[Jama]

This board seems nice! https://wiki.autosportlabs.com/CoilX

Edit: with screenshot of the schematic

I built that without the inverting op-amp on the end and it worked well.

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[PSIG]

This board seems nice! https://wiki.autosportlabs.com/CoilX

Interesting take on the concept, and a boost in the Zener voltage. As @Jama showed, Speeduino does not need the inverting opamp. I also noted along with raising the Zener to 110V, they also dropped the input capacitor. Hmm.

[dazq]

If you read on the ms site , there have been many component variations of this circuit over the years, different installs needing tweeks here and there .that circuit I used started life with ms avr , an avr offshoot of ms that went on to become vems!

[Sunglasses]

Just out of curiosity:

romP44's design looks like it will attach to the VR conditioner headers. I really like the idea to have it all compact in one place and just pull the small board out and put in another if I upgraded to a VR sensor.

But I would have concerns to route the coil negative through a Speeduino board. I read that the outputs of VR sensors can also reach amplitudes like 300 V which would be a sufficient range for the coil negative.

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This is a section of a UA4C board where it crosses the Arduino headers. I maked the traces according to the RPM+ / RPM - inputs. For my taste the distance to the solder pads would be very small to run such a voltage. Or is the solder mask good enough to withstand?

And secondly: Maybe it is my paranoia of electromagnetic interference, but I have a feeling that a periodic signal from a VR sensor is is a little more gentle on the circuitry than a surge spike, especially if the traces run nearby others which can pick up the disturbed signals.

Can anyone eliminate my concerns?

[PSIG]

... Maybe it is my paranoia of electromagnetic interference, but I have a feeling that a periodic signal from a VR sensor is is a little more gentle on the circuitry than a surge spike, especially if the traces run nearby others which can pick up the disturbed signals.

Can anyone eliminate my concerns?

IMO, your concerns are valid, and is among reasons ignition coil drivers are not commonly placed inside the ECU case. Likewise, strong signals are avoided in parallel traces for similar reasons. However, as there are so many factors involved in EMI, the effects are unknown until tested. Also, there is nothing saying you cannot place the conditioner circuit (or HV part of it) outboard of Speeduino, much like most ignition drivers are placed outboard or near the coils. I say to do whatever makes you giggle.

David

[Sunglasses]

Exactly, that is the point. I would not mind having this circuitry anywhere outside of the ECU, just like dazq or Jama reported earlier.
But inside the ECU case it is a different story. Of course it could work without issues but it depends, as always.

I think about trying it myself, to monitor some data before doing the conversion to EFI. I only wanted to give a quiet warning before romP44 makes a truckload of these

[romP44]

You are right, on UA4C it seems very close.
On NO2C, it seems bigger, so probably not an issue with this board.

[romP44]

Some progress on the PCB based on CoilX schematic.
Here is the gerber:

gerber.zip

(26.24 KiB) Downloaded 50 times

Feel free to comment it.

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[dazq]

You know you really don't need the opamp, it will work perfectly ok without

[romP44]

The op amp is used as a Schmitt trigger. Could avoid false detection thanks to hysteresis (belt and braces ).