Some transformer advice/help required

[Virus]

Hi guys/galls

Would appreciate some advice.  ;D

I intend to build a cdi circuit for my car, but with a slight difference and need some advice on a modification on the transformer.

I need to charge 2 x 1 uF caps at the same time,

normally the transformer would be 1 primary and 1 secondary winding for the transformer. 12v primary to ±200 v secondary.

Question:
When winding the transformer, on the secondary’s, do I need to wind the  2 wires together on the core, which will give me 2 separate secondary’s, to charge the caps.

Or

do I need to wind a single wire with a center tap (with equal turns on each side) to give me 2 separate secondary’s,
or would either methods be right.

Thanks

Theunis

 

[Hero999]

Each has its own advantages.

Bifilar is good because it ensures each winding has exactly the same characteristics but there will be a greater capacitance between each winding.

Centre tapped is easier to wind but the winding won't be quite symmetrical.


If you need to charge two capacitors, why not simply connect them in parallel?

 

[Virus]

Hero999

Thanks for your response, I need the caps to be isolated from each other, with common negative after each has been rectified, as each cap will be discharged separately, 

I did wind the secondary 2 wires is parallel simultaneously, but the transformer seems to heat up fast, and wonder if there would be a different way of winding it.

The idea is to save components/space and rather use 1 oscillator and charge 2 caps, rather than having 2 oscillator, 4 mosfets, 2 transformers, etc to get the work done. If 2 of each is the answer then so be it, but if I can save, hey why not ?  ;D

Any suggestions?

Thank you

Theuinis

 

[Hero999]

Can't you charge each capacitor via a separate diode?

Please post a schematic.

 

[Virus]

Hi Hero999

Attached 2 x jpg's, 1st the original schematic (I have changed the number of turns on the transformer Primary = 13 turns and Secondary = 360 turns), 2nd jpg (simplified circuit) is what I have in mind,

I did think that it should be possible to charge the caps using diodes but no idea how to do it, and them have them discharges them separately with separate mosfets trigger circuit

Thank you for helping me.

Theunis

View attachment 41927

View attachment 41928

 

[Hero999]

You could be able to connect two capacitors to the output of a single supply, each via a diode so each will discharge separately but you need to make sure the power supply is powerful enough to drive two coils.

 

[Virus]

Hero999

Ok. that would help. can I ask you for a diagram, I need to see how to connect the diodes, hand drawn will be just fine, if it's not to much trouble.

Thank you

Theunis

 

[Hero999]

If you, have ago, post it and I'll check it.

 

[Virus]

Hi Hero 999

Please be patient with me I am a rookie at this 

For all intensive purposes you can then charge multiple caps as long as the supply is capable delivering ?

Thank you for the feedback

Theunis

View attachment 41930

 

[Hero999]

That should work. You may need to connect a small capacitor (say 100nF) from the feedback to 0V for stability.

 

[Virus]

Thank you Hero999

I will be at it this weekend, and see how far it will go,

If I need to retard the ignition pulse/timing a little, which would be the best way to do it. It was mentioned that the CDI could advance the timing because of the fast discharge?

Thank you

Theunis

 

[Hero999]

No idea, I'm not a mechanic.

 

[Virus]

Hero999

I know you are not a mechanic you are a Electronics god, that is why I asked the question,

I mean can it be retarded/delayed electronically even made adjustable and how, one will still have the normal/mechanical advance and retard, but there should be a way to retard the timing every so slightly electronically. ???

Thank you

Theunis

 

[Hero999]

It should be easy to add a timer to delay the pulse.

 

[Virus]

Hero999

With the diodes I took a wild guess,

about the retarding the timing- I am totally in the dark, you will need to point me in a direction please.

With timer you maybe mean a 555 chip.

Please

Theunis