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Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Great shots Terry. I see you have a few hot pixels that I don't recall before. You're not shaking your camera to bits are you
I have to post just so you can post again before 48h. Work has taken a 17h chunk out of my day so no progress here.
Things for you to do - pulls pencil out. Hmmm... 1 Set your sensitivity for maximum and see all the rest of what is happening , not just the bright stuff. You should see ringdown on EVERY strike like on mine. 2 Try a streamer only shot. You might also see the harmonic effect of 10kHz on streamers or something quite different since your coil is quite different. I suspect you might have to bypass a SISG stage or so to fit that in your room. 3 I favour a log response. Is that feasible with your setup? 4 Can you run a 1MHz test frequency passing through your CT to see how sharp your response is? I also notice my strikes are broad compared with the ringdown. 5 Try a really short arc to ground
Great shots Terry. I see you have a few hot pixels that I don't recall before. You're not shaking your camera to bits are you
The dark enhancment was done differently. But it really is a 10,000RPM ultrasonic paint shaker, so camera damage is a possibility. But the camera is pretty old and I can live if I have to buy a new one
I have to post just so you can post again before 48h.
I just keep updating my old post like I did before
As to your points:
1. I am now at 0.1A/div and I can now see follow up oscillations (scope but camera too dim) right were they should be.
2. This coil does not do well in one shot mode. The streamers are really wimpy. It also has high coupling so the ringup is in only a few cycles.
3. I would have to find a whole new "log" set of scale resistors. Prolly not gonna happen soon since I like linear
4. It goes to 1MHz and then starts to roll off. Pretty predictable...
5. I will try to remember.
Here is on really great shot!!!
It is NOT super imposed! It must have hit just at the peak in the charging cycle and the coil was able to pump out three arcs in 60uS! Each red LED is 0.1A with positive to the right. The markers are 10uS. I don't know what it all means
If anyone is really board:
Pictures with an "a" are enhanced since they showed "something". I have not had time to really look through them.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Terry Fritz wrote ...
.... But it really is a 10,000RPM ultrasonic paint shaker, ..
Ultrasonic only for us over 50's. While driving a speaker with up to 100W via a frequency generator for my cornstarch stuff two days ago, my hearing frequency cut out was about 12 kHz, my 16yo was perhaps 17kHz and 14yo 19kHz.
Terry Fritz wrote ...
1. I am now at 0.1A/div and I can now see follow up oscillations (scope but camera too dim) right were they should be.
Nice, can you go lower easily?
Terry Fritz wrote ...
2. This coil does not do well in one shot mode. The streamers are really wimpy. It also has high coupling so the ringup is in only a few cycles.
See my 4 foot streamer below
Terry Fritz wrote ...
4. It goes to 1MHz and then starts to roll off. Pretty predictable...
Is that measured or predicted?
Terry Fritz wrote ...
Here is on really great shot!!!
I wonder about the frequency response of your unit. Brief events are giving pyramids rather than lines. I suspect you have less than 1Mhz bandwidth. Turn on maybe but turn off? The reason I say that is the largest spike/pyramid to the right has a small reading to the left at the same time.
Terry Fritz wrote ...
It is NOT super imposed! It must have hit just at the peak in the charging cycle and the coil was able to pump out three arcs in 60uS!
Are you really sure. I see lots of coincidences and the spark channel can remain hot and give similar shaped sparks for a while. If it was dependant on charging cycle we would see that happen all the time.
The scope can go to very low current. The bar graph scale is +-5V and the CT is 100:1 so it just depends on the load resistor (there must be some limit, but I would have to think about it).
The 1MHz is measured with an HP33120A signal generator and a TEK 3012 scope. I could look further if there is a worry.
I wonder about the frequency response of your unit. Brief events are giving pyramids rather than lines. I suspect you have less than 1Mhz bandwidth. Turn on maybe but turn off? The reason I say that is the largest spike/pyramid to the right has a small reading to the left at the same time.
See the lower strike in this picture:
The arc caused a positive "spike" to the right.
Are you really sure. I see lots of coincidences and the spark channel can remain hot and give similar shaped sparks for a while. If it was dependant on charging cycle we would see that happen all the time.
At 1/20th of a second, it is "possible". The chance of the same mirror alighning is 4^2. The chance of the cal dots alighning is about 20^2. The chance of a streamer hitting just right is say 10^2. This picture shows some bright LEDs but they are bright in the wrong places at the wrong times (time is down here):
So the odds are ~ 1/640000...
This is what the alternative looks like:
Possible.... The picture you have is pretty convincing though...
But this happens a lot:
Those markers just seem to happily alighn far too much (5 times in 64 pictures)....
This is an overlap on the same mirror:
This is what I would normally expect (a "rare" picture):
So it sure seems to me like fast multiple firing. It would be 30uS or 33,000BPS!!! Even the SISG "should not" be able to go that fast... Probably our first big "odd" thing to try and figure out.
I put a ton of these pictures in a printer friendly file at:
Sorry about the 13MB but the pictures are high-res even if I did crop them way down.
UPDATE: I checked the bandwidth of my Streak Scope. Here it is on top of the coil hooked to a signal generator:
Here is a 200kHz +-4.7V square wave:
Here is a 100kHz 20% duty cycle +-4.7V square wave.
Looks perfect!! But I should try to find why the three LEDs on the left are dimmer...
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Well, some progress. I have made up a LED polarity/oscilloscope unit and it doesn't work well but is interesting in other respects.
Photo 1 Circuit diagram. Xenon light is first in series because I thought that would be most sensitive. The main current path is through a 2W 10 ohm resistor shunted by a neon. What I want to do is to remove the nastiness of the spikes then use a 1MHz low pass filter with windings on a ferrite core and a ceramic cap. After that a TVS should be able to work to limit voltages to +/- 30V and the LED's will do the rest. The LED array was meant to read in decades but I probably I was asleep/drunk or otherwise having a seniors moment when I made it so it won't work as such. But I was very careful about groundplanes. Photo 2 is the front view Photo 3 is the rear view with the mostly covered neon on the left and two indicator diodes on the right which should be running within ratings and shouldn't blow. Photo4 Here is a spark about 2 feet. The 3 central LED's light, the right 4th is blown and the left 4th is probably OK but only on faintly and not well aimed at the camera. Now the sequencing of polarity is difficult to determine as I don't have as fast a streak as Terry. The spark is uninteresting but the very faint streamer lights up extensively. It demonstrated 2 things. Firstly a prolonged ringdown of greater than 30 cycles. Secondly the second frequency of about 10kHz that modulates it which I have shown before so it is not peculiar to this unit. So why the prolonged ringdown particularly as the xenon is not showing it. I wonder if my filter is ringing throught the 10 ohm resistor and when supplied with enough repeated oscillations with a streamer it rings for a long time. I does seem like it rings at about the spark ringdown frequency however and not the expected resosance of 1Mhz. I determined values by resonance at a lower frequency to determine the inductor value so I could have stuffed up. My frequency generator only goes to 500kHz. Photo 5 A 4 foot spark and lots of streamers. Photo 6 Just for fun with lots of sparks. Photo 7 A slow (about 200RPM) shot showing what I believe are a true sequence of sparks probably at the ARSG frequency, evenly spaced and this pattern was repeated in other shots. This is new information.
So thats it. Any thougths on the circuit resonance would be appreciated. It needs some adjustments yet but I only blew one LED in a long high powered session so a big reduction in mortality. I need to redesign the array so ignore that. Peter
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High speed Tesla spark photos
Each red LED is 0.1A with positive to the right. The markers are 10uS. I don't know what it all means 
