# Very first project - beginner stumped

Discussion in 'The Projects Forum' started by jayc73, Jan 6, 2014.

1. ### jayc73 Thread Starter New Member

Jan 6, 2014
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Hi All,
This is my very first project and I'm not sure if I'm heading in the right direction or not ...

What I'm trying to do is increase DC voltage.

What I'm working with;
I have a DC power supply generating aprox.15kv @ 0.5A
a power input point or destination point
an obstacle - 5k ohm resistor

In a nut shell, I have 15kv - 15kv , departure and destination if you will.
I'm aiming for 15kv - 30kv or there abouts

The problem I think I'm faced with is there is a 5k ohm resistor I can not physically work around / bypass and must remain in place as it is a noise suppressor .

In other words, all voltage supplied must pass through a 5k ohm resistor to reach the "destination point".

I'm pretty sure using a 30kv capacitor will bump the voltage up but what options do I have with the resistor ?

Jay

2. ### MrChips Moderator

Oct 2, 2009
12,642
3,457
Something is not right here. You are working with a PSU generating 15kV @ 0.5A?

What are you, a ghost coming back from the grave?

That thing is lethal. Get some professional help pronto.

3. ### jayc73 Thread Starter New Member

Jan 6, 2014
6
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Thanks for the warm welcome ....

Not quite lethal - its a CDI ignition coil, similar to what you would find under your car bonnet.

4. ### inwo Well-Known Member

Nov 7, 2013
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Are you of the belief that 1/2 amp at 15,000 volts is not lethal?

Is it because of the low duty cycle?

I believe you mentioned a capacitor. Could that be dangerous?

5. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
Then it won't deliver anywhere near 15 kV @ 1/2 A. It might draw 1/2A on the primary (12V side) but the current on the HV side is reduced by at least 100X.

FYI, an auto "coil" is not actually a coil at all, it's a flyback transformer so the current is reduced by the turns ratio that steps up the voltage which is typically about 100:1. When the points open, a voltage of about 200 - 300V jumps the points and steps up to about 30kV on the secondary.

6. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
Not likely lethal. I designed and built a CDI for my motorcycle. Total wattage is pretty low, spark shock can definitely make you jump but not lethal to a healthy person. It's about 2uF cap, charged up to 300 - 400V, then discharged into the primary of the "coil". Open circuit voltage can be upwards of 50kV, but current is very low.

Still, I would not advise screwing around with one.

7. ### inwo Well-Known Member

Nov 7, 2013
2,435
315

I've seen claims of 1.1 amp output for performance coils.

8. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
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I don't believe that could be possible because that would be about 30 kW of power.

Many perf coils run low impedance (1.5 - 2 Ohms) on primary because their drivers are low duty cycle. So, they shoot high peak currents into the primary for more spark energy but even with a 6A peak current on the primary, the secondary side is down by at least a factor of 100 because of the turns ratio.

The total spark energy is actually limited by the "coil" core which stores the energy to be delivered to the spark plug. Like I said, I have seen them make people jump, but I don't think they could kill a healthy person.

9. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
The quoted value of 0.5A is clearly impossible. Look at the size of an ignition coil. Do you believe it could deliver anywhere near 30 kW which is what 1A on the secondary would be? impossible. It's a flyback design and I would wager the core probably saturates at less than 10W stored.

Agree it is not something to fool with. The main danger for injury is jumping backwards and injuring yourself when shocked (seriously).

10. ### inwo Well-Known Member

Nov 7, 2013
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Sorry I got your post mixed up with OP.
Didn't delete it in time.
Got to get to bed......................

11. ### jayc73 Thread Starter New Member

Jan 6, 2014
6
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Sorry guys, error on my behalf

Manufacturers numbers on the CDI ignition coil are 15kv@ 0.05A ( 50 Miliamps).

What I'm trying to achieve is boosting the voltage the spark plug fires with as Methanol needs a bigger charge to ignite.
Yes, there are other high performance CDI ignition coils out there but most don't physically fit this particular application .
A higher output ignition coil doesn't really solve the problem either as the plugs are internally fitted with a 5kΩ resistor for rfi suppression which I assume, would kill +/- 75% of the higher output ignition coil voltage.

I can't use a non resistor type plug as there's too much sensitive gear surrounding the engine and rfi shielding would be horrendous.

I have seen plenty of modifications using capacitors or diodes but all with non resistor type plugs.

12. ### MrChips Moderator

Oct 2, 2009
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Discussion of automotive modifications is prohibited on AAC.

13. ### jayc73 Thread Starter New Member

Jan 6, 2014
6
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This thread I started has nothing to do with any type of automotive modifications .

Definition: Automotive - relating to or concerned with motor vehicles.

As a Moderator , you need to find the facts before accusing people of anything .
You have also done a great job of promoting the forum and welcoming new members .

By the way, here's the engine
Not really " automotive " or a " motor vehicle"

Thanks for the help mate

14. ### MrChips Moderator

Oct 2, 2009
12,642
3,457
As a moderator, I am not accusing you of anything. I gave you the chance to clarify what you are doing by not closing this thread outright.

You are the one that needed to provide the facts, not for me to have to dig it out from you.

Welcome to AAC.

15. ### MrChips Moderator

Oct 2, 2009
12,642
3,457
So let's get this straight.

Is this an ignition system for a radio control model engine?

If it is, why didn't you say so in your introduction on the first post?

16. ### jayc73 Thread Starter New Member

Jan 6, 2014
6
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I only gave basic information to begin with so I didn't confuse things any more than they needed to be - nothing more than just keeping it simple.

If people were interested in the application then they only need to ask.

I do agree with Moderator respect but " give it as you get it " is my view - ( no offense intended)

Thank you for the welcome ( insert thumbs up Smiley here )

17. ### MrChips Moderator

Oct 2, 2009
12,642
3,457

You could have avoided this unfortunate miscommunication had you stated up front your specific application, especially since you had read the TOS and you knew that automotive modifications were banned.

18. ### jayc73 Thread Starter New Member

Jan 6, 2014
6
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Yes it is.
The engine is a 30cc 2 stroke with a CDI ignition system.
Standard through to high performance plugs must be the resistor type due to RF interference with radio gear, electronics, gps, data logging, etc.

All I'm looking at doing is to try and provide the spark plug with more energy so the fuel (methanol) doesnt extinguish the the sparkplug's "ark"

Trying to work around the 5KΩ spark plug internal resistor is where I'm stuck.

19. ### inwo Well-Known Member

Nov 7, 2013
2,435
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Sorry, I was tired last night and didn't save my sources.

Here is the first one I found showing .3 amps peak current.
http://www.jegs.com/i/MSD/121/8252/10002/-1
I was totally surprised, but it is peak.
"Turns ratio: 100:1
Primary resistance: .02 OHMs
Secondary resistance: 1.38K OHMs
Inductance: 7 mH
Maximum voltage: 42,000 Volts (Tested with 6AL Ignition)
Peak current: 300 mA
Spark duration: 200 uS"

Then I went on to find one with 1.1 amps peak. Can't find it now.

Here is a special ignition system with 30amp peak output.
"A plasma spark as referred to on the internet or by ignition engineers means a high voltage ignition spark with a very large ignition kernel with peak currents exceeding 20 to 30 amps. The net energy output of a plasma spark is several 100s of times greater than a conventional spark."
http://www.aquapulser.com/performance_ignition/faq.html#q1

Back on subject:
OP.

I don't believe that your ideas for doubling voltage from secondary side will be successful.

You can't gain power that way.

bountyhunter has built ignition systems and may be able to steer you in the right direction.

Seems you will need a larger coil, higher power primary circuit, or both.

ps.
I'd like to hear from an expert if the short duration of these energy pulses render them safe.

Last edited: Jan 8, 2014
20. ### Dibubba New Member

May 15, 2015
16
2
Enquiring Minds Must Know. How did this end?

I built a 1.5KV device once (vdg generator). Later, on eBay, I bought a 3KV PSU for a measly \$250. The price to Heaven is Cheap.

That thing scared the crap out of me - and I DO NOT speak in a figurative sense. I ended up 22 feet away, with rather a mess to clean up, and paramedics. I sold it, because I have lots of projects to do before I cross my Rainbow Bridge: that beast was accelerating me toward it.

Is everyone enjoying their August 2015?!