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Re: [TCML] Capacitive Discharge Pulse Mode with my VTTC



On 9/7/2011 5:23 PM, Futuret wrote:
Roger,

Nice work.  It's not clear to me exactly how you applied the extra energy from the
capacitor and series choke to the tube plate... how the SCR was arranged circuit-wise to feed in
this energy?  Do you have a schematic available or a more thorough description
of the circuit?

Thanks,
John










-----Original Message-----
From: Roger Smith<rwsmith@xxxxxxxxxxxxxx>
To: Tesla Coil Mailing List<tesla@xxxxxxxxxx>
Sent: Fri, Sep 2, 2011 7:30 am
Subject: [TCML] Capacitive Discharge Pulse Mode with my VTTC


      The holy grail for many people who build tube coils is to get those

nice sword like sparks and there are several people on this mailing

list who have found some creative ways of getting them by pulsing the

plate voltage in just the right way to get the best spark growth .   I

have recently been experimenting with a rather low tech way of doing it

with my 3cx10000a3 tube coil.     I use a SCR in the cathode circuit to

start the pulse like you would do running in staccato mode and I charge

up a big capacitor capacitor in the plate circuit  and I have a big iron

core choke between the capacitor and the plate of the tube.  When the

capacitor is charged the SCR is triggered and the capacitor discharges

though the choke and drives the tube coil for some fraction of a second.



        Currently my capacitance is 7uf and the choke is 6 Henrys and I'm

charging the capacitor to about 20,000 volts.   The sparks I'm getting

are much more sword like than what I get in other modes and they are up

to 50" long  ( longer than what I get running staccato mode).      Here

is a link to a video .... http://www.youtube.com/watch?v=KxIEz_Q_hmo



Also,  here is a link to a time exposure of the coil running in pulse

mode... http://www.flickr.com/photos/29248051@N02/6104333777/in/photostream



Roger




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John, here is a link to the circuit diagram...http://www.flickr.com/photos/29248051@N02/6128920446/in/photostream

It is fired in much the same way as a VTTC in staccato mode with an SCR in the cathode circuit. Once it is triggered the charging transformer has to be turned off on tell the capacitor discharges so the SCR can turn off. Then the charging transformer is turned back on and after about half a second the SCR is triggered again. One pulse per second is the fastest rate I can do so far.

Roger
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