Believe it or not, Daniel Kramnik is only a Junior in High School and has built this Digital Salinometer for a Water Quality Science Olympiad event. The Digital Salinometer built by Daniel took almost 2 weeks and is capable of accuracy within 0.0014%. Daniel's entry ended up winning him first place at the regionals and he's now headed for the State competition in March. Amazing what high school kids can do these days!
"The entire circuit consisted of several parts: an opamp-based salinity-measuring circuit, a linear positive/negative power supply, a digital voltmeter, and a peltier device temperature controller.
In order to save time debugging (inevitably) flawed bread or perfboarded circuits, I designed custom circuit boards in Eagle CAD and etched them at home with ferric chloride. I won’t post my .sch/.brd files as that would make it too easy to copy this project for Science Olympiad, but I will share schematic image files and board image files (if you already know how to reCAD them for etching in Eagle, chances are, you’re already beyond this guide)."
It just doesn’t get any better than this. It’s time to gather the components, get the circuit boards made, lay down the parts, and write the code. When the dust settles, you’ll have built a super-fast 32-bit embedded computing machine that can converse via multiple logic-level serial ports, a true RS-232 port, USB, and Wi-Fi. If all of that data is important to you, just store it away on the onboard microSD card. And it does get better. Read More...