good afternoon.

i have a question i would like to pose.

lets say for example i have a circle with circumference of 10 cm.

i want to work out lets say the speed.

eg
in this circle is a thin wire attached to a pin.so if lets say a shaft is spinning in this circle,also with a metal wire which will pass past the other metal wire and thus make contact with the pin.

is there a formula to calculate how long it takes for the metal strips to cross or would it be better to manipulate the time and then just try determine how many times te two metal pieces have crossed(touched )

if a)the two mtal strips pass each other(pin high)and inside chip starts counting.
b)if metal strips pass each other again ( 1 revolution)

i am battling to get (within that revolution) the chip to count (seconds)
thus having the time taken.

please note that i havent actually programmed this,but it the point of departure-the starting point of the programming this that boggles my mind.