Ever since I upgraded from SmartThings to Home Assistant, I’ve been slowly adding more and more sensors and switches to automate everything around the house. One thing I don’t want to spend my time doing is checking on the salt level for my soft water machine. I wanted a reminder for when the salt level is low, but there doesn’t seem to be a good product out there that’s cheap and reliable.
At the end I went with a very simple idea. I’ll use a door sensor with a powerful magnet that sits on the salt. Once the salt reach a low enough level, it’ll trigger the door sensor and Home Assistant will send me notifications every week for refill.
First order of things is to prep the magnet. This 1″ neodymium magnet had been very useful for many projects of mine. Here I wrap the magnet in vacuum seal bag plastic, then wrap some duct tape to prevent any puncture damage, and wrap it in vacuum bag again. After that, I tie the magnet to a fishing line.
Next, I attach the fishing line to the lid of the salt container. I use velcro tape so that I can adjust the height when needed. It’s hard to see the magnet inside the bin but I try to position it near the corner so it won’t miss the sensor.
My salt level happens to be running low, so I can rest the magnet near the bottom and slide the door sensor around until it registers contact with the magnet.
It’s a very simple setup that is low cost and doesn’t need a power supply. The fishing line is attached to the lid so that the magnet is pulled back to the top during refill. The one drawback for this design is that there is something in physical contact with salt water, so you have to be very sure that the string and magnet you use will not corrode.
Fun In the Garage 