Water is a precious resource. Millions of people do not have access to clean drinking water, and as many as 4000 children die from water contaminated illnesses every day. Yet, we continue to be wasteful with our resources. The overarching goal of this project is to motivate more sustainable water use behavior and raise awareness about global water issues.
This is an instructible on how to crudely detect water flow in a pipe and drive an ambient display. I am using a piezo transducer, some LED’s and an arduino. The device is a rough prototype of what will eventually become a persuasive technology that motivates sustainable behavior and raises awareness about water use.
This is a project by Stacey Kuznetsov and Eric Paulos at the Living Environments Lab, at Carnegie Mellon University Human Computer Interaction Institute.
Living Environments Lab
The video below illustrates a previous version of this project, where a microphone is used instead of a piezo element to detect water flow. You will achieve better performance when using a piezo transducer, so this instructible details the piezo approach.
Special thanks to Briam Lim, Bryan Pendleton, Chris Harrison and Stuart Anderson for help with ideas and design of this project!
Step 1: Gather Materials
You will need:
– Microcontroller (I used an Arduino)
– Piezo Transducer (http://www.radioshack.com/product/index.jsp?productId=2062402)
– A few LED’s (I used 2 yellow, 2 red, 2 green)
– Candle holder or similar-sized container
– 1 Mohm (or other large value) resistor
– 4.7K Resistors (3)
– 1K Resistors (1)
– Low-value Resistors (for the LED’s)
– Clipping Wires
– Jumper Wires
– Mastic- op amp (LM613)
Step 2: BuildPost
Step 3: Test the Circuit
Attach the piezo to the circuit, and hook up the arduino.
The voltage divider sets the base voltage at 2.5V, so the base readings for the signal should be around 512 on the Arduino analog pin (half way between 0 and 1023). Mine fluctuates +/-30 around 520. You may see some fluctuation around this number.
Step 4: Calibrate Your Sensor to Detect Vibrations
When the tap is turned on, the vibrations of the pipe will cause the piezo to generate a fluctuating current. Since the base reading tapers off around 520, you can compute an amplitude around this number to detect vibrations. My threshhold is set at 130, but you may increase or decrease this depending on the types of vibration you want to sense and sensitivity of your particular piezo piece.
To test the signal, use mastic to attach piezo to a flat surface. Try tapping or scratching on the surface at different locations and different intensities see what type of readings you get on the Arduino.