Speed Reader

Ok, in my car i have a speed sensor (i presume summin like hall efect which runs off of the drive shaft) this gives out 1026 pulses for 60mph. Is it possible to time the gap inbetween each pulse so that i could do some math and calculate my speed?

Or you could count the pulses in a fixed time period and calculate your speed from that.

i thought about that, that way would be more accurate at higher speeds, the other way would be more accurate at slower speeds, altho, i dont think it would make much difference either way! say i was going at 10mph, that would be 2.85 revs or pulses a second, i think it would be more flexable to time between each pluse cus using a time frame to count the pulses would mean that it was slow to update the display if you allowed along enough time period to get the accuracy at slower speeds.

So i have an idea how to do it just not to put it in to code,

wait for low to high signal transition
do the math on the current timer figure
update display
restart the timer
loop back to beginning

it would be nice to design it so that it could go all the way to the top speed 140mph ish, i assume the ardunio would be able to reliably detect 40 pulses a second?

Are you aware of the PulseIn() function

http://www.arduino.cc/en/Reference/PulseIn

Looks like it’s just what you need.