Author Topic: My first DRSSTC on bricks  (Read 7241 times)

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #20 on: April 12, 2019, 06:32:13 PM »
I spent hours today on getting the autotune fixed version working,but after uploading the onboard blue LED lights up and can't communicate with it over serial(bluetooth module).I did the same changes with the UART_2 as before,changed clock to internal,bits per second to 9600,buffers size to 256.Is this a possible problem or I did something wrong?

I was not sure about the meaning of transient,now it's clear!

The "how to set phase lead if I don't see any overshoots across the inverter output" question is still active. :)

Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #21 on: April 12, 2019, 06:50:42 PM »
Why did you change the buffer size? But I don't think that is the problem. It slows down the communication.

You use SKM400 like me, so the default parameters should be not to bad. Activate transient mode and give the driver another lead_time and look if the spikes get better or worse.

Edit:
Checkout the new commit. The ESP32 interface was enabled by default and this uses the serial port. I disabled it by default. But over USB you should get a connection and then you can disable the ESP32 interface with: "set eth_hw 0" and save everything to eeprom with "eeprom save"

9600 baud is very slow ^^ if you want to enable telemetry later it eats up 50% of your bandwidth. For the SID Synthesizer you need at least 19200 baud
« Last Edit: April 12, 2019, 07:05:00 PM by Netzpfuscher »

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #22 on: April 12, 2019, 09:25:42 PM »
The cheap bluetooth module only runs on those low settings.Sadly I still can't communicate with the UD3 over the serial pins.The onboard blue LED is constantly ON,unlike the autotune bug version,where it was OFF.
Here are the settings:


Pinout is the default.I only have VCC,GND,TX and RX on the right way connected from the bluetooth module to the standalone development board,so no hardware connection issues.
Another error(?):


And here's another error which I think is more like a bug in PSoC Creator as it shows that UART_2 requires connection when it's visible,but I run it on internal clock:



« Last Edit: April 12, 2019, 09:33:00 PM by Laci »

Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #23 on: April 12, 2019, 11:03:56 PM »
First of all, 20 start cycles is waaaaay to high. A normal DRSSTC runs fine with 3. I think your feedback is still not working, if you get no output with 3 cycles.
Is the 130kHz resonant frequency correct? Have you measured it? When it is off by a big amount your coil will not swing up and you get no feedback.

Have you pulled the new files from github or did you only change some files manually? I have made several changes to the min library and other files when I implemented the ESP32.

Have you restarted the UD3 after you saved the disabled ethernet interface? The interfaces change only after a restart.

I get a error free build with the latest revision:


Please check if this works before you make any modifications. Some timing violations can be ignored.

Yes psoc creator has some bugs in the schematic with deleted connections. This should be gone if you restart creator.

You can set the task info in the "FreeRTOSConfig.h" Line 120 to 1 and give me the output of the "tasks" command, then I can check if the UART task is running.
« Last Edit: April 12, 2019, 11:12:37 PM by Netzpfuscher »

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #24 on: April 13, 2019, 09:54:41 AM »
Yesterday I set the startup cycles to 3.The 130kHz is about 10% lower than the secondary Fres.To start the coil I start transient,which locks the drive frequency to the startup frequency and feedback never takes over while the coil already produces 10 cm sparks.

I downloaded completely the new UD3.

Restarted everything many times,including PSoC creator and the dev.kit.

Here are the tasks.Many things are different after the UART_2 changes.The serial communication speed over USB looks a lot faster with the new version,have you speeded up all serial communications which might not be accepted by my bluetooth module?

Tasks without modifications:


With the UART_2 modifications:


Old(autotune bug)version which works:


Small update: the bluetooth module now runs at 115200 bps,the dev.kit still can't communicate with it.
The onboard blue LED is connected to pin 2[1] just like LED4,so if it constantly lights something is really busy on serial...
« Last Edit: April 13, 2019, 01:37:11 PM by Laci »

Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #25 on: April 13, 2019, 06:00:05 PM »
Check the latest commit.

It was a bug caused by me. I forget to enable the UART in pure serial mode. I also re enabled the blinken light ^^ 

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #26 on: April 13, 2019, 09:40:09 PM »
Woww,this fix was quite fast! ;D
I tested many functions and so far almost erverything works.While taking scopeshots I saw a strange high frequency after around the 3rd cycle.You know what that is. :D
-Yes that's the feedback which works but quite inaccurately.It stays at the same frequency,then in a 1 cm primary tap zone the frequency jumps from 130kHz to 240kHz.The new primary will be completed soon,with 11 turns of 8mm copper tubing and 4x wood holders in "+" shape.

I had to decrease the bluetooth module speed back to 9600 as the app couldn't receive long strings like a "help" command.Most of the settings in the app are pointless anyways so I might remove the unnecessary functions and leave it as a simple interrupter or make a better app in java.

Is this what they call "freewheeling current limiter"?  8)


Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #27 on: April 13, 2019, 11:16:20 PM »
Please use putty and make a "tune_p" from 80khz to 180khz and post a screenshot of the frequency response. 60V on the bridge should be enough for the sweep.

Have you installed a common mode choke in the feedback lines?

Why is your min_tr_current at 0? The default is at 100A. This is how low the midi velocity can modulate the current down.
Set the "offtime" back to 2µs this is a midi only parameter. It describes the minimal offtime between two pulses.



Offline Laci

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Re: My first DRSSTC on bricks
« Reply #28 on: April 14, 2019, 09:20:52 PM »
I finished the new primary.Like always,it's probably a complete overkill for a 50cm tall 12.5cm diameter secondary coil.Feedback is kind of working.It changes nicely when moving the tap point over around 5 turns,but at the desired frequency of about 140kHz it jumps up to 240kHz as before.Running an autotune gives correct values(140kHz),but it keeps driving at 240kHz.

The common mode choke isn't installed.The settings you mentioned are back to defaults.

5 turns(too high frequency):


6 turns(frequency is OK):

« Last Edit: April 14, 2019, 09:27:23 PM by Laci »

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #29 on: April 15, 2019, 09:28:09 PM »
Today's progress update:
I continued the mechanical assembly and it's almost done,the primary connections should be made.Did some tuning too,but I wouldn't speak about them until the design is completed(right now the peak primary current is found at 134kHz,but the drive is at 128kHz...)

The next electrical thing to add is the precharge circuit.I have some questions regarding that.If I'm right,the "bus" command turns ON or OFF Relay1 which should bypass the precharge power resistor(s).Can use "bus" command just after powering up,destroying fuses by the inrush or some additinal things are used to always avoid the inrush,like time delay or bus voltage sensing?
For current sensing can I use a module which gives 100mV/A?







Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #30 on: April 15, 2019, 10:02:19 PM »
Have you used a wide range for the autotune? The thing is, the UD3 divides the range in 127 frequency's and sweeps these. If you resonant frequency is not in this table it won't show up it is the nearest. I must test this function a little bit further. But 134 to 128 is not so much off ^^ I don't know how high the current was, but with more voltage on the bridge the result is more accurate. You can play a little bit. Also there are options for longer ontimes, more delay between the cycles and more averaging.

The precharge in default works like so:
"bus on" relay1 is activated and connects the precharge resistor to the mains. The UD3 measures the voltage on the bus and if it rises no more it activates relay2 which shorts the resistor.

You need a current transformer with current output (1000:1 works great). There is a shunt on the board and the UD3 senses this voltage and calculates the current with the ct2_ratio and ct2_burden. But if you set the burden and ratio right, you can use voltage output current transformer. You need to play with the calculation.

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #31 on: April 16, 2019, 08:46:05 PM »
I pretty much finished the assembly today.Sadly the results aren't quite good.I suspect primary EMI causing many problems,like UD3 turning OFF(or at least fault mode) after a few seconds of running,noisy gate waferom and even the bluetooth module disconnects.I was afraid of this,as shielding wouldn't be easy.Many pictures are attached below,feel free to watch them and -hopefully- correct me if I'm wrong or leave your suggestions.


Offline Laci

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Re: My first DRSSTC on bricks
« Reply #32 on: April 17, 2019, 08:14:52 PM »
Here's a video of the driver's strange behaviour at 50V.Basically it randomly changes ontime and the gate waveform is really noisy,even the bricks got warm.I noticed one capacitor arcing in the MMC,so I'm gonna rebuild it.Which one would you recommend,etching a small PCB with some large traces or just solder the series caps together by their leads and make the parallel connections with thick wires?

https://mega.nz/#!QXpAQCpD!VHqH3mPHddox_w0hZAlNTeqkEotdEfFRFYnVgWgklCk

Offline Fumeaux

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Re: My first DRSSTC on bricks
« Reply #33 on: April 17, 2019, 08:22:30 PM »
strange behaviour at 50V

I'm no expert by all means, but could it be that:
ontime changes is a result of current limiting
and
the current limiting is a result of the arcs?

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #34 on: April 17, 2019, 08:34:44 PM »
I don't think it's current limiting.For one,the current limit is set quite high and also the ontime changes randomly.I'd say EMI,but not sure.The arcing is happening due to high voltage.One thing that might happen is that the voltage rises at the frequency without that cap,then it arcs and the frequency changes.This should be gone after I remake the MMC.The gate noise is yet another mistery-it could be caused by wrong feedback,primary EMI to the GDT and primary EMI into the driver...
« Last Edit: April 17, 2019, 08:38:46 PM by Laci »

Offline Fumeaux

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Re: My first DRSSTC on bricks
« Reply #35 on: April 17, 2019, 08:51:47 PM »
The thing is that the arc cause the cap to short out which causes a current spikes. Fast changes of voltage/current and inductors don't go together too well. So it is possible that the current limit threshhold can met by a spike. Then the driver ramps the ontime down and back up.

How often does it ark anyways? And what do you mean by gate noise?

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #36 on: April 17, 2019, 09:01:40 PM »
I already took the MMC apart,so no more informations about it.  ::)

By gate noise I mean unwanted switching and spikes in the waveform.At the end of the video you might be able to see the sharp,almost vertical pulses,which increases the losses significantly.

Offline Netzpfuscher

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Re: My first DRSSTC on bricks
« Reply #37 on: April 17, 2019, 10:44:02 PM »
Have you connected the CT2 input to gnd? I think you have a floating input which picks up noise. The UD3 thinks there is to much current from mains flowing and ramps down the dutycycle / ontime.
This is one of the new features, a i2t Controller.

Online Mads Barnkob

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Re: My first DRSSTC on bricks
« Reply #38 on: April 18, 2019, 09:51:49 PM »
Great progress and big thumbs up to Netzpfuscher for the support!

You driver is just sitting in a plastic enclosure, I always use a metal box which gets grounded, switching noise is pretty massive so close to the primary coil. My large DRSSTC can knock out my camera at 50 cm distance when running with a static load.

Looking forward to see your first sparks on the UD3 and also a big thank you for sharing your fault tracings on the UD3, this will all help future builders!
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Laci

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Re: My first DRSSTC on bricks
« Reply #39 on: April 19, 2019, 09:05:15 PM »
You driver is just sitting in a plastic enclosure, I always use a metal box which gets grounded, switching noise is pretty massive so close to the primary coil. My large DRSSTC can knock out my camera at 50 cm distance when running with a static load.
A metal enclosure could probably save me from the few days already spent on troubleshooting.I have more space now,since moved the inverter and MMC to one side and I'll look for some metal boxes.
Right now the only thing I'm sure about is that EMI causes many problems.Even moving the driver box around changes the output.The driver still limits pw when the box isn't under the primary and stops driving as well as refuses to change pw from 0 when it's under the primary.

With 50V on the bus the driver gets crazy over 50us,but that depends on the distance between primary and driver box.
Gate at 50us:


Gate at 60us:


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Re: My first DRSSTC on bricks
« Reply #39 on: April 19, 2019, 09:05:15 PM »

 


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