To all: I suspect the plasma effect will work fine with just about any ignition coil from older American cars. The 5000 ohm, low performance, secondary is not of concern for this circuit. If you are jumping straight to a car modification, then as Aaron says the CDI makes it easy, but it is not the heart of the phenomenon. I pulled a coil from a 60's vintage Ford truck that was abandoned and left out in the rain (not mine...). Works fine. I'm sure your local junk yard has many.
I would encourage all to get the effect working with the simple relay based replication, and go from there. That will allow testing of components more easily.
What creates the plasma spark effect is to first get a big enough spark, via the coil, that will create a low enough resistance (or negative resistance) in the spark gap, which will lower the voltage across the gap, which in turn will allow the capacitor to dump its charge through the diodes. As soon as the capacitor starts discharging ( which will be at a much higher amperage than the coil was), I believe the coil is no longer important to the effect, so there may not be much advantage, IMHO, to the expensive coils if all else is working properly.
I have my HV supply (0-200V) on a variac, so that I can slowly turn the voltage up. One can see the spark start at a weak level, then get stronger as the voltage goes up, and then suddenly the spark is strong enough that the capacitor starts discharging into the gap with the attendent strong effect at ~130VDC. The difference for the threshold is only +/- 5-10 volts, quite a sudden transition.
The diode string only needs to stand off the initial break down voltage of the gap (with some head room). If you widen the gap, that initial voltage will go up. It is hard to measure unless one has the proper high voltage probes. It is not difficult to damage equipment with this circuit! An old tube type Tek or HP scope would be nice. I am hoping to use a current transformer to measure the peak current in the discharge. That is the other aspect of the diode rating, which has to withstand the expected high avalanche current.
So far in my project, as of today, I have a modified single cylinder generator running well. All the external circuitry is powered from the mains supply. I can see the effect of a more complete burn with the plasma spark, just in terms of smell. I'm using propane for experimental purposes, and I know what the usual smell of such a generator is like. The plasma spark makes for an almost odorless emission. I can run a leaner mix as well. Once all the bugs are out of the standard configuration I will move on to other tests, like water vapor.
I would encourage all to get the effect working with the simple relay based replication, and go from there. That will allow testing of components more easily.
What creates the plasma spark effect is to first get a big enough spark, via the coil, that will create a low enough resistance (or negative resistance) in the spark gap, which will lower the voltage across the gap, which in turn will allow the capacitor to dump its charge through the diodes. As soon as the capacitor starts discharging ( which will be at a much higher amperage than the coil was), I believe the coil is no longer important to the effect, so there may not be much advantage, IMHO, to the expensive coils if all else is working properly.
I have my HV supply (0-200V) on a variac, so that I can slowly turn the voltage up. One can see the spark start at a weak level, then get stronger as the voltage goes up, and then suddenly the spark is strong enough that the capacitor starts discharging into the gap with the attendent strong effect at ~130VDC. The difference for the threshold is only +/- 5-10 volts, quite a sudden transition.
The diode string only needs to stand off the initial break down voltage of the gap (with some head room). If you widen the gap, that initial voltage will go up. It is hard to measure unless one has the proper high voltage probes. It is not difficult to damage equipment with this circuit! An old tube type Tek or HP scope would be nice. I am hoping to use a current transformer to measure the peak current in the discharge. That is the other aspect of the diode rating, which has to withstand the expected high avalanche current.
So far in my project, as of today, I have a modified single cylinder generator running well. All the external circuitry is powered from the mains supply. I can see the effect of a more complete burn with the plasma spark, just in terms of smell. I'm using propane for experimental purposes, and I know what the usual smell of such a generator is like. The plasma spark makes for an almost odorless emission. I can run a leaner mix as well. Once all the bugs are out of the standard configuration I will move on to other tests, like water vapor.
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