I'm considering an arduino project to work as a speedometer for my bike. I have just bought a hub dynamo which outputs 6V a/c and thought i could use an arduino to count the a/c modulations and from that work out the speed of the bike. Then output the speed to a small 2 or 3 digit LCD screen. Firstly,i don't want to power the arduino from a battery, i want to use the hub dynamo for that - how do i best do that? Secondly, i estimate that there are approximately 30 oscillations of the hub dynamo a/c output per wheel revolution. With a 700mm dia wheel, at 25km/hr that works out to be about 95Hz (Maybe half that depending on the polarity of the magnets within the hub - i need to connect an oscilloscope to work out exactly how many magnets there are per revolution and how the voltage output behaves)
Can an Arduino measure 95Hz signals reliably or is that a bit fast?
Will I run into problems powering the arduino with the same thing that i am trying to measure?
If anyone has any thoughts on this, or any guidance which would be useful early on please let me know.