Hi all. Well I finally did it. I constructed the design from Luc's first design and works great. This is using just the SPDT switch, and the spark is really bright. I put a piece of paper between the electrodes and the fired. The paper shows a bit of black and a small hole in it, this was done using no water. I am using a non resister type plug. When using a bit of water I don't really see of hear a difference in the spark. What I did observe was that, inside the base of the electrode, that a clear type of gel had formed. Also that sometimes when I didn't get the BIG spark, I could see what appeared to be water bubbling, but the plug was not even warm. I wonder what was happening? I am just learning about electronics with the help I find on some very good web sites. This is really exciting and has made me learn more
Mike

One possible problem I see with the circuit setup is the HV is connected directly from the coil
to the spark plug, so some of the LV is dissipated across the HV coil.
This would cause a lot of loss of power from the LV circuit. 

I would place a small spark gap in series with the HV terminal just after it leaves the coil, which won't let LV enter the coil.

From what I understand the HV is only providing an ion trail for the LV to discharge across the water in the spark gap.
(Just like the HV does with a Xenon Strob Tube)
And the Lower Voltage High Current capacitor discharge does the work of producing the explosive power.

So we want to keep as much of the LV as we can, but loosing a little HV in the second spark gap won't make much difference.
This is a very simple modification to test.

Hi Troyd1
I suggested that a few posts back,but got no responce,spose.they didn't think much of that,also to fit the plug on the horizontal,they are a lot of those engines about,then put a cup over the end of the plug,leaving a hole in the top of the cup to put the water in.
happy hunting
peter

Quote from: resonanceman on July 21, 2008, 10:46:59 PM
Plasmastudent

Can you  explain  a little more  the  circuit  you  used?
So far I am  assuming    you  drove  an aftermarket   coil  with   a 75 Hz pulse .




I  was planning  on using   Allcanadians    circuit  from the  Tesla  challenge  thread ........ If  I  can  get it  pulsing  fast enough .   

Because  of  the  size  constraints   from using  a  standard  plug  shell  the  gap in the  final   gap  will  be  relatively  small,     Circuit  will have to  be fine  tuned  so it  doesn't  have to much   voltage .   
The   gap  needs to be  triggered   by the   plasma and water  as it moves through the gap .
To  much  voltage and it  will  arc  continuously.


As far as a couple of  pulses  being enough ..... I don't plan on  counting  on that.
So far  it looks like    at least with a  cold engine  the   vapor in the   cylinder   can  condense out  very quickly ..... (  implosion )   I plan  on  being able  to   start   the  plasma   just  after  TDC  and   continuing   as long as  required to  keep  the   gasses from  going into implosion  mode .
I am thinking that  firing  15 or 20 degrees  starting   at TDC  might  be practical  with a cold engine . 
The   extended  firing  would  be like using a  choke ....  it  would not  be used  all the time .   

gary

Hi Gary ( Resonanceman ),

I went to local electronics shop that sold kits, built a jacobs ladder kit that drove a 12V car ignition coil at 75 Hz and produced a pulsed 50KV 75 Hz output.

I also had another thought about how to handle multiple pulses of power to the spark plug. Assume at this stage for my thoughts below we are using 240 V  AC mains power. we could use an inverter but for the moment lets use the mains ( its easier for experimentation purposes and its on tap ).

Thought 1 -

Since AC becomes 0 Volts then 240V 50 times per second during the 50 cycles/second, we might be able to use this as a 50 Hz pulse to the plug gap. I havent tried it ( yet ) but its cheaper than heavy duty triacs etc. Downside is you need to limit current ( use light globes or resistor ) and its sensetive to any stray capacitances or inductances. But you get a 50Hz pulse to the plug while its switched on.

Thought 2 -

Use rectified DC. Buy a heavy duty 400 V 10-20 Amp MOSFET of similar size used for trams and trains. Trams use PWM for speed control, and do switch pretty hefty currents at high voltage, so these components exist. Downside may be cost ( havent priced these yet )

Thought 3 -

Same as 1 but use a triac to switch the voltage on at 90 dgrees ( max amplitude ) on the sine wave. This would give you 2 pulses/cycle that could then be controlled or even create DC pulses if you want to get fancy. If you also wanted to do it, you copuld use this to produce a stepping sine wave if you had access to 3 phase AC power and could shift the phases using caps. This is a less likely option given the complexity. A carefully configured PWM setup could be also used similar to this.

Hoping to have some results back soo for everyone. Might even do a first youtube if I get good results :-)

Cheers & beers

Steve

Quote from: ahchoooo on July 22, 2008, 11:53:21 AM
I tried the simple circuit by Luc but I can't get the HV spark when the diodes are connected to the spark plug. Only when the diodes are disconnected, do I get a strong spark. This is contrary to the result as reported by Luc. I am using a 350uF, 450V capacitor, 10 1N5408 diodes in series connected as in the diagram, a variac tuned to 110V as power source through a bridge.

I also tried using different number of diodes, from 1 to 10. I noticed that when the diodes used dropped to less than 5 or 6, the sparking will stop completely, indicating the possibility that the HV output from the coil got shorted out through the diodes.

Since I cannot remove the resistor from the spark plug, I also tried with carbon rods (extracted from battery), copper rods, metal screws etc as the spark gap. I noticed that with the diodes disconnected, the spark generated is quite strong and sometimes the color is very white and bright. However, the effect is not consistent. Since I was manually charging the capacitor, and then discharging the capacitor by touching a wire to the capacitor terminals, the spark generated from touching the capacitor is also quite bright, often brighter than the spark at the spark gap.

I am curious as to why I cannot duplicate the result of Luc. 
Any help is appreciated.

James

Upon further testing, and checking the simple Luc wiring, it is now clear to me that the diodes allow the capacitor charge to bleed through the ignition coil. Since I was manually switching between charging the capacitor and firing the coil, the time it took allowed charges to bleed through the coil. So I have to change to auto switching by using some solid state relays, so that the switching will be a lot faster. Only then can I test to see if the diodes perform any function.

BTW, the resistance of my spark plug is 3.6K. I tried but the top cannot be screwed off. So I will have to find another plug.

Another thing I noticed is that it seems the spark is a bit stronger if the polarity of the spark plug is reversed, ie +ve ground. Also, increasing the spark gap on the plug produces a stronger spark also.

James