tune coil

Posted on Feb 4, 2014

And normally tuning is not easy: you`ll fire the system up and try to notice the spark length, shut it off (and pull the plug!), re-tune (move the tap on the primary), fire it up again and try to remember the spark length of the run before, and do it all over and over again and again until the spark length is maximized. But things canbe much easie

tune coil
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r: by using a tuning coil, tuning can be done on-the-fly: online - while the system is sparking. You immediately can see if more or less turns will be optimum for the spark length. My tuning coil will give me something 0-20uH additional inductance. So I can tune (+/-20% from optimum value) my 2"-TC with 3 turns, my 4"-TC with 4 turns and the BlueThunder (10"-TC) with the full 21 turns. I`ll use a 12VDC motor (with gear box) to turn the moving tap (consisting of 6 spring loaded contacts) of the tuning coil. Up to now I tested it with 12V, amperage is only up to 200mA. Detecting the end positions will be a bit tricky. I`ll try to mount two levers which will be moved by the tap or better by the guided "block" at the axis so that the point of maximum inductance available can be adjusted. This levers will activate micro switches(EDSw1 and EDSw2) - of course well isolated from the voltage in the primary circuit. The isolated lever will have some mass and friction, so I perhaps have to load itby an additional spring to help thespring in the micro switch. The micro switches (EDSw1 and EDSw2) are intended to activate a bistable contactor (BiCo) which will change the direction of rotation. However the switches will activate the bistable contactor (BCo) not directly. There is a good reason to add an additional contactor (SwCo1 and SwCo2) for each end detection micro switch (EDSw1 and EDSw2). This is because of the way the tuning coil...

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