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Re: Fw: OL-DRSSTC 9 - Better trigger!!

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Scott,

The trigger used to just make a single current pulse like this:

http://hot-streamer.com/temp/OL-DRSSTC-05-06-002.gif

This would trigger the thing into oscillation:

http://hot-streamer.com/temp/OL-DRSSTC-05-06-003.gif

Problem was I needed about 140V on the buss before this would fire the circuit (this was also before the bias resistors really spiked up that current!!))

But by taking out the resistor, the Q of the circuit went up to like 6 and the added diode allowed current to flow in the reverse direction so it oscillated as a long ring down:

http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-001.gif

This long powerful ring is able to start the oscillation with only 20 volts on the buss.

Of course, the ring has to be close to the same frequency as the coil's primary. thus, a inductor was added to adjust the trigger's frequency:

http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-005.jpg

The coil is just in series with the trigger loop through the CTs. I should probably put it on the schematic too....

BTW - I will pass this to the list too since others may be wondering the same thing.

Cheers,

        Terry


At 03:18 PM 10/16/2005, you wrote: 
Terry -

One question on your update #9 (below):

"I took out the 2.7ohm resistor and added a reverse diode across the SIDAC.
I added a loop of "primary" wire to the trigger loop so I could tune it
right to the Fo frequency of the primary coil. So it runs much like the
original OLTC did. There is not much to it (it really only needs "one"
cap...)"

Exactly what did you mean when you stated "I added a loop of primary wire to
the trigger loop". I'm not sure exactly what changed here, or where this new
loop of primary wire is physically located. Please elaborate .....

Thanks!
Scott


---- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, October 11, 2005 6:22 PM
Subject: OL-DRSSTC 9 - Better trigger!!


> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi All,
>
> The OL-DRSSTC coil now triggers at any input voltage so the power can
> be "fully" controlled by a variac!  I went to a "fully resonant
> tuned" trigger pulse and it will now fire "anything"!!
>
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-001.gif
>
> The trigger pulse is a big 35 amp 96kHz decrement sinewave now that
> lasts for about 8 cycles!  It will start up any lazy ol-DRSSTC
> :o))  It could probably even power a little Tesla coil all by itself,
> but it is only 5.3mJ/bang or 0.32 watts.  Almost 1 inch by the Freau
> equation...  Might be useful for "enyweeny" coils:
>
> http://www.roffesoft.co.uk/tesla/enyweeny/enyweeny.htm
>
> The drive circuit is here in the upper right:
>
> http://hot-streamer.com/temp/OL-DRSSTC-08.gif
>
> I took out the 2.7ohm resistor and added a reverse diode across the
> SIDAC.  I added a loop of "primary" wire to the trigger loop so I
> could tune it right to the Fo frequency of the primary coil.  So it
> runs much like the original OLTC did.  There is not much to it (it
> really only needs "one" cap...):
>
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-005.jpg
>
> One could probably fiddle with the part values as you please.  The
> SIDAC "could" probably push 80 amps!!  Peak current is controlled by
> the firing voltage and primary loop impedance.  The voltage ringup is
> able to keep the circuit in conduction until the cap energy is used
> up.  Really cool!! ;-))
>
>
> With a test load, the circuit fires right up!  Yellow is primary
> current and blue is the trigger circuit loop current.
>
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-002.gif
>
> At 60BPS, this heated the IGBTs to about 40C with the fan in place
> (could use a "better" instead of the "cheapest" fan...).
>
> I hooked it to the full coil and tuned it for some nasty primary
> currents and it started and ran fine:
>
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-003.gif
>
> The firing pulse train looks like this:
>
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-004.gif
>
> So that is where I am...  Things to do...
>
> A simple inrush current limiter could replace the big blocking
> inductor for less power but a far smaller size...
> The fan needs to be "better"...  Maybe a big CPU fan, but I don't
> have the low voltage to run it...
> I need to put back in the 150nF primary cap and 16uH primary to
> optimize it all much better.
> I need to get a few more parts from DigiKey....
>
> BTW - I think DK#  P12241-ND  2.4uF 400V poly caps could directly
> replace the 2.5uF caps from Richardson...
>
>
> Cheers,
>
> Terry
>
>
>
>
>
>
>