DIY Electronic Ignition Conversion

Recently, a friend of mine acquired a 1966 Honda CB77, and I offered my help in the rebuilding process.  Part of this process includes updating the electrical system, and modernizing where it won’t affect the aesthetic of the bike.

The first modernization on the list is converting from electromechanical points to a fully electronic ignition.  Unfortunately, while there are a few commercially available kits, they all run well into the hundreds of dollars.  Fortunately, there really isn’t much to a basic electronic ignition conversion, and it’s a fairly trivial DIY endeavor.

My approach is very similar to others (especially the ubiquitous PAMCO conversion), in that it’s based around an ignition IGBT triggered via a Hall effect latch.

Before I get too much into discussing the design, it’s perhaps best to review the principles behind a conventional ignition system.  (Caution: physics ahead).

So, the obvious purpose of the ignition system is to make a spark – but this is easier said than done.  The spark needs to jump a gap (the plug gap) in an atmosphere of compressed air and fuel, reliably, and at a precise time.  Why is this so difficult?  Well, the dielectric strength (effectively the maximum potential applied to a material before conduction occurs) of air/fuel under 10:1 compression is on the order of 15 *million* volts per meter.  With a typical plug gap of around 1 millimeter, the potential required to have any spark at all is around 15,000 volts!  If we want a potent, reliable spark, it’s best to up that value by about a factor of two.  (These values are all within ‘cosmological accuracy’, but ballpark figures are all we need here).

Alright, so we need roughly 30,000 volts from a 12 volt system.  How?  Well, more physics of course!

Physics gives us a neat trick for not only generating such high potentials, but also for doing  it at a precise time we can control by fairly simple means.  The phenomenon is called counter-EMF, where Ec = -L (dI/dt).  This says that the potential across an inductor caused by a change in current is proportional to the current’s rate of change.  So all we need to do is rapidly change the current flow through an inductor, and we’ll have some high voltage across that inductor.

Now, it’d be nice to say that’s all we need to do, but there are some caveats that require a little more engineering cleverness.  The first problem is that 30,000 volts is almost impossible to control directly, as most insulators become conductive long before this (which is the whole point).  Second, high inductance coils require longer times to fully ‘energize’ (due to the same phenomenon) – this ‘energize’ time in an ignition system is usually called “dwell”.  So how do we deal with these issues?  Simple, instead of a single inductor, we use a transformer – two (or more) inductors sharing a common core.  In this case, our transformer is called an ‘ignition coil’.

So now we have something of a plan.  We take a transformer of say, 1:100 turns ratio; we use counter EMF trickery to apply 300 volts to the primary side, giving us 30,000 volts on the secondary side; then we use a spark plug with a tuned gap between the terminals of that secondary side, giving the 30,000 volts something to jump across and make a spark.  Perfect!  Now we just need to generate that counter-EMF at a precise time (which, ultimately, is what this is all about).

Until the adaptation of solid state devices in automotive ignitions, the current control through the primary of the ignition coil (and subsequently all aspects of ignition timing) was handled by points – a set of contacts acting as a switch between the negative terminal of the coil and system ground.  As the engine rotates, a mechanical cam opens and closes these two contacts at “precise” times with respect to the engine rotation. ( I put “precise” in quotes because anyone who has experience with points will tell you what a pain in the ass they are to keep properly adjusted.)  The timing is such that the points make contact at the beginning of the dwell period, allowing current to flow and ‘energize’ the primary of the ignition coil.  Then, when the piston is at TDC, the points cam separates the contacts, causing a sudden change in current through the primary (a high dI/dt).  This produces the aforementioned 300 volts of counter-EMF across the primary of the ignition coil, which produces 30,000 volts across the plug gap, and we have a spark – right when we wanted it.

Phew.  That was far more painful to write than to read, I assure you.

So, here we are, with a marginally functional set of points that do the job but require more maintenance than a modern human cares to invest.  Luckily, solid state devices exist that can handle switching of large currents (fully saturated ignition primaries can draw upwards of 5 amps), while incorporating internal clamping protection against high-voltage damage.  The most common of these that I’ve found is the 14C40L series of ignition IGBTs manufactured by International Rectifier.  Even at under $4 a pop, they are still the most expensive component of this project (even more expensive than the professionally fabbed PCBs).

On to the design:


So, how does it work?

The A1250 Hall latch can be in one of two states, and remains in that state until switched.  When ‘on’, its ouput is dumped to ground.  When ‘off’, the output is pulled high by the 10k resistor connected to VCC (I believe this particular Hall latch has an internal pull-up, but I feel it’s more robust in this configuration).  This normally-high line is connected to the gate of the IGBT through a 2k resistor (to prevent ringing on the gate).  The IGBT is an N-channel device, so the drain is connected to the ignition coil’s ‘negative’ terminal, and the source connected to ground.  C1 is simply there for decoupling, and D1 prevents reverse bias between the source and drain (this is redundant to the internal clamping circuit of the IGBT).

So, when the north pole of a magnet passes by the Hall latch, the output is pulled high, along with the gate of the IGBT.  This allows current to pass through the coil, energizing it.  When the south pole of a magnet then passes the Hall latch, the output goes low, pulling the gate of the IGBT low, causing a sudden cessation of current through the ignition coil primary, which leads to all the aforementioned physics voodoo, giving us a precisely timed spark.

So that’s all fine in theory, but does it actually work? Yes, it does.

Here is the PCB I laid out:


I know it’s not pretty, but it’s only intended as a proof-of-concept prototype and I wanted it made as quickly and cheaply as possible.  At $1.15 for 3 boards (fuck yeah, OSH Park), the only cheaper components of the build are the 1206 discreets.

Here it is, built:


Don’t ask about the Jolly Roger, it was my first order from OSH Park and I wanted to test their silkscreen capabilities.  And because I sort of want to be a pirate.

I’ve tested this thing with a couple of magnets stuck on a bolt and it certainly seems to function as intended, at extremely low cycle rates at least.  Solid state devices and magnetic fields being what they are, I have no doubts that it will scale up to higher frequencies just fine.  After all, even 15,000 RPM is only 125Hz.  Using a transistor in place of the Hall effect latch, and triggering with a 555 timer, I was able to get reliable operation well into the KHz.

The next step is to build a trigger wheel to hold the magnets and attach to the original points cam (to take advantage of the inbuilt mechanical timing advance).  My brother is a killer machinist who doesn’t seem to mind doing me favors, so I’ll probably lean on him for the final part.  Prototyping will probably be done in a very hack manner with PVC or somesuch, and you can expect updates in future posts.

Eventually I’d like to design around a microcontroller, so that all the advance (and even custom advance curves) can be handled electronically.  Right now I just wanted to make something cheap and functional, because these mechanical points simply have to go.

Oh, and speaking of cheap, final cost for a pair of these:  $11.72

Sure beats $200.

Other motorbike stuff to come:  Solid state PMA voltage regulator/rectifier, Neutral-disengagement-triggered headlight switch, Mechanical-to-digital speedometer & tachometer conversions, and probably more stuff that I haven’t even thought of yet.

39 Responses

  1. Nerijus

    Looks like this is what I was looking for my Izh Jupiter 2. I am not very good on electronic and have few questions:
    Will it work on 6v system? A1250 datasheet says that operational voltage start with 3 volts, but maybe different resitors should be used.
    Also schematic of trigger wheel would be really usefull. I am not sure how magnets should be arranged.
    Actually my project includes two stroke engine, but it shouldn’t be a problem. Maybe more complex trigger wheel will be needed.

    July 29, 2013 at 6:29 pm

    • Hi Nerijus,
      I just looked up the Jupiter 2, having never heard of it before. That’s an awesome bike you have there.

      The circuit I have laid out should function just fine on a 6v system without modifications. As you discovered in the datasheet, the Hall latch will operate with a supply voltage well below even 6v, and both VGE and VCE on the IGBT are well below 6v (max of 2.2v and 1.4v respectively). Just to be sure, I tested it with a 5v benchtop supply and an LED in place of an ignition coil, and everything behaves as it should.

      As for the trigger wheel, this is where things start to get a little complicated. The number of ignition modules – as well as the trigger wheel configuration – are going to be 100% application specific. In the case of the CB77 I’m working on, there are two coils, with cylinder 2 firing 180 degrees of *crank* rotation past cylinder 1 TDC, which is 90 degrees of *cam* rotation. Since I’m mounting the trigger wheel on the camshaft, I have to place the two modules so that the Hall latches are 90 degrees apart. I chose 180 degrees of dwell, mostly for simplicity. The really tricky part is phasing the trigger wheel to the crank rotation. The reason this is so tricky is because it doesn’t take much magnetic field intensity to set the latch, so the point at which the triggering occurs will vary with the strength and position of the magnets you use, as well as how far the latch is mounted from the trigger wheel. Regardless, it is very unlikely that triggering will occur exactly when the magnet passes the latch.

      I did a little research, and it would appear that your bike is designed with the cylinders firing 180 degrees of crank rotation apart (this would make sense, being a two-stroke; I just wanted to confirm asynchronous firing). In that case, the whole arrangement is a fairly trivial matter. You would need two ignition modules (one per coil), and you would have to mount them exactly 180 degrees apart. Then choose your dwell angle, which will dictate the angular separation of the magnets in your trigger wheel. Then you’ll have to play around with phasing the trigger wheel to the crank, so that the triggering occurs at the appropriate times. I’ve drawn some incredibly crude images to describe what I’m talking about. I hope they help. If you have any additional questions, I’ll do my best to answer.

      Trigger Wheel Example 1

      Trigger Wheel Example 2

      This second image (with the horrible, ms-paint quality magnetic field lines) is meant to illustrate why the modules are unlikely to trigger at the exact position of the magnets themselves. They will trigger when the Hall latch meets a field of sufficient intensity, perpendicular to its face. The necessary intensity is somewhere around 5 Gauss, which is incredibly small. With the appropriate intensity magnets, module spacing, etc.; you might be able to get it close, but it’s not really necessary. Just some trial-and-error to get the phase right and all should be well. All I’m trying to say is: It’s not the position of the magnets that really matters, it’s the position of the fields with sufficient intensity to trigger the Hall latch.

      July 29, 2013 at 11:19 pm

      • I should also add that I chose to have the Hall latch perpendicular to the PCB because of constraints involved in my particular project. There’s certainly no reason not to lay them flush with the PCB and use a trigger wheel with magnets embedded vertically (as is done with the PAMCO.) If you decide to go that route, a surface mount Hall latch might be a better choice, as they’re cheaper and smaller. Or, for that matter, only the Hall latch and its decoupling capacitor really need to be mounted by the trigger wheel – the rest of the circuit could happily reside in an external enclosure.

        July 30, 2013 at 12:32 am

  2. Nerijus

    Thank you for your response! Now I have full image of the system. I believe that tester or LED will help to make a proper phasing. Also, probably I will make adjustable sensors and also adjustable magnets on trigger wheel to make quick changes on dwell angle or firing time. As I understand it is best to use weak magnets and they should be located away from each other (diameter of wheel should be as big as possible).

    July 30, 2013 at 9:03 am

  3. hi will it work on cb350 and can u place led light for timing purpose

    August 1, 2013 at 7:18 pm

    • It should work perfectly on a CB350 (or any internal combustion engine, really), as long as the trigger wheel is mounted to some kind of mechanical advance. And yes, an LED should work fine for figuring out the timing. One thing to keep in mind, however, is that the LED will have current passing through it the same as a coil would. This means that it will turn on when the coil is saturating, and will switch off when ‘firing’, which is a bit counter-intuitive. Also, once on or off, the LED will remain that way until the next magnet passes the Hall latch – meaning you might not be able to just wiggle the trigger wheel back and fort past the Hall latch (like you normally could with points); you’ll likely have to make a full revolution every time. Also remember to use an appropriate current-limiting resistor with the LED. Somewhere in the neighborhood of 600 ohms 1/2W (for a 12v system) would be appropriate.

      August 2, 2013 at 6:12 pm

      • yasir

        Am in pakistan and am just unable to find hall effect sensor.but I found 1 in Computer power supply fan and it has 4 pins pls advice it will work? If yes May i attach led with 4th pin?

        October 1, 2013 at 1:52 pm

        • Hi, sorry for the delayed response, I’m knee-deep in midterm exams and that doesn’t leave a whole lot of time for other things. To answer your question, I don’t believe that such a Hall effect device would work without modifications to the design. Most Hall effect devices are either sensors or switches, and this design – without modification – requires a latch. This is a result of needing the coil to saturate during the ‘dwell’ period. You could certainly implement some clever logic with a non-latching hall device, but – if you’re looking to reuse e-waste components – an alternate method would be to use a photo interrupter (commonly found in all kinds of discarded electronics) and a notched disk. My first breadboarded prototype actually used this method quite successfully, but it was too large to fit in the location I had in mind. Good luck!

          October 5, 2013 at 3:58 pm

  4. JJ

    I’m going to build and testy one of these next week and install on my bike. Will be sure to let you know how it goes.

    August 30, 2013 at 12:14 pm

  5. jj

    ordered the parts, very excited to see how it works.
    i have a question, can i use your pcb file to get a proto board made? if not thats ok too as i know it’s your designed. where did you get the library file for the 14c40l. i cant find one for use with eagle cad anywhere.


    September 1, 2013 at 11:38 pm

    • Sorry it took me so long to reply, it’s the start of the Fall semester for me and things are already running at full tilt. As for my eagle files, you’re more than welcome to use them of course (link below), but they’re not really ‘production quality’. I just slapped the design together to get a ‘proof of concept’ prototype, and one that would work with my very specific setup. In a lot of instances, a differently shaped board with a different mounting arrangement – and even different components (a surface-mount hall effect latch, for instance) – would be much more appropriate. That said, I made some effort at trace and component isolation, as the ‘negative’ side of the coil can exceed 300 volts when ‘firing’, and I would recommend you keep such in mind when designing your board or modifying my design. Oh, and be sure to use some kind of isolation (i.e. a sil-pad or mica insulator) between the IGBT and whatever you mount it to, as the tab is very much a *live* terminal (connected to the ‘negative’ side of the coil, if memory serves). As for library files, the IRGB14C40LPBF I used is a standard TO-220 package, so I just grabbed any old TO-220 NFET in the eagle library and changed the name in the schematic.

      Eagle Files

      September 5, 2013 at 2:07 am

  6. Peter Frost

    Chris, Fascinating study in micro-physics, regret with the `technicalities` you`ve swung way out of my tree! However, I`m just commencing complete resto of a Jupiter3 & El/Ign is a must, so if you eventually market a kit put my name on one. Apart from the complexities of the triggering device would a 2 stroke system be easier to accomplish allowing that it requires no adv./retard mechanism or electronic `anticipator` facility, unlike a 4 stroke?
    Best Regards Pete.

    December 8, 2013 at 2:39 pm

    • Hi Pete,
      The physics of it really isn’t bad at all, I’m sure I’m just doing a horrible job of explaining it clearly. As for a kit, I’ve certainly thought about it, or even just putting together some more detailed instructions on getting this type of ignition setup built and installed. The problem is that every bike is so radically different from the next, that each kit would have to be tailored individually. Even worse for the Jupiter 3, they’re as rare as hen’s teeth here in the states (a shame, I’d sure like to get my hands on one). Honestly though, if you have the mechanical ability to restore a motorbike, I have full confidence you could fabricate a suitable trigger mechanism. The PCB I laid out was intended to be sort of ‘self contained’ on a single PCB so I could slap the whole thing under the points cover. Really though, the components don’t even need a PCB, and the circuitry can be mounted remotely from the Hall latch and trigger wheel. The trigger wheel is far less complex than I may have made it sound; it’s really just opposite magnet poles stuck ‘dwell’ degrees of rotation apart. As long as you can ‘clock’ either the trigger wheel or the Hall latch with respect to each other, then dimensionality isn’t terribly critical (as any phase error can be ‘clocked’ out).

      I’m really curious about your 2-stroke inquiry. I don’t have a lot of experience with 2-strokes, but I had no idea they don’t require any kind of ignition advance. My understanding is that ignition advance is intended to account for the combustion propagation delay with respect to the piston’s position as a function of RPM. I’m not sure why this would be absent in a 2-stroke. Either way, attaching a trigger wheel to the original points-cam mounting should seamlessly incorporate the machine’s factory-spec mechanical advance.

      Over the coming months I’ll be fully implementing this electronic ignition into the CB77 it was designed for, and possibly a few additional iterations. I plan to document the process with sufficient detail so as to be a starting point for others, which will end up posted here.

      Thanks for your interest, and good luck with your resto!

      December 12, 2013 at 5:02 pm

  7. Zach

    Chris, I want to say thanks for your tips and directions on this project. I used your ideas to successfully make a working electronic ignition for my CB350. Everything I needed to know was laid out beautifully, and with some thoughts from my electrical engineer brother-in-law, it was a cinch.
    Thanks again!

    December 12, 2013 at 8:47 pm

    • I can’t tell you how positively thrilled I am to hear that. Thanks for sharing, and good luck with the rest of your build!

      December 17, 2013 at 6:29 am

    • shane

      Hi Zach,

      I am trying to make one of these for a CB350 as well, would you be able to share your knowledge on this? And maybe some pictures and eagle files on this?


      July 14, 2014 at 6:12 pm

  8. Alan

    Is the eagle file for the PCB still available, as the above link says it was removed?
    Thank you

    June 17, 2014 at 7:03 am

    • Sorry about that, I didn’t realize the hosting would expire. A somewhat cleaner version of the eagle files can be found here:

      If you’re working on a CB77, however, it might be worth waiting a little bit. I’ve got a major revision of this design (specifically for the CB77) I’m about ready to roll-out.

      September 12, 2014 at 11:44 pm

  9. Derek Smith

    Hello Chris,

    I found your article very interesting and have a project you might be interested in.

    I have a Mountfield Strimmer, which is driven by a two stroke motor which in turn is served by a magneto ignition. It is a single cylinder unit. The points are directly activated by a fixed cam on the crankshaft and the magneto flywheel is fixed on the crankshaft by a keyway, all timing is rigid with no form of advance or retard. The only adjustment is to set the points gap.

    The piston has good compression, but the ignition is poor. When cold, the strimmer will fire up and run for a few minutes, but as the unit heats up, ignition starts to falter and eventually the spark is so weak that the engine stops and wont start again.

    I do not want to have to junk the unit until something mechanical breaks and cant be fixed or replaced – the unit is no longer supported by spare parts.

    The points are in good condition, so I have the option of clipping a small 12V battery to my belt and using it to power an external ignition coil, using the points to do the switching of the 12V into the primary, but this means buying an ignition coil and the extra weight of the coil on the strimmer.

    As an intermediary step, I am considering using an external 12V battery to saturate the existing magneto primary, and switch this using the IRGB14C40L Which in turn will be triggered by the existing points switching the 12V, that is, replacing the A1250 in your circuit with the existing points and 27nF ceramic capacitor.

    The spoiler to this route is that the flywheel magnets will still be acting and generating a field within the primary which may screw the whole idea up.

    You thoughts would be appreciated.

    June 23, 2014 at 9:11 am

  10. Derek Smith

    Hi Chris,

    I have just noticed from your circuit diagram that you are connecting the 14C40 to the -ve of the charging coil and then to GND.

    This means that the 12V +ve must have been connected to the other side of the charging coil, i.e. when the gate is ‘on’ the 14C40 is conducting and so passing current through the charging coil. Then when the 14C40 goes off, the physics voodoo happens and HT pops out of the HT coil.

    BUT, the coils I have so far found are negative earth (so far so good), and the charging coil and the HT coils are connected to a common ground (the neagative pin on the coil). So, in turning off the charging coil current, you are also disconnecting the HT coil from earth and so the 20K or so volts of HT tried to drive itself through the14C40 – I guess it will succeed and Pop goes the IC.


    June 23, 2014 at 7:11 pm

    • I’m sorry, I’m not sure I fully understand what you’re implying. It seems like you’re suggesting that the IGBT is somehow subjected to the high voltage of the secondary coil. This is no more true than in the case of mechanical points. You do raise an interesting point here about the broken ground reference, but I suspect the return path is just somewhat more complicated. If you look at a basic circuit diagram for any conventional ignition system, you’ll notice that when the high voltage secondary coil shares a terminal with the primary coil, a circuit is then formed *through* the battery (counter-intuitively, perhaps). So really the high voltage secondary is referenced to the 300 volts (counter-emf) on the primary which is itself referenced to the 12 volt system which is, of course, referenced to system ground. I suspect a Thevenin-equivalent circuit diagram would see this prove out.

      September 13, 2014 at 12:39 am

  11. Erik Lindgren

    Nice and simple design. I’m thinking of trying it out on my KTM 4-stroke dirtbike, which has some wierd electrical problems. Any idea about the current consumption? You mensioned 5 Amps, is that continously or just briefly before each spark.

    October 6, 2014 at 7:39 pm

    • Current consumption is a bit tricky in this case, it’s a function of engine RPM, coil reactance, and coil resistance. When left on (but not running), any coils left conducting to ground will only provide their DC resistance to impede the flow of current. If you have two coils, each at only 3 ohms, and both conducting to ground from a 14.6 volt system (and fully saturated), you’ll be pulling almost 10 amps(!) combined. At higher RPMs, the coils have less time to saturate, and current consumption goes down. Presently, on my test rig at ~10,000 RPM, current draw is down to about 1 amp (at 14.6 V) on my two-coil setup. However, at lower RPMs, current draw is sufficient to overtake the output capabilities of my (admittedly insufficient) benchtop supply. All that said, the current consumption is no more than would exist in a standard points setup. The electronics responsible for switching consume almost negligible power (once I’ve finished the tests I’m doing, I’ll take some readings with my 3478A and see what actual consumption is, but I expect it to be below 10mA for this design).

      October 6, 2014 at 10:56 pm

  12. Erik

    Thanks for your reply. Sounds like the charging system on the KTM should be able to provide enough power then. Waiting for some parts to try and fix the stock system now, but if I can’t figure it out this is a good (and fun) alternative.

    October 7, 2014 at 9:08 am

  13. Ed M

    Dear Chris,
    I am trying to build a replacement for a discountinued Pertronix Ignitor used in an Onan generator.
    This Ignitor will replace points directly.
    A crank cam moves a pin up and down to actuate either the points or a lever with a magnet.
    The magnet in the lever swings back and forth over the Hall sensor.
    There is no opposite magnet, unless there is a biasing magnet under the Hall.
    It looks like the coil primary has power all the time until the Hall is activated.
    That will interrupt the primary current.
    The points would also do that.
    I think that will be fairly easy to modify the circuit if there is a magnetic bias on the Hall.
    The original device is potted and hard to analize.
    Good page Chris.

    January 24, 2015 at 6:32 pm

    • If you’re relying on a mechanical cam arrangement, then there is no need for a ‘latching’ sensor, as the dwell is simply controlled by the cam profile. The basic circuit described above should work just fine, simply replacing the Hall latch with an appropriate Hall switch or a Hall sensor. Some types of Hall Effect based sensors do indeed come with a permanent or electromagnetic bias, but that may not be entirely necessary in your case. However, one of the major benefits of a Hall Effect based trigger is the possibility for a contactless (and subsequently maintenance-free) triggering arrangement. If it were me, I’d investigate fabricating a contactless trigger wheel in conjunction with a Hall latch. Failing that, I suspect a unipolar Hall switch with the above circuit will suit your needs rather well. Good luck, and thanks for commenting!

      February 8, 2015 at 5:06 pm

      • eduardo

        Yes Chris, after my post,I went to the Allegro site and found the unipolar Halls.
        Essentially, the dwell will be the same as with points.
        I bought some IRGB14C40LPBF-ND that should be adequate.
        Thank very much.

        February 8, 2015 at 6:18 pm

        • Indeed! Let me know it goes!

          February 8, 2015 at 10:02 pm

  14. Mike Nilson

    Great little project. I’m retrofitting a vintage 3 cylinder two stroke with your design. I’ve started ordering on digikey and was wondering if you have a parts list? The lists of parts is quite bewildering.
    Thanks for your great site. Mike in Canada

    April 4, 2015 at 2:41 am

  15. Eric

    Hello There,

    In your opening pages you say :-

    “Eventually I’d like to design around a microcontroller, so that all the advance (and even custom advance curves) can be handled electronically.”

    I have followed your articles and built a system using your circuitry and it is now on the test bench going through trials.

    I also wish to go along the microcontroller route if it is cheep enough and if I am capable of doing it !!!

    So did you ever get a microcontroller system working ??
    I appreciate any help you can offer me !

    Regards and thank you for a fine article !!!

    May 10, 2015 at 4:55 pm

    • I see it’s been some time since you left your comment; how go your trials? Did you decide to go the microcontroller route? As for their cost, I expect you’ve discovered by now just how cheap embedded hardware can be. Personally, I haven’t (yet) done a microcontroller based ignition controller, for the simple reason that I’ve really had no need for one (and I have far too many concurrent projects to work that one out just for giggles). Sooner or later I’ll revisit the idea. As such, I can’t give you much in the way of advice, other than suggesting you pore over whatever engine management design references you can find, especially the DIY / open source stuff. Whatever you come up with, I hope you consider releasing your designs within the open source paradigm! Good luck!

      August 19, 2015 at 12:57 am

  16. Rich

    A hall system used on MZ motorcycles works like this. There is a hall sensor and magnet on a sliding plate on the stator. Attached to the end of the crank is steel disc with a cut-out section, that spins between then hall effect and the magnet. When the steel is between the magnet and the hall, the steel blocks the magnetic flux lines and the system is off ‘points open’ condition. Then when the cut out is between the hall and magnet, the magnetic field triggers the hall sensor and is ‘points closed’. Finally when the steel section returns it cuts off the hall sensor again, triggering the ignition event. I like this system as the dwell angle can be controlled by the size of the cut out section.

    May 20, 2015 at 9:06 am

    • I’d be very curious to see that. Sounds a bit like a traditional reluctor setup. I actually considered a varied number of triggering options, including things like optical interruption and even contactless absolute encoding. When it came down to it, however, simple triggering with permanent magnets seemed the best solution (at least for what I was looking to accomplish).

      August 19, 2015 at 12:37 am

  17. Gerard Starks

    Was your CB77 project successfully completed? Thank you, Gerard

    June 20, 2015 at 12:01 pm

    • Not yet! The motor is still split and laid out on a workbench, though there’s been progress on the chassis. Unfortunately, still no real world testing for the CB77 ignition. Perhaps the coming months will prove more fruitful.

      August 19, 2015 at 12:27 am

  18. John Kasse

    Love the article. As one other poster mentioned, I have an old CB350 twin. The market is pretty thin for “affordable” electronics for these, PAMCO being one of the more affordable ones. A DIY “kit” for this would be wild ! I’m sure I could modify one of my old points plates to mount it all on…… a pair of good coils, and I would be in business….
    Thoughts ?

    July 14, 2015 at 5:36 pm

    • Hello Sir, and thank you for your kind words! A fully open source design has been the plan from the start, which leaves the door wide open for DIY, kits, and preassembled hardware. Now, you mentioned your CB350 twin… As it happens, I’ve been looking to expand the design beyond the CB77 I’m currently helping to build, and the larger/later CBs seem a very good place to start. If you’re interested in collaborating, it wouldn’t take much for me to get a board laid out and populated. I would just need some dimensions, and someone to work out the trigger wheel and do some testing.

      August 19, 2015 at 12:24 am

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