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By dener0987
#53128
Hey guys

I bought a module msd 6al. I was researching how I could wire and configure it.
I found this link in the megasquirt manual http://www.megamanual.com/ms2/msd6a.htm
In the wiring diagram shown it says to make a drive circuit with an IGBT and plug in the white wire. But I was wondering if I can't use the TC4424 itself to trigger the MSD. When configuring, I would put the spark outputs triggers on Going High and the spark output mode on Single Channel, is my thinking correct?

Best regards
By dener0987
#53144
PSIG wrote: Thu Sep 16, 2021 11:46 pm That sounds correct to me.
OK thank you for answering.
Now I'm thinking how to set the dwell settings. In the ms2 manual it says to set the Maximum Dwell Duration to 25.5ms and the Maximum Spark Duration to 25.5ms too, but I don't know if this setting applies to speeduino as well. Do you have any idea how this can be set up?
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By PSIG
#53147
MS has the 50/50 to use, but Speedy does not. I don't use CDI much as it limits Lambda range, but I'd just do trial and error using a minimum dwell and working-up as it needs it. The durations will be reduced as RPM requires it.
By dener0987
#53149
PSIG wrote: Fri Sep 17, 2021 12:25 am MS has the 50/50 to use, but Speedy does not. I don't use CDI much as it limits Lambda range, but I'd just do trial and error using a minimum dwell and working-up as it needs it. The durations will be reduced as RPM requires it.
Ok, minimum dwell can be 1 ms maybe?
What about triggering the MSD with the speeduino's own ignition output without an igbt do you think there might be a problem?

thank you
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By PSIG
#53150
If you wanted to do it with calculation, then you could figure your max rpm firing time, allow 1ms for firing (discharge) duration and the rest of the available time for your "dwell". Alternatively, set your firing duration and virtually any value for dwell, and let Speeduino reduce those values as-required when time shrinks at high-rpm. I would investigate both paths for best results. IIRC, Speeduino cuts firing duration before dwell, which is backwards for performance with IDI systems, but may work fine with CDI. Real-world testing will tell.

The TC4424 should work great, as it is a push-pull (high-low) signal device with 2 internal MOSFETs per-channel that alternate signal between Vcc and ground. The diagram you referenced does not use an IGBT, but a standard small-signal BJT. The TC4424 should work well for signalling the MSD box, and is capable of signalling a variety of CDI trigger systems.

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