Cool looking schematic.
What are your thoughts on using an LM7805 to cap the voltage on the RPM signal instead of a voltage divider? The reason I'd want to do that is it'll keep very high voltage spikes from damaging the board.
Or I could just use a 15k/5K divider which will allow up to a 20V spike. But then Vout at Vin of 12 to 14v drops down to 3v. Is that good enough for the Arduino to read? Digital low = 0v and digital high = 3v? Or does it need the full 5V to register a 'high' condition?
You need a series resistor to cut the current coming in and to isolate that part of the circuit (the one on the RPM sensor) from the inner part.Then you need ordinary (small) diodes to clamp what does come across the resistor to V+ and ground (i.e. one diode preventing the voltage from getting above V+ by conducting anything above V+ to V+, and a second preventing anything from going below ground - don't get these backward). Then a second, probably smaller resistor to go into the arduino's input.
You can use a zener as a single diode to ground - e.g. a 3 volt zener would clamp below ground to ground, and above 3 to 3.
Posted by: tzForce = mass * acceleration, and apparently you have acceleration and know the mass of you on your bike.Torque is force * distance (normal, i.e at a right angle), so if you know the diameter of the rear tire you know the torque there from the force. Then you have to go back through the gearing ratios (the drive chain, transmission, etc.) and determine if you want to account for friction.Work is force * distance (in the same direction as the force), which is also calculable from the acceleration. Power (watts/horsepower) is work per second, i.e around 750 foot-pounds per second.A lot of it is basic physics, but more of it is just getting the units to cancel out.
Acceleration is ft/sec^2 statically, but to be correct, it is dv/dt - change in velocity with time.Kinetic energy is 1/2 m v^2 and maybe that would be a better place to calculate the energy per second.