Tests of CDI Ignition Modules

[dsage]

Thanks Paul:
Propclock's SMD version of the ignition module is the cats ***.
Not as DIY friendly as the original but small is good IMHO. A nice improvement.

Perhaps you can post a picture of the assembly with the coil.

On the reed relay idea. I tried them. When I passed the magnet over it the reed it stayed permanently closed. Maybe the magnet was too strong?? Probably cheap reeds too. I had it on the module where the hall sensor normally goes so there wasn't too much current (welded contacts) Any ideas?

Also: Do you have a link to the coils. I did get them for your quoted price a few years back but....I've found the prices are really high now.

 

[DKGrimm]

Pardon my ignorance. I'm noticing potential (across the plug gap?) after the 50 microsecond mark but no current flow. Is this indicating the energy (ExI) is dumping off somewhere other than the plug gap, such as through heat, coil, or other losses?

No ignorance; good question. The plasma in the arc collapses when the current drops below a threshold value, and the spark plug becomes an open circuit again. The remaining circuit rings as energy remaining in transformer/coil inductance, stray capacitance, and other parasitic wiring impedances trade back and forth to produce a damped sinusoid. The waveform I posted in #154 is interesting; it shows two different ringing frequencies ringing at the same time. I imagine one could figure out just exactly what is resonating with what there, but all ignition systems ring at the end of the spark, and I've not spent the time and effort to analyze that part of it.

 

[DKGrimm]

You can derive mathematically that the magnetic energy is stored in the air gap and only there. The air gap can consist of a voids in the material or a created one. There is a difference in a saturated core and an unsaturated core. There are two types of transformer designs and they both have different purposes. So I am attaching some lecture notes you will or should find interesting. It talks briefly about this subject. Some references talk about distortion of the field and the volume available is not just in the physical area from the volume removed. If you want the high voltage to the spark plug it worth while looking at the right transformers.

Thanks for the attached notes. I'll have to find the time to check my own conversion table lists from post #135 to see if I made any mistakes.

 

[Zeb]

I just re-read Dsage's statement not realizing he had brought up the same thing. Reading on the phone is a bit limited with all the ads. It makes sense that anything happening after the current stops flowing is not of much use.

 

[rsholl]

Don, in post #154 is that CDI one of the open boards with the spark coil on the end of the CDI? If it is I may have a schematic of a circuit very similar to it and or the CH units. Just so you know, Bill Carpenter from CH worked with Rcexl to develop that circuit until Rcexl took over and parted ways with CH. The very early CDI units I sold came from Rcexl and I did some modifications to make it more user friendly. Let me know if you and or Dave would like me to post the schematic or email it to both of you.

 

[DKGrimm]

Don, in post #154 is that CDI one of the open boards with the spark coil on the end of the CDI? If it is I may have a schematic of a circuit very similar to it and or the CH units. Just so you know, Bill Carpenter from CH worked with Rcexl to develop that circuit until Rcexl took over and parted ways with CH. The very early CDI units I sold came from Rcexl and I did some modifications to make it more user friendly. Let me know if you and or Dave would like me to post the schematic or email it to both of you.

Yes, Roy, it is the open board with coil on the end as you say. For now, I'm trying to get my focus back on testing existing designs rather than designing new circuits, but when I get around to pursuing the idea of a possible hybrid CDI/Coil module it would be useful to have schematics of existing CDIs.

 

[rsholl]

This should be very close to the last CH and early Rcexl CDI. Hope it will give some clues as to what makes a CDI tick. My system is a little more elaborate but the basic concept is here.

 

[DKGrimm]

This should be very close to the last CH and early Rcexl CDI. Hope it will give some clues as to what makes a CDI tick. My system is a little more elaborate but the basic concept is here.

Thanks, Roy. Good minimalist design.

 

[rsholl]

That is pretty much the circuit I used for the Bare Bonz CDI so I know it works well for our small engines. Dave, if you want to play with that circuit, I have the parts for the step up transformer that I can send you. The step up transformer is the key to these CDI units.

 

[dsage]

Thanks for the offer Roy. But I'll pass for now. But I'll let you know.
I have a couple of the original modules I can play with. I'm not sure what module Don is using and whether he can access his transformer for testing his theories.
Maybe he could use a transformer to play with.

 

[DKGrimm]

Thanks for the offer Roy. But I'll pass for now. But I'll let you know.
I have a couple of the original modules I can play with. I'm not sure what module Don is using and whether he can access his transformer for testing his theories.
Maybe he could use a transformer to play with.

I'm trying to stay focused on testing existing designs for the moment. I'm running into massive obstacles with home maintenance and related problems. I can see getting into a CDI design at some time next summer to find out if added inductance in the HV output is plausible and worth the effort. I'd gladly pay for a couple step-up transformers just to be ready when the time comes.

 

[rsholl]

I'll look to see if I have any transformers already wound from the Bare Bonz CDI. What I was offering Dave was the coil form and E-cores. I should have been more specific I guess but it looks like you won't need them right away so maybe I'll be able to find some parts or even possibly wind a couple. Shoot me an email if you would Don so I don't forget.

 

[peterl95124]

You can derive mathematically that the magnetic energy is stored in the air gap and only there. The air gap can consist of a voids in the material or a created one. There is a difference in a saturated core and an unsaturated core. There are two types of transformer designs and they both have different purposes. So I am attaching some lecture notes you will or should find interesting. It talks briefly about this subject. Some references talk about distortion of the field and the volume available is not just in the physical area from the volume removed. If you want the high voltage to the spark plug it worth while looking at the right transformers.

HMEL, perhaps you've misunderstood the attachment you included, it says the energy PER-UNIT-VOLUME (they said "w / cm^3" but that's a typo, it should be "j / cm^3") of air is greater than iron by a factor of 10 to 1000 (because the reluctance of air is greater than iron by a factor of 10 to 1000). Peter.

 

[HMEL]

HMEL, perhaps you've misunderstood the attachment you included, it says the energy PER-UNIT-VOLUME (they said "w / cm^3" but that's a typo, it should be "j / cm^3") of air is greater than iron by a factor of 10 to 1000 (because the reluctance of air is greater than iron by a factor of 10 to 1000). Peter.

No, I did not miss understand the math or that statement. You need to evaluate the math of where the energy is. Look closely at the two transformer types and the resulting calculations. I have other simpler proofs that do not go into as much detail as this one. In fact look at the proofs which do not include any math. The power in Watts by the way is equal to joules divided by seconds, So joules/cm3 is meaningless without time period of seconds. Watts are power and joules are energy. Much like the analogy between Horsepower and Torque. In the final analysis you will see the symbol >..> which indicates that one quantity is so much greater to make the other one insignificant to its magnitude.
HMEL

 

[peterl95124]

No, I did not miss understand the math or that statement. You need to evaluate the math of where the energy is. Look closely at the two transformer types and the resulting calculations. I have other simpler proofs that do not go into as much detail as this one. In fact look at the proofs which do not include any math. The power in Watts by the way is equal to joules divided by seconds, So joules/cm3 is meaningless without time period of seconds. Watts are power and joules are energy. Much like the analogy between Horsepower and Torque. In the final analysis you will see the symbol >..> which indicates that one quantity is so much greater to make the other one insignificant to its magnitude.
HMEL

HMEL, you are contradicting yourself, at first you said it was mathematically provable that *ALL* the energy was in the air gap, now you're saying that the symbol ">>" means it is *MOSTLY* in the air gap, that's what I mean by misunderstanding. Also the paper you reference clearly states the *ENERGY* per unit volume is higher for air than iron.

 

[HMEL]

No, Sorry not contradicting myself. The math proof clearly proves the energy is stored in the air gap. You are beating the wrong drum. Well the symbol means that whatever is stored in the core is infinitesimal to that in the air gap. Obviously you wish to argue the energy is in the core not in the gap. You can ignore the math, the premise if you wish but you cannot ignore the science.

 

[peterl95124]

No, Sorry not contradicting myself. The math proof clearly proves the energy is stored in the air gap. You are beating the wrong drum. Well the symbol means that whatever is stored in the core is infinitesimal to that in the air gap. Obviously you wish to argue the energy is in the core not in the gap. You can ignore the math, the premise if you wish but you cannot ignore the science.

HMEL, the amount of energy in the air gap depends on the size of the air gap, the smaller it gets the less energy is in the air gap and the remaining energy is in the core, there's always energy in the core, otherwise an inductor or a transformer without an air gap couldn't operate. You can see this clearly in websites from folks that make them, especially ferrite cores where its easy to grind in a gap, they state a zero gap inductance and then less and less inductance as they grind in more more and more gap.

 

[HMEL]

HMEL, the amount of energy in the air gap depends on the size of the air gap, the smaller it gets the less energy is in the air gap and the remaining energy is in the core, there's always energy in the core, otherwise an inductor or a transformer without an air gap couldn't operate. You can see this clearly in websites from folks that make them, especially ferrite cores where its easy to grind in a gap, they state a zero gap inductance and then less and less inductance as they grind in more more and more gap.

 

[HMEL]

Not much energy is in that core. That is the difference between an inductor and a transformer. But believe what you wish. I havent seen anyone measure it. What you just said makes no sense. they state it but they cant prove it.

 

[peterl95124]

Not much energy is in that core. That is the difference between an inductor and a transformer. But believe what you wish. I havent seen anyone measure it. What you just said makes no sense. they state it but they cant prove it.

HMEL, that is not the difference between an inductor and a transformer, there are inductors without air gap (EG toroidal core), and there are transformers with air gap (EG neon sign transformers).

what do you mean you haven't seen anyone measure it, every single manufacturer of ferrite core inductors and transformers measures their inductance with zero air gap and with various thicknesses of air gaps (to lower the inductance to a customer need) as part of their QA, they all get the same result, zero air gap results in largest inductance and inductance goes down progressively with size of air gap. This is an empirically proven fact, it is now up to you to understand why <<===