Subject: Ignition triggers.
From: rotaryeng
Date: 8/31/2014, 9:59 AM
To: AA-1-Me



So I worked on updating the web site.

Please read and comment.

http://www.rotaryeng.net/coax.html


Paul Lamar


Paul,
   As I keep saying, his is too simple to work, but it does.   I
will have plenty of time to test one while I am waiting for my reduction box
to destruct, so will test a few including this in the process. When are
coils available??

Neil.

The kind you need for the Microtech EFI are still in R&D.
As soon as it works I'll let you know.

Paul Lamar

Paul,

Is it possible to put 2 units in the same metal box (the one that you put it in and pot it) to save space?
I am almost done with N45WE (Yay I have a plane again), and will soon get back to my rotary plane. I am working on the EFI but think it would simplify the system to have the ECU run the fuel system and let your system run the ignition. One concern:

The fixed ignition aircraft engines use 20~25 or so degrees as the fixed point with impulse couplings to delay the ignition during starting, and to let the spring speed up the rotation speed internally for a better spark. To make starting easier we would need to see if there is a way to incorporate the delay feature into the completed on-aircraft system I think. I am working on a Sonex also with the VW engine at 25 degrees fixed magneto timing. During starting I have to keep the mixture full lean until the engine is spinning as fast as it will go or it will kick back. A weak battery and it wont hardly start at all. If I delay the timing by as much as 10 degrees it starts better but with noticeably less power. Thoughts?

Kevin Alderman

It is a tight fit in a 2" by 3" box so putting two side by side would be about
the same.

Piece of cake with a micro computer :)

I got the Bascom book on the AVR. Here are some scans.

Super simple. My Golden Retriever Suzzy could learn to program in BASIC :)



Paul Lamar

I was leaning toward keeping the ignition separate from the ECU for several reasons RFI and noise among the most prevalent ones, but you are right sending a trigger signal would be no problem with the ECU. The trigger you are working on, will it take the single trigger and use that to initiate a 6 or so firing sequence or do I need to program 6 pulses from the ECU to make it work? The OEM computers that you are trying to interface with only send a single pulse, so I am assuming that the multiple triggers have to be taken care of internally to your system?

Kevin Alderman


Good idea. That spark plug and wire make one heck of a transmitter and
transmitting antenna.

Here are the scans right side up :)

The new trigger in R&D will take a pulse from a computer designed to fire
a smart coil like the RX8 coil or an LS1 coil. If it works :) These coil have delays
anywhere from 2 ms to 10 ms.

At 8000 RPM that is a lot of degrees :)

Paul Lamar

I understand what you are saying about the RX8 style trigger, and my code so far has a variable timing pulse depending on RPM and MAP. When the engine RPM is low the advance is right now at 5 deg, max at 25 deg, and under boost comes down to 10 deg for now. That might go up a little during testing. But like most ECUs I only send one trigger pulse. If your system will fire say 6 times at 8000 rpm, then it needs multiple signals to keep firing. This will likely come from hardware i.e. the trigger wheel, a programmed multiple pulse trigger in the ECU (only if you have access to the code) or if you are replacing the coil in say an RX8 the signal will have to come from inside your ignition since the RX8 ECU wont be programmed to do that. For simplicity I see a small ECU that will act as a controller for your ignition- it will take the signal from the ECU and provide the successive pulses to continue firing. This would solve several problems I think- if the ECU is sending a +5 of -5V pulse, the controller would take this signal, calculate RPM and send the successive firing signal pulses. Plug and play if you will. Your controller would simply plug into the trigger from the current coil, convert this signal to what it needs and off it goes.

Kevin Alderman


Yes that is what I am working on in R&D. Here is the current schematic.

However the current LI ignition will fire when you tell it. No delay. You can fire it onces or
fire it six times. You can fire it every 5 degrees or every one degree six times.
All it takes is a 5 usec (micro second) positive going 12 Volt pulse. You can
use the 2nd gen CAS to trigger the CPU and the CPU can then fire my ignition
multiple times. To condition the 5 volt pulse use a 2N7000 with a pull up to
12 volts.

Paul Lamar

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