Modify Velleman Kit - Transistor Assisited Ignition, kit no. K2543

The company hasn't replied, which isn't unexpected. Many places just aren't responsive to people looking for technical details. They just want sales.

Is there a way to look up the normal ignition coil values, or extrapolate the data from the known points/coil information?

Fyi, another vendor has two versions of the 6v coils, a large and small. The small matches the physical and elecrical characteristics of my stock coil; https://www.holden.co.uk/displaypro...Code=0350&agName=Ignition+Coils&pCode=030.020

sign216 said:

The company hasn't replied, which isn't unexpected. Many places just aren't responsive to people looking for technical details. They just want sales.

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Hmm, maybe allow a bit more time to get a reply. It was a federal holiday in the US yesterday, 2017_01_16 (Martin Luther King day).

rfranzk said:

Is there a way to look up the normal ignition coil values, or extrapolate the data from the known points/coil information?

Fyi, another vendor has two versions of the 6v coils, a large and small. The small matches the physical and elecrical characteristics of my stock coil; https://www.holden.co.uk/displaypro...Code=0350&agName=Ignition+Coils&pCode=030.020

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I couldn't find any information that would help.

spec

I got their response! Of course they answered after I posted. Here it is;

"We have done some test on 1 cylinder ignition systems with our coils. I'm sorry but they do overheat because of the long dwell angle. We do not make a coil that can with stand this style set up.

We have some 1 cylinder industrial stuff but since our ignition system is installed. We shorten up the dwell angle up a LOT to keep the unit from overheating. Sorry we weren't able to help you out."

Just keeping up with the thread. Couldn't the points be used to trigger a non-retriggerable monostable? Wouldn't this in effect cut the dwell time?

shortbus= said:

Just keeping up with the thread. Couldn't the points be used to trigger a non-retriggerable monostable? Wouldn't this in effect cut the dwell time?

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That was my initial thought but it is fairly complex. If you had a fixed pulse long enough at low RPM to limit the coil dissipation sufficiently, you would not have any dwell time at high RPM.

It is necessary to have an adaptive dwell approach where the dwell is adjusted according to the engine RPM. But this is difficult to do and there are complications when starting.

The other approach, as I keep saying, is to use CDI which solves the problem in one go.

spec

sign216 said:

I got their response! Of course they answered after I posted. Here it is;

"We have done some test on 1 cylinder ignition systems with our coils. I'm sorry but they do overheat because of the long dwell angle. We do not make a coil that can with stand this style set up.

We have some 1 cylinder industrial stuff but since our ignition system is installed. We shorten up the dwell angle up a LOT to keep the unit from overheating. Sorry we weren't able to help you out."

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What, exactly did you ask them? Can you quote?

spec

I asked them:

(1) At what primary current does the coil acquire full charge?
(2) What is the maximum allowable dissipation in the coil.

I also outlined the project, a vintage single cyl. 6v Italian bike with transistor assisted ignition.

sign216 said:

I asked them:

(1) At what primary current does the coil acquire full charge?
(2) What is the maximum allowable dissipation in the coil.

I also outlined the project, a vintage single cyl. 6v Italian bike with transistor assisted ignition.

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Thanks- those are the specific fundamentally important questions which they have not answered.

They have just given the easy/safe answer as I could have done in response to your original post.

What are you planning on doing now?

spec

The orig. small coil is 2 ohm and doesn't overheat. Could a resistor be added to the high performance coil, bringing it to 2 ohms, and protecting it? Or would that not work?

sign216 said:

The orig. small coil is 2 ohm and doesn't overheat. Could a resistor be added to the high performance coil, bringing it to 2 ohms, and protecting it? Or would that not work?

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That is exactly what I have said and also what the circuit in post #53 does.

If it will work or not depends on the answers to the two questions that you asked the manufacturer

spec

With the added resistor reducing current, would the high performance coil actually give better spark?
It's got 1:100 ratio of turns, and the small orig. coil had an estimated 1:40.

sign216 said:

With the added resistor reducing current, would the high performance coil actually give better spark?
It's got 1:100 ratio of turns, and the small orig. coil had an estimated 1:40.

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I have already described all this.

spec

Post 53 gives your schematic, but it's for a 12v system. Perhaps the Velleman sheet I gave you didn't have the 6v option. Attached new Velleman file does have the 6v option. Would it be a simple substitution of the listed resistors?

About the two SMPS units you recommended, one looks like a voltage "step up" and the other a step down. Which is appropriate?

You said "It is definitely not a circuit to build at the moment."
What can I do, to push forward the circuit's verification?

Hello Sign,

sign216 said:

Post 53 gives your schematic, but it's for a 12v system. Perhaps the Velleman sheet I gave you didn't have the 6v option. Attached new Velleman file does have the 6v option. Would it be a simple substitution of the listed resistors?

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Ah, I see your thinking. No, the circuit of post #53 is for a 6V system. 12V is only used to drive the gate of the NMOSFET. The 12V supply line is completely isolated from the coil and has nothing to do with the coil whatsoever.

The post #53 circuit is designed for the Flame Thrower (1.5 Ohm) coil, as we discussed and as shown on the post #53 schematic.

sign216 said:

About the two SMPS units you recommended, one looks like a voltage "step up" and the other a step down. Which is appropriate?

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Don't get hung up on the SMPS. As I said, it only provides 12V (at 160 mA) for turning the NMOSFET on and off fast.

By the way, the power supplies linked are not necessarily 'recommended' they are just 'typical examples'. Both SMPS will be acting as step up (boost) converters.

The SMPS of reference (1) of post #53 can only do Voltage step up, while the reference (2) SMPS can do both Voltage step up and step down.

sign216 said:

You said "It is definitely not a circuit to build at the moment."

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As I said, the circuit of post #53 is an outline to show you the scale of the project. For example the actual NMOSFET is not shown, although I have given a list of likely candidate NMOSFETs both in post #19 and post #58.

The next stage (hard part) would be to do a detailed analysis and optimization of the post #53 circuit, taking into account component tolerances, component stress, reliability, cost, part availability, environment, etc, etc.

sign216 said:

What can I do, to push forward the circuit's verification?

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You have not answered my question of post #68 about what you want to do. Are you saying that you would like to try out, at risk, one of the Flame Thrower coils.
If so, I can do the next stage of the design and, hopefully, come up with a practical implementation.
But it will cost you a lot of 'Like' votes.

spec

I'd like to do it. The original coil is almost 50 yrs old, and due to be replaced. Upgrading the ignition would be great, especially since the elec. system is "adequate" on a good day. Also this would greatly extend the life of the points, a big plus since Benelli did not make them easily accessible (you have to remove the kickstarter lever, and the left footpeg + crankcase cover). Other bikes (like some Brit ones) had a more thoughtful design, with easy access to the points.

OK, I will have a go at a practical circuit.

But please remember that I am working from paper only and do not have the benefit of development facilities at the moment.

Also, there is a risk that the coil simply will not survive with 30W dissipation.

spec

I suggest it would be wise to do some concept proving tests before we go the full hog with the complete design.

Do you have a 6V 4A power supply? A 6V battery would do.

spec

I can get a 6v battery. I'll pick up a new battery for the bike.

sign216 said:

I can get a 6v battery. I'll pick up a new battery for the bike.

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If you are getting a new battery for the bike can I suggest that you get as higher capacity as possible, say 20AH rather than 7AH.

spec

This is what I propose for the feasibility tests.

(Test #1) Connect a 1 Ohm resistor in series with the primary coil of a Flame Thrower (1.5 Ohm) coil (total resistance 2.5 Ohms) and see how hot the FT (1.5 Ohm) coil gets in free air when you connect the coil with series the resistor across 6V or near.

If you had some means of measuring the surface temperature of the FT1.5 Ohm coil that would be handy.

spec