Re: Paging the old ignition gurus (long).

On Sun, 06 Sep 2009 23:26:16 +0100, Harry Bloomfield
<harry.m1byt@xxxxxxxxxxxxxxxxxxxx> wrote:

T i m was thinking very hard :
Indeed. I *think* the trigger coil is set at 90 degrees to all the
other coils so not directly affected by the rotor magnets. However,
between one pair of magnets there are two soft iron fingers that reach
from adjacent magnets, creating a magnetic field, parallel to the gap
between said two magnets (so also at 90 degrees to them and now
parallel to the trigger coil).

I would hazard a guess that the range of what is needed as a trigger
pulse would have quite large margins. Probably something as simple as a
12v battery with a 100uF cap in series, then fed to the trigger input
would be enough to cause it to fire, when connected briefly.

Understood.

Add a 10k
resistor across the cap to discharge it and it would then be able to
repeatedly fire it.

Ok.

Maybe a home made impulse signal generator would
provide a means of firing it at regular intervals -All very much guess
work, but a starting point.

I may have a similar trigger coil from an old stator I could try when
I get the spare CDI unit.

Getting back to the heavy duty coils....

Are we assuming these feed the ignition unit directly, or that it is
fed from the 12v rectified DC? If the latter obviously you cannot
simply feed this from a transformer.

Indeed. I believe the *heavy* heavy duty coils feed the rectifier >
battery / lights etc

I think I understand the other single coil feeds the capacitor
(probably through a single diode or bridge). This was the one that
produced the most voltage from my hand rotation of the flywheel. This
would be the cct I would simulate with a transformer.

Cheers, T i m
.

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