1. Control a 12-volt pump's speed and flow output, and
2. precisely measure that output in ml/second,
3. send that information to a nearby computer, and take commands from it.
And all this for less than $100 or so in parts.* We used an Arduino Duemilanove development board, a new $25 flow sensor from Jaycar in Australia, and other common components. And we started with open source ideas from these guys, who I discovered through this book.
This figure shows the Emriver Em2's recirculating flow path. The valve array and notch gage could be replaced by this device.
Working with our Em2 model (or any other small model), students can use the Arduino (or another small microprocessor like it, we're still experimenting) to create and measure hydrographs, to monitor long term experiments, even to produce real-time graphs of hydrographs they create manually.
How cool is that--to create and digitally plot a real (though miniature) hydrograph in real time? Has this been done before?
I'm telling you, and any competitors we might have, about this because the beauty of open source design is that it's good for everybody. If your business involves keeping secrets from your customers, you're not a good company.
*And hundreds of hours of development work, and the use of a big lab and big brains trained at great expense, etc. And this thing hasn't been put in a waterproof box yet or tested for durability or safety, and isn't ROHS compliant for European export, and who knows about software support? Don't get too excited. But it has great promise!