Do you plan on testing the ignition system that you designed as well
as the
555 EFI?  Any time frame?

Joe Berki
Limo EZ

Yes. I have everything I need to test that. I am not sure when I'll
get to it. Here is the idea for the new guys.

These are inductive coils and they normally require a computer.
Inductive coils are turned on for a period of time and then
they fire when the current is suddenly turned off. This off time
is called dwell. If the dwell is too long the coils over heat.
If too short you don't get full spark energy.

The breakthrough on how to make this stand alone and work without
a computer just occurred to me. The trick is to slot the trigger
wheel and use a  IR photo transistor, an IR emitter LED and FET switch
instead of a magnetic pickup or Hall Effect sensor. These devices
put out a single narrow pulse. Not what we need.

When the IR photo transistor sees the infra red emissions from the
IR LED it turns the coil current on using a high voltage FET solid
state switch. In the case of the GM coil the FET is built in. I used
something like this for years on my computerized road test equipment
and it is very reliable and durable. Also tolerant of dirt and dust.

It will work with just about any stock inductive plug on coil system
including the Corvette GM coils. The length of the slot controls the
dwell time. The end of the slot controls when the coil fires.

I have been thinking about this problem ever since the stand alone
coil on plug systems first appeared. How do we get rid of
the computer?

If you want to fire the leading and trailing plugs at different
times you can use four slots with four photo TX's and four
LED's other wise each photo TX fires both leading and trailing
plug coils at the same time.

Now some of you electronic types might say "why not just
use a 555 one shot with a fixed pulse width to turn on
the current in the coil for a fixed period of time triggered
by a magnetic sensor or Hall Effect "?

The problem with that is the spark timing will vary with RPM.
You want the plugs to fire at 22 degrees TDC over a wide range of
RPM's so that approach will not work.

Basically this thing works like distributer points.

Aircraft engines run in a very narrow load band so a 22 deg fixed advance
is typically used. Aircraft engines run in cruise mode 99% of
the time with a fixed prop load unlike an auto engine that runs
at 40 HP while driving down the freeway  and variable load during
acceleration and hill climbing.

Once the current in the coil (charging) reaches a peak the spark energy
is independent of the time it takes to fully charge the coil.
The GM coils are fully charged in 5 ms.

We are not looking for ultimate sophistication here. We are looking
for a simple cheap ignition system to use with a carburetor.

I have the GM DS580 part number 12558948 coil.

That works. I got it to fire every 2 seconds or 30 RPM with a dwell
time of 1 second. Also at a voltage of only 6 volts. I am impressed.

It does not automatically fire at 100 ms. That was a false alarm.

This thing is working so well I can't believe it.
I won't need a slot or movable segment  in the trigger wheel at all.
Just a 180 deg tab sticking out which will lower the cost of a laser
or water jet cut disk. As you can see from this scope picture
(img 1023) it fires on the rising edge. The tab is 180 degrees.
The spark last for about 1/2 msecond.

Super simple and super cheap for an ignition system.

I'll redraw the disk after Christmas as I am leaving for
Robin's cousin's hous for a few days.

Merry Christmas

Paul Lamar