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Homemade CDI ignition

Discussion in 'General Electronics Chat' started by SimonTHK, May 9, 2011.

  1. SimonTHK

    SimonTHK Member

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    ok so does anyone know where you can buy such an ignition coil? 300v primary 30kv secondary 100 gain? I cant find it anywhere.
     
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  3. SABorn

    SABorn New Member

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    I have not read this entire thread but what i have read it would look that this has lost the plot of how the average ignition system works.

    Most small motors have a winding in the flywheel / stator to produce the voltage needed for the ignition system and another winding for the battery system, these are independent of each other.

    Some systems have a inductive pickup on the outside of the flywheel for the spark timing and as already mentioned there will be 2 targets for a twin cylinder 180 degrees apart.

    A lot of the CDI units charge the capacitors via the ignition windings and are triggered to fire the coil by the inductive pickups, it is all a very simple system.

    The OP said 1 plug stopped working , then followed shortly by the second plug.....Have you actually tried replacing the plugs as they can go short circuit, which sounds like the cause of 1 plug to fail before the other.

    If you need to remove the potted glue to get things apart than heating the glue/resin with a heat gun (Hot air) will make it go soft and crumbly when hot and can be carefully dug out, in most CDI systems it is the SCR that fails and if replaced normally the unit will work.

    A close friend of mine has a business in repairing motorbike ignition systems and it is a common practice to replace the SCR's, rather than removing all the resin/glue to access the scr he often just solders a new one to the bottom of the board as scr's normally fail open circuit the old ones can be left in place.

    After testing the board is resealed with resin.

    The biggest fault is the use of 400 volt rated SCR's and upgrading them to 600 volt SCR's often cures the problem.

    Pete.
     
  4. dave

    Dave New Member

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  5. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    It is hard to recommend a source without knowing where you are. HobbyKing has many ignitions, including one for a twin. Ebay has several ignition coils for the Zenoah 2-cycle engines. I personally have used those coils with homebuilt ignitions. Most hobby ignitions operate with a 300V primary and >20KV secondary.

    RPM may be a factor to consider. Hobby engines peak out at to 10,000 to 12,000 rpm. If you are running faster, particularly with a twin , you may need to look at coils/systems for motorcycles.

    Here are some links to the above:

    Zenoah 62/45/23 Ignition coil ZEN262971311 | eBay

    HobbyKing Online R/C Hobby Store : Replacement CDI Ignition for FTL Engines
    HobbyKing Online R/C Hobby Store : Replacement CDI for Turnigy HP-50cc CM-6 Plug
    HobbyKing Online R/C Hobby Store : Replacement CDI for XYZ 50cc & 26cc-A Engines
    HobbyKing Online R/C Hobby Store : Replacement Complete Ignition Set for Single Cylinder Gas Engines

    For a twin: HobbyKing Online R/C Hobby Store : Replacement Twin CDI for CM-6 Spark plug

    John
     
  6. SimonTHK

    SimonTHK Member

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    Thank you saborn
    You say two pickups on a 2 cylinder. But it only has 1 exiter coil, the other is the charging coil. So where is the two pickups? Kawasaki flywheel and Stator 650 SX Magneto X2,TS,SC NR For Sale - DragCars.com
    Can the two pickups be the negative and positive signals from the exiter coils? And they are not placed with 180 degree difference, so should the microprocessor know this difference? And be programmed from that? I guess it should. Luckely I JUST found a complete manual for a 650sx and I got it cheap. Ill receive it next week and hopefully it can help with the details.

    Ill test more now with spark plugs. I wont tare my CDI apart before I tried another one.

    Changing the SCR shouldnt be a problem if I can just get into the parts. It was NOT possible at all with my bad attitude CDI, which is a tuned CDI.
     
  7. SimonTHK

    SimonTHK Member

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    I have no idea if any of these CDI can be used. They have to be programmed for my 650sx and if it will trigger a pickup on both negative and positive inputs or only 1 of them. I have absolutely no idea! They are build mostly for RC models which most often only have 1 cylinder.
    I was looking for the specific transformer that can generate 30-40kv from 300v. Just a small piece of cobber wires around an iron core :) I might aswell just make my own.
     
  8. SimonTHK

    SimonTHK Member

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    They seem quite expensive. I was hoping for a small iron core with wires.
    I dunno if I am going to build it, right now I am just getting alot of info, trying to figure everything out. I have two reasons to do this. Fun and budget, both of these have to be fulfilled for me to make it. Time doesnt matter.
     
  9. shortbus=

    shortbus= Well-Known Member

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    A coil pack from a GM 3.1L, 3.6L, or 3.8L front wheel drive car will do what you want. They have two plug wires per pack and those engine use the"waste spark" method of firing. The ignition on those engine(as are most modern engines) is CD.
     
  10. SABorn

    SABorn New Member

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    Personally i think you have received a lot of bad information here and if you start buying coils from here, and CDI units from there, and other crap, you will waste your money and end up with a pile of useless junk.

    Step back and work through the problem, step by step, and not assume what the fault is.

    The flywheel and stator you linked above shows two coils in the stator, 1 is for the ignition system the other is for battery charging, at a guess i would say the top one that is wrapped up, is the ignition and the bare copper one (at the bottom) is the battery charging system.

    The photo dont show the outer of the flywheel, and there might be two targets on the outer for the pickups, or it could be done with how the magnets are spaced within the flywheel.

    You can test the voltage out of the stator to the ignition, to do this you require a diode and a capacitor of around 400 volt rating, 1uF should be ok.

    The diode is placed in series with 1 stator lead and connected to the capacitor, the other lead is connected to the other side of the capacitor.

    A multimeter is used to read the voltage across the capacitor.
    Crank the motor over and you should see a voltage on the meter of around a few hundred volts, this proves the stator is generating power and not likely to be the fault.

    You can not test this without a capacitor as the AC voltage spike will be too narrow and the meter will not record it, the capacitor stores the charge long enough to be read by the meter. (DC reading)

    Be carefull as the voltage will be high and can bite you bad if you touch it, not enough current to kill you, but by hell it will wake you up.

    I would be hard pressed to think there is not a coil on the machine already for the spark and dont see why it is recommended for you to go shopping for a new one, coils seldom fail, it is normally the CDI or other controlling system (black box as often called) that fails.

    Pete.
     
    Last edited: May 12, 2011
  11. BrownOut

    BrownOut Banned

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    Maybe you should read why he can't use the coil before criticizing the information he gets here.
     
  12. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I didn't even get the idea of fixing/troubleshooting it with correct parts. In fact I didn't even realize it had a CDI ignition. So, I'm confused.

    Plugs have to be replaced. Period. Plugs foul because of engine issues. Inspecting the plugs (knowing what to look for) gives you an indication of what's wrong.

    A weak point is the spark plug cables.
     
  13. SABorn

    SABorn New Member

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    Well i looked and cant see the post that indicates why the coil cannot be used.

    Perhaps you can point it out, or tell me the exact reason why the coil cant be used.

    It obviously use to use a coil of some discription.

    Pete.
     
  14. BrownOut

    BrownOut Banned

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    Rite Cheer. http://www.electro-tech-online.com/threads/homemade-cdi-ignition.118584/#post974243

     
    Last edited: May 12, 2011
  15. SimonTHK

    SimonTHK Member

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    thank you I will try this out. I wouldnt shop for a new coil, only a transformer :) but I think I am gonna build the transformer myself or try and fix the old CDI.

    Generally people come up with alot of thoughts in here. I know some of it myself, some not. Getting ALOT of inputs is 100000 times better than no inputs at all, so my situation is perfect. Yes I can see that the transformers and CDI units linked too in the few last posts are way off what I need. Im glad I can see that myself :)
     
  16. jclaudii

    jclaudii Member

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    To OP...2 stroke engines are a fun hobby of mine, especially those on 650 x2's and older Polaris watercraft. check out the forums over at GreenHulk Personal Watercraft Performance Forums for all your watercraft needs. Many of them have posted over at the pwctoday forums once and even the SBT one's before they got all updity. There is some talk on the net and on the above forums about using 750 stators on the 650's. If you go over there, introduce yourself in the 650 section explain what you trying to accomplish and ask for a better understanding of how the ignition system works...they will probably give you the best/longest lasting method to do what you want.

    Here is a link that uses MSD parts to do alot of what you want:
    http://www.google.com/url?sa=t&sour...sg=AFQjCNGva0q_iLTmoBTEIlllkaSdxqO7sA&cad=rja

    If I was going to play with my ski as much as you are, and I have thought about it...I want to convert either the x2 or the polaris slt750 over to electronic fuel injection...now that would be a fun audrino project :)
     
  17. BrownOut

    BrownOut Banned

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    If you start a thread, please provide a link. I would like to follow along.
     
  18. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Who recommended he get a new coil? The OP asked for that information.

    @SimonTHK,
    Winding the spark coil is not quite that simple as you describe. The ones I have seen were wound in segments with separators to prevent arcing between layers. The other transformer (i.e., the one that is used to get 300V from a battery, if needed) is quite easy to wind as separation of the windings is not that critical. I have seen both coils fail. When I am talking about models, I am referring to some relatively large engines, such as this one: Desert Aircraft.

    John
     
  19. SimonTHK

    SimonTHK Member

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    Yes I wrote this :) When I said coil at that point, I meant the 300v to 30kv transformer, and that might be wrong to express it like that. What I wanted from the beginning was help for understanding a CDI circuit. I got alot help and I concluded that I had to get a new transformer/coil. I look for that now, and it aint easy to find.
    Meanwhile I also got the idea that I MIGHT can get into my CDI box, even though I said I couldnt. But this is a different model from my old model where I couldnt get in.
    So now I am going to try and fix my own first (since the help made me realice thats possible), or make my own transformer/CDI circuit.
     
    Last edited: May 12, 2011
  20. SimonTHK

    SimonTHK Member

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    I have never got any good help from PWCtoday, but I will check the other site out. Electro tech online is allways a very helpfull area
     
  21. SimonTHK

    SimonTHK Member

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