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Variable ignition interrupt circuit?

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halvoric

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Hi, I am not an EE, but a motorsports enthusiast and hobbyist. Hope I can get some help here.

My project is to design and build a circuit to interrupt the spark ignition in a two-cycle IC engine, for a single (but adjustable in On and OFF portions relative to trigger event) pulse in the 20 to 500ms range. The purpose of this circuit is to enable a "Wide Open Throttle" gear shift (aka "flat shift"). The idea is to trigger the circuit with a microswitch that closes at the beginning of the mechanical gear linkage motion cycle, so that the ignition cuts out momentarily (slightly unloading the gear train) just as the gear-change mechanism is applying force to the gear change shafts. (In this application the clutch is not needed or used except for starts from a dead stop.)

The application uses a solid-state (capacitive discharge) ignition circuit, exciter coil, pulse coil, and ignition coil. My plan is to have my circuit close the "kill-switch" circuit, which is a normally-open circuit between the exciter coil and system ground. I believe this "kill-switch" circuit, when closed (and when the engine is running), shorts a 100-200VAC current (from the exciter coil) to ground.

I think that given these application variables I need the following design parameters:
Power for my circuit (9VDC would be best);
Ability for microswitch input to trigger shorting of VAC circuit (solid-state relay?);
Ability to adjust delay between microswitch closure and shorting pulse ON event from 0 to 500ms, regardless of whether trigger microswitch is closed or open;
Ability to adjust shorting pulse OFF event (duration of pulse) between 20ms and 500ms, regardless of whether trigger microswitch is closed or open;
Circuit must reset (go back to ready state) 200ms after pulse OFF, regardless of trigger microswitch still being closed;
Would be nice to debounce or isolate the circuit from microswitch noise.

I think a 555 timer and a SSR is the way to do it, as a monostable multivibrator (one-shot) where the output of the 555 switches the relay on and off. I found a circuit that uses two pots (cermet?) and two diodes (zener?) to make the ON and OFF output of the 555 adjustable.

Any ideas or thoughts? TIA
 
A few other points: I'm not certain the circuit to be grounded (or interrupted) is AC or DC. The ignition could also be interrupted by opening the circuit between the exciter coil and CDI unit.

Also, would it be better to accomplish this subsecond switching with MOSFETs and a logic gate rather than a 555 timed SSR relay?
 
On second thought, there is no option to interrupt the exciter coil circuit to the ignition coil. I have to accomplish it by closing the connection to ground, kill switch circuit.

Any help?
 
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