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Any questions you have before you begin buying, building and installing.
You should really start your own project. :)

The 123 will only be useful for a fuel signal. You would still need the 123 to control the ignition.

You will need to determine the pulse the 123 is sending to the coil, and I would suggest it is probably best set up as a distributor .

This link to the wiki may help you, https://wiki.speeduino.com/en/decoders/ ... istributor

What I am not clear about is how you connect it up! As its probably 12v to the coil, and Speedy is expecting a 0-5v signal, some sort of conditioning is probably expected. It is possible that as its the ground side that is switching, then perhaps just a diode to catch any fly back. I'm really not sure.

Would someone please advise @Edce how to proceed. :)

2 cylinder flat twin. 123 is sitting on the cam and running a wasted spark coil.
By edce
@LPG2CV : I am progressing my own project which has a flywheel prepared with magnets detected by Hall sensor. But I am a knowledge freak as well. That explains why I also would like to know about just one pulse per cycle being capable to fire injectors. I also guess the output from a 123 unit is 12V, so a step down convertor to 5 V is necessary. An electronic designer sees some possibilities here I am sure. Any candidate on this forum ?
By dazq
With single coil /distributor triggr setup you normally use a optoisolator circuit to protect the speedy from the HV pulses.
Have a search on here fo the input trigger threads that have proven circuits and even PCB layouts .
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Ignition coil negative triggering can be as simple as a 1N4004 diode from the coil(-) to VR1, set to Hall/Direct, and use the pullup jumper. The diode blocks positive VBAT and flyback from the coil, but passes grounding during dwell for the pullup. Result is a 0V-5V (actually ±1V-5V due to diode Vf) alternating signal into Speeduino. A small added cap (0.22uF or so) may be needed to filter the brief negative pulse on coil firing. This is very similar to the well-proven 12V/HV input in the Speeduino Wiki, and part of the inherent design of several competitive systems.
By edce
Many thanks PSIG, seems to be simple. Is it possible to provide a sketch for the less educated in electronics ? Reason : the blocking direction of the diode shall be clear, as well if the cap shall be parallel or in series. Thanks again !!! I now have a good solution for my try-out bench set-up. I can use the 123 unit for the ignition. The injection system is about ready to be started and with your solution for the cam puls, I can apply for sequential injection. :) :)

Unless you know different, the 123 will be putting out wasted spark, so you won't get sequential.

There are limitations in speedy fw as to the TS options that work for 2 cylinders. Its feasible you can select 4 cylinders and connect the ones you want. If you select 2 cylinders, you may want to select odd fire and set the second cylinder to 360*.
A logic analyser is useful and fun on the bench. PC one are not expensive. :)
By edce
@LPG2CV : The waste spark is clear for me, but the one cycle signal from the 123 unit can be used as one cam pulse per cycle for the sequencial injection. At least that's what I am reading in the Speeduino manual. Pls correct me if I read the info in the wrong way. Pls check page 95 of the manual.
Though the 123 is positioned on the end of the cam, it sends a signal every revolution, not every cycle. the same as a points system would with the 2, points cam lobes. Its not going to be an issue as there will be two squirts per cycle. Basically, one will be just before, or as the induction stroke starts (5* before TDC is default). The other will be on the back of the inlet valve, ready to be inducted with the first one. Its a very common system.
By edce
@LPG2CV : I meant indeed one revolution . You indicate a cycle to be 2 revolutions for a 4 stroke engine, right ? Did you check page 95 ?

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