Hi ChrisHelvey,
The Briggs magneto has both a moving magnet and under the flywheel you have a set of conventional contact points. When the points open the magneto fires.
Automotive computer ignition systems typicaly have 2 input sensors to detect crankshaft position, one provides a TDC reference signal and the other is ofset so as to provide the signal to fire. The second signal actually is several degrees in advance of tdc and is the signal which gets delayed, but never later than the tdc signal.
I think a good approach would to be to follow that example. You could build a lookup table to provide an advance curve, based upon RPM.
A small disc with 1 or 2 holes could be used to trigger 1 or 2 photo transistor sensors, installed in place of the contact points. I say 1 or 2 because you could use 2 sensors and 1 hole or 1 sensor and 2 holes to get 2 distinct signal pulses.
Home Machinest Magazine had an pic controlled gasoline engine featured a few months back which had solinoid valves instead of a camshaft and was equipped with electronic ignition. Here is a website featuring the authors engine: http://rbowes1.11net.com/dbowes/
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
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There simply is no "Happy Spam" If you do it you will disappear from this forum.
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