Build Log - Modulated SGTC / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Build Log - Modulated SGTC

1 2 3 next

Move Thread

LAN_403

Art

Tue Mar 29 2016, 11:40AM

Registered Member #57369 Joined: Fri Sept 18 2015, 01:24PM
Location:
Posts: 66

Hi Guys :)

I thought Iâ€™d share as I go. This one has worked well as a mess on a table,
and now I aim to replicate that setup in a fancy finished version.

Probably the most risky part Iâ€™m proud to say is still continuous... an inner connection to the torus :D
Now with that done Iâ€™ll pot the inner of the tube with whatever I can find.
Cheers, Art.

Centre Torus Connection:
Magic Connection Zps1ocfooeq

Inner Groove:
Groove Zps5orx5q9x

Clear Epoxy:
Epoxy Zpslpf0qans

Phil33ts

Sun Apr 03 2016, 11:15AM

Registered Member #57473 Joined: Sat Oct 03 2015, 03:21PM
Location:
Posts: 11

This is nice. How did you make torus?
Can you give us the exact specification of the coil, height, wire diamater, resonant frequency, etc?

Mads Barnkob

Sun Apr 03 2016, 11:41AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Could you please elaborate more on the "modulated sgtc" part of this project?

Art

Sun Apr 03 2016, 11:44AM

Registered Member #57369 Joined: Fri Sept 18 2015, 01:24PM
Location:
Posts: 66

Hi :)
I didnâ€™t make the torus, itâ€™s available from eBay (150mm).
The outer diameter is 34mm, and the height is 33cm.
The wire will probably never be replaced, itâ€™s vintage enamel and cloth covered wire :D

I didnâ€™t do any math, just wound more turns for secondary than I thought Iâ€™d need in case I wanted to unwind some.
Itâ€™s performed well as a slayer exciter and as a SGTC,
so I just aim to replicate what was on the bench, but in a nicely finished way.

A bit of progress... but now stuck waiting for parts to continue.

Secondary Clear Epoxy:

Secondary Epoxy Zpsioucqonu

Teir 1 & 2:

Stand A Zpsbvi6ryrb

Primary Formed:

Primary Form Zps9iullrzp

Bench Test Video:

Sorry Mads Barnkob, you must have just jumped in there as I posted.

I plan to use a DC SSR to pulse modulate the power supply to the ZVS driver.
I donâ€™t think it would get to audio frequencies, but perhaps a visible strobe.
I got some desirable effects just touching the supply to the positive battery terminal myself at varying intervals.

Assembly A

Benjamin

Mon Apr 04 2016, 04:30AM

Registered Member #54655 Joined: Thu Mar 19 2015, 05:56PM
Location: BC, Canada
Posts: 82

When I hear "modulated SGTC" I would think of something like a DC power supply to charge the cap bank at a high BPS rate and a MIDI triggered spark gap. I haven't seen this done before and I think that it would be pretty cool.

Sigurthr

Mon Apr 04 2016, 06:57AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

I initially assumed he was going to adjust the voltage feeding the cap, maybe with a magnetic amp or something.

hen918

Tue Apr 05 2016, 04:43PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

It might be easier to start / stop the oscillator/driver by pulling the gates of the MOSFETs low via a couple of diodes. Will have to try this out at some point. May be possible to turn a Mazzilli driver into a Voltage controlled power supply with pulse width modulation. It might be quite slow to react though.

Edit: I presume it's a Mazzilli and not some other ZVS driver...

Art

Wed Apr 06 2016, 03:08AM

Registered Member #57369 Joined: Fri Sept 18 2015, 01:24PM
Location:
Posts: 66

I hadnâ€™t thought about disabling the driver (it is one of those cheap ZVS driver from eBay driving a flyback).
That could save a solid state relay, which would be nice :)
I would assume though, it still wouldnâ€™t get to audio frequencies.

So far I havenâ€™t had as much luck replicating the results achieved on the bench now that itâ€™s partially assembled.

This is a typical video frame from when it was working in bits on a table.
From there, it now has a larger torus which I expect to lower the frequency and require more turns on the primary,
or a wider primary for the same capacitor array.

Discharge Zpsdy2vuado

nmoderator edit:

Hi again Guys :D
Testing the primary LC circuit and secondary with larger torus today with an RF signal generator and scope,
I measured the secondary resonant frequency at 707kHz (without any wire simulating streamers),
and the primary LC circuit was more than 100kHz higher with all of the inductor's 13 turns used.

Adding another 1000pF capacitance (from initially 2000pF) brought the primary LC
down to about 50kHz below the secondary resonant frequency (about 650kHz).
Considering just about anything I do should lower the secondary f further,
I suppose the primary still needs to be down lower.
I just used all of the capacitors I have at the moment for the current cap array.

If the 13 turns primary was maintained, which of decreasing the coil pitch or increasing the coil diameter
would be expected to increase primary inductance further?

dexter

Wed Apr 06 2016, 12:17PM

Registered Member #42796 Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195

Art wrote ...

If the 13 turns primary was maintained, which of decreasing the coil pitch or increasing the coil diameter
would be expected to increase primary inductance further?

both :)

play around with java tc. is quite good

Art

Wed Apr 06 2016, 01:52PM

Registered Member #57369 Joined: Fri Sept 18 2015, 01:24PM
Location:
Posts: 66

I meant which of the two is most effective to try first,
but I suppose Java TC is a practical way to find out :D

It also occurred to me that I have the next size down fancy torus as well,
and it should lower the resonant frequency of the secondary to add it to the top load.
Another thing Java TC should help with getting an idea about!

moderator edit:

Ok Guys, what gives?? :D

I have measured the secondary at 700kHz,
and the primary LC circuit at 650kHz with 13 turns,
so I should be able to lower coil turns slightly to increase
frequency of the primary circuit up to the 700kHz.

All of this measurement was done with the test unit assembled.
I tried to keep the video down to 30 seconds:

The still photo at the end is where I actually begin to get some output,
which is only about five turns with all the same setup!

1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob