I think I may have found a source for transformers - I recently bought one of those electric fly swatters. It has a basic circuit inside to take 3V, convert it to ~8V AC (19kHz) and it has a center tapped x-former that converts it to ~178V AC, does a very basic rectification (and somehow it ends up generating what my meter says is 980V DC though the capacitor is rated at 250V) circuit and a 250V .22uF cap.

Considering they're only $5 and the transformer is the ideal size (physical appearance anyways) I think I may try creating the circuit with one. Is it possible to modify the circuit to run with a center tapped transformer? (It is CT on both sides if that matters) If we didn't have to wind our own transformers, it would be very nice. I may try a variation of the original circuit as well. I'm pretty certain that it would run on 5-6V DC just as well (if not quite a lot better) than 3V. The transistor in the circuit is unlabeled.

I'm sorry, but this transformer will not work........the power is mutts to low to load the capacitor in fast rate for the bobine.
I've try several transformers, a e-core or ferritring like we describe on the site (or bigger) will do the job.

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We gone do some calculation to understand the powerboard,

To get a big/strong spark, we need Joules.....a lott of Joules, mega Joules.
For a good spark and a high rpm we need about 90 mJ. (45 mJ for ~8000 rpm)
This Joules we get from the capacitor and the high voltage coil on the powerboard.
If we have 300 Volt from the coil and the capacitor is 1 uf, we have (0,5*C*(U*U)) = (0,5*1*(300*300)) = 45 mJ
With this calculation you can see we don't have enough Joules.
Wat can we do about this.....
Increas the capacitor, but you get a longer load time....not good !
Increas the voltage, easy to do......more windings.
If we have 600 Volt from the coil, we get (0,5*1*(600*600)) = 180 mJ, we need only 90 mJ !
Now we can decreas the capacitor to 0.5 mF, this will also decreas the laodtime from the capacitor to 1/2 of the normal loadtime.
If the laodtime from the capacitor will be shorter, the rpm will be increas.
We need also some current with this voltage.
A easy way to do this is to wind prim two windings (to gether) on the coil (2x 20 windings of 0.5mm).
The sec-winding must be increas to ~1200 of 0.1mm to get ~600 Volt.
BTW, don't forget to make the resistor of the ocsilator smaller ~1/2 of the normal value for a higher rpm.
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Hay guys this is some real good work you have going an here. i have been following this with great intrest for some time now and was just wondering if the project was still active or if the circuits and programs that are up on the [link=http://www.modelbouw.gompy.net/newcdi/newcdi.htm]http://www.modelbouw.gompy.net/newcdi/newcdi.htm[/link] site are the final developments. i have to congradulate u guys on the work u have done on this. this is some good stuff.

Maybe a short discription (howto) is missing, but it's the final development.
A howto in Dutch isn't a problem, but english isn't my first language so it's harder todo.
The CDI is foolproof, easy to build and no exotic components, thats wat we (JMJ and I) want.
Last modification was the low rpm (0-1800 rpm), it wasn't stable, but this is fix now with the new c-code.
Some members of my club use the cdi and also one is fit on a 50cc racebike.

Thats awsome look forward to it. I have a 28cc Ryobi for a spartan executive that is in want of a conversion and a mate at my club has a 100cc chainsaw engine fro a Gee Bee so that will be hot. thanks again for the work you and JMJ have done an this project it is some top stuff.

Thanks from the guys at Croydon Aeromoders Club Vic Australia

P.S a description of the transformer would be good bit confused about that thaks

Hello, can you tell me where did you get the T1 - Bobine, or how it is made.

Thanks.

If you mounth the hallsensor 40 degrease BTDC.
The engine will start with ~ 15 degrease BTDC (easy start) and on 1800 rpm it wil jump back to ~35 degrease.
This is normal for allmost all engines, but you can changed it in the Exel-sheet.
After the 1800 rpm, you can make a advange curve by your self with the Exel-sheet.

The bonine I use is from a 50cc pocket/mini bike

See [link=http://home.online.no/~jon-mj/making_the_transformer.htm]this page[/link] how to make a transformer.
The configuration of a ferritring or E-core transformer are the same.

Sometimes you try to help people, send them a (free) pcb and after all you don't hear anything off them.

Bigboat: What is a bonnie? Do you have a photo of one? Capt,n

I've no idea wat (who) a bonnie is, but a bonini is a other word for bobine.

Hi guys,

I am new to groups, but this topics really stirred my interest.
Will catch up soon.
Thanks

This project is a thing of beauty. "$90 for electronic ignition!" No more

I'm glad there are smart people out there to help us electronic Magoos out.

We are very curious who have allready build the (new)cdi and how it works on your engines.

Hi,how can i trigger the pic (pin 7) witht an inductive pickup( like on a scooter)? i dont want to use a hall.I am thinking trough an optocoupler ,but i am not sure how pin 7 must bee?high or low? thanks.

I hope you guys get something working good soon....life is short!!!! Capt,n

The fly swatter transfor needs a rewind. Charlie helped me with mine and if you soak it in laquer thinner it will basically fall apart. Then you can rewind to specs. The reason I am using this is that I found you have to buy a large quantity. I bought 12 around $1.50 on sale. I let the lady know if she has any more with broken strands I would buy them also.
I am also winding a toridal transformer which is fairly small and the core I am using is comparable to Digikey pt. P12722-ND. They are 5.70 Can. for 10. I think these would be better as I am finding the ears on the swatter transformers break very easily. Wind your wire on a shuttle and sit down and watch your favorite sport and when it is over you have one made. Also if needed you can pack on the extra turns.
John

Here is a link to a thread in Gas Engines in which a problem with an initial spark as soon as the ignition is turned on is described: http://www.rcuniverse.com/forum/m_5098867/tm.htm

The initial spark caused the motor to start unexpectedly, and the operator got caught by the prop. Does anyone have experience with this open-source design giving an initial spark on start up? Thanks.

This CDI generate only a spark AFTER the first magnetodetection.
The timer needs this first detection befor he can calculate the time for first spark.
You don't get a spark by switch on/off the CDI.

Actually there can be a spark when you power up an ignition. This is taken from CH Ignitions' instructions that come with every module I buy from them.

SAFETY NOTE: The ignition can fire one time when the switch is turned off or on. Stay clear of the prop when turning the ignition off or on. If the engine would happen to be on compression, it could kick over.

Hope this clear things up.

I'm trying to order all the components from this place http://www.mouser.com/ and they only sell the lp2950cz in bulk of min. 2000. Is there a replacement for this IC?

You can use all lowdrop regulators, but not the LM78(XX).
This regulator(s) needs a voltage 3Volts higher as the voltage you need behinde the regulator.

OK, Bigboat, I found one. It's called LD1117. It is in a TO220 housing but has a different pin setup. I looked at the PCB layout an it is not a problem at all to change it around a bit.
I still struggle with the choke. I'm not familiar with these things (chokes) and I'm not sure what I have to look for. I found something on the site I mentioned above but it cost more then two dollars which makes it more expansive then the pic chip. Would you have a number for the one you used or something like that?

Yoram

You can see on the website, we use differend kind of chokes.
Ferritrings or T-cores, but they are all the same.
JMJ starts with ferritrings, but it's a hell of a job the put 400 winds to the ring.
I foundout we can also use t-core transformers, but they are more expencive as rings.
It doesn't matter wat you will use, it's more wats easyer to get or have.
One you don't forget, all winds MUST into the same direction.

Bigboat, I meant the 1mH choke, the one that looks like a resistor. I found it on that site but I have to buy a minimum of 1000. Can I use something else instead of it?

Yoram

Take a old wireresitor, cut the wire some where and wind about 10 a 20 winds of 0.2mm around the resistor and you have a choke.
It's nothing more then to eleminate some spikes of the HV-part.
You can even try the it without the choke (shortwire), only if there are some problems you need it.