Author Topic: Mazilli ZVS Driver Modification Problems  (Read 4719 times)

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #20 on: January 31, 2020, 10:22:46 PM »
Sorry, my mistake. I am using the 1200v IGBT's, part number IHW40N120R5XKSA1 and your right about the UF4007's. In both broken circuits I have at least 1 broken UF4007 and I think both zeners are dead (realized I was testing them wrong after the fact so I'll double check those zeners today).

The gate supply I used is just an old transformer connected to mains. I use a full bridge rectifier and a smoothing cap on the secondary and while drawing 100mA through the 220ohm resistor it reads 25VDC at the cap. With no load its a bit more voltage at the cap, but I cant recall how much. So I would still need a Zener diode unless I want to take some coils off the secondary, which I might. My other option is that I have a laptop charger from my old broken down computer. It puts out 16.5V and 3.65A Could this work with the appropriate resistor?

Good news on the P-fet front though! I did manage to get them to work. I had to keep the voltage at 18VDC to make sure I didn't damage the IGBT gates, but it worked. I'm going to order some 17V 5W zener diodes soon, but if they give me trouble I'm opting for the laptop charger or altered transformer. Good to have those options in place.

About the TVS diodes. They're cheap enough so I'm going to get some, but looking at the ratings has me all turned around again. Let me see if I understand this correctly. Normal operating voltage that the IGBT sees is pi x 170 = 534VDC. However from the power feed inductor to the source is half this value, putting it at 267VDC. That would mean I want a TVS diode with a working voltage as close to or slightly over 267VDC but a clamping voltage low enough to protect the UF4007, so 400 preferred to 500V max? Also, does it matter if they are uni or bi directional?

That's interesting about the low power oscillation. I think I' going to poke around at that a bit and will most likely include it as a start up switch in the final version.





« Last Edit: January 31, 2020, 10:31:08 PM by Andrew321 »

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #21 on: February 01, 2020, 04:51:52 AM »
16.5V for gate drive can work.  There is some advantage to a higher voltage and zener clamping, however.  For a given current, the resistance is higher, so closer to a constant-current source.  That way the current doesn't drop as much at the IGBT's Vge plateau voltage, about 9V for your part at 40A.  Your 25V transformer solution could be fine, but 0.1A limits gate-drive current options.  Small 24DC supplies are somewhat common too - laptop style or even wall-warts.

Concerning TVS diodes, yes I think you understand.  The 1.5KE300 family should work well for the transformer center-tap, or two in series for the IGBTs collector-to-emitter.  Since they're fairly cheap, multiple sets in parallel is a good idea, to make sure the total energy stored in the power-feed inductor can be dissipated.  For this use, uni or bi directional are both fine.  Use whatever is cheaper.  (Uni-directional, of course, need to be wired the correct way around.  Bi-directional devices are just two uni-directional ones in series back-to-back in one package.  The extra forward-biased device slows down the speed a bit for very-fast voltage spikes.  ZVS circuits don't generate such fast voltage rise-times.)

Keep having fun!  And, good luck with your final voltage-multiplier use.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #22 on: February 07, 2020, 05:45:01 PM »
Good news! It worked! I was about to give up and settle for less input voltage  when I decided to test something. If you remember I built my two E  sections of the transformer out of two UU sections glued together to form the E (4 U sections in total). On the central limb of the E I had the primary and on the outer limbs two secondaries in series. My gut told me there was something there so I separated the secondaries to test each one. I don’t know why, but one coil produced more power than the other. I just tested my drawing an arc at 60VDC input and one was hot and fiery while the other more blue and wispy. Testing the resistance of each coil showed they were about the same (16.6 vs 17.1 ohms) So my guess was that cheap amazon cores are to blame. I swap the coils around and sure enough its one limb gives more power than the other (forgive my lose use of the word “power”).

I decided to pull the whole thing apart and used just 2 U sections. I rewound a new primary and secondary for each limb and used acrylic to introduce a core gap of 2mm. From what I understand, core gap is one way to introduce leakage inductance and reduce coupling factor. No idea what mine is at, but it seems to work! Only problem I’m having is that at max input voltage the alligator jumpers and wires get so hot the plastic casing on them starts to melt! Easy fix though: more litz wire in the permanent set up.
 I no longer hear the oscillation and I can push it all the way to 170VDC input. For the gate drive I use 220 ohm resistors and found a different transformer that, after being rectified and filtered, put out 40VDC. I will continue to test and will be posting the complete constructing with pictures, parts, and links to videos once its done. I just need to look up how to build a soft starter because I’m worried If I were to just plug this thing into the wall it would just explode. It draws 14.5amps while pulling an arc at 120VAC input so it will trip the breaker if I used it for too long.

Thanks again for all your guys help.

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #23 on: February 08, 2020, 05:13:57 AM »
Great to hear of your success!

My soft-start is just an incandescent light bulb across the switch.  That gets oscillation started at low power as soon as line-voltage is applied.  A power resistor would work as well.  Another option that I might try next time is a diode from the gate-drive supply.  If your 40V transformer has enough current capability, you could do that, starting your ZVS oscillator at 40V before switching in 170V.

A single secondary winding is good too.  The two separate ones are less efficient even if working properly - more wire for a given voltage.  I'd guess that the issue was a defect in one of the windings - perhaps a shorted turn, rather than an issue with the cores.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #24 on: February 08, 2020, 04:42:46 PM »
I forgot about that! Here I am thinking about getting relays and mosfets and all sorts of stuff to build this soft starter, but really all I need is a high wattage load to start up (like the light bulb) and then a switch to bypass it once its started up.

Your idea about the gate drive transformer for start up is interesting, but I'm not sure my transformer can supply enough current. Something I'll have to check out. If I did choose this route I would leave the negative wire connected to the emitter and then a diode from the positive to the "line side" of the power feed inductor (not sure what to call the side of the power feed inductor that attaches directly to the capacitor). Once started up I should just be able to turn on main power. Would the start up transformer be constantly supplying current long side main power? Should I toss in a start up switch to disengage the start up transformer once full voltage is running?

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #25 on: February 08, 2020, 06:29:10 PM »
Yes, that's the correct connections for the gate-drive soft-start diode.  There's no need to switch it off.  That's what the diode is for.  Once line power is switched on, the ZVS input inductor is at 170V.  The diode blocks that 170V from feeding back to the 40V gate-drive supply.  (Without a diode, the gate-drive would fry at 170V.)

If your power is rectified line voltage without filter capacitors, then it will drop below 40V momentarily at each line voltage zero-crossing.  The gate-drive supply will feed a little bit of current at those zero-crossings (120 times per second).  Shouldn't be an issue for this case either.

If you go with gate-drive, I'd love to hear how it works.  I haven't tried that option yet - didn't think of it quite in time for my last ZVS project.  Expect it will work, and avoid a high-power resistor.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #26 on: February 10, 2020, 12:09:08 AM »
More good news Dave! The low voltage gave drive soft start works! I had to make a few changes, probably will make more later, but as is:

The gate drive is rectified and smoothed with a capacitor. When just the gate drive transformer is pugged in 20VDC is seen at the capacitor, when drawing an arc it drops to about 18.5VDC. The soft start current idles at about 0.2A and tops out at around 1A while pulling an arc. When main power is applied, soft start current drops to 0A (as expected) and the gate drive voltage rises to 21.1VDC and only drops to 20VDC when drawing an arc.

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #27 on: February 10, 2020, 05:29:33 AM »
Andrew,

Wonderful!  I'm thrilled for you, and for the confirmation of what I plan to try next time I make a ZVS circuit.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #28 on: May 05, 2020, 06:10:36 AM »
Its been a long while! I meant to upload all this sooner but life got busy. Now I have all the time in the world so I thought I should get back with the results :) I'm very happy with it and have more plans an modifications in store. Here are the only videos I have!

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 I wanted to make better videos but my HV coil shorted through the oil and now it needs to be rewound. Ill get to it eventually but its not high up on the list. At the moment I am doing away with the center tap and using two inductors (opinions on this?). I want my driver to do double duty. One for HV stuff and the other as an induction furnace. I have the crucible and everything, but making it works as an induction furnace is not so easy. With the coil large I can use it to heat wrenches and screw drivers. I never tried to get them red hot because it was drawing 20+ amps and I'm working off a 15 amp breaker. With nothing in the coil it draws almost 15 amps using the same resonance capacitor bank as the HV project (I think 1.5uf?) but when I put something in the coil the IGBT's failed. So I thought I need to greatly reduce the capacitance. I drop it down to 10nF and it draws about 4 amps with nothing in it and 6 amps with a screw driver in it. But it failed again and now I'm waiting for more parts to arrive. I know its not HV stuff, but I thought I would share.
« Last Edit: May 05, 2020, 02:59:30 PM by Andrew321 »

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #29 on: May 06, 2020, 06:13:59 AM »
Nice Jacob's ladder video - looks a lot like mine.  The first HV arc video looked impressive too.  Enough voltage to start an arc at that distance is going to stress your transformer.  Takes careful oil-filling under good vacuum to avoid air bubbles that generate corona and lead to failure.  I think kludesmith has good posts on vacuum filling.

Induction coils are generally to low inductance to run from a 120V-fed ZVS oscillator.  Most induction heater designs run from lower voltage higher current DC input, or use a transformer on the ZVS output to convert to lower voltage and higher current.

The other consideration for these ZVS oscillator circuits in general is that oscillation drops out of the resonant Q gets too low.  (Inserting the object to heat lowers Q.)  When oscillation drops out, current ramps up in the supply input inductor until something fails.  For the Jacob's ladder arcs, which also lower Q, the oscillation will switch to the higher frequency of the transformer's leakage inductance.  Such a scheme might work for induction heating too.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #30 on: May 06, 2020, 03:10:29 PM »
Hey Dave! I defiantly drew some inspiration from you. Its cool stuff and mounting it on a piece of wood is very simple.

I don't have a proper pump for this stuff. I just use a fridge pump plus a little 5 volt pump to get enough out. I think the next one I make ill warm up the oil before hand to help with penetration. I'm also going to double up on the layers of paper in-between coils. Even so, I think the only reason it broke is because I was getting corona streamers coming off on of the transformer output terminals so I decided to see what would happen if I connected the other side to ground. The streamers got bigger, then it shorted and died... FOR SICENCE!

I had to look up what Q factor was and I think I understand. High Q factor means that there are many oscillations ringing naturally and thus the ZVS driver doesn't need to supply too much power to keep it going. However, when power is being drawn the Q factor is dampened and more energy is required to keep the oscillation going. A large enough draw could cause the oscillation to stop completely and you end up with a short in one of the IGBT's and ka-boom.  With the Jacobs ladder the reasons it continues to work is that it can fall back on the transformers no-load oscillation frequency. Do I have the right idea? It just seems odd to me that something should work at lower voltage and not higher. Low and high voltage seems like an arbitrary distinction when you talking a difference of 100V on the input. What I'm trying to figure out is why exactly it works on 60V every time no problems, but 120 its such a mess. Seems like I should just be able to get the properly rated parts and everything should work like normal.

The only reason I'm wanting the 120V ZVC induction heater is its simple and doesn't require a big transformer. I have a big transformer, but I like the challenge. In the end I have enough parts for 2 or 3 attempts before I call it quits and build 2 circuits. one for HV and one induction.

Offline John123

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Re: Mazilli ZVS Driver Modification Problems
« Reply #31 on: May 06, 2020, 06:17:55 PM »
Holy crap those arcs jump a pretty large gap!

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #32 on: May 07, 2020, 06:08:16 AM »
Yes, ZVS oscillators stop oscillating when the Q is too low, which means the load impedance is too low compared to the resonant L and C impedances.  At low Q, the sine-wave doesn't ring down low enough to turn off the other IGBT, so it remains on and current ramps up.  Initially one IGBT is taking all the current as you said.  When the current ramps up enough, that IGBT's forward drop gets too high to keep the other IGBT off, so then both conduct.  Current continues to ramp until something fries.

Transformer leakage inductance limits how low the Q can get.  It's the transformer's shorted-output frequency, which is it's leakage-inductance, with the resonant capacitance, that keeps oscillation going.  That's a higher frequency.  No-load is the frequency that it starts at before an arc forms, which is a lower frequency (the transformer's full primary inductance, not just leakage inductance).

What sort of coil are you using for induction heating?  The issue is with normal copper-tubing coils used with internal water cooling.  Those typically have relatively few turns that are spaced from each other, so low inductance.  It's the low inductance that needs low voltage and high current (for a given frequency).  At high-enough frequency, the voltage goes up.  But the ZVS oscillator will have trouble as the frequency gets too high for the IGBT switching.  If your heating coil is more like an induction cooktop, then 120V will work fine as long as the Q is high enough.  Induction cooktops typically run with low Q, with an absorbing pan very close to the coil.  Adding a series inductance could fix that issue, behaving like a transformer leakage inductance.

Have you measured frequency with your induction heating experiments?  Of course, at lower voltage to measure without frying.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #33 on: May 07, 2020, 11:01:59 PM »
Thanks John! They jump a maximum 14" and I estimate 400KV. I have plans for even bigger ones  ;D

Dave, this perfectly describes what I'm seeing when things fail. There is about a 75% chance only one IGBT will be shorted and broken. I normally save the others for tests later on. So I guess that's the one that gets stuck on and it dies before the other one does. When I use the salvaged ones they both fail 100% of the time things break down.

So if I'm understanding all this correctly, leakage inductance can be seen as an inductor in series with the primary coil. Its this leakage inductance that limits the current and how low the Q can get.  So all I should need to do I add an inductor in series with my heating coil? Seems simple enough.

I'm also realizing that the capacitor bank needs to be fairly large. When I used a much lower capacitance the frequency short right up. It was upward of 225kHz. For induction heating I guess you want to keep the frequency low, about 10-30kHz.

The coil I'm using is a 1/4" copper tube. Its not water cooled yet, because I'm still working out the kinks, but it will be eventually.

The one test I did with the low voltage was with IRFP260N MOSFET's and I was only watching the current. I made a small coil to put a screw driver in and as I did I watched the current creep up to 60 amps. 10 amps over its max rating at 25C for about 5 seconds blue them up pretty good. Even the heat sink was too hot to touch lol.

When the parts eventually come in (delays with shipping and all) I'll build and get back to you with more details. Well, as much as my DMM will tell me lol.

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #34 on: May 08, 2020, 06:26:50 AM »
Some induction heating works better at such high frequencies, especially heating more conductive metals such as aluminum.  The ZVS switching elements need to be able to handle the frequency.  Many IGBTs will struggle at 200+kHz.  So, for most uses, more capacitance for lower frequency is good.  But that makes the impedance lower, so more current at 120V direct input.

To prevent Q from getting too low, my simulations and experiments suggest 0.85 maximum coupling factor.  That's equivalent to a series inductance of 39% of your induction work coil if the series inductor is lossless.  For real conditions, I'd suggest a series inductor of at least 50% of the work coil inductance.

Still, if the resonant impedance is too low, the current can get too high just due to that low impedance, even when Q is still OK.  The IGBTs and power-feed inductors need to handle that current.  At 120V, you may end up with a very high-power heater and no way to turn it down.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #35 on: May 09, 2020, 09:42:12 PM »
It works! I took a small ferrite transformer core and wound some wire around it runs smoothly :) Only issue was that the wires on it got hotter than the crucible lol. Some goes for the two power feed inductors. I assume that the losses you were talking about are in that heat? I switched out the 14 gauge wire with litz wire I made of 100 strands of 30 gauge wire. it runs considerably cooler now. I'm going to make the same modifications the power feed inductors.

I'm tweaking it to get the frequency higher as well. After some trial and error I have it drawing a little more than 10 amps and the tank circuit frequency is 41kHz. I know that with IGBT's the higher the switching speeds the more losses are incurred. I have them on a big heat sink with a cooling but when you say that at 200kHz they struggle, is that just with heat dissipation or it is a limiting factor for how quickly they can be switched?

Also, I got LTSpice. No idea how to use it, but I drew my circuit on it just to share. S1 is my low voltage turn on and S2 will not be powered unless S1 is on. Without the mandatory low voltage start the whole thing just dies.


Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #36 on: May 10, 2020, 04:06:24 AM »
Did you intend to have gate drive powered from the transformer output (left side of R1 and R2 to top of C1) rather than the high-voltage as shown?  Great that you have LTSpice.  With yahoo groups gone, I'm haven't looked where the LTSpice user group has migrated.  There's lots of information floating around on how to use it.  Start with it's built-in help.

Yes, you could probably get those IGBTs oscillating at 200kHz, but with increased power dissipation.

Great that you now have first-hand experience with the value of litz wire!  The power-feed inductors will be helped some too.  Since a significant fraction of their current is DC, litz won't make as much difference there.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #37 on: May 10, 2020, 06:11:05 AM »
Woops! Your right! R1 and R2 should be connected before D5. The intention being that I'm driving the gates from the transformer output. That's how I have it on the workbench, just got to make that fix to the diagram. I also removed a series inductor.

I'll for sure be learning more about LTSpice, seems like it would be very helpful.

Its amazing the difference litz wire makes. The power feed inductors don't even get warm and the series inductor still gets hot, but I think it might be doable. I discovered that litz wire should be wrapped in tape though. A few turns on one of the power feed inductors got scratched and after running for 1.5minutes shorted through the inductor and blew an IGBT :'( The crucible got too hot to touch in that time so I'm hopeful that given more time it will get hot enough to melt copper and iron. Tomorrow will tell!

Offline davekni

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Re: Mazilli ZVS Driver Modification Problems
« Reply #38 on: May 11, 2020, 12:09:53 AM »
Yes, it's best to have an outer covering for litz wire.  Some comes with that already.

One more detail to fix on your schematic:  Now the bottom of L4 is on the low-voltage supply.  Once you learn how to simulate and plot node voltages, it makes finding such mistakes easy to do yourself.  I presume the actual construction is correct.

What core (if any) are you using for the series inductor L5?  Can you tell if the core is heating more than the wire?  Core losses can often be higher than copper losses.  BTW, have you measured inductance of L5 compared to L6 (your heating coil)?  If L5 needs to be 40% or more of L6 to prevent oscillation from dropping out at low L6 Q, but if it's high, say 100% or more, it may be hard to get enough power into L6.
David Knierim

Offline Andrew321

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Re: Mazilli ZVS Driver Modification Problems
« Reply #39 on: May 11, 2020, 04:49:58 AM »
Woops! I didn't even notice it until you pointed it out but your right. L4 should be connected to the high voltage, not the low voltage. That's how it is on the bench, guess I should have taken a bit more time drawing that circuit haha.

The core does get hot! At first I used 9 turns on a PC40 transformer core. Litz wire was 100 strands of 30 gauge. The wire got warmish but after running for about 3 minutes the core was almost too hot to touch. So I thought maybe if I got another of the same core (I have three to spare) and super glue them together it wont get so hot. So I glued them together and doubled up on the litz wire (200 thread and managed i think 6 or 7 turns) and I was able to run it for 10 minutes before the series inductor got so hot I couldn't touch it. I've been trying to find out the solution to this problem and from what I'm thinking its just that PC40 isn't up to the task? I'm running at about 45kHz and 10 amps. maybe an air-core coil is the solution?

I don't have any tools to measure inductance so a lot of my work is trial and error. If I remove/add capacitors/coils from the series inductor how does it change the current and frequency? At one point I got it drawing 4 amps at a bit of 900kHz. I think I've struck a good balance, but is it possible that while I might be drawing 1200W a lot of it isn't getting to the crucible?

also, these are the cores I'm using for the inductors:

https://www.amazon.ca/gp/product/B076B97Q4B/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

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Re: Mazilli ZVS Driver Modification Problems
« Reply #39 on: May 11, 2020, 04:49:58 AM »

 


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September 28, 2020, 09:15:09 AM
post Re: Stroboscopic photography & motors
[Digital Compact Camera]
Zipdox
September 28, 2020, 09:09:45 AM
post Re: type of driver
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 28, 2020, 08:39:30 AM
post Re: Stroboscopic photography & motors
[Digital Compact Camera]
klugesmith
September 28, 2020, 08:16:46 AM
post Re: Polyphonic Interrupter with STM32F103C8T6 (Bluepill)
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Zipdox
September 28, 2020, 01:27:07 AM
post Re: Polyphonic Interrupter with STM32F103C8T6 (Bluepill)
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
September 28, 2020, 01:14:46 AM
post Re: Rogowski current probe
[Laboratories, Equipment and Tools]
flyglas
September 28, 2020, 12:30:58 AM
post Re: Rogowski current probe
[Laboratories, Equipment and Tools]
Hydron
September 27, 2020, 11:48:35 PM
post Polyphonic Interrupter with STM32F103C8T6 (Bluepill)
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Zipdox
September 27, 2020, 11:43:14 PM
post Re: Rogowski current probe
[Laboratories, Equipment and Tools]
flyglas
September 27, 2020, 11:01:13 PM
post type of driver
[Dual Resonant Solid State Tesla coils (DRSSTC)]
octopus1
September 27, 2020, 10:51:03 PM
post Re: Easy to build Polyphonic MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
September 27, 2020, 10:44:43 PM
post Re: MIDI videos from my DRSSTC1/2/3 demonstrations/shows
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 27, 2020, 09:44:58 PM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 27, 2020, 09:20:32 PM
post Re: Easy to build Polyphonic MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
futurist
September 27, 2020, 07:49:49 PM
post Stroboscopic photography & motors
[Digital Compact Camera]
klugesmith
September 27, 2020, 07:08:06 PM
post Re: Led Closeups with Mobile phone and lens .
[Smart Phones]
klugesmith
September 27, 2020, 06:43:46 PM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 27, 2020, 06:42:46 PM
post Re: Finding accelerometer location inside a phone
[Smart Phones]
klugesmith
September 27, 2020, 06:36:41 PM
post Re: steam engine
[Capacitor Banks]
plasma
September 27, 2020, 02:32:14 PM
post Re: Easy to build Polyphonic MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
September 27, 2020, 02:02:53 PM
post Re: Easy to build Polyphonic MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
futurist
September 27, 2020, 12:24:20 PM
post Re: Easy to build Polyphonic MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
September 27, 2020, 12:52:36 AM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 26, 2020, 11:06:04 PM
post Re: One NOS ac flyback is nice. Finding its identical twin 3 months later is awesome
[Transformer (Ferrite Core)]
profdc9
September 26, 2020, 10:48:41 PM
post Re: Rogowski current probe
[Laboratories, Equipment and Tools]
Hydron
September 26, 2020, 05:27:37 PM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Zipdox
September 26, 2020, 04:32:53 PM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 26, 2020, 04:17:51 PM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
GKnapp
September 26, 2020, 02:06:04 PM
post Re: Rogowski current probe
[Laboratories, Equipment and Tools]
flyglas
September 26, 2020, 10:57:58 AM
post Re: DRSSTC Tuning for Music vs Big Sparks?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 26, 2020, 08:55:27 AM

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