My 160 (?)mm sstc

[oneKone]

So I think it's time for my next coil... I'll be using the same basic driver everyone uses (22/21 pair) except the one thing I'm not sure of is to buffer the interrupter signal through the same 74hc14 as the antenna buffer or use a seperate chip to reduce on interference (this is an absolute guess)

My local hardware shop sells 150mm PVC pipe (I'm guessing around 160mm od) so I'm thinking about 450mm wind length using 30awg wire I have laying around, with this I should get about 1500 turns (the wire measures 0.3mm).

For the inverter I was going to go with a 40n60 fullbridge as I've ordered some igbt from AliExpress and am keen to see what they go like.

This coil is really just to use up the existing wire I have before I order more..... Any criticism is welcomed.

[Mads Barnkob]

It will be a fairly large SSTC and you should at-least use a full-bridge and as high DC bus voltage as you can, in order to get long sparks.

SSTCs does not scale well in matter of spark length output when building them bigger, unless you make a inverter that can work into a few turns / low impedance primary coil.

If you are feeling adventurous, you could try to make a internal primary coil, I always wanted to try that, but never did

[oneKone]

It will be a fairly large SSTC and you should at-least use a full-bridge and as high DC bus voltage as you can, in order to get long sparks.

SSTCs does not scale well in matter of spark length output when building them bigger, unless you make a inverter that can work into a few turns / low impedance primary coil.

If you are feeling adventurous, you could try to make a internal primary coil, I always wanted to try that, but never did

I was thinking with the DS bus supply voltage to make a simple inverter capable of 500v but would be current limited, and just run low bps.

I'm interested in a internal primary coil now! I can't seem to find any examples though.

[Mads Barnkob]

It will be a fairly large SSTC and you should at-least use a full-bridge and as high DC bus voltage as you can, in order to get long sparks.

SSTCs does not scale well in matter of spark length output when building them bigger, unless you make a inverter that can work into a few turns / low impedance primary coil.

If you are feeling adventurous, you could try to make a internal primary coil, I always wanted to try that, but never did

I was thinking with the DS bus supply voltage to make a simple inverter capable of 500v but would be current limited, and just run low bps.

I'm interested in a internal primary coil now! I can't seem to find any examples though.

I think there is some E-field issues which could result in flash overs between secondary and primary, but in a SSTC where the peak current/voltage is lower, it might not be an issue. The interesting part of a internal is that you can have a lower impedance with the same turns, compared to it being on the outside.

[ldm314]

I am also considering running my primary on the inside. Biggest drawback I see is the difficulty tuning the primary.

[Mads Barnkob]

I am also considering running my primary on the inside. Biggest drawback I see is the difficulty tuning the primary.

A SSTC does not have a resonant primary circuit, so there is no need for tapping points on the primary coil. So that is not a problem.

[oneKone]

Ok,
So got back from holiday on Friday and got started on the coil! I wound the secondary but roughly got 1230 turns..... I was hoping for 1500.... Tomorrow I'll get a few coats polyurethane on it.

[futurist]

Looks great, how did you count turns?

[oneKone]

Looks great, how did you count turns?

i divide the wind length by the diameter of the wire. at the time i couldn't find the tape measure so the reading wasn't as accurate as i'd hoped.   

[futurist]

I started making simple turns counter with STM32 and hall sensor, but somehow managed to fry the sensor
Just ordered few more sensors

[ldm314]

Ok,
So got back from holiday on Friday and got started on the coil! I wound the secondary but roughly got 1230 turns..... I was hoping for 1500.... Tomorrow I'll get a few coats polyurethane on it.

Looks great, just winding by hand it looks like?

[Mads Barnkob]

Looks good oneKone

Looks great, just winding by hand it looks like?

Most of the time its actually quite easy to control just by hand, and takes much less time than making a rig, a rig is however needed for the drying varnish, atleast for a good even result. It was only my large DRSSTC3 where we built a rig for winding.

[Hydron]

I built a winding jig for both my coils. Building the jig took longer than winding, but I'm glad I did - as Mads mentioned, you also should have it for evenly coating the winding afterwards.

As for counting turns, I did such a poor job on centering the coil in my jig that the run-out was big enough (5mm or so) to activate a microswitch I placed underneath it once per revolution. A hacked together microcontroller program counted the turns (=1920 for my big coil), and I then used the resulting turns-per-length number to work out how many my next coil (using the same wire) had without bothering with the micro again. All very rough and ready but did the job well enough i think.

[ldm314]

I built a winding jig for both my coils. Building the jig took longer than winding, but I'm glad I did - as Mads mentioned, you also should have it for evenly coating the winding afterwards.

As for counting turns, I did such a poor job on centering the coil in my jig that the run-out was big enough (5mm or so) to activate a microswitch I placed underneath it once per revolution. A hacked together microcontroller program counted the turns (=1920 for my big coil), and I then used the resulting turns-per-length number to work out how many my next coil (using the same wire) had without bothering with the micro again. All very rough and ready but did the job well enough i think.

That's a great idea on having something to do turn counting. I'm practicing with some recovered wire paper towel tubes. When I go to make a serious one, definitely will build up a jig.

[futurist]

This is what I came up with, couldn't be any simpler
For speed control I use 555 PWM from ebay

[oneKone]

So after being busy working and fixing my car's! Damn harmonic balancer! I can finally give the Tesla coil some attention.

I've made the controller which is an updated version of the last, I think one more revision and they should be flawless! (To me anyways)


Hopefully this weekend I can make some real progress.

[oneKone]

It's amazing how sometimes the most idiotic ideas outweigh logic. I connected a half bridge of the ixgn60n60 with no tvs or heatsinks just to see if the coil would run. After I got excited it overheated and a module died.

So lesson learnt..... Don't get too excited,  follow the basic rules... So just waiting on some more igbts now, I guess now I have time to make the Steve wards burst mode interrupter.

[Mads Barnkob]

Haha, yeah no heat sinks are not a great idea when it comes to high current pulse work, that really needs something to take those peak temperature rises to a better average level.

Reminds of once I made a SSTC into a DRSSTC without feedback driver I just measured the frequency with a counter and adjusted a signal generator manually to drive the bridge, needless to say, it died from hard switching

[oneKone]

So I finally got some fgh60n60 from China. I've killed 4 igbt before I realised the pulse of the coil was drawing too many amps. I haven't calculated it but I added a inrush current limiting resistor, value 4R7. I'm almost starting to think I might abandon this coil and move on to smaller coils. I feel like they're a bit safer.



So for size reference the PVC pipe is 160mm od.

[CCX191]

Woah, that's pretty nice. I'm looking forward for more updates! Going to work on my coil after my major exams Busy studying lately .

For smaller coils, any thoughts on the type of circuitry you are going to use? Was thinking to make some miniature tabletop sized tesla coils. PLL circuit seems interesting especially the one from E-Schmok