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Messages - profdc9

Pages: 1 [2] 3 4 ... 12
21
I converted the "Game of Thrones" theme to 2 channel MIDI for an event, here it is.

Dan

22
A relay might work, but it is slow and requires a lot of coil current to operate.

Perhaps use an optoisolator such as the 4N28/4N35 to pull the signal to ground if there is undervoltage.

23
Does your controller have undervoltage protection and is it set up correctly?

If the gate drivers on the controller are nor forced off as the voltage falls when power is removed then you may get shoot through blowing the IGBTs.

Dan

Hi I’m new here,

I want to build a DRSSTC for my state-certified technician final project.
I have from now on roundabout 38 weeks.
I’ve already started.

In the past I've already tried to build a DRSSTC. I got about 10cm arc from this coil:

Primary: 5 Turns 6mm²
Secondary:
110mm Diameter
370mm length
0,1mm enameled copper wire diameter (I think this is far to low)
100x280mm topload
72kHz resonant secondary resonant frequency
fixed coupling

I think it's better when I make a complete new coil.
Is this coil good?
* final.txt


I already built:
H-Bridge
Interrupter (Steve Ward)
Control circuit
Gate driver (I don’t use GDT)
Galvanic isolated power supplies for the gate driver

I’ve tested all and it works as it should. (At least I think so)
I don't have tested the feedbackfunktion I just used my funtiongenerator.

I made some H-Bridge tests with a 75W Alight bulb.

Voltage at bulb:


When the interrupter stops the H-Bridge the last falling edge is not straight, it’s more like an e-function.
I don't have a picture of this because I killed yesterday one of my IGBTs....
I Switched the 5V off while the H-Bridge was oscillating.
Both IGBT switched on I think, because of a wrong signal and the short-circuit current killed them -.-
So I made this highly professional paint picture:


Is this curve ok?? or really bad??? Idk...

Which ferrite core is good for the feedback is this one here ok (I have some of them here from my first coil):
https://www.reichelt.de/ferritring-59770027-ft-140-77-p7921.html?

I've added the circuit diagram
I uploaded some pics as a zip file to my dropbox (can't attach them here cause they are to big):
https://www.dropbox.com/s/jcgcy6su8wmc3cz/Tesla.zip?dl=0

Greatings from Germany

Vaclav

24
Electronic Circuits / Re: Offgrid 48V solar to 24V battery setup
« on: May 20, 2019, 11:30:34 PM »
Are those monocrystalline or polycrystalline solar cells?

One thing I was wondering about such a setup is the feasibility of setting up a wireless repeater that would charge a battery.  What kind of average power over 24 hrs over the year do you think you could get?  Problem is in the winter at 55.6 N the amount and number of hours of daylight are relatively low.  But perhaps an average of 40 watts is feasible?

Dan

First test with all 3 panels on a sunny day

/>

25
I'm working on a mmc bank for my dual mot tesla coil, is it absolutely necessary to add bleeder resistors if I can easily discharge the capacitor? The terminals are close enough together that I can easily put a metal rod across them with the help of a well insulated pole. And wouldn't they discharge across the secondary coil of the transformer anyway? Can I simply short out the ends of the capacitor bank or must I discharge each capacitor individually? Thanks in advance for any information.

I made a dual mot tesla coil, and I discharged my capacitors with a rod across the safety spark gap.  However, if you forget to do this, and don't have bleeder resistors, the charge could easily kill someone.  Also, discharging the capacitors this way is hard on the capacitors, and occasionally even high quality Cornell-Dubilier capacitors have been known to explode if accidentally shorted.  I included twelve 33 megaohm resistors in series across each metal-oxide varistor as a bleeder.   I also had to include about 1000 pF of capacitance @ 20 kV for RF protection as well.

I have to say having built both a rotary spark gap MOT tesla coil and a DRSSTC, the DRSSTC is much more fun, and in some ways, easier to build.  Getting the rotary spark gap to work reliably was very hard.  The spark gap wheel is very hard to balance.  But I am happy to share details of how I put it together.  The schematic of my dual MOT tesla coil is attached.

Dan

26
If you look at the transformer with an equivalent "T" network, there is a shunt arm that is in parallel with the secondary and therefore isn't in series with the gate, and a series arm that is.  I would think the leakage inductance from the series arm is something like A_L N^2 K where A_L is the inductance of a single turn, N is the number of secondary turns, and K is the flux coupling constant (0 to 1).  I would think that a bifilar winding on a high permeability core has a K pretty close to 1, but it could be an issue I suppose.

Dan

Quote
The purpose of the gate resistor is to suppress oscillations of the series LC circuit formed by the IGBT gate capacitor about 3000 pF for the IGBT you have chosen) and the inductance of the connection to the gate.
Wouldn't you have to add the GDT leakage inductance to this?

27
I will venture an answer to this...

The purpose of the gate resistor is to suppress oscillations of the series LC circuit formed by the IGBT gate capacitor about 3000 pF for the IGBT you have chosen) and the inductance of the connection to the gate.  This is one reason why the connection to the gate should be kept as short as possible, and the signal is carried to the gate using a transmission line of some sort, for example, a twisted pair of a cat 5 cable which has a characteristic impedance of about 100 ohms.  Many gate drive transformers already use cat 5 twisted pairs so this is convenient.  The gate is a load on this transmission line that is very much like a short circuit being a large value capacitor, and the capacitor formed by the two conductors of the transmission line adds only a little extra capacitance to this.   If the gate resistor resistance is too large, the RC circuit formed by the gate resistor and the gate itself has a rise time that is lengthened and therefore slows down the transition of the gate.  If it is too small, you get the oscillations.  So for example, lets say you have 3 cm of trace which has a inductance of perhaps 20 nH.  The impedance of the LC circuit formed by the trace and the gate is sqrt[20 nH/3000 pF]=3 ohms.  To critically damp this LC circuit, you would use a 3 ohm resistor.  This would result in a RC time constant of (3 ohms)(3000 pF)=9 ns.  This does not increase the transition time of the gate that much.  Typically you err a little on the side of a higher resistance, so that 5 ohms is a typical series resistor value.  The value of the resistor is not that critical because in practice it is difficult to measure some of these quantities in-circuit.

Dan

Hi all I am new to the forum. I have built quite a few Spark gap style coils throughout the years and am now trying my hand at my first DRSSTC. I am going to use loneoceans UD2.7 c for the driver and his 80mm Full bridge board for the bridge. I will be using FGA60N65SMD for the igbt's. I am having trouble wrapping my head around calculating the gate resistors values. Could someone point me in the right direction to a good place to read up on this ? I tried using the calculator but I am at a loss as to how to figure out the maximum gate drive current the driver is capable of. Better stated what do I calculated it off of? My assumption is the current of the mosfets that drive the bridge and if so is it x1 since there is a gate resistor per igbt or total current x4?

Any help would be greatly appreciated. Thank you

28
The UD2.9 changes the way that the UD2.7C works.  I modeled it in Qucs (Quite Universal Circuit Simulation) and I attached the schematic below and show the screenshot.

The way it works is a little different than the UD2.7C.  In the UD2.7C (see schematic below), the overcurrent condition clears the second D-latch U7B unconditionally.  This latch output Q is ANDed at U5D, goes through a double NOT gates U8D/U8E and clears U7A, and then is ANDed with the TL3116 outputs at U5B/U5C to turn off the drivers.  The latch U7B can only be reset by another interrupter edge, so once the overcurrent condition happens during a pulse, the driver stays shut off until the interrupter edge reoccurs.

The UD2.9C on the other hand works like this:  When an interrupter pulse comes in at U8C, the diode/capacitor network causes a brief low edge signal.  This sets BOTH U7A/U7B and allows pulses to start.  If J16 is open for not skip pulse operation, when the overcurrent condition occurs, U7A is cleared.  This in turn takes a path through U5B, U8D, U8E, and then resets U7B, similar to what happens in the UD2.7C.  U7A and U7B can only be set again by the rising edge of another interrupter pulse, and so the behavior is the same as the non skip pulse, even though it is arranged a little different.

If J16 is closed, then while the current in the primary is ringing down, once the overcurrent condition clears, the signal from U4 Q is conducted through J16 and allows U7A to be set.  This turns on U7A Q and then if the interrupter pulse is still continuing, the output of U5B is high and so the signal is also clocked in on U7B, reenabling both D-latches and so the driver turns back on until either the overcurrent occurs and U7A/U7B are shut off again, or the interrupter pulse terminates and the output of U5B is low and shuts off U7B.    One other feature is the presence of the transistor Q5.  This transistor prevents another interrupter pulse edge from turning the driver back on if there if at that moment there is an overcurrent condition, so one can not force the driver on excessively and risk damaging the transistors with excessive current.

Typically I don't get a problem with dead time because I use a gate driver transformer to drive the upper and lower transistors with opposite polarity windings.

You can take a look at the simulation below where I verified I could turn the skip pulse on or off depending the connection of the jumper.

Dan



Hello guys, I want to use a skip pulse driver for my Tesla but I'm lazy to design and programming a CPLD driver :p . So I decided to create a skip pulse driver for full bridge drsstc without any programmable devices.
I found peoples who already worked on a logic skip pulse driver ( https://4hv.org/e107_plugins/forum/forum_viewtopic.php?p=1&id=178230#post-178230 and https://highvoltageforum.net/index.php?topic=346.20 ) but I don't understand how they work.

First I begin with the logic of the UD2.7 driver and I added 2 D flip flop. It seems to work on simulation  :D : http://tinyurl.com/yyan2agj


But i have a question about the switching of IGBT : How the driver generate the dead time to not short-circuit the half bridge module ? I didn't find any information on the UD2.7 drive about dead-time generation but I'm using it and it works so I believe it have dead time...


And if you have some advices to improve the skip pulse logic of my driver It will be usefull  :) thank you !

29
Solid State Tesla Coils (SSTC) / Re: Flat Secondary Coil on PCB?
« on: May 02, 2019, 02:06:27 AM »
The only thing I can offer here is another reference. This coil is still early days but it is a drsstc.
https://hackaday.io/project/165112-pcbtc-gan-edition

Thanks for the link.  That looks like an awesome project.

Thanks to you both for the info.  It gives food for thought.  I didn't think I was the only one who thought of this, but obviously there's been some movement here. :)

I was thinking of keeping the primary and secondary on separate PCBs so I could stack several secondaries to get more turns, and also I put the sense coil on the other side of the secondary board so that it there is less of a chance of having a coil strike damage the circuity (if it is possible to have a streamer that long).

dan

30
Solid State Tesla Coils (SSTC) / Re: Flat Secondary Coil on PCB?
« on: May 01, 2019, 07:34:33 PM »
You wouldn't happen to know of a video of it in use?  I am curious to see how they work.  I was thinking of adding a buck converter before the half/full bridge so that I could modulate the power with an audio signal.

Dan

Hello

I know that such tesla coils work, because they are sold commercially: https://highvoltageshop.com/epages/b73088c0-9f9a-4230-9ffc-4fd5c619abc4.sf/de_DE/?ObjectPath=/Shops/b73088c0-9f9a-4230-9ffc-4fd5c619abc4/Products/TESLA_MINI_v1.2_

In the description you can see the technical data of the coil, it has 120 turns: https://highvoltageshop.com/epages/b73088c0-9f9a-4230-9ffc-4fd5c619abc4.sf/de_DE/?ObjectPath=/Shops/b73088c0-9f9a-4230-9ffc-4fd5c619abc4/Products/TC12_flach

Greetings
Phoenix

31
Solid State Tesla Coils (SSTC) / Flat Secondary Coil on PCB?
« on: May 01, 2019, 05:54:26 PM »
I was thinking about designing a small kit-based Tesla coil where rather than the seconary coil being a solenoid, it is a flat spiral.  Of course the secondary inductance goes down, but is there any reason this shouldn't work?  Flat spirals are already used for resonant power transfer applications (e.g. wireless charging and induction cookers).

The board I designed has (I calculate) about 1 mH of inductance.  It is about 150 turns of 0.13 mm wide traces separated by 0.15 mm.  This is the thinnest I could fit in the design rules of the process.

Anyways I was up late last night and drew up a PCB.  The hole in the middle is for a post to put the topload on sticking up from the PCB.  The hole on the edge is to connect the ground.  There is a six turn coil on the back that is used to sense the current in the secondary for feedback purposes.

I was thinking too that I could stack the boards to get more turns and place a thick HDPE insulator between them.    The center of each coil would be connected to the ground of the next in series, and these would be stacked as to be placed over the primary coil  so that the board would intersect  the magnetic field lines of the primary coil.

Here is what I drew up last night:



Any comments about this design?  I want to call it the "Conversation Piece" which would be a little tabletop SSTC coil.  It would be powered by 12-30 VAC.

Dan

32
I made a bobbin using a sheet of high density polyethylene a while back.  I should take a picture of it, but I would have to clean the oil off of it. :)

The sheet was about 6 mm thick.  I cut four 80 mm wide, 150 mm long pieces and made a rectangular long tube with the edges of the pieces glued to each other.  To adhere the polyethylene to itself, I used a butane torch to flame treat the polyethylene so that I could join the four sides together with epoxy.  Then I field off the corners of the rectangle to smooth them somewhat.  I was able to wind 500 turns of 0.25 mm magnet wire around it.  I had some large U-shaped ferrites which then were inserted into the bobbin.

It was one of the first things I did when getting started in high voltage and it was very difficult to get working figuring it out by myself.  After I was done I wrote a document on it.

https://drive.google.com/file/d/0BwFicJLV0O4jYlQ0ejJ6NE9XVE0/view

Dan

33
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 31, 2019, 05:47:08 AM »
I moved the OC LED backwards so the potentiometers may be better separated, there should be plenty of space now.

Dan

34
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 30, 2019, 07:13:05 AM »
I have to confess I had an ulterior motive for designing the SSTC circuit this way.  I hope to try to use to make an induction heater using the SSTC board.

Basically, use a feedback coil rather than antenna near the workpiece to drive it into resonance.  So I designed it with some stuff that may not have been necessary.  I did not really worry about the dead time but I thought I should look into it after you brought it up.

If you need even less dead time, you can swap R5 and R11 for 4.7k resistors.  The limit is that the overcurrent circuit can only sink 6 mA and so if the resistors are too low resistance, the overcurrent protection does not work.

Dan

35
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 29, 2019, 02:28:57 PM »
Well you have to realize that there's a lot there in the PCB Pack and it could always use some improvement.  But I wanted to try to create something so that all the circuits one needs could be in one place like Mads with his series of guides.  One of the hardest parts about building a Tesla Coil is trying to figure out where the accurate information is, and this was a struggle for me getting started, so feedback like yours is a big help to try to make the situation better.

As for the dead time issue, here is my understanding of it.  When driving an inductive load like a tesla coil primary, one achieves ZVS (zero voltage switching) for a half/full bridge by having a dead time between the turning off of the upper/lower transistor and turning on the lower/upper transistor.  When both transistors are shut off, there is still current flowing from the inductor.  The current is diverted from the transistor that is now shut off to the the body diode or reverse pack diode of the other transistor.  Since the other transistor is now in forward conduction, its voltage drop is near zero.  So you do get some energy loss from excessive dead time which is current X diode drop voltage X dead time duration.  Now the other transistor is turned on at nearly zero voltage which results in a lower switching loss.   The disadvantage of excessive dead time is you get a little more loss in the reverse diodes but the benefit of ZVS switching for the on condition and a low probability of shoot-through.

Dan 


Well ! This certainly took a different turn, I wanted to make a test circuit for GDT’s, and it resulted in a circuit change !

Dan, thank you very much for your help with this. More than likely I will use this driver in a TC build in the future so thanks for troubleshooting and making changes.

One thing that I am not clear with is jumper settings, so far I figured out AC/DC input jumper, but others are a bit harder to figure out from the schematic ( for me at least ).

I’d like to do a test with FG connected to the antenna input next.

36
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 29, 2019, 02:23:28 AM »
I have a solution to greatly reduce the dead time.

Replace D3 and D4 with 1N4148.   They are 1N5819 in the design.  I will update the schematic.

It should work much better, here's a screenshot.  The dead time is now 320 ns.

Dan


37
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 29, 2019, 01:22:05 AM »
I looked on the output of my board.  I get a 880 ns dead time.  I am not sure why you are getting twice as much.  Even this is kind of high for the switching time of the CD40106 with 15 volt supply.  I should probably have a board revision and use a CD4027 and use both the Q and not Q outputs which would change at the same time.  This would also ensure 50% duty cycle, but would add an extra part.

I don't think it's a problem to have zero voltage in the gate drive transformer.  The overcurrent shutoff in fact does exactly this, where it forces both gate drivers low to turn off the MOSFETs. 

I have a plot of the gate drive signal when the antenna port is drive by 200 kHz with a signal generator.  The dead time is long which might lower power output however.



38
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 28, 2019, 04:36:20 AM »
I don't think it should be a problem.  The body diode of the one MOSFETs should go into conduction after the other MOSFET is turned off.   It is a longer dead time than I have observed but it should probably be ok.

Note that the SSTC should be driven using the antenna feedback.  The built-in oscillator is mostly to "jump start" the oscillation of the Tesla coil.



39
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Next Gen DRSSTC
« on: March 25, 2019, 07:35:14 PM »
Apparently there have been updates to the pinout that I have not incorporated into Psoc5-power yet, so you might want to hold off.  You don't need the board if you want to breadboard it.

I could update it if I get an updated pin list.  I haven't looked at the latest PsoC creator project lately to see what the new assignments are.  I think there is support for Ethernet now.

Dan

40
Solid State Tesla Coils (SSTC) / Re: Chinese MOSFETS/IGBTS
« on: March 25, 2019, 05:09:01 PM »
Yes that is the GM328.  I have one of those as well.  They're excellent little diagnostic devices.  I was thinking of something like this, but more specialized to power MOSFETs and IGBTs.

Dan


The differences in the copper backs will outweigh the differences in the silicon.  Have you guys seen these cheap little testers?:



From here:

https://www.ebay.com/itm/172557508334

That is a quick, cheap, non-destructive way to weed out the fake FETs.  The Rds number is usually off by a fair amount, so to further test I put 10A through one and measure the voltage drop.

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