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I frequently receive inquiries about how my sensor works and why it’s more affordable and less bulky compared to others. People often ask if it can be used on their water meters.

I initiated this project a year ago with the intention of monitoring my annual water usage and learning how to conserve water. Upon researching existing designs, I discovered that most sensor-based products focused on proximity sensors, which resulted in bulky housings and limited precision. Hence, I explored alternative methods, leading to the development of the following sensor.

Principle

The image below depicts a meter commonly used in many Dutch households.

A red disk rotates with each liter of water used, and an arrow on the disk indicates the consumption in milliliters.

The Muino water meter is positioned over the water meter itself, and light sensors detect whether the disk is under the light sensor or not.

The water meter reader has three sensors placed 120 degrees apart, enabling the identification of the water meter’s position. A green low-power LED enhances the contrast for the light sensor, making everything that is not green appear black and white.

Electrical Signals

The signals produced by the three light sensors are sinus waves. Auto-correlation is used in our implemented model to precisely determine the position of the water meter. After calculating the position, the amount of water used can be accurately determined.

The three signals, spaced 120 degrees apart, go to our implemented model, ensuring precise position identification and water usage calculation. A rotating disk, is represented on a scale from 0 to 14. When the position reaches 14, it starts again from 0, like a loop. In our model, it’s crucial to keep track of whether a new cycle has begun. This indicates that a new liter (unit of measurement) has started. So, we’re essentially monitoring when the position resets to 0, signaling the start of a new cycle or liter.

This is how the Muino water meter sensor combines principles from three-phase electrical engineering with different sensing techniques.

Why So Cheap?

The sensor utilizes simple light sensors and a WiFi module, making it cost-effective. Large-scale production allows for low sensor creation costs. The affordability is also attributed to the project being a hobby, driven by passion rather than financial motives, eliminating significant risks.