an inductive pickup around the sparkplug wire should get you a nice pulse each time the spark plug fires but remember the phases of a 4 stroke engine (intake - piston down intake valve open, compression - piston up valves closed, power - piston down valves closed, exhaust - piston up exhaust valve open). The spark plug only fires every other revolution. Once you have the pulse from the inductive pickup it should be buffered to provide a nice square wave pulse of uniform voltage such that it's easy for the processor to use and not a potential hazard to the processor due to spurious high voltages (cooking the buffer circuit while in development, sorta ok.... cooking the processor, well not so much!) . from there it's just software and the incrementing of a counter with each pulse.
On Sun, Apr 6, 2014 at 6:33 AM, Stacy Cottles <[email protected]> wrote: > I am building a web-controlled lawn-mower. I would like to be able to read > the RPM off the gas-engine. I would prefer to piggy-back off of the > spark-plug if possible since it fires faster as the engine spins faster. > Just started on this but would love suggestions. I have a Beaglebone Black > running Angstrom and I am using NodeJS to control GPIOs. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
