HVDC Biased Ignition Coil

Ruptor

Joined Apr 26, 2009
44
I've found that adding more resistance between the coil and the voltage doubler has eliminated the "filtering" problem and the circuit no longer destroys the inverters. However, I've come across another problem.

Adding resistors in-line with the circuit has proven to be problematic, as the resistors keep burning up. Anything below 420 or so ohms would work for a while without heating whatsoever (not warm to the touch), but then suddenly burn up. I wired a 60w light bulb in-line with the circuit and discovered why the resistors would suddenly fry. For some reason, something sets up a continuous arc instead of a quick spark.
This is confirming what Bill told you in post #6 the 300V is practically shorted out when the spark fires so 25R at 300V is 12 Amps and it will continue until either the voltage clapses or something blows up.
 

Thread Starter

Pinhead

Joined Jul 10, 2009
12
I believe I came upon a solution. 30 ohms between the inverter and the doubler, and 350 to 400 ohms between the inverter and the coil. The spark isn't as "hot" as is unrestricted, but the spark plugs will last exponentially longer. Using this resistance the spark event is still visually 3 to 4 times stronger than the original Kettering system.
 

DC_Kid

Joined Feb 25, 2008
1,072
why not deploy some sort of peak-&-hold circuit. you might be able to use the LM1949. all you really need to do is build a pulse timer (555) and link it somehow to the firing order, and, proper transistor(s). this way you can control the current and how long without using resistors.
 

DC_Kid

Joined Feb 25, 2008
1,072
Because, really, I have no clue what you're talking about, much less how to implement it...
you are trying to achieve the goal using all passive devices. i think you need more sophisticated control.

the LM1949 allows current to flow at two levels, peak and then hold. these are set using external components. the LM1949 is triggered by a pulse width signal. so in essence you can control the peak current flow to protect the inverter output, the hold current (which is less than peak), and the duration of the whole thing so you can control when to shut it off. take a look at the LM1949 datasheet and info http://www.national.com/mpf/LM/LM1949.html

i would suggest rectifying the inverter output (after voltage doubler) and dump a large charge of DC into the burn.

also, in your post #1 your schematic shows the voltage doubler connected to the plug via a high PV diode. so doesnt this mean you are doing half wave rectification of the inverter's AC output, hence you're missing half the energy?
 
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Thread Starter

Pinhead

Joined Jul 10, 2009
12
Also, in your post #1 your schematic shows the voltage doubler connected to the plug via a high PV diode. so doesnt this mean you are doing half wave rectification of the inverter's AC output, hence you're missing half the energy?
As I understand it (and measure it), the voltage doubler is putting out ~330 volts DC fully rectified already...

you are trying to achieve the goal using all passive devices. i think you need more sophisticated control.

the LM1949 allows current to flow at two levels, peak and then hold. these are set using external components. the LM1949 is triggered by a pulse width signal. so in essence you can control the peak current flow to protect the inverter output, the hold current (which is less than peak), and the duration of the whole thing so you can control when to shut it off. take a look at the LM1949 datasheet and info http://www.national.com/mpf/LM/LM1949.html

i would suggest rectifying the inverter output (after voltage doubler) and dump a large charge of DC into the burn.
I'll have to do some serious investigation. :)
 
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