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my 1st SSTC

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raff

Thu Oct 01 2009, 08:20AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

finally my 1st SSTC.. but still FAR from tuned... with the topload mounted, I dont know the EXACT Freso.. but with 510pF, I guess its in the 350-450KHz range.. not sure... still need to MAKE a porper torroid topload for accurate Freso calculation.... I used 4046 because I cant get an HC14 to oscillate...too bad.. on my current setup, the antenna is situtated BELOW the secondary coil, else I dont get good breakouts... its maybe becuase Im only running 50Vdc to H-bridge....

specs:
secondary 4.2" diameter x 10" Length x awg#32
estimated turns = 1135
F reso = 323KHz <no topload>
h/w ratio = 2.4:1

pri 3T 5" dia awg#12 solid wire

using 4046 (10k,15k,510p) + 555 interruptor + discrete GDT driver
gdt ratio 1:2

power supply 50Vdc @ 2A... for testing purposes
MOSFET used IRF630A..for testing if discrete gdt driver works.. and it does!

****STILL NO RF GROUND YET****

vid

2.8" arc to GND

btw, is this normal for SSTC w/o proper RF ground, HV breakouts happen at the "GND" end of the secondary coil? just see my video.. the YELLOW WIRE IS the GND end...

any inputs apreciated..thanks!

-Ralph

Frosty90

Thu Oct 01 2009, 08:55AM

Registered Member #1617 Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139

btw, is this normal for SSTC w/o proper RF ground, HV breakouts happen at the "GND" end of the secondary coil? just see my video.. the YELLOW WIRE IS the GND end...

Yep it sure is normal. One of my SSTCs had base current feedback, and one time I left the ground disconected, and huge amounts of corona/small leaders formed from the base gnd wire, cooking my driver circuitry. But even if the ground is connected, a grounded electrode near the top can appear to 'emmit' short sparks/corona. With the same coil as above, if I held a screwdriver near the top of the secondary, the discharges from the secondary would dissapear, and I'd get 10cm 'swords' coming off the screwdriver!

Cheers,
Jesse

raff

Thu Oct 01 2009, 10:13AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Thanks for the reply frosty

I have noticed also, running the 4046 in CW mode (pin5 5 to GND), I have a *different* setting with the 10k trimpot as when it is in interrupt mode(4046 enabled by 555 timer through pin5)...

anyways does ringing in the GDT likely to kill a MOSFET?

running in interrupted mode , MOSFETs are cool to the touch(barely warm)... but when in CW mode, it heats up EASY! esp now that I have 3T only in primary...

Im using 27R gate resistor and 1:2 ratio gdt ( 11T primary // 22T bifilar secondary) ... are this TOO MUCH? Im sorry I cant give any tech specs on the torroid Im using but its defintely ferrite, it came from a photocopy machine, I think its from the signal filter/s... A friend gave it to me...

should I just lower turns count? say 4T//8T? and 5R gate resistors?

lightlinked

Thu Oct 01 2009, 10:40AM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115

whats your gate drive supply voltage? if its 5 volts 1:2 is fine but if its 12 volts 1:2 would be for IGBTs in which case you should do 1:1 for mosfets @ 12 volts. its best to have 1:1 and run the gate drivers close to the desired gate voltage.
the leads to your GDT should be a lil tider twisted pair or coax
do you have a scope to see how bad the ringing is? if you scope the bridge the bridge supply must be isolated.

raff

Thu Oct 01 2009, 01:01PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

my gate drive supply voltage is regulated(7812) 12V... but its not using UCCxxxx chip, but discrete using npn-pnp totem pole ang P-N channel mosfet as output..same as the one on ctc-labs site... my current setup using 1:1 ratio resulted only in heating (and death of mosfet/s) ... it cant switch on fully... the discrete gdt driver is also a half-wave...

I dont have a scope but I use this

to test my windings...it can "see" the ringings..

I think its not too much of a problem? or is it? maybe I just have to use 5R and 4T pri/ 8T bifilar sec for GDT..

raff

Fri Oct 02 2009, 12:26PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

some more pics...

I know THEY are small... hey its *only* FIRST LIGHT

just posting it here for safekeeping

curently, Im upgrading my oscillator circuit.. im still using PLL.. and *Added* NOR circuit to "mix" the 555 interruptor and PLL/VCO... CW/INT switchable.... and re-making again my discrete GDT driver to a full-bridge one... gdt ratio will NOW be 1:1 as opposed to my older half-bridge gdt driver with 1:2 ratio...

now back to BUSY mode..

till next post!

Arcstarter

Fri Oct 02 2009, 04:08PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I would suggest using a ground. You could even use the mains earth ground, but there is always the slightest chance to wreak havoc on electronics. Never happened with me, i guess i am lucky

About the spark *from* ground to the topload, even sstc's with a proper RF ground do this when you have a large toroid. All of mine did it, including the mini-sstc, and a PLL audio mod coil... That is just what happens.

Looks good so far

raff

Sat Oct 03 2009, 12:32AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Hi thanks for the reply.

yeah will definitely ground it...later ill pound a 4 foot steel rod to earth.. here in our city, we dont have earth GND(3 prong wire) on mains...

I have finished covering with alum duct tape my 1.35" x 9" torroid but I thinking maybe just metal "disk" with breakout will do.. need to experiment..

MRacerxdl

Sat Oct 03 2009, 02:10AM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

Here I didnt have mains ground too, before I made my ground with a steel rod on the ground, I was using aluminium foil on the ground. 1mÂ² works good for sstc's. I use it as ground for many times, and worked good. But the rod its better.

raff

Sun Oct 04 2009, 10:35AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Ok I finally made a REAL EARTH GROUND

2.5 feet iron rod pounded to earth real hard..

some more pictures

the complete setup, minus topload.. PS is 50Vdc 2A

Im still experimenting with the coupling... here shown VERY low coupling and LOW turns count (3T)..with 8T, mosfet IS COOL BUT smaller arcs

4046PLL osc (with 10K pot for finetune) + the 2 pots for 555 interrupter.. using full bridge GDT driver (still need to upgrade this though.. + N-P MOSFET totem pole as final outputs)

10R + 13V zeners are underneath

and of course the video

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