I was surprised at the size of the capacitors
  so that added a bit of square inches to the
  PC board. Back in the old days (60's) we used
  large metal can capacitors that were oil filled
  for our CD systems and vac tubes of course.

  Those caps store the spark energy instead of
  being stored in the coils. CD coils
  run cool as they are simply used as pulse
  transformers.

  Boards cost about 65 cents per square inch
  Plus a fixed cost of $55 for tooling.

  The caps are the 4 big boxes in the center of the PC
  Board. I'll use my favorite heat sink and
  TV connector for the output to the coil.
  This is for one spark plug on one rotor.
  The trailing plug does not need it and
  and any back up ignition can be used on the
  trailing rotor.

  This requires 4 Hall Effect devices
  per plug to trigger every 10 degrees for
  40 degrees after 22 degrees BTDC.
  In other words 20 BTDC, 10 BTDC, TDC and
  10 degrees after TDC with no RPM limit
  such as MSD's have problems with.
  One cap for each spark.

  The whole idea here is to see if it will
  cut the fuel burn.

  I'll see if I can get Mazdatrix to test it on
  the dyno. I'll loan it to them for use on
  what ever engine they are fooling with at
  the moment.

  It uses one 400 watt 220 Volt AC off the shelf 12 V power
  supply for up to 6 PC boards if you want to implement
  that many on a 3 rotor.

  Paul Lamar

It would appear that isolation devices are needed between the four 2mfd caps
and the coil.  When trigger is low, there is a low impedance to ground thru
the lower FET of the half-bridge, essentially putting the caps of the
untriggered drivers in parallel with the coil.

  Victor Roberts,

Yes I see what you are saying. It is helpful I have other engineers looking
over my shoulder.

I need some more switches in there.
Thanks Victor. Do you have any suggested circuits?

Paul Lamar

The current configuration still leaves the 3 untriggered caps with one lead
open. This does not put them in parallel with the coil or am I missing
something?
Dick Handverger


Thanks Dick.
First condition.  All caps are fully charged through the coil.
This group is in series with the coil. The problem Victor pointed out was
when any lower gate closed all caps now in parallel would be discharged
through that gate bypassing the coil as that would be the path of
least resistance. The coil would see no current flow.

I think I need Triac's in series with all caps to prevent that from
happening so only the coil sees the sudden increase in current.

Triacs are bidirectional switches unlike most semiconductors.
They look like a relay contacts. Relays contacts don't care
which way the current flows.

All Triacs need to be on when no trigger pulse is occurring so
the caps can charge through the coils. Only the Triac that
is associated with the trigger pulse stays on when the trigger
occurs.

I have yet to figure out the logic on how to do that
short of a computer. Any suggestions?

Here is an incremented schematic.

Paul Lamar