Reading an engine's pickup coil

Hi all,

I want to play around with driving an engine's ignition system using an Arduino. That is, I want to build a TCI with an Arduino. I'm doing this on a 1982 Yamaha Virago 920 engine (v-twin). It has two pickup coils to know the crankcase position when it needs to fire.

So mainly my question is, how do I read the pickup coil signal from the Arduino? I'm an electronics circuit noob, so extra explanation about how circuits work (or just links) would be much appreciated.

In the wiring diagram, each pickup coil has two wires, and the coil is displayed as a little spring icon. I don't think it's a hall effect type sensor, but I'm not really sure.

Ignition systems can get complex.
Might be a daunting task if you are new to the systems.
There are many systems out there, tried and proven.
Might be a good start.

One example here with a PIC12C675 microcontroller.

Overall though, don't know why you would need to change the ignition to start with.
I had a 1981 Yamaha Midnight Special for many years and had zero ignition problems.

I'll be honest, there's no real reason I'm doing this other than because I think it would be a fun challenge, and because I want to learn how about the components and circuits involved. I have a perfectly working ignition TCI (in fact, two of them).

What makes an ignition system complex?

Many aspects of whatever design you might dream up or copy from somewhere.
What I said was they "can" get complex, and your asking here shows it is complex right from the beginning as you apparently have no understanding.

Google tci motorcycle ignition system modifications and see how many have gone before.

One aspect is any mod, if the machine is used on-road, would more than likely need certification from any regulatory authority as you are changing the original design.
I think the following flowchart might be good reading for you.

I probably wouldn't ride with it, again it's more for a fun project to see if I can do it. If it helps, I'm not going to do it, I just want to learn how to do it.
I also live in an area which doesn't have any kind of required safety certification.

I know that the TCI switches ground off for the ignition coil when the appropriate pickup coil is passed in the crankcase, causing a spark at the right moment (possibly timed later or earlier for maximum efficiency). I want to learn how I would achieve that, getting a signal from a pickup coil doesn't seem like it would be terribly difficult, but I've been doing some googling and haven't found anything.

As the engine wont run if you disconnect the ig system your first step would be to read the signal from it while everything is connected.

As a first step I'd suggest you read the voltages on each of the two wires with the chassis as a reference. If you dont have a multimeter you WILL need to get one - something like this will do for most purposes

Digital XL-830L LCD Multimeter Voltmeter Ammeter Ohmmeter OHM VOLT Tester | eBay

Multimeter won't cut it if the pick up is a coil.
Scope would be handy.

I think I would look at fitting separate sensor , then you don’t compromise or risk damaging the existing ignition system. Easiest would be some form of optical pickup/slotted disc )

It’s difficult because the electrical environment is very noisy ( you’ll need a nice power supply for the processor) and the signals from ignition pickups can be “difficult” for a beginner to deal with ( you’ll need some form of external circuit). You’ll need to mechanical ability to fix up any new sensor .
An oscilloscope would be very handy for this job to look at pulse outputs etc .

Not an easy “ early on” project , provably very frustrating and you’ll fall off whilst fiddling with it

I'd not suppose the OP has a 'scope. A DMM would likely tell us if the sensor has supply and signal connections.