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Messages - Thunderstruck

Pages: [1] 2 3 4
1
MUR860s are not TVS diodes,but ultrafast recovery and works as freewheeling diodes. ;)

Yes, that... what you said  ;D

But they deal with the same thing, right ? Feedback from an inductive load ?

2
I cannot figure a couple things, one is due to inexperience in interpreting component data sheets:

1. What is the maximum Gate voltage on IRFP460 - I gather its about 10V but not sure
2. GDT from the driver outputs about 34V peak to peak, which is way too high for IRFP460, how do you bring the voltage down so it can be handled by the gate ? Only way I can think of is changing primary to secondary winding ratio.

1) The gatevoltage for the IRFP460 is +-20V. (+- mean you can put everything between 20V and -20V on the gate)
* 91237.pdf
2) 34Vpp (Peak to Peak) means 17Vp (one Peak) or +-17V which is smaller than +-20V. So you are fine as it is.

You could bring it down either by lowering the secondary turns or lowering the gdt driver voltage (which may or may not be possible).

Two birds with one stone ! Thanks Fumeaux !
So, Vgs is what I needed... well I suppose now I know  :)

I tried lowering GDT driver voltage - it doesn’t like it, gets emotional very quickly
But, GDT output voltage is not an issue any more.

3
Solid state Tesla coils / Full Bridge Inverter from bits and pieces
« on: April 07, 2019, 08:27:39 AM »
Originally I wanted to build Profdc9’s full bridge inverter, I also wanted to build it using parts listed in the BOM, I even filled a shopping cart at Mouser with all the necessary parts - about $120 worth...

Then the power and gas bills came together...  :-\

So, because I have to act as a responsible adult (BORING), hobby has to wait for funding to be available again.

Then I remebered that I have some bits n pieces left over from my first SSTC attempt that might work together to make a functioning bridge using Profdc9’s full bridge PCB.

I have:
- 4 IRFP460 FETs
- 4 MUR860 Fast Diodes
- 4 WIMA MKP10 0.68uF 630V Polypropylene Caps

I think that there is enough parts here to make a circuit based on Steve Ward’s mini SSTC half bridge inverter, but full bridge instead and using above mentioned PCB.
Maybe my thinking is wrong, but to me it looks like just a matter of doubling the number of the components, and of course driving the FETS in the correct sequence.

Drive would be provided by Profdc9’s SSTC Driver.

So far I mounted the parts together, not exacly as one would expect, but if everything works well I reckon it will make a neater build.

I cannot figure a couple things, one is due to inexperience in interpreting component data sheets:

1. What is the maximum Gate voltage on IRFP460 - I gather its about 10V but not sure
2. GDT from the driver outputs about 34V peak to peak, which is way too high for IRFP460,   
    how do you bring the voltage down so it can be handled by the gate ? Only way I can think of is
    changing primary to secondary winding ratio.

I’d appreciate if someone could help with this - even if you tell me that this contraption will never work the way I imagined.

Image 1 Snip from Steve Ward’s schematic that i want to duplicate in a full bridge configuration
Image 2 Parts on hand
Image 3 Build so far - TVS diodes are bent like that because I wanted to put them under the board, but later realised it wouldn’t work  ::)
Image 4 This way FETS get a huge heatsink that can later serve as a base for the coil - of course keeping in mind that the transistors must be isolated from the heatsink, otherwise there will be a lot of angry Pixies in that sink, waiting to bite.




4
Beginners / Re: Keep or throw away ?
« on: April 07, 2019, 07:33:15 AM »
Could those bricks be used as rectifiers? You could rectify a transformer to make a good welder. Of course you probably already have one. :-\


Hi AndreiRS,

I suppose they could be used for a welder, but welders are so cheap these days it is not worth the trouble. Only thing you’d get out of it is “I made it myself” feeling.

5
Beginners / Re: Keep or throw away ?
« on: April 05, 2019, 05:05:16 AM »
TDK-Lambda HWS1500-48 Power Supply
48V, 32A, 1500W
Brand new cost $1970 AUD

Rescued two from a dumpster, both worked ok, then one just stopped. I have no schematic or experience to repair it.
I managed to narrow down the fault to one of three boards, but I am not comfortable poking around the PSU while powered up.
Board that you can see on top is faulty. When replaced with the board from the other unit, everything works fine.

Maybe I should scavange the parts and put it back into the bin ?

6
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: April 01, 2019, 01:09:56 PM »
Happy to say that both outputs are working now ! It took some time to resolve, but it was worth it.
It turned out that UCC is not faulty, it was something much much more basic - poor solder joint on U2 mosfet.
Anyway as you can see below, wave forms are quite good, a bit of ringing but that is to do with GDT's I suppose.


7
Solid state Tesla coils / Re: GDT Experiments
« on: March 30, 2019, 09:44:36 PM »
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

I have no idea how much dead time is enough for the correct operation of a SSTC, I suppose I’ll just have to build one and see what happens, then adjust accordingly.

Since you are looking for feedback, there is one more thing that I noticed when assembling the driver.
Two pots are very close to each other, which is not a problem if you are using 16mm pots or panel mounting them, but for some reason in Australia I can only get 17mm pots which are just a little bit too big if you mount them directly onto the PCB.
I had to remove some material from each of them to make them fit.
I am not sure if anyone else had a similar problem with slightly larger pots, but moving each pot only by 1mm in opposite directions would help.

Also, one of the pots will come very close to touching the opto-isolator if opto-isolator is mounted into the ic socket. Again, this is not a problem if pots are mounted onto a panel.



8
Solid state Tesla coils / Re: GDT Experiments
« on: March 29, 2019, 11:27:55 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 
[/quote]

To be honest, I stumbled on that issue, I was not even aware that is an issue, but I am glad that it lead to an improvement.
So far I built 2 circuits out of your github pack, interrupter and driver, both working well ( yet to program Attiny85 and try Midi function on the interrupter )
I also had Pcbway manufacture your half bridge and full bridge PCB's, so I might try to put one of them together as well.

Anyway, I did more tests on my driver board.
Image 1 shows waveform with dead time of 1.16us
I swapped UCC37322's with TC4420's to see what is going to happen, and as Dexter pointed out, TC's are slower therefore the problem  got worse, as you can see in Image 2.
Not only did the dead time increase to 2.2us, the waveform itself has a weird spike in it.

Then I put the UCC's back and replaced D3 and D4 with 1N4148's, dead time reduced to 230ns - Image 3
I also added 270 Ohm resistor to get rid of the voltage spikes.

Image 4 shows waveform at 200kHz with FG connected to the antenna input
Image 5 shows all 4 GDT outputs running, only CH 1 has 270 Ohm resistor connected, rest show voltage spikes.

9
Solid state Tesla coils / Re: GDT Experiments
« on: March 29, 2019, 05:51:11 AM »
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.

10
Solid state Tesla coils / Re: GDT Experiments
« on: March 28, 2019, 12:57:32 AM »
Part number from Digikey is 296-3503-5-ND, CD40106BE.
From what I gather, deadtime is not a bad thing, right ?  Gives time to the devices to switch off and on completely without running into each other ( going linear )

11
Solid state Tesla coils / Re: GDT Experiments
« on: March 27, 2019, 11:21:29 PM »
That waveform confused me a bit until I realized that there is "deadtime" in the signal. Only recently I watched a video on YouTube on that topic - quite glad I recognized it in the waveform.  ;D

You have about 1.8us of deadtime in both shoots and i can't figure it out how...
The Half Bridge SSTC schematic doesn't have any built in deadtime and the TC4420 have delay times less than 100ns and matched Rise and Fall times of 25ns or are you using different IC's?

I am using UCC37322 instead of TC4420, so that might be the reason.
I also wondered what causes the dead time ( well to be honest I would not know what does it even if there was a dedicated component )
What controls the dead time was going to be my next question.

I already had spare UCC’s, so I did not want to spend more on TC’s since they are interchangeable in this case.


12
Solid state Tesla coils / Re: GDT Experiments
« on: March 27, 2019, 08:59:31 PM »
Yep thats it, nice work, do you have a link for Profdc9 scematic and witch core did you use if I may ask. If you add a little load resistance in paralell with your transformer output you might be able to get rid of those spikes at each transition

You can find Prof’s schematic, and a lot of other useful stuff here:
https://github.com/profdc9/DRSSTC-PCB-Pack
It is under Half Bridge SSTC

Core i used in the first screenshot is EPCOS, Al 5400 T35 material, 27mm OD ( ball of wire on the photo below  ;D )

Second core is also EPCOS, Al 13500 T38 36mm OD ( connected to the driver on the photo below )


13
Solid state Tesla coils / Re: GDT Experiments
« on: March 27, 2019, 12:46:44 PM »
I built Profdc9's Half Bridge SSTC driver and connected the GDT's I built. This time I'm getting half decent results, waveform actually looks ok.
As you are probably aware, this is all quite new to me, so I am quite excited achieving things that many of you achieved years ago and consider them ordinary. But, it's all about fun, right ?

Screenshots below show output of two different GDT's I made.

First image shows waveform from a GDT I previously tried running from a FG only with terrible results
Second image is a waveform from a GDT made with 11 turns of CAT5 cable - all four pairs of wires. Signal from 2 only shown.


That waveform confused me a bit until I realized that there is "deadtime" in the signal. Only recently I watched a video on YouTube on that topic - quite glad I recognized it in the waveform.  ;D






14
Solid state Tesla coils / Re: GDT Experiments
« on: March 25, 2019, 12:56:36 PM »
Thank you for all the comments, a lot of useful information there. It is definitely not a case of just winding some wire on a core.

Clinical definition of insanity is tepeating the same thing expecting a differnet outcome. :o

So I decided to have another attempt  ;D

This time I got 3 different cores:

125-3320 Al 13500 T38 
212-0982 Al 5750   N30
212-0976 Al 7000   N30

I managed to wind 11 turns through the T38 core and got exactly the same result as before.
Logical conclusion is that the way I’m driving the GDT’s is inadequate ( somebody already mentioned this )
I will have to build a test rig, fortunately I got a few PCB’s for profdc9’s SSTC, I reckon that will do just fine.

Strangely enough, yesterday I wound a GDT ( not really caring about how it will perform ) just to test my UD board and got a perfect waveform, go figure....




15
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: March 24, 2019, 08:35:33 AM »
Update:

Today I connected a couple of GDT's to the UD aaaaand I got mixed results. Good news is that half of it is working - GDT 2 works as advertised, GDT 1 - nothing !

Let's start from the beginning:

UD is supplied with 24V DC, connected to profdc9's interrupter via IF95T fiber optic receiver.
65-70kHz signal is supplied to the feedback connector.
I made 2 GDT's for testing purpose only and connected one to each output.

Board powers up fine, power LED comes on, signal LED turns on as soon as the interrupter is turned on.
( Earlier OCD LED would turn on too, it would turn off as soon as the signal is supplied to the board - just like Mads predicted, but since I fixed that solder joint on D13 it does not come on any more )

Image 1 shows output from GDT 2 which looks fine, and output from GDT 1, which is not so fine.

So, I did some signal tracing...

GDT 1 is driven by  a pair of Mosfets, U1 and U2
Mosfets are driven by IC9, UCC27423
U1 - is driven by pin 7
U2 - is driven by pin 5

I compared the output signals on pins 5 and 7 on both UCC's  ( IC9 and IC10), and discovered that pin 5 on IC9 outputs strange waveform ( pin 7 on IC9 outputs the same waveform as pin 7 on IC10, so probably it works fine ).

Image 2 shows output from pin 5 on IC10
Image 3 shows output from pin 5 on IC9

So, I think that I have faulty UCC27423. I do not have any spare ones, but I am more concerned with removing the existing one without a desoldering station.

Image 4 shows the offending part.    At least solder joints look good....

By the way, as far as GDT waveform is concerned, do not ask me how I did that because I have no bloody idea.
I even started a separate thread to document my attempts - mostly failures to produce a decent waveform from a GDT.

16
Solid state Tesla coils / Re: Chinese MOSFETS/IGBTS
« on: March 23, 2019, 10:07:54 PM »
I wanted to ask the same question, for example IXGN60N60C2D1 IGBT’s are listed as obsolete from Digi-Key and Mouser, but there is plenty available on eBay and very cheap too.
A lot of stuff on eBay is counterfit, so I suspected that the same would apply in this case.
I also looked at some large caps, good price, but after a bit of searching I found that they are 100% fake - identified as fake by the lettering, units used for capacitance, etc.

Usually, if it sounds too good to be true, it is too good to be true.

For example, look at this thing, AUD $14, judging by the marks on the metal parts, it is made by a blacksmith  ;D


17
Dual Resonant Solid State Tesla coils / Re: UD 2.7C Build
« on: March 23, 2019, 08:03:58 AM »
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 ?

18
Solid state Tesla coils / Re: GDT Experiments
« on: March 20, 2019, 09:07:04 PM »
You did also choose cores with almost identical properties, its not even a 1000 permeability in difference, so you will only see the differences from number of turns and how tight coupled the wires are to eachother/the core.

What kind of test jig did you use? A driver IC --> GDT --> MOSFET gates?

Did you see this practical design guide / experiment? http://thedatastream.4hv.org/gdt_practical.htm

Mads, in both cases it was the same core. I did say 5 different cores in my original post, what I wanted to say is 5 different ways ( twisted, straight, trifillar, etc. ). I was expecting to see at least a half decent waveform because it is a high permeability core, especially after watching a few videos.
Test signal was supplied from the FG directly, i do not have a driver circuit to test the GDT with.

I suspected that my FG is not really capable of driving the GDT...
I read that guide a few times, only thing missing is screenshots of waveforms after each attempt.

The one thing missing from Burnett's advice: reduce the driver impedance.

Was that testing with a function generator (50 ohms)?  Looks about right for it.

Tim

Tim, yes I tested the transformer with my FG which is a little bit ancient  :)

19
Beginners / Re: Keep or throw away ?
« on: March 19, 2019, 10:02:41 PM »
I still say that if you want for a giant flyback or induction heater they will switch a lot of power of you know what you are doing. they may not be sutible for a DRSSTC because they are slow and old Technology but if you want something to mess around by all means. Do you have a special project in mind and what kind of resources do you have?

These came out of a very old CNC machines which were sold for scrap from the company I work for.
Capacitor bank came out of EDM - Electric Discharge ( Machining ) Machine, Wire Cutter to be exact.
As far as mechanical engineering resources are concerned, I have access to everything from a hand drill to a Water Jet machine that can cut 100mm steel plate.

With electronics, I have a small bench in my garage with some basic equipment ( scope, FG, soldering station, multimeter, etc. )
As far as expertise in electronics is concerned, it is a case of a lot of desire, but limited understanding. I understand a lot more than an average person, but there is a lot of empty spaces in between.

20
Beginners / Re: Keep or throw away ?
« on: March 19, 2019, 09:11:09 AM »
I like that idea ! Audio amplifier with a transistor larger than an iPod  ;D

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