My diodes arrived yesterday, so this morning I finished setting up my plasma circuit and used two small brass nails as electrodes. Here is a full diagram of my plasma system, for those who are interested:
With the AC side disconnected, I can open the spark gap to approximately 1 inch wide and still get a spark from the coil. With the AC side connected, I need to narrow the gap down to about 1/8th inch to stop the spark preferring to travel to ground using the hot side of the AC. The issue here must be resistance of the hot AC reference resistance of the spark gap, the resistance of the gap needs to be lower for the spark to prefer that avenue. I'm thinking of employing another string of diodes on the hot side to allow me to play with wider gaps.
Some other observations I made this morning:
- The intense plasma spark is so bright, even wearing sunglasses, that it hurts your eyes after a very short time. I stopped at Lowes on my way to work and bought a #10 viewing pane for a welding helmet to use as a shield so I can view the spark.
- The plasma sparks crack is quite loud, when misting water onto the electrodes it more than doubles in intensity. The normal plasma, without water, is creating a white 'ball' approximately 3/16th inch in diameter (estimated) with a corona that then goes from the brilliant white fading down to an orange / brown color. When you add the water mist, the corona becomes much larger and tends to shoot out from the plasma ball in various directions. Now that I have the welding shield, I will try and catch some video of it on Monday.
- I tried removing the right hand single diode from the circuit and used a 70a 1000v bridge rectifier instead to bring the AC side of the circuit to DC. With this in place, a plasma spark cannot be created at all. Perhaps I need to reverse the polarity at the gap for this setup?
- If I remove the capacitor from the circuit, I can still create a plasma spark (with the occasional misfire) if I keep the frequency low enough. However, even at low frequency (2-3 sparks a second) the ends of the nails were glowing red hot within about 10 seconds. I would have assumed that the capacitor added the ability to dump a much higher current into the spark, therefore, I'm confused as to why the opposite seems true in this case.
I purchased some tungsten carbide dremel drill bits at Lowes today and am intending to try them as electrodes to see how the material holds up. Berylium Copper seems to be a preferred choice, although, I'm not sure where I'd source some from.
I also want to experiment with putting a resistor of about 50 ohms behind the positive electrode of the spark plug to control the rate of discharge from the capacitor. The problem here is that I need it to be able to take about 50kv and approximately 200 watts. If anyone has any suggestions of where I could source or how I could build such a beast I would be very grateful.
Russ.
I just posted a new video showing my plasma spark system running at high frequency, both with and without water mist and with and without a high tech UV shield (pair of sunglasses) over the camera lens.
I've made some small changes to my circuit:
The coil is now water cooled as it tended to get hot!
The DC 47uf capacitor has been replaced with an AC rated capacitor.
As you can see from the video, I'm having issues with plasma spark misfires. I tried increasing the capacitance to fix this, but it does not appear to be the issue. The rate of misfire seems to be the very similar, despite the speed at which I run the spark circuit, therefore I'm inclined to think that the issue is related to something else.
Any ideas?
I fixed the misfire issue this morning by putting a single diode between the AC live from the outlet and the coil. Now it fires every time, even at high frequency.