I cut the voltage to 420 from 560 because I have not received the 650
Volt 1 mF
capacitors yet. This is about 1000 RPM. Watch the movie and you can see
the blue flashes in the middle of the screen. The circuit is basically
the same
as the outboard/Vespa circuit but the high voltage power supply works off
a 110 volt wall socket instead of a charging coil. I am using the latest
hi tech solid state switch called an IGBT instead of an SCR shown in the
outboard schematic.
IGBT Insulated-gate bipolar transistor is a three-terminal power
semiconductor device
primarily forming an electronic switch and in newer devices is noted
for combining
high efficiency and fast switching. It will dump up to 50 amps through
the coil primary
winding in less than a microsecond. The coil is basically used as a
pulse transformer
so it runs much cooler than when used in an inductive mode. It also
fires immediately so
there is no dwell time needed. In this set up I am using a stock 2nd
gen Mazda coil
with out the igniter.
The 1 mF 450 Volt cap is charging through a 1.5 K resistor hence the
visible charging curve
you see on the O-scope. This high value resistor may not work at the
higher RPM's but
prevents the IGBT from shorting the high voltage supply. I plan to
experiment with a choke instead.
Paul Lamar
Congratulations on the spark!
Henry
Thanks henry. What do you think of putting a diode across the coil
to aglow the coil to ring?
Paul Lamar
Paul,
I assume that you are using a circuit similar to the Mariner Ignition. I
also assume that you are thinking about back emf, creating a high
voltage spike at the end of the discharge cycle. I would say that you
can add a diode to prevent high voltage on the cap, but I don't think
you have too much of a problem as capacitors can discharge most of its
energy rather quickly. Once the energy is discharged, and used up
immediately as a spark on the secondary side, the remaining voltage, and
current, if any, from the capacitor should be limited, and it can be
dissipated through the primary winding to the ground rather quickly.
Especially when you notice that there is not much heat building up on
the coil.
So my two cents: The ringing is most likely a minor issue, but it does
not hurt to add a diode there.
Henry
Yes on the Mariner circuit. Here it is. IGBT instead of SCR.
Paul Lamar
