wvmarle:
In most cars the RPM signal comes in the form of a digital signal, too. E.g. a block wave with one wave for each rotation (or a number of waves per rotation) - count the frequency to get to the RPM.The dimmer could be an analog signal, also a digital one: look at PWM (pulse width modulation).
The complication you're left with is in the hardware, particularly how to protect your electronics from all the noise. That is actually not even all too complicated, it's just a bit of work to solder it down properly.
Its a 1979 car, the speedometer is driven by a rotating cable, So I must buy a device to transform that as pulses. 16 pulses per rotation..... But the question is, the faster the car moves, the faster the pulses will come. How can I be sure that I wont loss signals while reading ..... the pulse generator has its frecuency depending on the speed car, and the arduino loops in whoknows frecuency. What it pulses are generted faster than arduinos loop frecuency.
Another question, I guess Arduinos cannot support multihtreading, so how can I know the speed If I cannot have a separate thread to count the pulses and compare then in a time lapse...???? Should I only receive and publish the data gathered from the cluster and do the maths, interpretation, comparissons, etc etc etc on the Android app to ensurace a light running script on my arduino?