kingofl337

How much precision in mS or uS does a micro-controller need to properly control timing +/- .5deg. I'm trying to use a micro to delay the charge time on my Toyota COP's. But, according to my scope I'm firing the coils (going low) late by about .02mS.

JasonC SBB

0.5* at 7200 RPM is 12 us.

Joe Perez

iTrader: (8)

Simple math, really.

7,000 RPM is 117 revolutions per second, or put another way, 42,000° of crank rotation per second.

So one degree of crank rotation is 1/42000 of a second, or about 0.024 milliseconds.

Thus, your 0.02ms error is slightly less than one degree. That's pretty trivial.


edit: Jason beats me to it.

kingofl337

And Now I Know

So, being off .5deg at 7200rpm is probably ok?

Thanks Guys

Ben

iTrader: (33)

If it's late, probably fine because you can tune around that. If there's added jitter, then do not want.

Matt Cramer

If it's ALWAYS 0.02 ms too late, you might be able to build some compensation factor into the software.