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Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
Yep, this is CW just like all previous revisions. Interrupted coils just don't appeal to me ^_^
Confident that things were running reliably and efficiently enough, I made the executive decision to increase the drain feed voltage to 120VDC. The little aluminium box gets a bit hot for my liking, but it's all in a day's work. What do you expect when you try to pump hundreds of watts from such a small package? =)
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Nice work BP - how long can it run like that before overheating/death/whatever?
It's always too much heat and not enough arcs when you get things small like that... And we don't like interrupted stuff (then it's easier just to build a DRSSTC).
I mostly ran my coil by 'touching the clips' like that too
But you did prove my PLL-feedback hunt was vain in the end. Oscillator is best choice for this topology as it seems.
waverider wrote ... Here is one that I am working on at the moment...
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
Marko,
wrote ... Nice work BP - how long can it run like that before overheating/death/whatever?
I'm not really sure I want to find out! I don't want molten silicon-epoxy-goo messing up the inside of my nice box, should I ever want to improve the design. =P
wrote ... It's always too much heat and not enough arcs when you get things small like that...
Or in this case, too much arc and not enough heat. I think it is some kind of miracle that the secondary doesn't flash over. This kind of power results in wilted/drooped secondaries. The PVC gets hot enough that it starts to soften, and keeps on bending over until enough turns short.
But if you look carefully at the beginning of the video, can anyone else see the spark in a place where sparks are bad?
wrote ... And we don't like interrupted stuff (then it's easier just to build a DRSSTC).
I agree almost completely, with the notable exception that interrupting a coil is a great way to decrease the power draw and keep semiconductors cooler!
wrote ... But you did prove my PLL-feedback hunt was vain in the end. Oscillator is best choice for this topology as it seems.
I don't think it's quite in vain. I find working with a fixed oscillator best during development, and then when you've got everything bulletproof, you can muck around with tracking at a lower power. Feedback has its place.
Andy,
wrote ... I didn't clock how small it was until I saw that to247 device mounted inside the box.
I think that's possibly why I'm not getting so many replies to this thread; to most other people it looks like "just another tabletop coil".
Without actually endeavouring to build something this small, I don't think many can appreciate the high running frequency or the touchiness and compactness of the class-E drive circuit.
I like the analogy that the sheer volume of plasma produced by the coil would not fit within the box that provided the power!
And when was the last time you saw a CW brush discharge that was almost as long/fat as the secondary from which it emanated? =D
wrote ... Makes me want to get back into this stuff again
Great! (That's part of the purpose of this thread.)
I'm hoping to see some other attempts at small or HF coils. (Thanks again Bill; I think this is as far into 'coiling' that my girlfriend will get -- she was probably only holding the coil because she was unaware of the dangers, hehe)
Mates,
wrote ... Do you think we have a chance to see the full schematics?
You can derive a schematic from the photographs I have posted, if you wish.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I think that you need to take a picture of it next to a coke can, and sumbit it to be featured on the news page
What is the actual spark length on this baby? My 811a coil had a similar (abit somewhat larger and considerably lower frequiency) sized secondary producin 4-5" or spark, but the box under the secondary was a solid 20cm by 20cm by 15cm and it was pulling 15a off the 120v line And that was on halfwave rectified.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Something you might be interested in Matt---look closely at the first frame or so of that video you posted a few posts back...I think I see a quick spark on the topmost turn of the primary. That could get bad fast.
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flaming mini TC with single IRFP450
click to download the video (~3MB)
click for just the still image
And that was on halfwave rectified.
Beats my "micro" coil by quite a margin 
.
