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Messages - profdc9

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1
Solid state Tesla coils / Re: Chinese MOSFETS/IGBTS
« on: March 24, 2019, 04:37:50 PM »
I wonder if there's some simple tests that could be built into a device for identifying MOSFETs and IGBTs, kind of like the GM328 component tester that you can get on ebay cheaply.

For example, without really high voltages/currents being applied, one can look at:

1.  Gate capacitance with a grounded source/emitter
2.  Threshold voltage
3.  On/off time could be done by sending a periodic square wave to the gate, and then putting the drain voltage and gate voltage into a logic gate.  Using an AND logic gate measures the on-time which is measured using the duty cycle of the time that both the gate and drain are high logic level, and the off time is measured by a NOR gate, which measures using the duty cycle the time the gate and drain are both low logic level.
4.  By using a current sense resistor, the phase lag between the collector or drain current and the emitter-collector or source-drain voltage can be measured so the switching losses can be estimated, again using the duty cycle measured using a logic gate.
5.  Collector-emitter saturation voltage for an IGBT or Rds for a MOSFET.
6.  Body diode or reverse diode forward voltage.

To avoid damaging the device and to keep the costs of such a device down, I am avoiding anything that directly measures the maximum voltages or currents a device can handle.

A cheap device to identify fakes could help alleviate the problem.

2
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: March 24, 2019, 03:22:14 PM »
Beautiful assembly job!

By the way, if you attach a 3.5 mm female plug to the Sound +/- input, you can try out the sound interrupter feature.

Make sure you adjust the minimum Ignore Interval and Pulse Width when you use it so that you don't try to pulse the coil too often or too long.  Start with a short pulse width if you have any doubt.

Also, you can hook an earphone up to the digital + output if you want to listen to your interrupter before you use it with the coil, or you can look at it on your scope.

Also, you can solder header pins into the ISP connector if you want to use the board with a AVR programmer directly so you don't have to use a separate fixture.

Dan

Interrupter is almost complete, Attiny85 is missing because programming is a bit more complicated than I expected.
But, it is partially functional without  the Attiny, enough to check if UD2.7 is working correctly.

I connected them together using a bit of fibre optic cable, and to my horror UD did not react to the input ! Input signal LED stayed firmly off.
After a bit of scoping and tracing the signal I discovered that I did not solder one side of D13.
Note to self: Missing solder joints are bad for functionality
After I soldered the diode, signal LED came on and started flickering in sync with the interrupter.

So far I confirmed that the UD powers up ok, and receives the signal.
I need to check if the outputs for GDT’s work correctly, is it possible to do that without C33 and the inductor in place ?

3
Solid state Tesla coils / Re: Chinese MOSFETS/IGBTS
« on: March 22, 2019, 06:39:37 PM »
You might be able to use them as low current/low voltage devices, but it's too easy to take a small die and put it in a big package.  Big dies cost more but are the ones that have the high voltage and/or current ratings.  Often you can find substitutions of fakes where the substitute superficially behaves like the real part, for example, LM358 dual op-amp for TL082, or one pin compatible logic family for another.  Sometimes, the substitutions are rejects of the real part that don't meet specifications, but might be sufficient for hobbyist purposes.  Occasionally, the parts are other parts relabeled which is easy to find.  But things like high power MOSFETS/IGBTS are almost invariably fakes because its too easy to substitute small die parts for large die parts.

You might try lcsc.com which might save you some money over digikey/mouser.  I think they have more to lose by counterfeiting because they are trying to establish a reputation as a parts supplier.

Dan

4
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: March 06, 2019, 04:27:03 PM »
The fiber optic connector is from Industrial Fiber Optics.  You can get it from digikey

https://www.digikey.com/products/en?keywords=IFE97

The plastic fiber is not easy to find.  It might be better to order both the IFE97 and the plastic fiber from Industrial Fiber Optics directly, but it is more expensive.

If you want to attach your own fiber optic output rather than using the LED, there is a port J15 with +V, zero volts, and a digital output.  You can build a simple circuit with a NPN transistor and the LED of your choice instead on a little external perfboard with literally three components (resistor, transistor, and LED).

Dan

I studied loneoceans’s instructions on initial power up of the board, nowhere did he mention that GDT’s must be connected, he even mentioned that if there is no GDT’s connected, there should be no signal on the outputs.
So, I gathered enough courage to power up my board, I set my power supply to 24V DC at 200mA max.
To my relief, blue LED came on, and there was no smoke leaks anywhere, current draw 0.02 A.
So far, so good  :)

While I was procrastinating whether to power it up or not, I built an enclosure for it.
PCB’s for the interrupter are on their way, most of the components are available locally. Only problem is fibre optic connector - can’t find it anywhere.

5
Dual Resonant Solid State Tesla coils / Re: My first DRSSTC on bricks
« on: March 04, 2019, 12:58:48 AM »
I made a board for the CYC8KIT-059 based UD3

https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/Psoc5-power

so you don't have to etch a board.

Dan

That's right, 500kHz is the maximum for the UD3.

Perfboard is not ideal for a high current gatedriver. I would prefer SMD mit big ceramic decoupling to keep the switching noise out of the driver.

I drive my SKM400 with a 13 to 10 GDT with 24V on the GDT driver so you get 18V at the gate.
Thanks for the suggestions!I'll try to etch a PCB and use 10uF THT X7R capacitors,two in parallel for each N-P MOSFET pair(IRFZ44NPbF and IRF4905PbF).If I succeed to modify an ATX PSU,then I can change the gate drive voltage.
I also received a CY8CKIT-059 board and checked your UD3 firmware,but some files are missing.Do you have a simpler firmware something like the UD2.7 or I should make one on my own?

the universal driver can do 500khz but the SKM400 probly can not what frequency is your coil? your snubber will not work if you are soldering to aluminuim. at least bridge the cap connection to the screws with copper at the end of your assembly
The SKM400 bricks definitely can't do 500kHz,but hopefully they can 150kHz.I plan to enhance the MMC connections or even make a completely new one if this fails.The snubbers are good,1uF and mounted directly to the bricks with the screws.

6
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: March 01, 2019, 03:55:35 PM »
Yes the OneTesla code is there.  You will need an AVR programmer and avrdude, which costs $5 on ebay, and the hex file is already there.   There are instructions in the folder with the software.

Dan

The standard interrupter has four modes:  standard test mode, which is basically pulsing the interrupter periodically for a particular pulse length, burst mode, which is to try to get briefer, more intense sparks, the MIDI interrupter, which can be used for playing MIDI files from a computer through USB, and the external audio sequencer, which if you play a tone like, for example, from a guitar, will generate a set of pulses with controlled length.  You can see it in action here

The code for the ATTiny, is that the onetesla usb midi code that you have a folder backwards in the same git? I did not find a clear description of which software was for it.

7
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: February 28, 2019, 05:20:33 PM »
I build both of the lineinterrupter and the standard interrupter and they both work.  However, I did tweak the standard interrupter slightly since I built it to make it more similar to the line interrupter.  I am fairly certain they both work.  The thing I tweaked on the standard interrupter is the MIDI support to correct something to be consistent with the lineinterrupter so they should both be nearly identical now.

The lineinterrupter triggers off of the 50/60 Hz AC cycle line to best match the power factor of the bridge to the peak of the AC cycle.  The idea is it allows the capacitors to charge during the cycle before allowing the interrupter to fire.  I did not have a problem blowing any oscilloscopes or anything like that, but because the power I have is limited I was not able to push this hard without tripping the overload in the breaker.

The standard interrupter has four modes:  standard test mode, which is basically pulsing the interrupter periodically for a particular pulse length, burst mode, which is to try to get briefer, more intense sparks, the MIDI interrupter, which can be used for playing MIDI files from a computer through USB, and the external audio sequencer, which if you play a tone like, for example, from a guitar, will generate a set of pulses with controlled length.  You can see it in action here

/>
Hopefully that helps you understand the state of it.  So I did build both, but the standard interrupter has a few fixes in it from the last tested version.

Dan

8
Dual Resonant Solid State Tesla coils / Re: UD 2.5 Schematic?
« on: February 05, 2019, 10:10:44 PM »
Check out the DRSSTC PCB Pack.  You will find schematics, gerbers, and lots of other useful stuff

https://github.com/profdc9/DRSSTC-PCB-Pack

Look at ud27c

Dan

9
Transformer (ferrite core) / Re: How to design a 7.5kV AC source?
« on: January 18, 2019, 04:25:14 PM »
I'll venture a solution...

Use a full-bridge or H-bridge of MOSFETS such as the IRF820, where each side is driven by two 50% duty cycle square wave signals of different frequencies with a difference between the frequencies that is the output frequency you want that would drive both sides of a small ferrite transformer primary.  For example, if you want 1 kHz, you would drive one side perhaps with 200 kHz, the other with 201 kHz.   You could rectify mains power for example to power the H-bridge, for example, from 220 VAC to 300 VDC, with a full-wave rectifier, and use a buck converter or even a small variac on the primary side to adjust the DC voltage on the bridge.  A ferrite transformer, for example, with a 10:350 turn ratio so that you could transform the 300 VDC voltage up to the 7.5 kVAC range.  A high voltage polypropylene capacitor (perhaps 1000 pF?) would need to be placed on the secondary output of the transformer to filter high frequency (200 kHz) and leave a clean sine wave, or you might have to build a pi lowpass filter if you want the high harmonics really attenuated.   You will probably also need a DC block capacitor as well in series with the primary winding.   What I've described is open loop and I think to close the loop you would need to use an optoisolator to feedback a signal to the buck converter to regulate the voltage, or you could just put a resistive load (like a 10 megaohm 10 watt resistor) to try to provide some stability to the output voltage and act as a bleeder resistor if you don't need super accurate output voltage.

Dan



10
General chatting / Re: 迎词、来
« on: January 10, 2019, 06:56:59 PM »
I too made a pulse skip driver, based on analog hardware (the UD 2.7c).

If you have been able to get sword-like sparks, or even some interesting results using pulse skip behavior, please share it.

The driver I designed is at

https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/ud29

And the thread where I show the waveforms and results is

https://highvoltageforum.net/index.php?topic=346.0

Thanks for any experience you can shared about your pulse skip driver behavior.

Dan

Hi, everyone.           
I am a 24-year-old Tesla coil hobbyist from Wuhan, China.
My job is Chip Technology Support Engineer.   
       
I have 11 years of Tesla Coil hobby experience.           
The first Tesla coil was made by winding the coil with a mineral water bottle. The arc was only 2 cm. ;D           
At present, I have done DRSSTC, QCWDRSSTC and some CLASSE design experience.     
     
 I just finished the design of "Yunbao" jump pulse driver the year before last, see it           
https://4hv.org/e107_plugins/forum/forum_viewtopic.php?id=179388
This is part of my work page.
https://i.youku.com/i/UMTEyMDQ1MzYw/videos?spm=a2hzp.8244740.0.0

‘Yunbao’pulse skipping driver

Recently, I am developing UD3.3A for full digital signal input phase shifting.


At present, I am completing the work of writing the hardware logic of the phase shifting part of the alternating hard switch bridge arm.
Hope to share with you more! Thank you!  :D

11
Hello, and happy new year!

I laid out a version of the board that is mostly SMT 0805 for those who prefer that.  You can find it at

http://github.com/profdc9/VNA

A picture of it is below.

As a note, I was thinking about how to make the choke more broadband.  I think it could be done if the choke was a 50 ohm coax such as RG-174 or RG-58 wrapped 5-10 times around a high permeability MnZn ferrite like would be used for a GDT.    I think such a choke could probably work all the way from 30 kHz to 500 MHz.  The only disadvantage is that the impedance range of the analyzer might be reduced a little on the high end because of the capacitance of the coax adding a shunt reactance, so keeping the coax as short as possible is important.  I am not sure how to add a switchable capability unless I put a jumper block on the board to switch as the issue is that the parasitics a toggle switch would introduce would likely reduce the range of the impedance analyzer itself.  It's very tricky to get something to work over many decades of frequency.

Dan



12
I haven't hooked it up to the analyzer yet to the coil, but I'll give it a try sometime.  Mostly done antennas and filters and the like, but it should be able to measure the impedance of anything you can clip leads to.

I was thinking of adding a crude spectrum analyzer and frequency counter/measurement capability to it as well.  The second port receive port could be used with a frequency swept source to perform some spectrum analysis with up to 10 kHz IF bandwidth.  The dynamic range won't be great, but it doesn't cost anything except some additional software to write.  Also it is possible to count pulses with the microcontroller so as long as I get the frequency of the LO within 10 kHz of the signal to be counted, the pulses could be counted to determine the signal frequency by adding the measured frequency and the LO.  These features will be slow but the hardware needed to support them is already on the board and is minimal.

Dan

Thank you very much for sharing Dan, you got such a pace at new designs and implementation of existing ideas to fit the Tesla coil and high voltage branch.

I would very much like to give this a go as I only have a special audio dedicated spectrum analyzer and the spectrum analyzer functionality on the Rigol DS1054z is very rough. So a 30 kHz to ~500MHz would make a nice addition to the instrument shelf. With a simple selector switch different chokes could be selected between for different measurement ranges.

Did you try to make some measurements with a simulated load on the secondary coil? If you add a piece of thin copper wire with 6 smaller branches on it, that in size corresponds to the spark output it would give and compare that with unloaded results.

13
General chatting / Re: Merry Christmas and Happy New Year to everyone!
« on: December 23, 2018, 04:52:06 PM »
Thanks Mads for running the forum and support HV hobbyists!  Merry christmas to you and your family.  Let's all hope for all kinds of new ideas and experimentation in 2019 and keep things fresh and interesting.

Glædelig Jul og Godt Nytår!

Dan


14
You can find the git project at

https://github.com/profdc9/VNA

What is a vector network analyzer? It is a tool for measuring impedance, reflection, and transmission.  The one I designed works on one port from about 30 kHz to 470 MHz, and on two ports from about 300 kHz to 470 MHz (though I have not tested transmission that much this high).

How does it work?  You connect a short, open, and 50 ohm load to the transmit port to calibrate the reflection, and then connect the transmit to to receive port to calibrate the transmission.  Then you can connect a load to either the transmit port, or from the transmit to the receive port, and get its impedance or transmission/reflection characteristics.

What can this do for coilers?  You could connect it to your coil and directly measure the impedance of your coil.  For example, if your system has multiple resonances, you can sweep them with very fine frequency resolution and see the upper and lower frequencies.  You can also directly measure the "Q" of your coil for example.  Basically it can measure impedances between about 2 and 10000 ohms at RF frequencies.

Does it cost a lot?  Probably about $40 in parts or so to build.  I tried to make it as easy as possible, it uses mostly through-hole parts but one surface mount part.  It even has a touchscreen.  I designed it mostly for ham radio use at HF/VHF, but it should be useful down to 30 kHz.  To be more usable at lower frequencies, it is best to put a slightly bigger common-mode choke onto it, which will make the minimum frequency lower at the expense at somewhat reducing the maximum frequency because of parasitic effects between the turns in the choke.  But even with a bigger choke it should be usable at least to 200 MHz I think.  Here's some pictures of it in action.







You can also hook it to USB and looks like a USB serial device and you can type commands at it to get data off of it.

Anyways, I know this is not high voltage, but it could be useful for high frequency circuits in high voltage.

Dan


15
Dual Resonant Solid State Tesla coils / Re: TO-247 IGBT for DRSSTC
« on: November 12, 2018, 08:35:12 PM »
I have not used the transistors you are talking about but looking at the data sheet they seem to be limited to 280 A also.  I used the FGH60N60SMD on my DRSSTC, and two of those in parallel, to have a full bridge of 8 transistors total, and so far it has held up to all the abuse I have subjected it to.  According to the data sheet these only have 180 A peak pulsed collector current relative as compared to the transistors you selected, however, the maximum power dissipation and average collector current ratings are higher.  I'm not sure why it would be this way, as I would think that the average and maximum peak currents would scale together.  I have attached the datasheets for both for you to look at.  I have been intended to try a different IGBT with nearly identical characteristics to the FGH60N60SMD but unfortunately with lower maximum power dissipation rating because the FGH60N60SMD seems hard to get these days.

Dan

http://www.onsemi.com/pub/Collateral/FGH60N60SMD_F085-D.PDF

Hi Dan,
I know this post is a bit outdated,but do you remember if the 20N60A4D's had the 300A limitation?I just want to know the possibilities of my current SSTC setup for upgrading to a DRSSTC.My transistors are 30N60A4D's with a lower pulse current rating than the 20N60A4D's(240A and 280A) in a full bridge configuration.

16
General chatting / Re: Hallloowweeen
« on: November 03, 2018, 04:35:07 PM »
I considered getting videos, but some parents get kind of uppity when you video their kids, so I decided against it.  I have to say though that by-and-large the people in my neighborhood have been fairly tolerant and open to the crazy neighbor that creates lightning in his garage. :)

Dan

Nice with a little local display, did you get any videos of it?

Halloween is not a big deal in Denmark (only shops and commercial interests tries really hard to make it a thing to sell more stuff), there is a few kids or houses with a little decoration. We have our "kids dress up" holiday in February called Fastelavn https://en.wikipedia.org/wiki/Fastelavn

17
General chatting / Hallloowweeen
« on: November 01, 2018, 04:19:50 AM »
Hello,

I just wanted to mention that tonight I set up my Tesla coil and it was a big hit with the kids in the neighborhood.  Nothing excites the trick-or-treaters like a musical lightning machine on Halloween.  I played Hall of the Mountain King, Night on Bald Mountain, Toccata and Fugue, Funeral March of the Marionettes, as well as other tunes.

Dan

18
I don't want to threadjack, but I have worked on a PCB layout for this

https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/full-bridge-multi

The snubbers should be placed very close to the emitter/collectors of the IGBTs I think.  In the design below, there are two snubbers that are placed in between the hi and low side of the half bridges.  The PCB layout uses almost all of the copper on the board to try to minimize inductance.

If the snubbers are very close to the emitter/collectors than there is a bit more tolerance of the connection of the bus cap.  I also made a braided connection between the bus capacitor and the PCB.  There are three pairs of positive and negative bus wires that are braided together so that the counter-flowing currents flow along the nearly the same paths to/from the PCB.  When shorting the bus connection wires together, I measured about 100 nH of inductance.

Dan

19
Which interrupter are you using?  Since the note seems to be totally absent and not just muted, it looks to me like either the interrupter has some sort of limit set in the MIDI note it will play.  It is also possible that the MIDI file is set up incorrectly.  For the oneTesla interrupter that I use, for example, all notes must be channel 0 or they will not play, and if more than 2 notes are played at once, one of the two notes are stopped (it only has 2 note polyphony).  If you want to examine this the MidiEditor program is very handy:

https://www.midieditor.org/

I also attached some music that I adapted for the oneTesla interrupter if that's what you're using.

If you want, you can look at the DRSSTC PCB Pack I made

https://github.com/profdc9/DRSSTC-PCB-Pack

The "interrupter" project is a multiple function interrupter and includes the oneTesla MIDI interrupter on it if you want to build one yourself.  You will need an ATTINY85 and an AVR programmer.

Dan

20
Dual Resonant Solid State Tesla coils / Re: My first DRSSTC
« on: September 24, 2018, 05:39:01 PM »
Your GDTs look ok, they are probably ferrite toroids if they are black and have a high permeability 6000 to 9000.   I am not sure what kind, but it's probably ok as it is.  It can be a problem at the higher frequencies if the ferrite has too low of a bulk resisitivity.  You can tell this because you can take your multimeter and measure the resistance between two nearby points on the toroid perhaps a few mm apart and you will see that it reads in the 10 to 1000 kohm range.  Higher is better, but with MnZn usually higher permeability means low resistivity, so there's a compromise.   Really high permeability 8000-10000 is usually used for low frequency (<100 kHz) switching power supplies, while permeability 1000-3000 is used for medium frequencies (100 kHz to 1 MHz).  The 77 mix is good up to 1 MHz, but the permeability is lower than what you have, but if you are using CAT5 twisted pair the leakage inductance shouldn't be a problem.  At any rate, if it's working, don't mess with it.

Dan

Hi Dan,
Here is my GDT's. First CAT5, all bifilar winding but hi initial permeability iron core. (6000 to 9000) They all have similar results. I will also experiment with ferrite core on your suggestion

Now i have better result with phase lead. First image no phase lead, second with adjut phase lead.

Edit: image add attachments

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March 19, 2019, 01:32:32 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General chatting]
Mads Barnkob
March 19, 2019, 12:20:34 PM
post Re: Strange gdt waveforms
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
March 19, 2019, 12:15:22 PM
post Re: Which varnish to use to coat the Secondary?
[Solid state Tesla coils]
Mads Barnkob
March 19, 2019, 10:46:50 AM
post Re: Keep or throw away ?
[Beginners]
Thunderstruck
March 19, 2019, 09:11:09 AM
post Re: Keep or throw away ?
[Beginners]
Mads Barnkob
March 19, 2019, 08:24:31 AM
post Re: Keep or throw away ?
[Beginners]
Teravolt
March 19, 2019, 01:51:51 AM
post Re: Keep or throw away ?
[Beginners]
Thunderstruck
March 18, 2019, 09:56:42 PM
post Re: cute-qcw Tesla Coil
[Dual Resonant Solid State Tesla coils]
Weston
March 18, 2019, 07:55:52 PM