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programmable cdi, looking for a good project or kit

Discussion in 'General Electronics Discussion' started by David M., Apr 19, 2014.

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  1. David M.

    David M.

    Apr 19, 2014
    I have a 2 cylinder, 4 stroke, opposed 180 degree 1000cc engine that has a old points and distributor, I want to convert it to a programmable cdi, I need it to work without a battery, the engine has a stator coil assy already, start timing at 8 deg then advance to a total of 30 degree by 2000 rpms.

    Does anyone know of a project schematic, electronics kit, or kit to use on such a engine?

    Thank you for your help

  2. bob weir

    bob weir

    Sep 10, 2014
    hi. we both share a desire to update a 4 stroke engine with a modern digital cdi ignition.
    how is your search going ?

    the critical thing that my 225cc 4-stroke engine has for its old analog circuit is a coil that picks up
    and makes a 1/2-sine-wave when a magnet on the flywheel zooms by.

    the pickup coil and magnet are still there. and are being used for my creation.

    at the least your engine needs to have some way to tell you crankshaft position.

    no , i havent found any all-purpose kit, but i have found a cdi ignition circuit that should work.
    the rest of the job is to get some way to sense engine rpm and send the fire signal to the cdi
    circuit board according to the timing curve.

    this is something i've been working on in MPASM assembly. and am about 2/3 the way
    with having a 'beta' version. lots of testing will be needed though.
    let me know if this is of any interest.

  3. Bluejets


    Oct 5, 2014
    Worked on a CDI system with others and it may be of some interest to you.
    It was for single cylinder model aircraft engines and used it's own oscillator for HV but you could change the HV section to whatever you want as most bikes have a HV generator coil built in.
    It used the 12F683 and all the code is there for a version that seemed to work ok so that would save you some time on a timer board perhaps.
    As I said, the assembler code is there so you can change that to suit your needs also.
    Somewhere around post #108 should get you going.
    Others have since tried to improve/change/modify the system but not to the point where it was as successful as this particular one.
    The modded unit went to another site and uses a 12F1840.
  4. bob weir

    bob weir

    Sep 10, 2014
    Bluejets - thanks for the reply msg and link. and , you are right, on giving it a look it is of some interest.
    and further on down the road it is expected that their coding methods will be adopted. for now tho
    i'm reminded of being in the 2'd grade with learning coding and understanding how a CDI works.

    my ideology has in mind a person seeing what i am doing and being able to begin a
    practice of their own immediately. the choice of a baseline uC is to keep things as simple as
    can be. plus to learn if it'll do the job of ignition timing , and if not why not.

    this approach assumes a person has lots of time and is under no pressure.

    a '683 is an intermediate level uC. something a 5'th grader might be tackling.
    starting with a 12F683 is for the experienced uC programmer. in the code you cite the author
    is using the interrupt and comparator capabilities. these features are not available in a 508/509.
    (baseline level uC's). and we dont know if the author needed to begin here or what his reason was.

    i have other problems with the 683 code. like where is a flow diagram or even just some
    'pseudo code' of what he's up to ? and the timing diagram for whatever engine he is working with ?
    plus i have no idea what his timing reference marks are. and is his engine 2- or 4- cycle ?
    and couldnt he have used label names with some reference meaning to the task at hand ?
    and is he available at all to support others who want to learn his code and need some help ?

    trying to make sense of the big picture nyemi had when he wrote this code with only this assembly
    listing is a time to 'just say NO'. it is smarter of a person to work out the problems on the
    path already chosen and under development. until there is good reason to change horses.

    absolutely i do want to know what others are and have done with this matter of making
    ignition timing for an engine be digital. but not with a unorganized presentation that has
    you searching all thru a year + worth of msg's trying to figure out whats happening and why.
    i think that's more for the person who is still searching & in the starting blocks.

    if you have any of the background study notes for that 683/1840 project that would aid
    a beginner then could you post links to them here.

    meanwhile its back to experimenting with the Microchip LPC board and a 508

    Last edited: Oct 10, 2014
  5. Bluejets


    Oct 5, 2014
    Many reasons for using the 12f683 over the 508, one of them being the 683 can be programmed many times over during development whereas the 508 is a "once program" only.
    Other things not so obvious but a check on the data sheet would clarify this.
    The CDI is not an easy subject to begin with and I'm certain if it was possible to simplify the program it would have already been done in the development.
    There is another extended system using the 12F1840 but this advances even further to include additional memory , access to telemetry etc. etc. but still unfinished.
    Whereas the 683 was running in the link provided without any modification other than perhaps modifying the curve.
    On the 683 this was done by changing the excel sheet and copy and pasting new data into the assy code and then reprogramming the chip.
    Whereas the newer 1840 was to be done via a PC onscreen display and in circuit programming.
    Most kids are pretty savy with operating modern day electronics but this is not the sort of thing for a 10 or 11 year old I would imagine.
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