Re: [TCML] CW magnifier

[Steve Ward <steve.ward@xxxxxxxxx>]

Carlos, what about possibly a spinning breakout point so that you can
visually fill the area with sparks, but not need so many points?

Modulation via grid drive should be acceptable in an on/off kind of
modulation (which is what i believe you are thinking).  Just make sure you
get the grid bias negative enough to keep the tube off, and you may need to
look at driving the grid to its max to allow for higher pulse current on the
anode.  Some form of switching feedback to get the frequency (and switching
phase) correct would be important to keeping the performance good and the
tube happy.  Just feeding it from a constant frequency source may not work
so well, typically the Q of the coil is too high and the streamers detune
it, so you never find the sweet spot.

Steve

On Sun, Apr 3, 2011 at 1:22 AM, Carlos Van Camp <
carlos@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> Hi phillip,
> The arcs I am getting now are about 30-35" long with a CW input of 25-30kw.
> (the machine is capable of 50kw continuously)
> There are 6 electrodes on the secondary top load, each producing its own
> brush of arcs.
> They are like thick flames of plasma which branch into many tendrils of fat
> bolts.
> The problem is I need 2-3 times this to make the art piece asthetically
> pleasing and functional.
> To ad to the problem, the coil is also sound modulated... So Going pulsed
> instead of CW means losing some sound quality in order to gain spark
> length...
> I have no experience with pulsed valve coils, but have started down the
> track of making an audio interface circuit that converts the audio into a
> controlled square wave to feed onto the valve.(my electronics knowledge is
> pretty basic)
> I am not sure at this point weather to follow conventional thought, and
> pulse the cathode to ground, or to follow my gut, and drive the grid of the
> valve with bursts of rf (at the appropriate frequency of course)...
>
> Carlos
>
> ----- Original Message ----- From: "Phillip Slawinski" <
> pslawinski@xxxxxxxxx>
>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Sunday, April 03, 2011 10:58 AM
>
> Subject: Re: [TCML] CW magnifier
>
>
>  Carlos,
>>
>> What kind of performance do you "need", and what are you getting now?
>> Quasi-continuous mode coils are different than transient mode coils where
>> you can just keep pushing power into the coil to get longer sparks.  With
>> QCW coils you reach a point where greater power input will only lead to
>> streamer splitting, and branching.  To effectively make long QCW sparks
>> you
>> need to carefully control the top voltage so that the streamer does not
>> split or branch.  You can't get that sort of control from a simple
>> transformer and doubler arrangement (typical in many VTTCs).  The best I
>> have been able to do with MOTs and a doubler on my coil was 35".
>>
>> -Phillip Slawinski
>>
>> On Fri, Apr 1, 2011 at 22:43, Carlos Van Camp <
>> carlos@xxxxxxxxxxxxxxxxxxxxxx
>>
>>> wrote:
>>>
>>
>>  Thanks everyone for the feed back.
>>> Yes, I take your point about the CW coil already increasing the coupling,
>>> so your probably right... No real advantage to going to a magnifier...
>>> My main reason was the ever search for longer arcs! I have a large CW
>>> coil
>>> (valve driven) that is not putting out the arc length I need, so I am
>>> just
>>> looking for ways to improve it...
>>> I am not ready to go down the full electronic driven path at this point
>>> and
>>> I dont think I have the knowledge to pull it off anyway.
>>> So I will stick to my valves, and look at pulsing it to improve output...
>>>
>>> Thanks,
>>> Carlos
>>>
>>>  _______________________________________________
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>
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