ah yes...with a magneto we don't have this problem as the source coil is already set up to make the high voltage needed to charge the cap...

DC-DC converter: DC battery voltage goes through an oscillator and comes out as AC which then gets bumped up to high voltage AC by the transformer coil (both toroid and double E core can be used) and then gets converted back to DC with a bridge rectifier.
all this is needed because trying to put DC straight into a transformer makes a big bang

dave

I have used various US made ignitions and a good friend makes one (Al Diem).
Al explained to me how the various ones made in USA operate-and some of the pros and cons.
Iam not versed in this design area.
anyway - his early, simple one used much the same current -at any rpm . later ones use more current and produce more current out of the coil..
Anyway - I have been running various ignitions made overseas -in Czech Republic.
Some are made by Falkon and the others -are not identified.
Here is what seems particularly interesting to me .
ALL use fully shielded plugs -some with machined caps that have nicely cast rubber insulators in them .
One has the high tension lead attached to the spark unit via a Co-axial connector -which is the same as used on my tv - I checked it -it fit.
The advantage is in repair and ability to fit cables and caps for differerent size plugs.
All appear to have a timed out to OFF circuit- to shut down an idle system
One has a built in tattletale which reads out via a small LED -and the two example I now have -work perfectly -
just read the LED by placing a tach in front and the rpm (1/2) appears
4400=8800).
it is very handy. You can read when testing or after a flight.
A feature I would like --is a heat sensor which -perhaps reads the plug base temp - when a preset temp apears,- it could -perhaps cause an intermittant stutter of the engine - letting you know you are running to hot -or hotter than intended.
Isn't there anyone in th USA setup to make some integrated ignitions?
What I now see are nice working units but where is the innovation?


.

Great stuff Dave!
Let's hope that people will see the difference and move on from all this silly "Kettering" talk for aircraft engines.

Thanks Dave. That was an excellent description and was the type of information I thought was needed.

Bruce

I thought this page might be interesting reading. Dave is definitely on the right track. http://ourworld.compuserve.com/homep...ition/CDI.HTML
One of the main reasons I incorporated the PIC in my board design was expandability. Dick Hanson posed a question on thermal management. One of the main reasons I used the PIC in my system was so it could eventually include fuel and thermal management. I would be curious to know how sophisticated a system modelers would buy and what they would consider a fair price to pay for it. Thanks to Dave for the coil links. I believe this unit will work but I think their shipping is a bit high. http://www.amazing1.com/transformers.htm I did find a company willing to sell small quantities (that means less than 100 pieces) of coils and I am presently testing one now. I am sure it will only work on a true CDI system because it does not have the turns ratio need by lower voltage systems.

Roy Sholl

Thanks Roy. These links provide excellent information from both the theoretical and practical perspective. I had a question about one of the coils (transformers) for sale on the "Information Unlimited" Website (second link). Was the CD25B transformer the one that you thought might be suitable for model engine use? With 25KV output it seems that it has enough voltage to fire model engine spark plugs. Also, should I ASSume (thanks, Ralph) that the input needs to be 300V (300V capacitor) for the output to be 25,000V, and that the turns ratio is approximately 83:1 ?

Thanks,

Bruce

Correct on the CD25B coil. Depending on the coil being tested I have found that the input voltage can be in the 200 to 300 volt range. I believe engine compression affects the coil output as much as anything. I have a new California compliant Weed Eater 25cc that I have done some testing on and have been able to run it on some small coils at 150 volts input. This engine doesn't have much compression when it is hand cranked but it turns a Master Airscrew 16X10 at 6,600 and it is still stock including the muffler. I have been unable to measure the KV while an engine is running but I am sure for the range of engines being converted today it will be in the area of 10KV for low compression engines up to 20KV for higher compression engines. If I find a reliable way to measure the voltage on a running engine I will post it for everyone. I am trying to finish testing the latest coil that I recieved last week. The lead time for an order is 4 weeks and if the coil passes initial testing I hope to be able to offer it for $15.00 and could possibly include either a spark plug wire installed or shipping.

Thanks,
Roy

I am not sure on this....but maybe 17,000-20,000 Volts may be high enough. With the spark plug gap set a .020 that voltage may jump it just fine??? I am thinking to high of a voltage is going to cause radio glitches and burn through insulation in coils. Just a thought. Catch you later .....Capt,n

Here are some motorcycle coils I acquired recently ( approx $10 each) and am hoping to use.
Sorry about the picture quality, but you should get a good idea of size.

There was a rule of thumb when i was in school that for spark to jump 1 mm in dry air you need 1000 volts

I use this"MAGE FUSE" ignition .

Tomy, Tell us more about your ignition system. Can you share some details ?

Is that a CD ignition? ( must be, I see the small toroid coil, but no little box).
What engine do you use it in?
Looks very small and compact!

this is a factory build CDI ignition . only weigh 83g . and use epoy seal all inside incase crash or humidification . this ignition are using 4 or 5 cell battery . very strong speak. aluminium shell and ferrite ring can eliminate all EMC interfere . but only one things , this is not repairable but it's reliable I use this ignition on my S.P.E 40Z engine . 40cc ,1600g total weigh , sway 20X10 prop up to 6400rpm . very good ignition and engine .

How much does the ignition system cost, and can you send it to U.S.A.??

Thanks,
AV8TOR

this ignition are 69USD per set. and will coming to USA at June

Tommy

Let us know where in the US we can but these. I want to give one try and put it on my Ryobi or Homelite conversion.

Thanks

they are two company selling my Ignition in USA, one is in New York .
Jyandec Business Management Corp
45-59 215 PL
Bayside NY 11361
Mr Jiande ChU
--l(FAX) 718-428-5819
[email protected] <[email protected]>

other one is :
Soonest Express. 533 Airport Blvd Suite 219 Burlingame CA 94010
Tel: 650-283-9000 Fax: 650-342-0185
[email protected]

Mr Jerry Ho

find one who close to you and contact them

Tommy

HEY everyone. If anyone wants info on how to build or where to get parts for building CDI ignition Let me know.Has anyone had any luck with the auto advance using the PIC ?

Does this CDI use off the shelf components? Is it a 5 volt system? What info is available? My system uses a PIC micro. I have also found a source for the spark coil and they should be here in a couple of weeks.

Roy

Yes it uses standard components that you can find at mouser or digikey.It operates off of 4.8-6.0 volts.The transformer that I use is a e core. and parts for that are avilable too.I have been making my own transformers.I get around 300- 400 volts from them. I have schmatics and part #s

Does anybody know where I can get ignition coils from? other than ch.Thanks

Good luck...You won't likely find any smaller, certainly not any better......And unless you buy 500 or more at a time, probably not cheaper....

Hi

c_moore

I am using with success high voltage coils from Honda Transalp , TEC brand, all the modern japanese motorcycles small displacement are with CDI and the coils perform well.
If you have no problem with a bit of weight go to HV motorcycle coil.
Also you can use recycled HV coils from Byke repair shops.
I have bought a new and make test and after when all runs properly I switched to recycled to avoid mistakes and focusing only the coil.
In the back of coil you will find two tabs the green is positive and black is negative and must be connected to the negative of battery.
I am tested many hours in a test stand in a 38 cc Homelite chainsaw engine and flown a Weedeater 18 cc with the Tec coil, no problems, make a shield in the HV cable and things go well.
Have luck
Jose

http://home.online.no/~jon-mj/cdi_ignition.htm

Check this site for a scratch built cd ign.