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Lightweight Electronic Spark Ignition for 2 cylinder engine

Discussion in 'LEDs and Optoelectronics' started by Malcolm Shore, Nov 21, 2016.

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  1. Malcolm Shore

    Malcolm Shore

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    Nov 21, 2016
    I am quite ignorant about electronics - My career was as a mechanical engineer so be gentle with me!
    I want to find a lightweight ignition system for a 2 cylinder gasoline engine running at 7000 rpm max. Basic info:
    2 cycle, 2 sparks per rev, NiCad/Lipoly battery for power - (Voltage ??).
    I hope there's an enthusiast here who may help
    Thanks

    M8
     
  2. Bluejets

    Bluejets

    4,604
    976
    Oct 5, 2014
    Lightweight as in physical or electronic terms??? :)

    Your request is rather broad requirement so I'll give you a rather broad answer.
    There are many types.
    Basic transistor assist for use with kettering coil system.
    Then the others.........CDI, TCI

    The latter get rather involved even for me at times so I doubt you could handle the understanding (given your opening admission) as it even gives my poor old noggin a work out.

    They are out there though in many different forms and in many forums.

    The reason I state the difficulty for you is most are not written with a home builder with little electronics or programming or engine theory in mind. One must, at most times, follow the flow of discussions, disregarding the nong-heads and their comments as the projects are open source and as such open to every tom Dick and Harry to comment.
    Reading back can be a task as some go to the hundreds of pages with improvements or deletions, sometimes they just plain run out of steam.:(

    Other than that one could assume and just show you a ready built unit for twins.
    The application is model engines around 30-50cc but should not make much difference as the larger engines(if that is your intent) should be a bit lower compression anyhow.
    Basically though you would have to suck it and see I guess. :eek:

    https://hobbyking.com/en_us/replacement-cdi-ignition-for-ftl-twin-engines.html

    For a bit of specs data on the single cylinder type (nothing shown for the twin) , go to the address below and hit on "files"
    https://hobbyking.com/en_us/replacement-cdi-ignition-for-ftl-engines.html
     

    Attached Files:

    Last edited: Nov 22, 2016
  3. Malcolm Shore

    Malcolm Shore

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    Nov 21, 2016
    Bluejets - Thanks for the info. I'll take a look at this. If I have any further questions for you, will it be ok to ask them here?
    M8
     
  4. Bluejets

    Bluejets

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    Oct 5, 2014
    Sure, why not? That's what this is all about here.

    Might pay to be a bit more precise on just what you require as I outlined above.
     
  5. NMNeil

    NMNeil

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    Oct 3, 2014
    On a side note how would the ignition timing work?
    I see from the instructions that they set the timing to about 30 degrees BTDC so I'm assuming that the circuitry will detect the pulse from the hall sensor and using the time between pulses will either give a long delay at low revs to set the timing to within a few degrees of TDC before firing the spark or lessen the delay until you have the full 30 degree advance for higher revs.
    Would make an interesting project using discrete IC's rather than an MCU.
     
  6. Bluejets

    Bluejets

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    Oct 5, 2014
    There is no advance /retard on those units.
     
  7. Malcolm Shore

    Malcolm Shore

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    Nov 21, 2016
    I was going to use a transplanted points system which I think would have provided fixed timing, but I know those things are antique.
    I have fabricated parts for a system (like a chainsaw or lawn mower) which is about as simple as can be but a bit weighty, and requires a good 'pull' on the starter to get a decent spark. I think i am right in saying CDI or similar gives a strong spark at low rpm. I will likely adapt what I have to carry the Hall-type sensor and buy the twin system from H-King and give it a go.
    Question - my knowledge of the Hall system id that there is a fixed sensor and a rotating 'point' attache to the rotating part. Is that 'point' a magnet or just a ferrous metal trigger? In my pre-retirement days I know we used steel gears with teeth and a proximity-sensor to count revs.

    Merry Christmas to all!!

    M8
     
  8. NMNeil

    NMNeil

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    Oct 3, 2014
    That's going to make starting damn near impossible. Every time the piston is rising on the compression stroke the spark will fire and never let the piston get to TDC.
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    The rotating point, as you put it, when used in conjunction with a hall effect switch is indeed a small magnet,
    The ones I use here are about 3mm dia and 1mm thick.
    If you are modifying an existing system then you have to be aware that ferrous metal can be a problem for the magnet and it's effect on the hall switch. I usually mount the magnet in a brass flywheel or an aluminium disc attached to the crankshaft. Once again bearing in mind any ferrous metal in the vicinity.

    There is another option to use the hall effect with steel gears.
    One places the same magnet ( correct polarity ) on the back of the hall effect switch. You can read about this on the site for Allegro. Hall effect I use for ignition systems is the A1120EUA-T.
     
  10. Bluejets

    Bluejets

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    Oct 5, 2014
    There are millions of engines out there that use the fixed ignition system.
    Usual placement of ignition points or whatever is around 28 degrees btdc.
    Usually they are of a type where a particular rev range is required e.g. water pumps, rotary hoes, timber saws, on and on and no, it's not a problem for starting.
     
  11. NMNeil

    NMNeil

    109
    10
    Oct 3, 2014
    So the ASE classes I took to get my Master Certification were all wrong?
    Going to ask for a refund.


    [​IMG]
     
  12. Bluejets

    Bluejets

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    976
    Oct 5, 2014
    That's advance/retard, not fixed ignition.
    No, not wrong, just a different application.
    Motor vehicles and the like require the best ignition points to give maximum performence/ efficiency over a wide range of speeds and loads.
    Not so with the applications I outlined earlier.
     
  13. Malcolm Shore

    Malcolm Shore

    4
    0
    Nov 21, 2016
    Quite correct Bluejet - my ol' Norton 500 International's Static ign timing is 5/8" BTDC. it would give you a kick back once in a while but once mastered, the technique was easy.
     
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