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Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
I was going to use the antenna, but someone told me it would be much better with a CT. I was told its a transformer. How exactly do i connect this to the SSTC circuit? I think if i understood, the 200 coil secondary on the CT, one end goes to the tesla coils secondary ground, and the other end goes to earth ground. But where does the primary go?
Also..for a 2X10" tesla coil, what is a good ratio to do? 1:200? 1:50?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Sorry, i forgot to actually explain it well... And i have not been on MSN.
Basically, you have a one turn primary, and something around 50-200 or even more, on the secondary. I used 3:200 ratio for my mini sstc.
The wire from the bottom of the secondary, that goes to earth/RF ground, is where one side of the primary hooks up... The other side hooks to the RF ground. I used mains ground, because it is a much better ground than the ground i had.
One side of the secondary is grounded to the common ground of your mini sstc driver circuit. The other side is connected the same as the antenna, except you use a 1Kohm or possibly 10Kohm resistor, to limit the current the fast diodes on the 74hc14 have to clamp. Other than that, your circuit stays the same, and to use an antenna, you just jumper across the resistor.
You should also put a burden resistor in parallel with the CT's secondary. Just try 100 ohms, maybe a watt. It needs to be carbon film or something has has almost zero inductance.
If you do not get correct feedback, or rather no breakout, connect the primary of the CT the opposite way. In other words, if side A was connected to the secondary base wire, and side B was on the earth ground, connect A to the ground and B to the secondary. This is called phasing. If it is phased wrong, it will be running 180 degrees out of phase, which will turn the IGBTs on at the exact wrong time.
It is very simple once you have experienced it, or even read up on it. To make it easier, here is a schematic from Steve Ward's drsstc (don't worry that it was from a drsstc, it should be connected to the sstc the exact same way). Remember, you should put a paralleled resistor. Otherwise, there will be more voltage, which would make the limiting resistor heat, and it would make the 1n4148 diodes have to clamp more often.
Registered Member #2315
Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161
hi guys.
Im about to try this too.. I have a *small*ish torriod ferrite to use as CT... I got about 22 turns using single UTP wire... if 74HC14 still dont work with this, I will use the 4046 internal inverter(and no VCO)..
Registered Member #2315
Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161
killa,
hows your CT feedback going? mine works! with 22T .... it worked *a bit* for the 74HC14 .. but I guess 22T is not enough or 74HC14 input is NOT too sensitive enough that I used the 4046 chip (buffer + OR)...
now I made another CT 42Turns 915uH.. will be testing it later...
hey arc, thanks for that burden resistor tip.. it DOES help!
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Try the 5 pack of ferrite toroids from electronic goldmine, I wound the hole thing with 22 gage magnet wire (about 100 turns), and it has not failed me yet.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
I'll have to get back to you raff, tryiing to get things working first before I start that CT...Having a bit of issues that seem to be slowly coming down. Thanks for the tips though!
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Quick question on Min SSTC circuit
with 22T .... it worked *a bit* for the 74HC14 .. but I guess 22T is not enough or 74HC14 input is NOT too sensitive enough that I used the 4046 chip (buffer + OR)...
