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. Bot switches
can never be on at the same time.  Also the AVR 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 happened to Heath Kit? I was looking for them a while ago and could not
find them.

Dale Davies


Out of biz probably.

Paul Lamar