New small SSTC

[Bambinz]

News, now works, bad but works xD
The problem was the layout, I have made some connection too long duringe redesign (The connection between the capacitor and the primary coil). Now I have shorted all connection (are shorter also respect the first version). In addition, now the coil is above the coil and not away like in the version of the video.

However now I obtain a little spark and absorbe very high current, about 5-6A. Probably is due to the poor tuning of the C12 because I have used the old capacity, but the inductance of the connections and the parassitic capacitances are varied due to the change of layout.

Tomorrow I continue with the test!

Thank you very much !!!

[Bambinz]

Now work like in the first video, little bit better.

I have noticed that without interrupt the coil produce only 3mm-4mm of spark and consume a lot of current like 7-8A. The coil work very well with a low duty-cycle (betwen 0-10%).

I think that is due to the very low inductance of the primary coil (Only 1 turns) that results in an high peak-current because the reactance at the risonance is very low.

I think that this mini tesla coil work very well because:
  1. Low inductance of primary coil = High primary current and High ratio L2/L1 -> Higher voltage gain
  2. Very high coupling, probably will be in the range of 0.7-0.8. Therefore results in a very high efficiency and then the high coupling not cause problem because we use small power.

[Bambinz]

Today I have start-up again the tesla-coil without change anythings and .... MOSFET it dies

Therefore I have decided to reproject the driver, the new versions will be base on the the leonsocean schematic: https://www.loneoceans.com/labs/sstc2/  but with some modifications.

- 1) The secondary will be the same
- 2) The primary will have the same size and 1/2 turns (not 1+1 because will be used an half-bridge driver)
      I will use an high coupling and a very low primary inductance to have an high voltage gain and an high primary current. I think that is the key to obtain a good spark from  this small
     teslacoil
- 3) Use an STM32F1 to control all the system
- 4) The inductance of the primary will be in the range of 0.1uH -> At 1 MHz will be a primary reactance of 1 Ohm, therefore with 24V of supply will obtain like 24A that is to mouch, therefore I
       will limit the duty-cycle to about 10% to have an RMS current in the range of 2-3A maximum.
-  5) I would like to add a mosfet protection(Snubber and short-circuit protection) to not kill to many mosfet xD
-  6) Use a better mosfet that support higher voltage, to prevent the destruction. Therefore the driver will be drive an high capacitance mosfet respect the actual mosfet.

Other suggestions? Can be works?

[Bambinz]

I'am starting to project the new tesla-coil driver with some interesting features.
If you want and if you are interested I can open new thread with the description, schematic, layout and the software.

[Mads Barnkob]

I'am starting to project the new tesla-coil driver with some interesting features.
If you want and if you are interested I can open new thread with the description, schematic, layout and the software.

Yes, please do start a new thread for a new project, instead of updating your first thread

[Roit]

Hi

I hope it's okay to ask a question. I've built the same coil but haven't been able to test it yet, my problem is getting the Hex code down on Attiny13. i have tried with arduinoisp unsuccessfully. How did you program your chip?

[Bambinz]

Hi all,

The minitesla still working   
Now I would like to do a PCB to minimize the parasitic inductance!
Instead of driving the mosfet with the feedback transformer, can I use a gate driver ic like the UCC27425?

I would like to try to do use this system: https://www.loneoceans.com/labs/sstc2/sstc2schematicv10.jpg but to drive the push-pull configuration. To reduce the number of components

In addition I have realized the configuration in the link with a bigger coil, but with a 50W transformer (24VAC 2A) I obtain only spark of about 3-4cm. Probably due to the low input power

[Mads Barnkob]

Instead of driving the mosfet with the feedback transformer, can I use a gate driver ic like the UCC27425?

I would like to try to do use this system: https://www.loneoceans.com/labs/sstc2/sstc2schematicv10.jpg but to drive the push-pull configuration. To reduce the number of components

You need the GDT (gate drive transformer) between your UCC driver and the MOSFETs for isolation between logic and power sections. If you want to omit the GDT, look into "high side mosfet drivers", but that is often more complex than a simple passive component like a GDT.

[Bambinz]

Instead of driving the mosfet with the feedback transformer, can I use a gate driver ic like the UCC27425?

I would like to try to do use this system: https://www.loneoceans.com/labs/sstc2/sstc2schematicv10.jpg but to drive the push-pull configuration. To reduce the number of components

You need the GDT (gate drive transformer) between your UCC driver and the MOSFETs for isolation between logic and power sections. If you want to omit the GDT, look into "high side mosfet drivers", but that is often more complex than a simple passive component like a GDT.

I want to use the Push-pull configurato, therefore the two mosfet is refered to ground. In this way I Can drive it with the ic, no?

EDIT:
I would like to increase the power of the mini SSTC. I have a transformer of 150VA 2x15V.
I have think at two topology, half-bridge with voltage doubler like the loneoceans configuration to have +-42V on the inductor.

Or a push-pull with a voltage doubler to have +-80V on the inductor. The advantage of the push-pull is that doesn't require the GDT and I will have higher voltage but the layout is more more critical.

Which configuration is better for my application?

[Magneticitist]

This is a really cool coil that got me into that circuit a little while ago. I haven't tried making anything as small as his but I've had some pretty cool setups using the mosfet stage alone. The long arcs only occur when biasing the fets just right and getting the GDT just right. Doing initial research on coiling I wouldn't have thought something like that would be able to operate so clean just from a little GDT and no gate drivers. I've made several of them without replicating the Skori or Tefatronix circuits exactly but I've noticed the push-pull stage in general is a pretty handy way to drive pretty much any small coil so long as the high currents are kept in mind. I've tried even IRFP250's with what I consider some success and even have a couple that use pulled 1:1's as GDT's. The interrupter is pretty essential but I find running some of them from around 15-20v continuous to be manageable for short periods pulling hot arcs. To get anything close to a 6 inch discharge I need to run them at 24v at least but really closer to 30v or 35v is where I like. I also had one which ran beautifully from 2.5v and under lighting floros quite nicely from a good distance, something like close to 3 feet and at that voltage it pulled about an amp. It was using IRFZ44N's which is actually what Tefatronix ended up using in his finalized build, not the logic levels IRL's. Someone had commented to me that he tried the same setup with similar goals as yours in mind and while I'm not sure where he ended up he told me he was able to drive it at around 100vdc by adding more turns to his primaries. The GDT is of course the critical component here being that it's doing all the high speed switching work.

My most successful test build ran at about 1.4mhz and crapped out on me due to the GDT arcing at the windings, the downside of using a pulled 1:1 with thin insulation and not running the thing legit grounded. It gave me about 6 inch discharges with the right topload and interrupting from 33v and I could actually run it from a little boost module from a 12v lithium pack. I learned that was a bad idea later when the little 35v output caps on the module popped. It was very simple though.. just the two 250's, couple 15v zeners, a 10K pot, one cap, and the GDT. With something like a 3x2.5 inch coil it pulled about 3-4A at 12v with a relatively loose primary coupling. Pulling arcs would bring it to 10A or so, nice hot yellow ones. The tight primary coupling is something I just haven't been able to do because I can't insulate it from the secondary well enough at voltages exceeding 24v or so. The arcs WILL find a way through or around without an extremely effective insulation. Only enough air space seems to do the trick along with some insulating. I ended up turning that build into one which gave a nice little decent bushy CW discharge with some power to it at about 30V 5A.   

The only difference in how I run mine is that I started off using a master PWM which drives the circuits instead of interrupting them by pulling the gates low. I use a TL494 to get variable frequency and duty and inject audio signals into the coils through that. My favorite one now is one almost identical to the one which crapped out, and I've been using it for wireless transfer testing after noticing I was accidentally transmitting to a nearby coil on my table. I couldn't figure out why my coil sounded like it was arcing somewhere in the circuit instead of out at the breakout point until noticing the small spark coming out of the nearby coil. It will drive a 12v automotive blower wireless pretty good from around a foot away at around 30-45watts.

Right around when I was really starting to get into trying to build a better one I started getting into the Steve Ward circuits and got lost in trying to troubleshoot my way through his Mini SSTC.