A new ignition circuit

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I attempted to use an Arduiuo to control the timing advance of my model engine and could never get it working. the Electromagnetic Interference from the ingition system always (eventually) killed the micro controller. I went from a CDI to a TCI (transistor controlled ignition) which was supposed to be quiter from an EMI standpoint. I used resistor spark plugs, I used a ballast resistor, I isolated the microcontroller, I used lots of local decoupling caps and an inductor isolation circuit with an encolsed metal case, I used a seperate battery and opto isolators.... I spent way too much time trying to get it to work until I finally abandoned the project. If you can get the arduino working, you need to let me know what you did. I wrote some really neat code to control the spark advance, but to no avail. Good Luck.
Your experience with Electromagnetic Interference (EMI) struck a resonance with me. Ignition systems generate an unbelievable amount of high-frequency energy that can couple into any circuit they happen to be near. Analyzing coupling between circuits is anything but intuitive. I spent a good part of a 40-year career dealing with EMI in aircraft avionics systems, and it can be done, but it's a humbling experience. H-field (magnetic) coupling is the culprit more often than not. Visualize the path the spark current takes and how it might couple to the control circuitry, either through common impedance (like a common ground path) or by H-field coupling (like between parallel wire runs). Try to assure a single-point ground reference between the spark stuff and the control stuff, and keep the control stuff away from the spark current path.

Experiment. You will probably be amazed at what actually works! Good luck.

Who cares who it offends! If thats what you want to do then thats what you do. I would love to see it completed. Better idea! Go with dual plugs and 10 coils! Hahahaha!!!!
I agree also don’t forget the spark plug wires automotive wires are 7 or 8 mm although the big top fuel magneto wires can be even bigger they can dwarf the intake manifold tubes on model engines .
The Person Steve mentioned in post 255 is Dave Bowes. His engine is called EVIC and has had various iterations. A pretty impressive project.
He has electronically controlled solenoid valves and practically everything else. The control circuitry has SEVERAL PIC processors. He has become the master at eliminating EMI and RFI from his circuitry. So it can be done.
I believe he wrote a couple of articles for Strictly IC, Home Shop Machinist and Model Engine Builder.
Not sure why the link to his web page shows up as "index" but here it is.
I see he commented with some suggestions in the next post.
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Some tricks to making electronics immune to spark EMI/RFI:
Put a 10K carbon comp resistor in the HV wire to the spark plug as close to the plug as possible.
Use an EMI filter on the input to the micro from the Hall Effect position sensor. Digi-Key part # M9935CT-ND
Put ferrite sleeves on all the wires to the micro board including power leads, sensor leads and any leads to external devices like LEDs or displays. Digi-Ket part # 240-2112-ND
Twist all wires to and from the micro bord including those to sensors, battery wires, etc.
Not sure the Digi-Key part numbers are still current since I haven't ordered them for a few years.
Hope this helps. If you still have problems contact me directly.
Dave Bowes

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