Looks impossible, Dwell meter accuracy
now first project, ignition module simulator, working, need build dwell meter.
it needs measure accurately 500 rpm 6000
pick off coil, hardware de-bounce, filtering, opto-coupled & level shifting,
average number of measurements
display on 2-line lcd every couple of seconds
only measurement has exact. don't mind time-outs update display.
quick math says won't work.
at 6000 rpm, 4-stroke 4-cylinder produces 200 sparks per second event time total of 5 ms each.
so if want measure pulse width within 1 degree, need 14us accuracy. (5 /360)
clearly 5ms up/down timers not job on uno.
recommendations? i thinking of interrupts got quite wrapped around axle on it. bad put hard work in isr? thinking using 1 measuring total cycle time ( tach) , other measure pulse width. kind of alternate isr control came back. ok. need average of bunch of pules widths , average of cycle times, not in exact same cycle.
it needs measure accurately 500 rpm 6000
pick off coil, hardware de-bounce, filtering, opto-coupled & level shifting,
average number of measurements
display on 2-line lcd every couple of seconds
only measurement has exact. don't mind time-outs update display.
quick math says won't work.
at 6000 rpm, 4-stroke 4-cylinder produces 200 sparks per second event time total of 5 ms each.
so if want measure pulse width within 1 degree, need 14us accuracy. (5 /360)
clearly 5ms up/down timers not job on uno.
recommendations? i thinking of interrupts got quite wrapped around axle on it. bad put hard work in isr? thinking using 1 measuring total cycle time ( tach) , other measure pulse width. kind of alternate isr control came back. ok. need average of bunch of pules widths , average of cycle times, not in exact same cycle.
clearly 5ms up/down timers not job on uno.i'm not sure you're talking 5ms resolution. millis function gives 1ms resoution. micros function gives 4us resolution. , 1 of timers set no prescaler can 62.5ns resolution.
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