barnbiketom
newbie
Reged: Nov 06 2009
Posts: 2
Loc: NW Pennsylvania
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Hi all! I'm searching for an AUDIBLE way to tell when the ignition points open, to time motorcycles with magneto ignition. You time the engine by moving the points thru a small window in flywheel. ( no battery in the system, just flywheel w/ magnets, points,condensor, primary coil, and secondary coil). I currently use a self-powered light and CLOSELY WATCH the brighness of the bulb but therein lies he problem..the difference between points open and points closed is very minute in terms of circuit resistance and sometimes almost impossible to tell when the points open!! the primary coil can not be removed from the circuit, since it is under the flywheel and connected in parallel to the points.
in most instances, when using an ohmmeter, points closed indicate 0-.5 ohms.
when the points open, it indicates 1.5 to 2.0 ohms!! that reading is because the primary coil is internal to the flywheel and can't be disconnected for the timing check!
There is a "BUZZ BOX" available but i would rather build my own. with an oscillator or buzzer??
any ideas ?? thank you in advance..tom
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mackortoyota
rookie
Reged: Jun 02 2009
Posts: 80
Loc: Ohio
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Okay I adapted a circuits to have a threshold of about an ohm. Below this the led is on, above this it turns off. You could add a transistor controlling a little buzzer
across the led output. 
I adapted from the following circuit from Dave: dc current indicator.
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Xubuntu 9.04 for the win.
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barnbiketom
newbie
Reged: Nov 06 2009
Posts: 2
Loc: NW Pennsylvania
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that is really neat! But I am concerned that some bikes or engines may have different readings, maybe some have both readings under 1 ohm...others may have 1.x ohm closed and 1.XX open. I was thinking more of an oscillator of some sort with a CHANGING tone in relation to the open/closed points. simply CHANGE in tone will suffice.
If not that then is there a way to guarantee any circuit to operate in any circumstance..???
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