RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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.

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

Yeah,interestng..what ignition is that??

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

dave

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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?

RE: Scratch Built Ignition???
 

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:D, try making a good small coil for a cdi[sm=spinnyeyes.gif]

RE: Scratch Built Ignition???
 

Second the motion :D
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 :eek:

RE: Scratch Built Ignition???
 

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?

RE: Scratch Built Ignition??? Denso coil
 

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.

RE: Scratch Built Ignition???
 

Replied in your PM.

RE: Scratch Built Ignition???
 

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!

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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.

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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:D

dave

RE: Scratch Built Ignition???
 

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]

RE: Scratch Built Ignition???
 

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:D

dave

RE: Scratch Built Ignition???
 

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?


.

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

Bruce

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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.

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

I use this"MAGE FUSE" ignition .

RE: Scratch Built Ignition???
 

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

RE: Scratch Built Ignition???
 

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!

RE: Scratch Built Ignition???
 

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 .

RE: Scratch Built Ignition???
 

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

Thanks,
AV8TOR