnace burner. After some research, I decided to modify an Aqara contact sensor for this purpose. Here’s how I approached it and the lessons I learned along the way.First, I considered the Sage Doorbell sensor, but it lacked the necessary features like battery capability and heartbeat. I then turned to the Aqara sensor, which is compact and uses a CR1632 battery. The main concern was ensuring that the external wires wouldn’t cause any EMC or static issues. Upon examining the board, I noticed a capacitor to ground and a 500K resistor into the processor, which I felt provided a sufficient safety margin.The wire I used was #28 stranded with silicone insulation, which is extremely flexible and doesn’t melt during soldering. Here are the steps I followed:1. Preparation: I carefully examined the board to understand the layout and identify the necessary points for modification.2. Wiring: I soldered the wires to the board, ensuring a secure connection without damaging the components.3. Testing: After assembling, I tested the sensor to ensure it was detecting the contact points accurately.The result was a reliable solution that now monitors my furnace burner effectively. This experience taught me the importance of thorough research and careful modification. It also highlighted the versatility of the Aqara sensor, which can be adapted for various purposes beyond its original design.If anyone has similar projects or questions, feel free to reach out. I’d be happy to share more details or help troubleshoot issues!