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That ignitor module (Read 123 times)
FinnHammer
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Re: That ignitor module
Reply #15 - 06/16/25 at 11:27:06
 
I just took a scope picture of one full cycle of ignition timing, and the result showed that the engine, cranked by the starter, (sparkplug removed) rotates at 5.868Hz (cycles per second) corresponding to 352 RPM.

Looking closer at the previous closeup of the timing peaks reveals that there is more like 16 mS between the peaks.

Calculating like before. I get the first peak to arrive 34deg before the other. If that last one is positioned 3 deg. before TDC as Mike has shown in his ignition curve thread, then it means that a stock system can time from 37deg. before TDC.
But it would not be difficult to mount small neodynium magnets exactly where they are desired to be, to place the trigger pulses at appropriate timing points.
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FinnHammer
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Re: That ignitor module
Reply #16 - Yesterday at 11:14:08
 
I am back here with a report about the Ignitors way of handling the ignition timing, during start and during driving.
And does it have a cut off function at 10K RPM?
There are 2 synchronization pulses coming into the module, one positive, one negative, and it was my theory that by applying 12V to the module via the black wire from the starter relay, the negative one of these pulses would be chosen to time the spark early. And when this voltage is removed as the starter relay is disengaged, then the ignitor picks the positive pulse as the timing reference.
Initially, this seemed like a trivial task to perform, but It was not. My function generator, although (or perhaps exactly because) it is an advanced one, could easily generate the required train of pulses, but only up to +- 10Volts, so I had to design a level shifter that could boost the output to +-31V, this voltage being the limit of my bench supply.
The picture here shows the schematic of the level shifter, with the floating battery driven gate driver supplies needed to make the 2 MosFets switch reliably.
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Level_shifter_circuit_diagram.jpg

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Re: That ignitor module
Reply #17 - Yesterday at 11:14:17
 
So far so good, I now have the circuit built on a makeshift breadboard, not pretty, but it works.
The test rig looks like this: It contains the level shifter, with the associated batteries, to the left. At the botton the +-31 volt supply is connected.
Top right is the terminal strip where the Ignitor module is connected, and the small square dot left of it is the switch which can supply 12V to the black wire.
Left of the rig is the 12V supply to the Module.
All in all 5 power supplies to perform this task.
(And at this point, I am still nervous that I shall fry the module when I turn the supplies on)
Top right in the picture is the high voltage probe, which will measure the voltage drop on a resistor that is acting as stand in for the ignition coil primary coil. At this point I am not interested in generating sparks with the associated high voltage ballihoo. I just need a voltage step indicating if the current through the ignitor is interrupted. This means that the voltage across th resistor will be 12V when the coil is charged, and it drops to 0V when the ignitor disconnects the coil.
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The_test_rig.jpg

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Re: That ignitor module
Reply #18 - Yesterday at 11:14:27
 
This scope picture shows the relevant waveforms for the test.
Yellow and cyan traces show the signals out of the function generator, the magenta trace shows the signal out of the level shifter. The level shifter not only boosts the voltage to +-31 volts, it also combines the 2 discrete pulses coming from the function generator.
When I took this picture the voltage was turned down to +- 10 volta, one cannot be too carefull.....
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The_relevant_Waveforms.jpg

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Re: That ignitor module
Reply #19 - Yesterday at 11:14:37
 
The tests did not bring any usefull conclusions.
Even after reconfiguring the test bench to supply +-60V into the trigger input, did I manage to make the module respond to the trigger signal in an even remotely coherent manner.
The only exception being at 3000RPM, where it locked in and produced reliable trigger: and where there is enough time to establish a current through the coil for the successive firing.

It is true that my trigger signals are pure square waves, whereas the signal from the timing coil of the bike are more like sinusoidal. This may be the culprit, although it is beyond mee how a comparator can miss a fast pulse.
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good_3000RPM.jpg

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Re: That ignitor module
Reply #20 - Yesterday at 11:14:50
 
But just as often it would go like this: No ringing, no spark.
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Bad_3000_RPM.jpg

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Re: That ignitor module
Reply #21 - Yesterday at 11:15:10
 
Then there were the most frequent response which would occour over the range of revs, like this totally erratic response.
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Re: That ignitor module
Reply #22 - Yesterday at 11:15:28
 
Just as a reminder, I made a mock up of a traditional points breaker ignition system: A 4.5mH coil (the flat disk which is a high voltage transformer coil I made a couple of years ago), a 300nF capacitor and a nice little switch (the black square thing) hooked across the capacitor, just like a breaker point.
This is what it looks like in hardware:
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Conventional_system_mockup.jpg

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Re: That ignitor module
Reply #23 - Yesterday at 11:15:39
 
When the switch is opened, and current stops flowing into it,  it is a property of a coil, that it will try to maintain this current flow. To this end, it induces a voltage large enough to do so, and with this voltage it drives a current into charging the capacitor, spending the magnetic field in it during the process. When the coil is demagnetized, it is the capacitors turn to act, and it discharges through the coil, depleting the energy it had stored, and building the magnetic field back in the coil. Only a bit of the energy is lost due to the resistance in the coil.
Like a seesaw, this goes on and on untill eventually all energy is lost as heat.
This is a well known phenomenon, it is called the LC ressonant ringdown, and it was waveforms like this I was hoping to see.
I will have to do some measurements with the module in the bike to try to find out what I am missing.

If you feel like diving a bit deeper into the function of the good old points breaker system, here is the absolute best article I have found that covers the subject:


https://ttypes.org/conventional-ignition-systems/

To be continued
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The_ringdown.jpg

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