The traditional CD ignition uses a switching power supply to develop
the 300 volts used to charge the capacitor. That is the main reason
they are so expensive. I come up with one idea a day. Not always
new however. I spent quite a bit of time trying to build such
a switching supply with less than satisfactory results. It worked
most of the time but not always.

I used a chip called a half bridge driver that was supposed to do the job.
Every once in a while it would turn on both the high side and low side switches
with disastrous results.  When hooked to a car battery as much as 100 amps
could flow through the circuit.  Not a good thing. Of course it literally
exploded. The early Aussie CD ignition had the same problems.

My idea is use a cheap AVR board to do the half bridge driver job and
things can be controlled down to several nanoseconds. Both switches can
never be on at the same time.  Also the AVR's A to D's
can be used to monitor what is happening and shut the silly thing off if
things start to get out of hand.

Way back in the 70's and 80's we used the circuit
called "DC-power-supply" which was fairly reliable. I think Heath Kit was making
a CD ignition kit in those days. My use of CD's goes back further than that to the
days of the vacuum tube thyratron in the 1950's.


Paul Lamar

What is this thing you call 'vacuum tube?'

John Duncan                   

http://en.wikipedia.org/wiki/Vacuum_tube

"In electronics, a vacuum tube, electron tube (in North America), or
thermionic valve (elsewhere, especially in Britain), reduced to simply
"tube" or "valve" in everyday parlance, is a device that relies on the flow
of electric current through a vacuum. Vacuum tubes may be used for
rectification, amplification, switching, or similar processing or creation
of electrical signals. Vacuum tubes rely on thermionic emission of electrons
from a hot filament or cathode, that then travel through a vacuum toward the
anode (commonly called the plate), which is held at a positive voltage
relative to the cathode. Additional electrodes interposed between the
cathode and anode can alter the current, giving the tube the ability to
amplify and switch."

http://en.wikipedia.org/wiki/Thyratron

"A thyratron is a type of gas filled tube used as a high energy electrical
switch and controlled rectifier. Triode, tetrode and pentode variations of
the thyratron have been manufactured in the past, though most are of the
triode design. Because of the gas fill, thyratrons can handle much greater
currents than similar hard vacuum valves/tubes since the positive ions carry
considerable current. Gases used include mercury vapor, xenon, neon, and (in
special high-voltage applications or applications requiring very short
switching times) hydrogen.[1] Unlike a vacuum tube, a thyratron cannot be
used to amplify signals linearly."

Paul Lamar