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Thread: 4217 and optical pick-up

  1. #1
    patrickB Guest

    Default 4217 and optical pick-up


    I want to buy a 4217 CDI unit for my Kreidler racer.

    But , could I use a signal ( square between 0 and +12 V ) from a optical sensor to trigger the CDI via the Hall sensor input.?

    The first flank ( most advance ) should it be rising or falling?

    Should I use the same signal width ( +- 45° ) depending on the max advance ( +- 25° ) I want to use ?

    I can't use the normal systems.

    Kind Regards



  2. #2
    patrickB Guest


    Answer from Bret:
    Hello Patrick,

    I’m not familiar with a Kreidler racer but if it is a single cylinder 12 volt application that is a good starting point. Most if not all our systems operate off a 12 volt square wave signal, does your sensor incorporate a magnet of some kind? Most advanced is the falling edge. It is better to go with a longer signal width whether it be a timing tab or magnets in series that way if you need more timing adjustability it will be there. I am skeptical about the optical sensor you are thinking of using though. Normally this is triggered by either a Hall Effect sensor part number 4154 sensing a series of magnets in an aluminum flywheel or stock magnetic pickup sensing a timing tab on your flywheel. Not to say this would not work it just has not been tried before, not to my knowledge anyway. Please let me know if you have any other questions. Thanks, Bret

  3. #3
    patrickB Guest


    Hello Bret,
    Thanks for the quick reply.
    The problem is I have a flywheel full off magnets for the lightcoil ( that i also need.)
    I have mesured the output from the inductive pick-up for the normal CDI ignition.
    I have added the picture off the signal ,and for me it can't be used for the MSD CDI.
    So the only option I have left is a optical system.
    The flywheel wil be painted mat black and a zone off 40° will be bright white.
    I will make a sensor ( I am electronic engineer ) whith a reflective omron sensor to trigger the MSD cdi.
    Everything will be closed to prevent dust and water to get in
    It will be no problem to amplfie the square signal to a 0 to +12 V range.
    As I understand the signal must be at +12 V and drop to oV on the most advance trigger signal and go back to +12V after a 40° zone.
    This zone wille be the angle off the white part on the flywheel.

    Greetings from Belgium.

  4. #4

    Default 4217

    Hello Patrick,
    The optical pickup you are thinking of using should work fine, with an emphasis on "should" as this has not been tested before as trigger source for the 4217. I would recommend a degree wheel of some sorts off your crank to verify timing accuracy. In the software there are a few options for "tach in". The two you will be choosing between will be "msd hall" or "raw hall". I am thinking "raw hall" will be the correct choice but if it is not and your timing is off try "msd hall" and this should fix it. I am definitely interested in the outcome of your project so please let me know if you have any questions on anything. Thanks Bret, MSD Powersports Tech

  5. #5
    patrickB Guest


    What's the difference between msd and raw ?


  6. #6
    patrickB Guest


    What would be the average power consumption off the unit at 12V ?
    It's strange that you don't use a high voltage coil input , as this coil is availible on many small 2stroke engines.
    Also mine :-)
    So the power consumption at the battery is an important issue.


  7. #7

    Default 4217

    Hello again Patrick,
    The difference between a MSD and a Raw hall is this;
    The MSD Hall is referring to our part number 4154 Hall Effect sensor used on our small engine controllers. This pickup requires a 12 volt input and triggers off a magnetic signal. A Raw Hall is pretty much any other aftermarket pickup, such as the one you are planning on trying. That is a basic explanation. I can go deeper into detail if you prefer, let me know. The 4217 draws .14 amps or 2.2 amps at 16,000 RPM. Thanks Bret, MSD Powersports tech

  8. #8
    patrickB Guest


    "That is a basic explanation. I can go deeper into detail if you prefer, let me know"
    Please do.


  9. #9

    Default signal

    Hello patrick,
    On the MSD Hall, the 4217 will see is a reading of low and then once the signal is seen the signal will go high indicating the trigger point. On a Raw Hall it is just the opposite which is high and then low. The 4217 will give you a timing tab reference at idle, if this number is off the charts- usually over 60 degrees, then the wrong Hall Effect is programmed into the software. Hope this helps. Thanks, Bret- MSD Powersports Tech

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