Tato,

Willdo and Rambo are right. I loved the idea of a cheap, simple ignition that I could "mass produce". After many months of frustration, ordering new coils and transistors, etc, I've come to the conclusion that aI ignition from CH or RC ignitions is the best way to go. You pay more up front but have a bolt-on solution that is bullet-proof. When I factor in the purchase cost of a second coil, 2 transistors, shipping, the waiting, and the mess of re-soldering connections, I probably have spent the equivalent of a professional setup.

I agree that they would be better suited to a lower rpm environment.

Just my 2cents.
Doug

Hey folks,

I just banged out a couple of Emails on some stuff I found. DC to HV DC converters. Here are the specs, Input 0-5 VDC/ Output 0-300 VDC. Weight 4.5g. If Im correct this is the perfect triger for true CDI coils. No home made coils!! I have spent the last 2 days in a logic circuit manual and think I may be able to make a low cost advance unit. Im waiting on the price of the DC to DC converters but the timing should be able to be varied with an osscillator IC and an NPN transistor.

Mike

Mike,
i've also looked at some of those converters and the prices were astronomical! the euro ignitions use an off the shelf double E core transformer that includes the feedback coil.

and seeing that you're electronically literate[8D]how about an advance circuit using one of the frequency-to-voltage converters like the LM-2917?


dave

I'll get the hang of this. I hope I can do a better job keeping up in the future. Sorry for the delay. Here is the latest Weed Eater 25cc that I converted to take to the Toledo show.

rsholl: What ignition system did you use on the 25cc engine/ Thanks Capt,n

Yeah,interestng..what ignition is that??

Also,does anybody know how to hook up to the stock coil's primary but bypass trigger coil?

Mitty, the old points triggered coils can be found on just about every old dead briggs mower engine....check your local junkyard.
with a little prying the big metal "A" core slips apart to free the coil. you then add your own smaller core and you're ready to go. they're still a bit heavy but they do work.


dave

It's the one I designed using the PIC micro controller. The unit pictured with the WE25 has a CH coil in it. I also use D&B coils. I originally used CH ignitions when I started converting the Echo engines. I would like to thank Bill and the gang at CH as they were very helpful and do build a great ignition system. I have the parts but not the time right now to add electronic fuel control to my ignition system, that is one of the main reasons I developed the system I did. Right now the HV coil is the primary cost of building an ignition system. What are your thoughts on using a 12 volt battery for an ignition system. I also looked at an inductive system which uses less parts and at 12 volts doesn't need a DC-DC converter. The HV coil becomes more critical, as far as turns ratio, and maybe the new Li-Poly cells would work. I'll try to post a picture of just an assembled board. So far the email from my post (150) sounds like most would rather buy a complete system as opposed to one in kit form.

Roy

Roy, what are you using for the converter, toroid or E core??

dave

Unfortunately it is a special wound coil. I am quite sure it is an E-core. I have been over the same paths many of you have been over. Like many of you I could not find suitable off the shelf items to build a good DC-DC converter. Here is the pic of the board I just finished soldering. I will continue to hand assemble until volume dictates otherwise. I enjoy these sessions but it is hard to keep up.

Thanks, Roy

Greetings All,

Hey Roy:Nice work on the surf. mt. pc., hope to see more on your project.

Just read the entire thread. Yikes! Good material, a few ruffled feathers. Hmmm.... [deleted comment] fault me if you like:

I'm trying to come up with an easy to make advance method too. I would take it on for fun. I love the challenge, hey, just tell me it can't be done. With no challenge you might as well lay down in the pine box for a nap. Good nite Ollie! I am considering the beat frequency overlap (or lack of) between the hall sensor (whilst der engine is running mine friend) and a stable oscillator. Think about how the vernier scribings work on a pair of calipers. It would be linear advance, not curved, and not as nice as a programmed chip set up as referenced earlier in this thread, but I'm not doing pylons. I'll post something if it bears fruit.

The coolest thing I found on this thread was the home printed circuit mfg. via the link to 5 bears earlier in this thread. My hand wiring method with buss wire could use a rest. Good stuff (insert Tim Allen grunts) Aghhhh Aghhhh

Thanks for the great reading & info!
Hope to contribute if I stumble onto something worth posting.
Doug

I did not make it to the Toledo Expo this year. Did anyone see or hear of anything new on ignition systems there? How about new gas engines???? Thanks Capt,n

Wake up...you people who would like to build a scratch built ignition. A fellow has posted about a denso coil. Check it out. His post is nearby and shoud be in this batch of good data. Thanks Capt,n

This is a good thread, but I wonder whether it should be split up. Some of the posts are about transistorized kettering systems, and the rest are interested in true CDI. A few are even interested in computerized timing advance. Looking back on this thread, when the electrical engineers among us start discussing CDI and computers, someone will pipe in with a question about TIM6 or modelectric coils. Neither camp is being well served: the kettering types are confused and the CDI'ers are distracted.

One of the hurdles to communication and understanding is that those following the kettering path probably don't even know what kettering means...

Another distinction needs to be made. If the goal is to putter around and learn about the workings of engines, then scratch-build. If one prefers to have a reliable, quality, economical high-performance solution and to spend time flying the engines, then by all means purchase the packaged solutions (e.g. CH ignitions). To those in the second category: let us dedicated scratch-builders and tinkerers waste our time and money with our handfuls of DigiKey parts. No more chiding us to go out and buy the CH!

That said, shall we start a new CDI-only scratch-builders thread?

The CDI it self isn't magic or anything. You can get a running tested board from us at CH or from the "other" guy. at R.C ignitions,
for less than you can make one. If you want to tinker and become rich and famous, try making a good small coil for a cdi[sm=spinnyeyes.gif]

Second the motion
Hey Willdo, your "blue light" I sent on 2/25 just came back today, the envelope said
duplicated street name, suburb required..PM me a good address...Must have come on a slow freighter

For cheap coils, how about motorcycle/ATV coils like the Denso stick coils? A local motorcycle shop gave me a used one for free. Anyone have experience with these?

The Denso coil may work don't know for sure though. BUT what would it cost to buy a 100 of them???, thats the rub.
The current CH coil is .75x1x1" and weighs less than 1oz. This is the coil size we need in the $3 price range.
Then we can work on a $60 ignition.

Replied in your PM.

rwilder
Yes I do think that a " CDI only" thread would be good, I tried to make the distinction a few posts back, but I'm no expert in building them, and a little bit lazy, so I ordered an RC IGNITIONS unit.
You'll occasionally still get the same problem ( confusion between Kettering and CD ) though!

In reply to post 214, I would NOT like to see this thread split up between Kettering and CDI, and would like to keep the thread intact. I believe that the main source of confusion is the difference in design and coil requirements between Kettering and CDI spark generation circuits. I agree with post 220 that this confusion will continue whether or not the thread is split.

I believe that the confusion could be reduced or eliminated if an EE or manufacturer could briefly describe the design and coil differences between the two circuits so that we all could be on board here.

Bruce

I think that the confusion only arises when the average person hears the words "electronic ignition" and we don't realise that ignition systems can still be "Kettering systems" even though they use an electronic circuit breaker.
I do agree that we need someone who can give us a clear distinction between these systems.

Hi
To understand the CDI ignition you must have a good knowledge in electronics because to understand description you must have background in how
a) behaviour of discharging capacitor
b) thyristor
c)up converters (direct current to direct current)
d) oscilators
If not , you are confused with technical words and you loose the path, also you need it to scratch build your own and a lot of practice in other items also ( printed circuit building, measuring, winding, soldering,testing and tuning) you can not learn electronics thru building a CDI , it have a medium level skill needed and you lost time and money if not have it.
I am lost many hours winding and testing , but was a personal challenge, spend small amount of money because I recycled MANY items , if not think in spend and go to the shop.
Sorry my english.
I would like put a bit of light in this discussion.
The last part of post 214 is TRUE, I learn it in the hard way. For this reason I choose my SIGNATURE.
Many thanks for your time
Jose

i am neither but i do understand the diffs. my terminology may be a bit off so feel free to correct me.....

KETTERING: the energy for the spark is stored in the coils primary winding and then dumped through the secondary to increase its voltage. a high inductance coil works best for this and requires a high number (100-200) of primary windings and because of the need for the correct ratio between primary and secondary you end up with an astronomical number of windings in the secondary. add to this the need for good insulation between each layer of the secondary and the heavy iron core and you get a big, heavy coil. if you try to miniaturize the coil (like the modelelectric and gettig coils) you start giving up reliability.

CDI: something between 150-400 volts is stored in a large capacitor....when the ignition is triggered this energy is sent through the coil that acts only as a step-up transformer to get the high voltage needed for the spark. this is the same system used in flashes, strobes and stun-guns. low inductance is best here so you don't need more than 20 winds on the primary of the coil. the massive insulation can also be tossed out and a small ferrite core used.
the coils used in some of the CDI ignitions (magneto and battery) weigh less than 1/2 oz.!

whew

dave

A very good description Dave!,
Don't forget though, that the 150 - 400 volts DC has to be obtained ( in RC models) from a 4.8v - 6v battery, necessitating a DC - DC converter, ( usually a toroid type transformer arrangement) which I don't believe I am qualified enough to describe.

Maybe someone else can give a good description of this, and between us all we'll be able to clear up all the mysteries and misconceptions! [sm=idea.gif]