I wanted to control my garage door with the Sonoff Wifi Switch but found out that the device passes power through it instead of just closing a contact. Despite many requests on the manufacturers website forum they have not made the change yet.
You can convert the Sonoff Wifi Switch into a dry contact with a Soldering Iron, someSolder and a Cheap Dremel.
Danger: Make sure the unit is not plugged in before continuing.
Step 1: Run your finger nail around the base of the unit to separate the cover. I keep my nails really trimmed so I used a small flat head screwdriver. It’s fairly obvious where the seam is but if you can’t find it, leave a comment and I’ll add some pictures of the process.
Step 2: Removed the circuit board.
Step 3: Removed the pathways with the Dremel from BOTH sides of the circuit board as shown in the picture below. Hold it up to that light as shown to make sure you did not miss any of the connection. If you’re gap is too small the voltage will make the jump.
Step 4: Solder across the gap as shown so that the connection will actually close when the relay switches. You should be able to see what I’m talking about in the picture below. You can see the solder pointed to by the red arrow. If you can’t get the solder to stretch that far, you can use a single strand of copper from a stranded wire to give your solder something to hang on to.
Step 5: Test your product with a voltage meter to make sure it all went as planned.