Eric, I apologize for my ignorance but what is the pru? On Sunday, April 6, 2014 6:18:27 PM UTC-5, Eric wrote: > > I might be inclined to use the pru for this and just setup the pru as > escentially a hardware counter. There are likely ways to do so with timers > and interrupts and such but being more of a hardware guy than software I'm > inclined to use a more hardware approach and use the pru as a counter that > gets read every so often. the software for that then is escentially a > driver that creates /dev/rpm. > > Eric > > > On Sun, Apr 6, 2014 at 3:43 PM, Stacy Cottles <[email protected]<javascript:> > > wrote: > >> Thanks Eric for the suggestion. I'll have to figure out the inductive >> circuit to use. Do I have to use interrupts or is there something better >> for capturing the signal from the pickup? >> >> >> On Sunday, April 6, 2014 1:51:07 PM UTC-5, Eric wrote: >> >>> 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. >>>> >>> >>> >
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