The measure of the (washing) machine

Measuring the water use of a washing machine isn’t so hard, unless you have to do it unattended, silently, repeatedly, and do more than one machine at a time with one datalogger.

To tell what’s going on I need to know three things:

  1. How much hot water is used in a cycle?
  2. How much cold water is used in a cycle?
  3. When does the cycle start and end?  —so I can disaggregate individual cycles.

For (1) and (2), I’m using two Koolance flowmeters (see previous post). For (3), I’m using an electret microphone to detect the vibrations from the motor inside. Tom Igoe was very prescient in advising me to positively measure the activity of the machine, and Eric Rosenthal, Electronics Genius, was a great help in doing it in an elegant, low cost fashion (accelerometers are expensive, and tilt switches may not be as sensitive as I’d like).

The whole assembly is less than $1.00, (aside from the Arduino microcontroller) and the sensitivity can be tuned based on the resistance of the resistors.


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