A few questions

[ako]

Hi Voltage folks,

I am quite new here and reading now for a few weeks. I already have built and played around with an SGTC with a ZVS powered flyback transformer and diy rolled caps.
The first music I've heared came out of the same flyback transformer driven with an Arduino/NE555 controlled IRFP460.

My next goal now is to build (actually... have) a DRSSTC.

I say 'actually have' because I would have bought me a OneTeslaTS kit and built it in the hope having the feeling of 'building' a DRSSTC on my own and much more important in the hope of learning how everything works while expecting that it'll work when finished.

This brings me to my first question:

Is the OneTesla team still active somehow? Their products are out of stock since I am watching their site now for weeks and I also have contacted them via their contact form but I haven't received any reply at all.

Can I get a similar kit somewhere in Europe (I am living in Germany)?

Another question is:

Which PCB of those you awesome guys have created and thankfully provided here in this forum for us to download would be compareable to the one of the OneTesla kit?

As I would like to end up with a (you guys would say) small compact looking coil, which I can leave standing on a shelf without having my wife complaining about it. That's why I would like to have the primary on a PCB too (which in my opinion makes the whole construct look more neat).

Are there already some combinations with driver and primary PCBs available for download here already which I might have missed?

My next question:

I have already some parts salvaged (out of some big CNC machine motor drivers I guess) at hand. Can you guys have a look at them (I'll attach the pics when I'm done writing and don't know where they show up here) and tell me if I can make use of them? I am sure though, that - if - those parts will be nothing for my first compact build. But anyways, if I sometime succeed and build my first, I am pretty sure that it will be not my last... but my smallest.



I hope I did nothing wrong and didn't void any board rules and also didn't bother you with my questions.

I appreciate any help and advice and all of your work and information you guys have put into this forum so far.

[davekni]

Can I get a similar kit somewhere in Europe (I am living in Germany)?

The only other TC kit company I am aware of is Eastern Voltage Research (EVR for short).  My limited experience with them is mediocre at best.  I have helped a couple people get their EVR coils working.  I'd be happy to help remotely with debug of whatever you decide to build in the end.  This forum is a good place for such.

Hopefully you'll get other answers if there are any small integrated designs as you are searching for.

Good luck with your project!

[ako]

You see... with all googling and looking for kits and stuff this EVR site didn't come up though. I see it for the first time now. Thanks for the hint. They seem to have really a lot to offer. Unfortunately, besides their not really that cheap prices for their coil kits, they seem to be located in US too. So if I ordered a kit there, including tax fees and shipping costs, I really would pay disproportionately much for something I could get a lot cheaper with putting some brainjuice into it.

I am just doing my first serious steps with KiCad and EasyEDA in parallel and try to rebuild the OneTeslaTS board with the help of the schematics and the pictures they provide for download on their site. I know this might sound like am trying to be some sort of copycat and stuff, but I contacted them asking for all possible options for me to get their product, either by buying the kit or maybe by them providing PCB files (even with being ready to pay for that) so that I can order those at some PCB manufacturer. But like I said, unfortunately no reaction from them at all.

The schematics of their driver is pretty simple and I would easily be able to build it all manually on a perfboard, but I would like to use this opportunity and end up having some sort a semi-professional product when I'm done and not another completely DIY looking gadget flying around and collecting dust.

But if I really should be able to get  a compact driver built, the biggest hurdle still will remain the design of a PCB primary, as I am not that experienced or educated in the physics and formulas involved. I would need a significant amount of time (and most likely money) to get behind that. So if anyone here could give me some hints or links to maybe some sites with calculators like the JavaTC that would make my life easier, I would really appreciate that.

I already have most of the BOM of the OneTeslaTS in my bucket on ebay, including the gate drivers, the IGBTs, the 74HC*** ICs. All resistors and diodes and other small stuff I am pretty sure I have somewhere in my small parts boxes or still mounted on one of the bunch of boards from all kind of salvaged electronics that I have in my workshop. What I couldn't find so far is the primary cap with the same values and I am not sure about the current transformer. I have a few of those on some boards (like the one in the picture in my first post) and I would like to know if there is a way to test them to find out if they would suite? Any hints?

[davekni]

The schematics of their driver is pretty simple and I would easily be able to build it all manually on a perfboard, but I would like to use this opportunity and end up having some sort a semi-professional product when I'm done and not another completely DIY looking gadget flying around and collecting dust.

Perfboard builds are more likely to have issues with signal integrity, as most do not have ground planes.  A well-designed ECB will perform more reliably besides looking better.  I see KiCad used here more often than any other ECB tools, so started using it a couple years ago.  Powerful free tools well worth learning.

So if anyone here could give me some hints or links to maybe some sites with calculators like the JavaTC that would make my life easier, I would really appreciate that.

JavaTC should get you close enough.  Primary loss will be higher (Q lower) than JavaTC predicts due to actual thin traces instead of thick wire.  Otherwise it should be close enough.  If you want to learn FEMM, that would be the more precise and involved option.  Make ECB from 2oz copper to minimize loss.
For primary frequency adjustment, either include multiple spaced taps (ie. through-holes) along primary, or provide space for a few smaller caps across primary series capacitor to allow tweaking cap value.

I already have most of the BOM of the OneTeslaTS in my bucket on ebay, including the gate drivers, the IGBTs, the 74HC*** ICs.

Be aware that there are many counterfeit parts being sold, on EBay etc. and on Chinese specific sites too.  IGBTs are most likely to be questionable.  Other parts such as 74HC14 will likely work well enough whether genuine or not.  IGBTs might too.  However, these simple small DRSSTC designs lack lead compensation.  IGBTs are hard-switched (switched while conducting current), so experience higher stress.
BTW, IGBT bricks as shown in your initial post are generally good for larger lower-frequency coils.  Small ones are usually too high frequency for such IGBTs.

What I couldn't find so far is the primary cap with the same values and I am not sure about the current transformer. I have a few of those on some boards (like the one in the picture in my first post) and I would like to know if there is a way to test them to find out if they would suite? Any hints?

Primary cap is unlikely to be found in salvaged equipment, at least that's my experience.  Most DRSSTCs use an array of smaller caps called "MMC" for primary cap.  Sometimes small ones do have a single cap as in the OneTesla example.
I see one brown object at the bottom of your image that seems likely to be a CT.  Good chance it would work for a small coil.  100:1 is most common for such board mount CTs.  What equipment to you have around?  Scope and signal generator?  LRC meter?

[ako]

What equipment to you have around?  Scope and signal generator?  LRC meter?

Check, check and check. A Hantek USB scope I bought a couple of years ago, a Peaktech 3440 and one of those cheap LCR T7 Multi transistor testing tools.

[davekni]

A Hantek USB scope I bought a couple of years ago, a Peaktech 3440 and one of those cheap LCR T7 Multi transistor testing tools.

For measuring possible CT, LCR meter would be easiest, though might be a problem if LCR meter frequency is too low.  10kHz might be OK.  100kHz would be better.  Scope and signal generator will be more reliable.
Either way, I'd wind 10 turns of wire around CT core, through the hole where one wire normally passes.  Check pins for continuity.  Presumably only one pair will connect.  For LRC meter, measure inductance of pin pair and of 10-turn winding.  Turns ratio will be sqrt(inductance ratio).  For scope, connect signal generator to pin pair and run at ~100kHz.  Scope waveform across pin pair and then across 10-turn winding.  Voltage ratio is turns ratio.  Make sure signal generator output has no DC component.  Add a series capacitor to make sure.

CTs aren't difficult to make if you have cores.  Line input common-mode choke cores generally work well.  Other salvage cores are not likely to be good.  Large EMI filter beads can work as CT cores, but will require more testing to verify.  Same core options for GDTs.

[ako]

Another question which came up:

I see different schematics which mostly look similar but some use a combination of UCC37322 and UCC37321 and some use a pair of those two.

I'm sure that I get it right that the difference of those two chips is the inverted output. So a 1 signal on input gives an 0 signal on output with the inverted version and 1 input 1 output with the non-inverted version.

My question now is:

Is the result basically the same when I use a combination of those two chips and connect the output wires of the GDT to the IGBTs (technically to one half of the bridge) 1 to 1 to the IGBTs or when I use a pair of one of those ICs but inverting the signal by connecting the outputs wires of the GDT not 1 to 1 but flip the two wires for on half of the bridge?

[davekni]

Is the result basically the same when I use a combination of those two chips and connect the output wires of the GDT to the IGBTs (technically to one half of the bridge) 1 to 1 to the IGBTs or when I use a pair of one of those ICs but inverting the signal by connecting the outputs wires of the GDT not 1 to 1 but flip the two wires for on half of the bridge?

No.  When using same driver chips, input of one chip is inverted.  Simulation is the easiest way to understand.

[ako]

Alright... next question(s)

GDTs....

Is there a method (in addition to attaching a square wave signal to the input and the oscilloscope to the output winding) to find the right cores to use, when you have a bunch of them in all different sizes and colors, like I do (not only) here:


On the board from my initial post, there is this section, which strongly looks like a gate drive circuitry


The two red(ish) blocks on the left look (and behave) like GDTs. Datasheet is attached, but unfortunately only in german. Directly translated, the datasheet says those are "Ignition Transformers".
I did the signal/oscilloscope test (on ~340kHz the resonant frequency of the secondary + topload) and at a first glance, I would consider this here as a clean square wave output signal

Question is, is there some property (I lack the knowledge of) in the datasheet which would make these GDTs unusable for a DRSSTC?

On the section of the board there are also the two ICs on the right side. Those are TLP2200s and according to the (attached) datasheet they are gate drivers.
Would those be usable?

[Mads Barnkob]

Generally you can not use ferrite cores found in noise filtering, as GDT cores, simply because material could be a wide variety between coarse iron powder and well suited high frequency material, we just dont know. Color cant tell, grain coarse cant tell, shape cant tell. Its just a gamble, unless you pulled it from something you know is a 100 kHz+ circuit.

Industrial GDTs are in general pretty small, so that means its a thin wire and small core. Thus it needs more turns than a homemade 15:15:15 GDT driven at 24V. This means that its peak current capabilities is maybe 10-fold lower than a homemade. And all we want in a Tesla coil, where we overdrive the IGBT gates from normal +/- 15V to 24V, is because we want FAST switching. We want fast switching because we drive much larger currents than the switches are meant to handle, part due to resonance we get away with this, but we still need fast switching to keep the turn on/off losses within the hardswitching specifications of the IGBTs.

[davekni]

Question is, is there some property (I lack the knowledge of) in the datasheet which would make these GDTs unusable for a DRSSTC?

On the section of the board there are also the two ICs on the right side. Those are TLP2200s and according to the (attached) datasheet they are gate drivers.
Would those be usable?

TLP2200s are optical couplers.  Would require buffering of output to drive any significant gate capacitance.  Given the use of isolators, I'd guess the "GDTs" are more likely transformers used to generate isolated DC gate drive supply rails.  Even if they are GDTs, I completely agree with Mads' comments about those.

Is there a method (in addition to attaching a square wave signal to the input and the oscilloscope to the output winding) to find the right cores to use, when you have a bunch of them in all different sizes and colors, like I do (not only) here:

You can narrow down the list of possibilities, but any final use should include testing first.  Any core with a single winding is not suitable.  It is an inductor with an almost-certainly powdered (iron...) core.  The cores with two identical windings on separate halves separated by a space are likely line input common-mode filter chokes.  Those are quite likely to work (presuming they are large enough for your needs).    Other cores with multiple identical windings might be OK.  The largest bare black core in the image might be OK for a reasonably-high-frequency coil, but needs testing.  I have a couple bags of similar cores from a surplus sales outfit.  One is reasonably good, the other not.

[ako]

Alright guys...

the more I read and the more (barely) different schematics I study, the more I tend to say F it designing my own OneTesla clone board. I guess it's a better idea to take what's already been done and tested by people who really know what they're doing and go with one of those (and that's actually my question now) UDs which are available for download.

What is the most current version which I should aim for? For sure those 3.0 and up versions look really interesting, basically with their own operating system to tinker with. Getting the board ordered and (even SMD) soldering are really no big deal for me but what really annoys me is to get all the parts ordered... You mostly don't find all needed parts at one supplier, another parts you don't find at all with a reasonable delivery time... that sux... and beside all that, I most probably have all needed parts anyways somewhere on all those circuit boards which I have in my basement.

Does someone here maybe have a spare UD 3.0 or up to offer for sell? Netzpfuscher or someone else from Germany maybe? I would also take it as some sort of kit, so board and parts for self soldering basically.

[ako]

OK guys,

I guess I need to hear your thoughts now:

I have actually copied and built the OneTeslaTS schematics, wound a GDT after davekni's tutorial (thanks for that), connected a signal generator with a frequency set to the resonant frequency I will expect my secondary coil to have to the CT and connected the oscilloscope probes to the secondary windings and this is what I get now:


That's the current state of my build:


The lines stay flat until I set a frequency on the interrupter which I built with an Arduino Uno with a keypad shield and which I connect to the driver with a Toslink fiber connection.

Does this look OK so far? Can I continue to build the half bridge?

And... Do I read the schematics here at this place right when I say that the low sides of the secondaries of the GDT are connected to the IGBTs in a inverted way, like one low side to the gate of IGBT2 and the other low side of the other secondary to the emitter of IGBT1?

[davekni]

I have actually copied and built the OneTeslaTS schematics, wound a GDT after davekni's tutorial (thanks for that), connected a signal generator with a frequency set to the resonant frequency I will expect my secondary coil to have to the CT and connected the oscilloscope probes to the secondary windings and this is what I get now:

Is the signal generator wired directly to GDT or through driver?  If direct, output looks fine.  If through driver, amplitude is far too low.

The lines stay flat until I set a frequency on the interrupter which I built with an Arduino Uno with a keypad shield and which I connect to the driver with a Toslink fiber connection.

Most drivers are built to output signal only when light is fed through fiber.  Sounds like yours is opposite.  If so, that runs the risk of frying half-bridge if interrupter signal gets weak or disrupted.

Does this look OK so far? Can I continue to build the half bridge?

Picture looks fine.  Protoboard driver is small, reducing issues common with the lack of ground plane.  Still depends on back-side connections, number and location and wiring of bypass capacitors, ideally a grid of ground connections.

And... Do I read the schematics here at this place right when I say that the low sides of the secondaries of the GDT are connected to the IGBTs in a inverted way, like one low side to the gate of IGBT2 and the other low side of the other secondary to the emitter of IGBT1?

Yes.  One IGBT is on while other is off.  Depending on your specific IGBT parts and slew rate of GDT outputs, you likely will need a series resistor with parallel diode between each gate and it's GDT output wire.  That provides dead-time, time for one IGBT to turn off before other IGBT turns on.

[ako]

and another question... let's see if I begin to really understand how stuff is actually working...

In the OneTeslaTS schematic, if I wanted to swap the two UCC37321 with two UCC37322, in order to get it working, would I need to feed the \Q' output of the flip flop which directly goes to both EN inputs of the UCCs through another inverting gate of the HCT14 first?

Edit: ...or would it be sufficient to just connect the EN inputs of the UCCs to the \Q output of the flip flop instead of the \Q' (pin 5 instead of pin 6)?

[davekni]

In the OneTeslaTS schematic, if I wanted to swap the two UCC37321 with two UCC37322, in order to get it working, would I need to feed the \Q' output of the flip flop which directly goes to both EN inputs of the UCCs through another inverting gate of the HCT14 first?

No, EN pins are same polarity in both chips.  Only needed change is to swap direction of CT feedback wires to invert feedback polarity.

[ako]

Alrighty... things are evolving...

Reached first light, many - many - bangs and booms, coil rewindings, IC / IGBT orders and replacements on the road so far... I fell in love with ordering stuff from Digikey... shipment from US to Germany in 2 days. No shipping costs when order exceeds 50€... I was about to order 6 capacitors... would have cost me something around 53€ including shipping and taxes, thank god I had the idea to order 12 instead... no shipping costs, including taxes 59€

And now.... I am absolutely amazed... these just came in, ordered on Monday at JLCPCB.


Some of the bridge PCBs, the UD 2.9 and the Psoc5 from the DRSSTC PCB pack... Let's see how that will be going, going to start with the 2.9 Questions most likely to come up! Any already available and/or suggestions and tips are absolutely welcome.

[ako]

OK... first question... more a general one regarding capacitors and their values:

Can I use caps with the correct capacitance but with higher voltage rating than what is given in the BOM? Like if BOM says 1nF 50V ceramic but I use 1nF 2KV?

[davekni]

Can I use caps with the correct capacitance but with higher voltage rating than what is given in the BOM? Like if BOM says 1nF 50V ceramic but I use 1nF 2KV?

Higher voltage rating is fine.  Dielectric material is often more important.  Z5U and Y5V caps are almost worthless.  NP0 (same as C0G) is best, but not available for large-value caps.  X7R (and if necessary X5R) is appropriate for larger value capacitors.  There is still a wide range of performance within X7R, especially how much capacitance drops as DC voltage increases, sometimes down to -90% (only 10% of capacitance left) at rated voltage.

[ako]

Cool...

I am just assembling the UD 2.9 and I have almost all parts I need to finish it... except for three resistors - R13/R25 1.8K Ohm, R11 5.1Ohm and R3 51Ohm. Do I need to be precise with those resistors and their values or can I vary a little bit like e.g. using 2 10 Ohm or 2 100 Ohm in parallel or one 1K Ohm and one 750 Ohm in series?

And for the 51 Ohm the BOM says metal film... does it have to be metal film (if yes, why) or can I use carbon film resistors too? Just asking because I could still order carbon film type at Amazon and get them delivered tomorrow.

And... would you recommend using DIP sockets for the the ICs on the UD2.9 or is the driver robust at all, so that I don't need to expect the ICs like the 74s getting fried for whatever reason... I don't know how to be honest, but while dealing with the OneTesla type of driver I somehow managed to send those HCT74s and HC14s to hell on a daily basis