Well, I am working on a similar project, but have very little time. Still in the planning stage. To start with, you need this transistor to fire your coils (8 of them) https://www.google.com/url?sa=t&rct=...qY24EtGtItbi9g
IRGB14C40L is a to-220 package protected on all sides with zener diodes, overcurrent protection, and can handle 14A with a proper heatsink. very tough and hard to kill, except for thermal destruction. A positive 5v pulse on the gate triggers it. dwell time is not controlled. Just a slave unit. All oem manufacturers use this one....ALL.
Newark or digikey or mouser should have some decent prices.
Read this page on LT-1 electrical specs and optispark decoding. http://chevythunder.com/lt1_electrical_page.htm
LOW RESOLUTION SIGNAL:
Cylinder # 8: 7 edge counts wide (from Hi-res signal)
Cylinder #3: 12 edge counts wide
Cylinder #5: 17 edge counts wide
Cylinder #2: 22 edge counts wide
The other cylinders between these (1,4,6,7)= 2 edge counts
The next item I intend to use is an 1-to-8 demultiplexer, sometimes called a data distributor. I will use this data switch to redirect the ignition module's FIRE signal to the 8 transistors listed above. That way, I can still let the ECM control the dwell time. easy-peasey.
The hard part: making a counter-convertor for the optispark signals. I can deal with the 2 signals by gating them to one another with an "and" gate. Then I decode the counts to decide which cylinder to switch to with a decade counter. Use an edge-trigger strategy for both positive and negative going pulses. The problem is that between the pulses is a single 2 count slot. Shouldn't be too much trouble if I switch the "and" gate off with the 1st decode, and count the starting edge pulses from then on as TDC.
My time is still limited by the fact that I am chasing a toddler around these days.
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