Thorspark Electronic Ignition

[chaterlea25]

HI Alan, Stu,
Alan,  going back to the ET ignition conversion, the capacitor can be mounted in the rotor or 2 capacitors one on each coil wire (at the coils). theoritically apparently its better to have them near the points (cant remember why )
wiring off the cutout wire connection is also possible but then you are relying on a good brush connection. I have done this as a get you home bodge

Stu, I believe Alan is talking about the magnetic field of the electronic trigger rotor not the mag rotor??

Regards
John O R

[Alan @Ncl]

Thanks John and Stu
I think there is no real conflict of opinion beween Stu and Me because as John has said, I have now switched the focus back from magnetos (whence we had drifted, very constructively I hope) to the Thorspark system and my potential reservations, having seen one being 'dumped' on ebay.  In retrospect, I should perhaps have put my earlier schematic of the Thorspark system up there again with my spreadsheet (I am going to do so now).  As Stu says, what is inside the mag has no bearing on this since as far as Thorspark is concerned, the mag is only an autoadvanced drive shaft, and a housing to aesthetically hide the bits (Bob has actually, and rather ingeniously, replaced the mag armature with solid shaft).

Stu adds some useful info here though as I did not realise that Thorspark would use an AC coil designed for CDI systems (Is that Capacitive Discharge Ignition?).  Also, I accept if its AC we would use RMS.  Bob measured the resistance of his Thorspark coil at 5.5 ohms (don't know how we measure inductance though: is there auch a thing as a 'Henry meter'?).  Does that add up with an AC type Stu?  I have a twin output coil on the shelf from a Punto, that shows 0.5 ohms so I would not dare put it on 12 volts and wonder how it was used in situ?  Again, Stu might be able to enlighten me (but I digress a bit).

Thanks for your comments too John about the other half of the thread (magnetos).  I think you are right that feeding the capacitor though the end cap brush might be asking for problems long term.  In an earlier post I had two caps up beside the coils and perhaps that's where they should stay if mounting externally.  I think my concern her though was that although these would deal with surges from the external coil, they might not always accommodate surges from the magneto primary since if the brass segment was not lined up, at the point of breaking the current, there would be no where for the surge to go.  But I suppose it must always be lined up thinking about it as the slip ring is synchronised with the CB opening..

Like John, I seem to remember something about caps needing ideally to be near points, but I can't remember the reason.  I suppose if we think of the hydraulic analogy with a surge tank upstream of a control valve, it makes some intuitive sense.  Its all interesting stuff (well I hope it is!).

Alan

[MG]

I have a twin output coil on the shelf from a Punto, that shows 0.5 ohms so I would not dare put it on 12 volts and wonder how it was used in situ?

They are using something like that, with built-in current limiter:

http://www.alldatasheet.com/datasheet-pdf/pdf/25593/STMICROELECTRONICS/VB921.html


What you are looking for is called LCR meter, used to measure inductance, capacity and resistance.

Interesting thread indeed. Has someone ever actually measured the power consumption of the Thorspark system? Even if it is CDI, you'll need energy to charge the cap(s). The figures they state seem very small.

Cheers, Markus

[olev]

The yankee yamaha 650 boys have a neat system.
it could be similar to thorspark.
Check Pamco ignition on the attached link.
http://www.yamahaxs650.com/
I went within a knats whisker of trying to graft one into the A7 before I went my own way.
cheers

[Alan @Ncl]

Thanks Olev and Marcus
That picture in the Pamco seems to indicate a fairly simple circuit with a Hall effect transistor driving a power amplifier of the type flagged up by Marcus.  Only two components seem to be presemt; a pull up transistor (I think that's what they call them) and a zener diode.  Looks like anyone with a bit of electronics nounce (probably not me ) could knock up something like this relatively easily? 

I suspect that this is probably what is inside a Thorspark, basically. Makes you wonder why, if it can be done as simply as this, do some of the electronic systems you see look so complicated (even ones that do not have electronic timing advance)?

Marcus, I guess you are saying that if I were to drive the low resistance coil with a current limiting device such as the one you have identified, it would work as designed?

I had another thought about Stu's recent post on this too.  I don't know much about CDI ignition but would like to know more.  Do you think that the 0.5 ohm Punto coil I mentioned is designed for a CDI system and what exactly is 'reluctance'? Is that the same, or similar to, Inductance?  I know they talk about 'reluctors' in the context of car distributors (replacing points) but never understood the term.

Alan

[MG]

yes, these devices switch the primary coil and act as current limiter to charge it (with short circuit protection, etc), so actually are doing most of the job. Some external components are required, and you might want some more features and a way of triggering the spark, but it is relatively easy to build a basic electronic ignition module around one of these.

Cheers, Markus

[chaterlea25]

Hi Alan, Markus and All,
For your info, heres a CDI circuit  thats for a Morini 3 1/2
The original morini transducer and coil was a one piece affair quite expensive to replace (2 needed)

I got this circuit on the net somewhere and built 2 of it onto a circuit board, I potted the board into  plastic electrical box 3 x 3in and used some yamaha CDI coils from a breakers, the whole lot cost less than £20 and it would throw a spark over an inch
The Morini is now long gone

Cheers
John O R

[Alan @Ncl]

Thanks for the circuit and the info, John and Marcus.  I actually bought a Maplin kit for £10 (which by my reckoning works as in the diagram attached).  I wonder if this does more or less the same thing? It does not seem to have any current limiting capacity though!  I am not completely sure about the implications of positive earth either, if its used with a CB on our bikes (npn vs pnp and all that stuff).

Alan

[chaterlea25]

Hi Alan
the Morini system is self generating, (coil inside the flywheel)
It generates a high voltage to charge the capacitor , I measured it at around  100 volts 

Cheers
John O R

[kiwipom]

hi guys/alan, just keeping in touch between quakes, alan did you ever get that bike going haven`t seen you on the forum for a while,cheers, bob

[Alan @Ncl]

Hello Bob
Thanks for asking.  Afraid I gave up a few weeks back and have not been back to it since. Just had a few nice warm days that I should have taken advantage of but have missed the boat now it seems.  Your prompt has awakened me again though so might have another go this weekend.

Out with some friends tomorrow who have just come back from hols in New Zealand.  They loved it.

Alan

[kiwipom]

hi alan/guys, thanks for the reply if your friend came down to Christchurch they would have seen the vast amount of damage, it will be years before it is fixed. We are waiting for our insurance payout so we can move on but they like to drag the chain, if i decide to come back to u.k. i will be bringing the A10 with me it was so close to finish but now is back in storage,cheers for now, Bob

[Alan @Ncl]

Sorry to hear you were so badly affected Bob. Did not realise you were right in the middle of it all and down in Christchurch. Must have been bloody awful. We sometimes winge a bit about the weather a bit up here at 55 degrees North but at least we don't have issues like that to contend with.  Glad the bike survived in tact, at least, but pity its back on hold.  Best wishes with the recovery strategy.

Alan

[lawnmowerman]

Hi Bob

Hope you sort things out soon. If you do decide to come back to the UK then get in touch - if you end up back in Canterbury then you will not be far from me.

Jim