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Mains synced interrupter to achieve Sword sparks

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zzz_julian_zzz

Tue Sept 03 2013, 09:11AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Does anyone have an idea on the interrupter circuit used in this video on how did it manage to synchronously pulse with the AC mains with lower repetition rates? All i know is that it first squares the 60 hz sine using a zero crossing detector circuit, my question is, how can we derive lower repetition rate (let's say 5 hz) synchronously from the 60 hz square signal? Any comments is highly appreciated, Thanks!

-julian

Mads Barnkob

Tue Sept 03 2013, 02:31PM

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

The 2nd 555 timer sets a pulsewidth that determines how many zero crossings it will let pass, the lower pulsewidth, the fewer zero crossings will be let through.

HV Enthusiast

Tue Sept 03 2013, 02:45PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

What Mads said. There are generally two settings - one for Pulsewidth and one for amount of bursts.

the schematic you reference is the one originally done by John Freau VTTC Stacatto controller. My controller i offer below, is also based on that original controller and also includes feedback / requested upgrades from the TCML list which was done back in 2003-2004 i believe.

You can see our Stacatto Controller here.

Dr. Dark Current

Tue Sept 03 2013, 06:39PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

You can also use the 4017 decade counter if you want precision timing (it can be programmed for a cycle length anywhere between 1 to 10 pulses), or a cascade of two for very low repetition rates.

zzz_julian_zzz

Wed Sept 04 2013, 11:09AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Thank you all for the replies!

@Mads: yes i think that too but, would it still produce sword looking sparks? i mean, i thought that a sword spark can be achieved even only with 1/2 cycle (positive only - attached photo) of the 60hz AC mains and not with many or few half cycles with gaps in between(just like in the QCW drsstc - single half cycle smooth ramp)?. also, i forgot to mention that i am planning to replicate the one in the video above (as my coil being an SSTC not VTTC)

@EVR: "one for pulsewidth and one for amount of burst"
is stacatto controller can be applied directly to SSTCs? i mean, in the schematic i posted above, the output of the first 555 will drive the SCRs for the tube to connect to the ground, (is the output will just be the same if i put this output pulse on the interrupter or enablers?)

@DR. Dark Current: im still studying the capability and advantages of 4017 over the orig config of the cascaded 555 ics.

Please look below what i think is required for the interrupter(low pulse rate) output to achieve sword looking sparks (given that my SSTC is at 400khz) please correct me if you think im misleading on this, thank you very much.

Steve Conner

Wed Sept 04 2013, 11:41AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

In Steve's circuit, R7 controls the burst length (number of half cycles) and R13 controls the repetition rate.

The beginning of the burst will always be synchronised with a zero crossing, because the left hand 555 is triggered by zero crossings. However, I don't believe the end of the burst is synchronised. I think it relies on the SCR to stay triggered until the next zero crossing. This means that you can't connect the SCR gate output directly to an interrupter.

HV Enthusiast

Wed Sept 04 2013, 12:58PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

zzz,

If you download the manual, you can see all the timing diagrams and how the stacatto controller operates. This controller has been used for both VTTCs as well as SSTCs.

PDF MANUAL HERE

TwirlyWhirly555

Wed Sept 04 2013, 08:20PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

I have a simple circuit that uses a 120/230V - 9V AC transformer , two transistors and a few resistors and 4 diodes to produce a 5V square wave @ 100 Hz when using 50Hz mains , then feed that into a 4017 to divide the output by 10 to get 10 Hz pulses in sync with mians AC

Should be fine for 120 Hz aswell , will just get 12 Hz pulses from the 4017 .

I used to circuit to synce my VTTC to the mains frequency .

zzz_julian_zzz

Wed Sept 11 2013, 05:21AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Hi Guys,

Please check on my schematic posted below for the (SINGLE pulse interrupter- synced to only positive AC mains cycle) to achieve Ramped Voltage Envelope then Sword Spark. I noticed that my possible PRF output were only 60hz, 30hz, 20hz, 15hz, 12hz, so on... all factors of 60...

SIMPLE SCHEMATIC DESCRIPTION:

First, the 60hz sinusoid were converted to a square wave(which was not shown here how) - it is implemented using a step down transformer(230/9v) and a transistor.. This squares the signal(only one transistor were used so it is inverted-this signal is what i need to trigger the first 555 timer then spit a long pulse that is synced on the AC mains, then its output were inverted again to trigger the 2nd 555 timer in-sync with the first 555 timer and the mains.

i can vary the repetition rate by varying the ON time(potentiometer) of the first 555 monostable timer that triggers the another 555 (which is in monostable configuration too)- with output that can also vary from 1 half cycle to how many cycles I want(depending on the ON TIME too) - (problem here was the synced turn off of the pulse, but maybe a fixed potentiometer can determine that proper pulse length to get synced on AC turning off) but of course with respect to the PRF rate determined by the first 555 mono(which was also not shown here). - I believe that the AC polarity should be correct to be able to properly work on a sstc (the line that will pass thru halfwave rectifier diode on the bridge should be the 60hz reference signal of the interrupter too).

I was able to build the board for this, completed the circuit and it works in my scope! - but i was not able to test it on a actual SSTC to see the result if it will create a sword sparks... This weekend I'm gonna test if it'll work :) but for the mean time, do you think it will work? (in terms of spark appearance) Thank you!

1378876883 3964 FT156908 Sstc Staccato Controller

My question is that How many AC positive half cycles do a 350khz coil need to produce a decent swordish like sparks? and is it really necessary to make the interrupter to say "Go" at some point where from Zero going to + voltage? or can it say "Go" anywhere in between half cycle (1/2-peak, 1/4 delayed, etc..)? Thank you.

zzz_julian_zzz

Mon Sept 16 2013, 04:07AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

UPDATE:

Here is the result,

As you can see, the pulse repetition rate can be varied from 4 bps(hz) up to 60 bps (hz).
In conclusion with the above commentaries, SSTC staccato controller may not work correctly if directly plugged in to a sstc (as an interrupter) if the goal is to sync the mains and produce user varied PRF signal for an interrupter to obtain sword sparks.

thanks for the input guys :)

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