Author Topic: Newfangled ignition coils (Read 14733 times)

geoff_p · « **on:** July 12, 2012, 04:44:58 AM »

For my hit 'n miss engine I need an ignition coil. I had hoped to use the old familiar points + condenser + coil method, and there are plenty of circuits shown on the web about them but tracking down a suitable coil is not so easy over here in Thailand.

However, motorcycle coils are plentiful, at least the newfangled ones are. They seem to contain some electronics but with no indication of even the polarity, let alone the workings. (I know this because I just took one apart by melting-out the pitch that filled the case.) The only markings/label on the one I just bought are "MAX R" and a Google search for that just didn't help at all!

Can any of you explain
a/ How they work;
b/ How I might use a newfangled coil? I'll go away from points if I have to.

Cheers,

Geoff

krv3000 · « **Reply #1 on:** July 12, 2012, 09:13:34 AM »

hi i will find a pic that i have and sum info on the one im thinking of its the type that you will find on lawn mower engins they get trigerd by a magnet on the fly wheel i will post you the info tonight but whot i think you id describing is the ampleyfier IE ther is no ponts ther is just a magnetic triger on the fly wheel ther is a magnet this pases over the triger this sendes a small eletrikel pulse to the ampleyfier wich then trigers the coil to spark sos for the spelling

krv3000 · « **Reply #2 on:** July 12, 2012, 07:11:52 PM »

hi will this help

geoff_p · « **Reply #3 on:** July 12, 2012, 10:19:19 PM »

Thanks for that, KRV. Unfortunately, it doesn't help - the lower part of that pic is just about what I have been trying but with a new coil in its place. The primary current is something over 10 Amps (the books all say 1.5 to 2 Amps), and the coil becomes untouchably hot in a few seconds.

The type of magneto-coil depicted had no electronics in it, it was a simple transformer in effect.

The coil I have never went even close to the engine - it's mounted on the chassis, somewhere under the saddle - so it never gets a magnetic pulse, either as power or as a trigger.

The guts of the coil I broke-up clearly contains a circuit board with some resistors, a large capacitor and a power-transistor, all of which suggest the thing should be polarity-sensitive. But which polarity? My Honda motorbike's manual gives no indication.

I'm guessing that both power AND control-pulse must come in to the thinner wire - the fat one is HT to the plug - and there was a second, orange lead riveted to the core, which I assumed to be ground/chassis return to the battery.

Geoff

awemawson · « **Reply #4 on:** July 13, 2012, 03:44:36 AM »

Well lets do some (dangerous!) assuming. Assuming that the coil mounts to the chassis of the motorbike then the extension of the transformer core, which seems to be being used as the mounting, must be the polarity of the bikes chassis. Since about 1970 practically all vehicles have chassis negative, so I reckon that there's a 95% chance that the transformer core is negative, hence the other conection must be positive. It probably has a simple 'amplifier' ie current switch in this case so if you have powered it up probably the switch was permanently 'on' hence the high current draw - it will be expecting pulses from the sensor in the engine.

geoff_p · « **Reply #5 on:** July 13, 2012, 06:37:21 AM »

I made the same assumption, that chassis would be negative and the other connection positive

I agree that the electronics could be an 'amplifier' so as to convert the triggering pulse (presumably very low power) into a large-enough current pulse to energise the coil.

So now we have an earth/ground at 0volts and a +ve supply to the amplifier through the small lead.

How does it receive "pulses from the sensor in the engine"?

Geoff

tomrux · « **Reply #6 on:** July 13, 2012, 04:38:53 PM »

the majority of motorcycles use CDI type ignitions these days. you would be better of trying to get a coil of an earlier bike. you need to go back to the early 80. once they went electronic things got complicated real quick.

Tom R

David Jupp · « **Reply #7 on:** July 13, 2012, 05:03:53 PM »

May well also be designed to run via a ballast resistor in normal use (which is bypassed when cranking the engine) - this ensures a decent spark when cranking on a cold morning. So don't apply full battery voltage or it will overheat.

shipto · « **Reply #8 on:** July 13, 2012, 06:20:42 PM »

my understanding of these things is that voltage will only be produced in the HT side if there is a intermittant/pulsed voltage on the other side and they are just basic transformers. I suspect the electronics only supress bounced signals and/or interference.
So what I would do is take a wire from the negative end of a battery bolt or wrap it around the earth of the coil and then around the earth of the spark plug, then just brush the live wire across the positive quickly and see if a spark is produced.
I suspect that it will but I could be totally wrong so try it at your own risk.

geoff_p · « **Reply #9 on:** July 13, 2012, 07:37:56 PM »

My thanks to all of you for your contributions, though none seem to answer my original question "How [do] they work?"

Thailand has a terrible history of not looking after history: in a country of poorly-educated people, older stuff is just discarded when "new" comes along, and this is especially true of technology.

So my chances of finding an old-style coil in Thailand verge on not-likely-in-my-lifetime. But I do want to get my engine running, so I've by-passed the problem,

and have ordered a complete CDI system from Messrs Hobby King. I just hope I can adequately hide the blooming thing.

Part of my aim in the engine's build was/is to demonstrate older technology but I guess I'll have to moderate it to "mostly older technology."

Geoff

shipto · « **Reply #10 on:** July 13, 2012, 08:03:05 PM »

As i said a igintion coil is basically a transformer you have a pulsed signal going in one side and a pulsed signal is then produced on the other side. mostly transformers take high voltage and reduce it to a useable level but in a ignition coil they work the other way around taking a low voltage (12v) and turning it into a high voltage (usually many thousands of volts)
Again I am guessing but i think the electronics in modern coils simply filters out interference and bounced signals so you get one single and strong spark for each operation.
They will not transform dc voltage which is why yours is getting hot you are just short circuiting the low end coil.
this may explain it better http://science.howstuffworks.com/transformer-info.htm

geoff_p · « **Reply #11 on:** July 13, 2012, 10:51:25 PM »

With respect, shipto, I think you are barking up the wrong tree.

I'm not attempting to "transform dc voltage " and I most certainly am not "just short circuiting the low end coil". Shorting-out the coil would mean near-zero current through the coil (it all being by-passed by the short) so there would be zero heating.

My switch (lets call it "points") is in series with the coil-primary; the points are paralleled by a capacitor. What I haven't achieved is the 'ringing' that builds the primary volts to 200~300 volts as suggested by most descriptions of ignition systems.

As I said in my previous post, I've decided to use a new-fangled CDI system; I'm giving up guessing.

Geoff

Jasonb · « **Reply #12 on:** July 21, 2012, 02:37:56 AM »

Saw this a bit late, have a read of this article, although its about making a buzz coil it does also describe how to use it for a single spark. I also tells how to test the coil and yes the bar in the middle is the negative to both primary & secondary coils.

http://gasengine.farmcollector.com/Gas-Engines/A-Sparker-For-Your-Engine-June-1988.aspx

Click the image gallery tab to look through the various diagrames.

J

russ57 · « **Reply #13 on:** July 21, 2012, 05:12:23 AM »

Jan Ridder (ridder.nu) has done some work on ignition systems for small engines, -co-incidently he has just updated the section. May be some clues there, even if not directly applicable.

geoff_p · « **Reply #14 on:** July 21, 2012, 06:42:57 AM »

Indeed, Jason, Jan Ridder's work is fascinating - I spent most of an evening reading his page on ignition systems.

I had actually incorporated a piezo-ignition from a cigarette-lighter but found, quite independently of Jan, that the force required to 'squeeze' it is considerable. Of course, this is happening during the compression stroke so the poor old flywheel has to supply a lot of energy.

Anyway, as mentioned earlier, I'm going the CDI route: the system I ordered from HobbyKing has arrived and installation has begun.

Thanks for all your help and ideas,

Geoff

HS93 · « **Reply #15 on:** July 21, 2012, 07:05:01 AM »

Geoff stay over hear, you dont get the crap that you get on the othere site (Ma****m)

Peter

geoff_p · « **Reply #16 on:** July 21, 2012, 09:18:19 AM »

Whoops, sorry Russ, my opening should have read "Indeed, Russ, Jan Ridder's work is fascinating ..."
Geoff

andyf · « **Reply #17 on:** July 21, 2012, 01:10:30 PM »

Quote from: geoff_p on July 21, 2012, 06:42:57 AM

Indeed, Jason, Jan Ridder's work is fascinating - I spent most of an evening reading his page on ignition systems.

I had actually incorporated a piezo-ignition from a cigarette-lighter but found, quite independently of Jan, that the force required to 'squeeze' it is considerable. Of course, this is happening during the compression stroke so the poor old flywheel has to supply a lot of energy.

Anyway, as mentioned earlier, I'm going the CDI route: the system I ordered from HobbyKing has arrived and installation has begun.

Thanks for all your help and ideas,

Geoff

Geoff, as Russ says, Jan Ridders has added to his spark ignition page very recently. having found a small lighter circuit which isn't piezo, so no squeezing is involved. Too late now, I suppose.

http://ridders.nu/Webpaginas/pagina_blokker_vonkcircuit/blokker_crcuit_frameset.htm

Andy

geoff_p · « **Reply #18 on:** July 21, 2012, 03:31:03 PM »

I'm pretty sure that is the page I read (and saved-off for reference) but thanks anyway.

Foolishly, today I decided to re-thread my cylinder head for M10x1 for the CM 6 spark-plug - it had been M6 to suit my home-made plug.

Being unwilling to go to town to buy a 9mm drill (M10 tapping-size) I fiddled and faffed around and have ruined the cylinder head.

So tomorrow I'll just have to cast a new one, drat it!

Geoff

krv3000 · « **Reply #19 on:** July 31, 2012, 03:48:48 AM »

hi geoff p sos for the delay in the replay im gowing off a 125 singel silender engine right on the honder ther is a altanator with a flywheel on the out side of the fly wheel ther is a rased spot this is magnetised on the inside of the altanater hawsing ther is mawnted a triger coil as the magnet passes this coil it preduses a smale voltige thes then gose to the coil the electronics in the coil amplefiy the signel and produses a sparke

MrSleepy · « **Reply #20 on:** July 31, 2012, 04:20:58 PM »

If you do decide to use a CDI type ignition coil you may find this site interesting..

http://www.sportdevices.com/ignition/ignition.htm#differences

It shows the basics of how the CDI system works..and how the coil is energised by a generated 300vDC.. through a capacitor.
The spark being produced by the firing of a thyristor and subsequent grounding of the primary(through the capacitor).
Which may require you to add a microcontroller to obtain the required timing accuracy.

Rob

geoff_p · « **Reply #21 on:** July 31, 2012, 06:57:35 PM »

Many thanks to Rob for your link, which is most informative.

And to KRV: I worked out what you are saying and realise it exactly fits the motorcycle coils I have.

Where I had been trying to use these coils in 'the old-fashioned way' of interrupting a (DC) current through the primary, KRV's description makes total sense - a flywheel-magneto 'dumps' a short-duration, heavy current into the primary, which is of very low impedance.

It also makes sense of why my Thai motorcycle-repairman friend, who speaks almost no English, couldn't understand my problem - we were coming from diametrically opposed views, though we didn't realise it.

Again, thanks to all for your input.

Geoff

krv3000 · « **Reply #22 on:** August 01, 2012, 03:06:53 AM »

no problem geoff_p glad to hellp sos for me spelling

geoff_p · « **Reply #23 on:** August 01, 2012, 08:11:31 AM »

Well I tried Translate.Google.com for geordie first

, then I realised it was just spelling.

Cheers,

Geoff

News:

Author Topic: Newfangled ignition coils (Read 14733 times)