Looks reasonable the way it changes, but what do the numbers mean, is it degrees before the plug fires?
Looks reasonable the way it changes, but what do the numbers mean, is it degrees before the plug fires?
Even if we found dwell settings, and hack PCM to control dwell, at higher rpm we are doomed.
Since there will be overlap at coil charge. At any high rpm sitiuation there will be at least two coils that needs to charge simultaneously with 50% overlap.
So controlling 8 coils dwell with one est signal is not possible. We need at least two, preferably 4 est signals from PCM to make it work.
Kur4o, I think coil charging can be altered with a firmware-designed RPM switch (or dwell switch) installed in the LTCC unit. Not the smoothest method, but effective. Someone probably has a better idea, but this is just off the top of my head.
As I mentioned a few posts back the only thing I intend to do with the EST line is watch for the falling edge to know when to fire the currently sequenced coil that will already be charged. Also to get a running "picture" of spark advance.
Multiplexing or gating the EST line may be what it will fall back to for limp mode / loss of high res signal.
The more I think about this the more I'm tempted to also monitor ECT, MAP and possibly TPS. But I need to get it measuring RPM and spark advance first.
edti: I'm curious if anyone has a dead opti from a 94 or newer they'd be willing to part with. I have an extra optical sensor so I'd just need the wheel, spindle and hub minimally.
Last edited by spfautsch; 11-15-2017 at 09:33 PM.
Yes, it is possible. Ignore the rising edge of the EST signal. Don't use the EST line to signal coil charging at all. Instead, only use the falling edge of the EST signal inside the external module. The falling edges are always 90* apart plus or minus any timing change occurring.Originally Posted by kur4o
You do bring up an interesting point. Are there enough spare I/O lines to add the wiring for 8 coils? If there are, it could be possible to add the code for the 8 coils into the PCM. Not easy, but maybe possible.
Here are some pics of the board with the TPU processor.
Any help will be appreciated.
Current progress on an Atmega328 @ 16mhz demonstrating simulator mode: video 12.9 MB
Sorry for the shoddy camera work and mix-and-match leds, couldn't find my tripod and my led supply is dwindling.
This is targeting 4.5ms dwell @ 12v nominal. I'm no longer very familiar with "default" microsoft media players but with mplayer you can pause and then go forward frame by frame using the period key. At 3500 rpm at reduced time reference you can see two "coils" dwelling at once, and at 7000 three. Lower left led is #1.
Last edited by spfautsch; 12-04-2017 at 02:43 PM. Reason: fix urls
Now driving 3 GM 12658183 coils: video 27.0 MB
Again, apologies for the poor camera work. Only circuit change is addition of a tach driver pin on Arduino analog 0 - the yellow led I point to in the beginning. From left to right the plugs represent 4, 8 and 1.
Having seen some spontaneous Arduino resets occur with other projects that were triggered by commanding an a/c induction motor off, I'm somewhat surprised to see none here with all the electrons flying around and no noise suppression caps anywhere. After 5-10 minutes of running the simulation the coils get fairly warm (~120F) but the Atmega and the 5v regulator are cool to the touch. I haven't measured trigger current to verify but it seems like this will work fine driving these coils directly from the microcontroller outputs.
Similar to the dwell limiting on the truck coils, if you pause during the last low speed simulation sequence and step frame by frame you can see the coils firing (#1 is the bright white led) before the microcontroller has pulled the pin low and turned off the led. I don't have the necessary test equipment to measure when the dwell limiting is firing the coil, but it clearly is. So I don't think its safe to assume any of the LS coils have a "soft" dwell limiting system. Whatever the case, I doubt it will be a problem in a working application and if it is the dwell target can be easily adjusted.
Hoping to test out sequence detection on my car soon - hopefully this week. If that functions all that's left is to add voltage detection which should be dead simple. I don't want to count my chickens too soon but if everything works out I might be able to test fire the thing before I pull the engine out after the holidays.
Last edited by spfautsch; 12-04-2017 at 02:43 PM. Reason: fixed url
Good to hear you're making progress but your video links don't work. 3 coils have to dwell at a time at high rpm? Sure illustrates the limits with a single coil.
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