I just want to know how much water I consume. I live in Netherlands and here we have smart meters for electricity and gas. I can see instant consumption and totals per day, month, year. I want same thing for water.

Why? It can be used for automatic leakage detection and also for awareness of how much water I need per day and for what. Building this thing is also a great opportunity to learn new stuff.

First, I had to choose a measurement method. Most people seems to chose one of these approaches:

• Take a photo on regular intervals and then apply OCR
• Use inductive sensor

I wanted this sensor to work on batteries for years. So, I had to choose a low power measurement method. After doing some research, I've found TI's LDC2112, which is an inductive sensor used for keyboards. In low power state it consumes something around 6uA per sensor, which is good enough to start building a device with it.

I never designed an inductive sensor before and at the beginning I was worrying if I will manage to make all the calculations properly. Fortunately, TI provides number of application notes, which made the whole process a lot more straightforward and actually I enjoyed it. If you ever think design one yourself, definitely look at WEBENCH Coil Designer. It includes all the calculations and exports ready to use PCB designs in popular formats. Once the sensor was designed, I had to choose how to communicate the readings. I wanted to make the whole device to work on batteries, so Zigbee was an obvious choice. One challenge: my water meter is under the floor, but my Zigbee controller is in the attic. I considered to give Lora-E5 a try - I used it for a sensor for the mailbox flap and it works well. At the end I just decided to try more powerful CC2652P Zigbee module from EBYTE. It needs more current, but will see if I will manage to save the battery.