My city water rates are sky high so I was looking for a way to monitor my water usage and hopefully reduce it. I came across his paper "Single-Point Sensing of Whole-Home Water Activity" https://homes.cs.washington.edu/~jfogarty/publications/ubicomp2009.pdf . They call the system HydroSense.
Instead of using a water flow sensor at every faucet, tub, shower and appliance that uses water, a single pressure sensor is used to detect the water usage at every location. This is accomplished by learning and recognizing the unique pressure pattern when water is turned on or off at each water usage location. In this way you know not only how much water is used but also which location is using the water without the high cost and complexity of installing sensors at every location.
One of the objectives of the HydroSense systems was to make it portable for a quick and easy install. Therefore the single sensor/MCU was battery operated and could be installed on any water outlet including an outside faucet.
The following are the major components of the HydroSense system as described in the white paper.
· 9 Volt battery power
· Pace Scientific P1600 pressure sensor with a response time of less than 0.5 milliseconds http://www.pace-sci.com/pressure-1600.htm
· TI ADS8344 16-bit ADC http://www.ti.com/product/ads8344
· 20 MHz AVR microcontroller
· Class 1 Bluetooth radio
· Data collection PC with Bluetooth receiver
I don't need a portable system so I plan on mounting the pressure sensor in the basement plumbing. The HydroSense system uses a pressure drop to detect water flow but for very low flows there will be undetectable pressure drop. But even a slow water leak such as a dripping faucet can add up to significant water usage when it continues for a long period of time. For this reason I plan on also adding a hall-effect water flow sensor on the main water line. I think this will also help when used in combination with the pressure sensor to learn and detect the water characteristics at each water usage location.
If you read the HydroSense white paper you see they use some sophisticated mathematical algorithms such as Fourier transforms to detect the unique water pressure signatures at each water usage location. It appears all this processing happens on the PC after collecting the data from the AVR. I already have an always on PC I use for home automation which I can use for the data processing if it's too difficult to do with the MSP / ESI. The HydroSense system collects water pressure reading at 1KHz. My MSP / ESI based system may do some amount of pre-processing of these values.
I use Open Source Automation http://opensourceautomation.com/ for my home automation system. It already has the ability to log data to a MySQL database, create graphs of recorded data and send a text message or e-mail when an event is detected. I plan on connecting the water monitoring system into my home automation system so I can be notified if abnormal water usage is detected.
This is definitely the most complex MCU project I have attempted so I will be seeking help from the 43oh forum community.