Home › Forum › Ask A Member › Onto a new learning curve…CD ignition › Re: Onto a new learning curve…CD ignition
Diodes are one-way electrical valves, used to convert AC to DC, and capacitors are electrical storage tanks. Caps only store DC, they cannot store AC. Magnetos / CDI ignitions all produce AC, at their heart.
So you connect the diode-capacitor circuit across the leads from the flywheel coils to the power pack, the same leads you’d measure with one of the fancy DVA testers, and give the motor a few spins.
When the flywheel magnet & coil produce an AC pulse, it’s converted to DC by the diode and stored in the capacitor as a DC voltage – and there it remains. You then read that voltage stored in the cap (with your meter), as it is approximately equal to the highest level of the AC pulse.
Did that make sense?
BTW – no capacitor is perfect, nor is any diode a "leak-proof" valve. So the voltage stored on the cap will start to bleed-off, right away.. best to measure it ASAP. And believe it or not, just +measuring+ it will cause it to bleed off faster – that’s because the meter itself must tap some electrical energy just to generate a reading! Even in a digital meter, where there’s no meter movement to drive, the meter still sucks down the voltage..