Paddlewheel speed log

INTRODUCTION
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This is a design of a simple paddlewheel based speed log. The working procedure of the speed log is similar to those commercially available for boats ands yachts, but at a smaller scale. The incoming flow of water makes the impeller rotate. Each of the impeller paddles contains a small magnet. A simple electronics board counts each time a magnet passes the top most part. The velocity of the vessel over the water is proportional to the count (in reality it is not proportional, but for the intended use is perfectly fine to assume proportionality).

The intended use of this design is two-fold: for the one hand showing how these systems work; for the other hand, allowing the use of a simple and inexpensive speed log for small DIY crafts.

Although the use of a small size GPS could do much the same with more accuracy, I have developed this for use in a small size low-cost ROV (Remotely Operated Vehicle) for underwater exploration. There, there is no GPS at