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Messages - bozidar

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1
Here is the code (which I know is not perfect)  ;D
And here are a few videos  :)


2
I use timer 1 for one note and timer 2 for the other note. For now the signal has no noise.
 If you want I can post my code  :)

3
After each pulse I just added delay function  ;D
Holdoff time is 45 us.

4
Thanks for the answers.
I added off time to the code and I don't think the sound quality is much distorted so maybe I'll try it on DRSSC . ???



5
I'm using almost identical Loneoceans UD2.7, just with through hole components. In place of optic fiber receiver I'm using arduino nano with optocoupler . Arduino mega sends MIDI messages via bluetooth to an arduino nano (which I use as an interupter).
This setup works perfectly when I play only one note :)

This is a SimpleTesla interrupter that plays MIDI with multiple notes (6, if I understood correctly-   1:40 - 2:30 min)

And this is mine playing 2 notes  ;D

I guess Onetesla MIDI interrupter works the same way, right?
Can  someone post some scope pics of Onetesla output when playing 2 notes MIDI files?

Maybe the OCD will not allow the current to rise too much when the two pulses are close to each other, so could I just reduce on time?

6
Hello,
I wrote the code for arduino based polyphonic MIDI interrupter, for my DRSSTC, that can play 2 notes. But I don’t know if the pulses can overlap or be close to each other (like the pulses in the picture)?
Is it safe to run the coil with this pulses?

7
Hi, I just want to thank you again for your help and I want to share with you some details about my version of DRSSTC.
Mads Barnkob-I know that the surface of the topload must be much smoother, but for now, I am very happy with these results.
I use an Arduino Nano and an HC-05 Bluetooth module that are directly mounted to the diver board.For testing purposes, I used the android application Bluetooth Electronics that specifies the required frequency and pulse width that the Arduino nano generates. (code (test5-final.ino) and pic of app in attached files)
And to play MIDI files I used the android application MIDI Visualiser.
The phone is connected via a USB-MIDI converter to the Arduino Mega which sends MIDI messages via a bluetooth connection to the Arduino Nano located on the driver board.
The codes are not perfect because I wrote them quickly  ;D
I also modified the code I found on this forum. I've written several versions of the code so I'm not 100% sure what version I'm currently using- version 2 or version 3  ;D
Code BT_SENDING_FINAL is for Arduino Mega and codes drsstc_version_2 and drsstc_version_3 are for Arduino Nano for play MIDI songs.

Some more videos:

8
Since my chip (UCC27423) didn't arrive in time I couldn't wait any longer and just inverted the UCC27424 inputs with 74HC14 and also adjust a phase lead a little bit , and now DRSSTC works perfectly. :D
Thanks again for all your help.
Here is some videos.

9
Ok then I will buy the UCC27423 chip, it`s better than with 74HC14 and UCC27424.
I have GBU808 bridge rectifier (800V 8A). Is that enough for a 230AC or should I buy another that can handle more current?
I had a FB2510 (1000V 25A) but it burned out when the IGBTs exploded.

10
Can I just invert the input signals (2 and 4 pins of ucc27424) with 74hc14?

11
When buying parts for the driver I couldn't find the UCC27423 chip, so I thought I could use the UCC27424 chip.

How the gate drive can float between enable pulses when enable pins are connected to 9V?

After some experimenting with LTSpice I added a small circuit  (Picture1.png) to improve impulses at the beginning of the input pulse(from interrupter). In attached images you can see gate-emitter voltage (blue trace) and output pulse from AND gate (yellow trace) (second image) , input (blue trace) and output signal (yellow trace) of added circuit (1.png and 2.png) (Vbus 0V). After that I connected 24VDV on the bridge and the coil works  :D
The only problem is that sometimes some pulses are skipping at some frequencies, much like the one in the picture from the earlier post (https://highvoltageforum.net/index.php?action=dlattach;topic=722.0;attach=4990;image). I don't think it should be able to damage IGBTs at full Vbus. What do you think?
Another question, it may be stupid but I have to be sure. Should I connect the ground to the driver board when it is mounted in a metal housing?
I connected the other end of the secondary to the main ground as well as the IGBT coolers, metal case for the driver board and strike rail.

12
Here is some scope images with and without a screwdriver and circuit of my driver (Vge - blue trace). 1kHz 200us on time - input signal. I connected only GDT ,without OCD and feedback CT .
A similar thing with a screwdriver happened before IGBTs exploded. I wrote this in one of my past posts.

13
Unfortunately, the switching power supply was not a problem, because when I turned on the coil again at 310VDC two IGBTs exploded  :(
Luckily i had 2 spare IGBTs, and now my problem is the same as before. Sometimes the coil works properly and sometimes it does not. When I touch the feedback input with a screwdriver everything works as it should (Vbus 24VDC). I noticed when I disconnect 24VDC from bridge and touch the feedback input (with a screwdriver) I can hear audible buzz on GDT. And when I remove a screwdriver there is no more buzz on GDT. Then I connected only GDT (without OCD and feedback CT) and the same thing with a screwdriver happens. In attached images you can see gate-emitter voltages with (11.jpg) and without (10.jpg) a screwdriver.


This is written on the loneoceans site:
www.loneoceans.com/labs/ud27
Quote
Note that if you have no input signal in your FB jacks, the driver will not see any feedback, causing the drive to lock up. Here's a scope shot of a GDT output with a feedback input signal (left). But if you have a GDT attached with no signal generator input on the feedback, this will make a signal on the output of the GDT look like the above (right - where the driver doesn't know what to do), and will cause quite a loud audible buzz from the GDT with this associated output per pulse. This sound should diminish greatly with a feedback input signal.


So without feedback , the signal should look like last attached image.  Right?
Maybe my driver board is bad?

14
I`m scoping primary current with another separate CT (41 turns connected to 41Ohm resistor).
I've already adjusted phase lead before with proper oscilloscope as best as I can, so now I`m afraid to adjust it again (unfortunately I had limited access to that oscilloscope). First picture that I posted is taken by that oscilloscope.
After some experimenting at low voltages I decide to power bridge at full voltage (310VDC) and the coil didn't work at all (only some small sparks at 7KHz and 9us on time).
Then I replaced switching power supply which powers the driver (24VDC 10A ),because that's the only thing I didn't check, with classic iron core transformer with greatz , some capacitors and 24V regulator and finally the coil works (still skipping some pulses at low frequencies below 100Hz but it does not matter)  :D :D :D
I guess there was some interference between driver and switching power supply  :o
The coil produce around 30cm sparks at 200Apk , 1.5KHz and 30us on time. Given that the secondary is only 23cm tall I think this is a good result.
I'll post a video soon.
Thanks for all your help, especially davekni for the great tips and explanations.

15
I found out there was a problem in my oscilloscope (settings) that caused the signal not to display properly  ;D
I have a USB oscilloscope ISDS205B (20MHz, 48Ms) that can measure up to +-60V so I can`t measure voltage at  high side of primary caps  :-\
I fixed the emitter wiring and now everything is almost fine.When I turned on the coil for the first 2-3 minutes everything worked again as before, some impulses were skipped, but after that everything slowly returned to normal.
Here is some scope images after that.
First two pictures- yellow trace is feedback input from CT and blue trace is primary current (1V=1Amp)
Pictures 202,203,204 -yellow trace is Vce from one transistor and blue trace is primary current
Pictures 205,206,207 -yellow trace is Vce from other transistor and blue trace is primary current

16
Vbus is 24VDC.
Yes , the third picture is of the current feedback (450:1 on 51 ohm load) and yes , anomaly where the current reverses is repeatable. I think that's what happens when the gate signal have small duty cycle ( second picture).
I didn't know that for double emitter terminals. I'll fix it as soon as I can.
I'm using four paralleled primary wires but i patched them to a single pair of wires right next to the GDT.I shielded all wires with aluminium foil and put everything in shrinking tube.
In my local shop I can only find these caps for MMC so I hope that they ( 68nF 8kV) can handle  4.5 kV peak at 150kHz. I checked all the capacitors separately , with RLC meter , and they are all good.

17
I checked the diodes and replaced chinese chip LT1016 with MAX9013EUA (from farnell). The results are still the same. :(
I also checked phase of CT and phase of GDT.
In attached img can be seen some waveforms (filename of first 7 img is the frequency and on time).
At 1.9kHz and 196us everything is almost good and in attached img you can see what happens at 1.9kHz and 200us.
In last 4 images you can see bridge , driver etc.
Hope this is not too many pictures  ;D

18
After my last post  when everything was worked , yesterday when I turned it on again nothing worked as it should. So I just don't know what to do  :(
That's happening from beginning , one day it works and when I try the other day it doesn't work properly. Only works if I connect signal gen.Than I reduced feedback CT turn ratio to 1:450 but results were the same.
In attached img can be seen gate signal ( yellow trace )with CT  connected to the feedback input. ( blue trace - current) It's weird that things get a little better when I touch one of the feedback inputs with a screwdriver  :o
What can cause this behaviour , driver , CT , GDT or something else?

19
At yours suggestion I put a 6 kohm resistor ( I found a few 3w and one 5w and connected them in parallel ) across bridge output and I continued testing with signal gen connected to the feedback input. Unfortunately  the signal began to appear just over 200mV P-P and the signal at the gates was not symetrical. Than I connect CT feedback instead of signal gen and increased the supply voltage to 24V ( also 24V on Vbus ) and the coil works just with not symetrical gate voltages as you can see in attached images. I noticed that the  signal is symetrical at the end where the current (feedback voltage ) is higer. So can i just reduce the number of windings on CT so that I get more voltage at the feedback input?
Are these negative peaks dangerous for transistors?

20
I only use signal gen as feedback input because when I connect feedback CT nothing works( also with reversed wires ). I used 4 turns on my previous core with high AL value (11400 nH/turn²). I'm using power supply with adjustable voltage (14v to 24 v) , so I adjust voltage to somewhere around 17 v to keep Vge overshoots under 30v and I use the same power supply for Vbus. ( 1.5KE27CA TVS is connected across gate emitter). I connect 10Mohm res across every capacitor( 4 strings of 4 in series).

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