25-07-2020, 06:04 PM
If the ignition coil is on the backplate and has both primary and secondary coils, then it's independent of the battery anyway.
As the rotor turns, it will induce a voltage in both coils, though not enough to spark at the plug. But the way it works is, the primary is shorted anyway, by the points, and a current flows which opposes the approaching magnet. At the instant the points open, the current in the coil goes from something to nothing, which inductors don't like. So the secondary breaks down the air at the plug, a spark occurs, and current in the coil is maintained (a lot less, depending on the turns ratio, but then we can't have plug voltage at the points or else they would spark across in preference to the plug).
Trying to transistorise this would be rather difficult. Better to retain the points, and use an outboard coil, running from the battery.
As the rotor turns, it will induce a voltage in both coils, though not enough to spark at the plug. But the way it works is, the primary is shorted anyway, by the points, and a current flows which opposes the approaching magnet. At the instant the points open, the current in the coil goes from something to nothing, which inductors don't like. So the secondary breaks down the air at the plug, a spark occurs, and current in the coil is maintained (a lot less, depending on the turns ratio, but then we can't have plug voltage at the points or else they would spark across in preference to the plug).
Trying to transistorise this would be rather difficult. Better to retain the points, and use an outboard coil, running from the battery.
