Divide by counters.

Since I will be wanting to use two of the arduinos interrupts (one for car speed, and one for engine speed), I thought I could use a divide by counter to reduce the processing load on the arduino.

The engine is a 6 cylinder 4 stroke, so thats 6 igniton events every 4 revolutions. I was thinking I could use a divide by 6 counter, so that the output would be 1 event for the arduino to process each 4 revolutions.

The speed output is 9 (i think) pulses per revolution.

I thought that with two interrupts triggering rather fast and trying to write stuff to a serial LCD could slow the arduino down a fair bit.

Is this how divide by counters work? What would be some suitable counters? A divide by 6 counter (for the rpms), and a divide by 9 counter (for the speed)?

Yes thats how divide by counters work.

You could look at the 4017 to do the counting:

http://www.doctronics.co.uk/pdf_files/4017.pdf

By connecting output 6 or output 9 back to the reset pin you can divide by 6 or 9.

4 stroke engines - don't they take just 2 revolutions to do the 4 strokes?

Regards,

Mike

Ah yeah, 2 revs, 4 strokes :P

Was late:)