Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Mads Barnkob

Pages: [1] 2 3 ... 57
1
This is a Aethra Colour CCD Webcam that was part of a system made for remote medical diagnose / consultation for patients in remote locations.

The system was mounted in a car to be mobile, so a driver could visit patients and make a call to the doctor do complete the consultation within the patients home. The system was driven by a embedded PC with a complete circuit for the interface, audio/video and running all peripherals on a RS232 daisy chain. The whole setup used some kind of GSM link to transfer the video and audio signal, seemed to be a very expensive and complex setup.

Mainboard computer thread: https://highvoltageforum.net/index.php?topic=647.0


2
Electronic circuits / Re: Cost reduction in consumer electrics
« on: December 05, 2019, 07:33:01 PM »
It is quite interesting what you can get away with and still slap a CE (if it was in Europe, I assume you must have similar rules in US?) sticker on a appliance.

For this to be legal there would have to requirements of only using this on a properly fused, ground fault detector (RCD) installation because it does not look like its double insulated, which can lessen some demands for CE mark.

There is another explanation, you can almost get away with anything, there is no check of a product before entering the European market, requirement is only you have a CE mark on, to testify that you obey the rules/laws/standards, but in reality there is little to none reimbursement against those who break it with a intended bad product. It might get removed from a country by local authorities, but a widespread ban of a manufacturer is not viable as there is no juristiction outside of Europe. So the company in Szenchen changes name, rebrands the product and off it goes again :(

3
Electronic circuits / Re: Driving Nixie-tubes with arduino
« on: December 03, 2019, 01:24:00 PM »
When I built a Nixie tube clock I used common resistors for the Cathodes. I used high voltage NPN transistors MPSA42 to interface the 5V logic to driving the individual numbers.

http://kaizerpowerelectronics.dk/general-electronics/nixie-tube-clock/

4
Voltage Multipliers / Re: HV resistor in oil
« on: December 01, 2019, 09:17:38 PM »
I would say that all resistors, wire wound, carbon or metal-oxide are rated by their internal voltage limit, the out distance is almost always way larger than their rating.

Oil submerging will however help against corona and possible flash-overs due to unbalanced voltage sharing, so there is advantages when pushing them to the limit, but it will never extend their voltage specification. They are cheap enough, just add some more :)

5
It is a very old Swedish state owned company, from 1689 they make riffles and kept doing so for 300 years. Closed down in 1989.

But among weapons, they also did kitchen appliances, bicycles, motorcycles and power tools.

Their history in brief: http://www.husqvarnagroup.com/en/history-timeline#!/p/215

The C-core transformers are rated for full operation at given current, not like today's undersized MOTs with aluminium wires. I also took apart a Husqvarna model 106 industrial kitchen microwave oven and it had a 4 kVA C-core transformer that weighed 14 kg. You can see that here:


7
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: November 25, 2019, 10:16:22 AM »
Congratulations on getting it a working state!

Your topload seems very uneven on the surface, since you have at-least two other places with breakout than from your break out point. You will get longer sparks when they just come from one place, to get that topload much more smooth and maybe use a material with larger diameter for the break out point to avoid corona on the sides of it.

8
Solid state Tesla coils / Re: Feedback current transformer doesn't work
« on: November 25, 2019, 09:11:13 AM »
It could just be a copy/paste error from the Steve Ward SSTC5 / mini SSTC that he used as inspiration. The antenna single-wire feedback was suddenly replaced by a two-wire CT and it just got referenced to ground.



The diodes are there for clamping the induced high voltages on the antenna, since corona on the antenna is pretty normal, maybe he is just missing a DC blocking capacitor like Steve Ward uses with the CT feedback here:


9
Eh, well, I tried different resistors, I can't get it to oscillate (74HC14). With a capacitor between pin 1 and ground (and much lower capacitance value, like 100k) I got some oscillations, but very inconsistent and very low peak voltage (barely 1V). I don't get it...
I'll try that feedback transformer like this one http://www.loneoceans.com/labs/sstc2/sstc2schematicv10.jpg
They use a core with 50 turns on it. What would be the ideal core (AL value) ?

We typically all make coils in the region of 40 to 500 kHz, here I have found that for all GDT, CT etc, the rule of thumb of somewhere around 5000 AL+/- 1000, will work fine. Just be sure to have the material right aswell, I have used N30 a lot. There is however also other materials in the same size core / permability range.

10
I would not put my money on those current transformers (even though they are free from many kinds of power electronics). I attached the datasheet, for 70 kHz you are looking at some 40-50% derating of the V/uS rating and it is only specified up to 110Arms (~150Apeak) which is way too low for a DRSSTC, a coil like yours is able to push some 500-800 Apeak.

GDTs are very easy to make with CAT5 network cable, you can see how I did + calculations here: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/ stick with 1:1:1:1:1. Which leads me to another question, what kind of driver are you using? If you only have UCC driver chips on the output stage that is too weak for driving bricks!

Are your bricks heating up? Since you suspect linear operation only? Do not fear too much about IGBTs getting damaged from that, they can dissipate a lot of power. If you can touch the heat sink there is not a problem.


11
Spark gap Tesla coils / Re: SGTC MK1 - An Accomplishment in Progress
« on: November 20, 2019, 07:16:24 PM »
They would have to be put in series, positive|negative - positive|negative for doubling the output voltage, whether or not you will destroy one from imbalance or not... its not exactly practical to add balancing resistors :)

Here is one that did that, on a single ZVS driver
/>
From my own experience, you have to push them real hard before they start to have corona on the outside enclosure and flash-over is not far after that, at the end of this video (input voltage was around 140VDC)


12
Hi Zanikk and welcome to HVF :)

First off, it looks like a really well built coil and setup overall, you have done your home work.

What is the resonant frequency of your secondary + topload? What is the resonant frequency of your primary tap point + MMC?

It looks like you are using some regular 3 pin current transformers used for maybe 50 Hz mains current sensing? What are those two black current monitors? Since you say it works at low voltage, but at higher it stops working, maybe you are saturating those current transformers?

Another simple test, have you tried to reverse the polarity of the primary wires or feedback transformer?

Low voltage testing can be misleading due to IGBT output capacitance being relative to C-E voltage, the higher voltage the lower output capacitance, so you will always see higher switching spikes at low voltages, yours looks a bit over damped so its actually a slow charging instead, just guess work.

13
Dual Resonant Solid State Tesla coils / Re: coil Tesla in the space
« on: November 19, 2019, 11:28:10 AM »
My artistic impression


14
Spark gap Tesla coils / Re: SGTC MK1 - An Accomplishment in Progress
« on: November 18, 2019, 12:21:53 PM »
Your proposed series connection could work, but it requires the upper secondary winding of your custom transformer to handle 15~30kV relative to the lower secondary and primaries, which are essentially at ground potential (compared to 30kV).  15~30kV is whatever voltage a single flyback output can generate.  If you can construct a custom transformer with such HV insulation, I'd suggest making your own flyback large enough to drive your project directly with one stage.  If you do try your series design, I'd add a connection from the negative (return) secondary pin of the upper flyback to it's primary.  This provides a path for any leakage current from you custom input transformer, preventing it from damaging the upper flyback.

Reversing the polarity on one of the primaries and turn one flyback transformer around, mid-point ground them and you will not surpass the voltage rating of the single transformer. But if it makes it necessary to redo the whole grounding scheme.

15
The circuit part with the drivers are on a breadboard, I know those things has a lot of parasitic capacitance, but I don't know about parasitic inductance. I was about to design a real circuit for this, but wanted to fix that heating problem before.
Yes, my IGBTs are heating quite a bit too.
Is it something common to use a little heatsink on the driver chips ? I also planned to add a bigger capacitor on the top of my tesla coil, to reduce the resonance frequency. Is 220kHz a high frequency for a SSTC ?
And do you have any tips for my circuit design to avoid those parasitic inductance ?
Is it a good idea to power my circuit through a 7812 regulator? Or it add even more potential parasitic oscillations ?
I'm using an old CRT scope for my tests. It can't measure a frequency as high as 30MHz.

A SSTC driver on a breadboard will work fine! Steve Wards Mini SSTC / SSTC 5 is a solid build, its easy to get running and very reliable, so we are looking for defective or wrong components here.

First I would like to question the GDT core material and AL value, are you sure that this core is suitable for the job? It is not coated and its material structure looks too coarse to me. A bad GDT core could explain your issues as you are properly driving the IGBTs in the linear region all the time. More GDT waveform troubleshooting: http://www.richieburnett.co.uk/temp/gdt/gdt2.html

220 kHz is far from the limit of this circuit, I built them up to 350 kHz.

Your pictures of the gate resistors on a PCB connector is no-go! You need your gate resistors mounted directly on the IGBT/MOSFET gates.

A 7812 is plenty to drive this coil at 220 kHz, even in CW mode, it might need a heat sink though :)

A good old analog 30 MHz scope is good enough to troubleshoot a SSTC at 220 kHz, you need to tidy up your wires, twisted, short paths etc, that kind of inductance optimization gives results, trying to measure them makes no sense if you are going to measure on long wires anyway. Only measure for high frequency ringing if you did all you could to reduce inductance first.

Ok, thanks you for all those information. I'm using 47 Ohm gate resistors, but discharge time is way too high (and charge time too). But if I lower them to, let say, 10-15 Ohm like everybody does, will my drivers heat even more ?
And why full bridge SSTC shematics aren't that commmon ? Primary voltage amplitude is twice as high than with a half bridge right ? Or maybe it's too hard to drive, and lead to problems like mines.

You want to switch your mosfet to switch as fast as possible = minimal heat. Large gate resistors = long switching times and = higher heat.


Actually you want to "Switch as fast as slowly possible", meaning that if you switch too fast you get ringing, but too slow and you get higher losses, you need to find the golden in-between :)


Another piece of advise, I collected some little information about SSTC design here: http://kaizerpowerelectronics.dk/tesla-coils/sstc-design-guide/

16
Dual Resonant Solid State Tesla coils / Re: coil Tesla in the space
« on: November 15, 2019, 05:40:33 PM »
Hi Alex, that is already in use in space today, it is called plasma thrusters: http://www.esa.int/ESA_Multimedia/Images/2018/06/CubeSat_micro-pulsed_plasma_thruster

Actually Weston of this forum have made amplifiers just for that, maybe he will answer if you got more specific questions :)

He showed the amplifier here: https://highvoltageforum.net/index.php?topic=820.msg5443#msg5443

17
So how much higher voltage rated MOSFETs could be used? Or have you tested?

The offline (230VAC~325VDC) fed ZVS drivers have always been a widely sought topology but it almost always ends up in flames :)

18
I received this on the Tesla Coil Mailing List ( https://www.pupman.com/mailman/listinfo/tesla ) today:

Full topic: "4. Bill Wysock's scrapbook, Frederick Finch Strong's scrapbook, T. B . Kinraide Archive, H. G. Fischer Blueprints, Electrotherapy Museum Archive, Unpublished Letters/Lectures of Tesla Family (Jeff Behary)"

Message:
Tesla group:

Some recently published photos, scrapbooks, and archives.
Not an easy thing to do...but I figured having the information out there is better than it dying with me or friends, or getting scrapped (like the Tesla family archives).
If these things were found 100 years from now they'd be considered national treasures and no one would think twice to publish them.
It's harder when it's friends.  Most of this stuff was never meant to be published... but are too priceless to be lost.  Right or wrong, I'm sorry either way.
My goal is to upload 50,000 pages by the end of the year.  The last few years have been too much.

Bill Wysock's Scrapbook and Photos
621 pages:
https://archive.org/details/billwysockscrapbooks

Tesla Technology Research
160 pages
https://archive.org/stream/billwysockscrapbooks/Bill_Wysock_TTR#mode/2up

Unpublished Letters
691 pages:
https://archive.org/details/electrotherapymuseumletters

Dr. Frederick Finch Strong's Scrapbook and Archive
Part 1:  429 Pages:
https://archive.org/details/ffs1scrapbook
Part 2:  337 Pages:
https://archive.org/stream/ffs1scrapbook/FFS_2_High_Freq_Currents#mode/2up
Part 3:  104 Pages:
https://archive.org/stream/ffs1scrapbook/FFS_3_Ajax_Replicas#mode/2up

Electrical Discharges in a Vacuum
92 Pages:
https://archive.org/details/VacuumDischargeTubesLowResolution

A selection of 11x17 blueprints from H. G. Fischer Corp
1427 Pages:
https://archive.org/details/HGFischer11x17Blueprints

T. Burton Kinraide Archive
5020 Pages
https://archive.org/details/QuestForKinraide5026pgs

Electrotherapy Museum Booklets:  1996-2003
4390 Pages
https://archive.org/details/electrotherapymuseum19962003

Jeff Behary,
or what remains of him.

19
Please do post some pictures / video of your setup, it will make it much easier to help you. It is not a beauty contest, so do not worry too much about how it looks, we all made coils that was more or less appealing to the eye :)

When you pull an arc, you are grounding or short circuiting the secondary coil, which is a very hard load on it. This pulls the frequency of the secondary LC circuit down, perhaps your circuit looses track and can not generate a new pulse and it stops. 

Pulsed mode will allow you to run with higher voltages than CW, so that is often a reason for getting longer sparks, we pulse the coils in order for the electronics to cool down between pulses of overload!

5 vs 1 turn is a huge difference! Calculate your primary reactance and you will see why you get smaller sparks. I actually put together a small SSTC design guide: http://kaizerpowerelectronics.dk/tesla-coils/sstc-design-guide/

20
The HP T-620 Thin Client is a powerful little machine, that with ease can be hacked into using a random 19VDC PSU and run Windows as any normal PC, easy and cheap PC!

This thin client was thrown out, without anything else than the box itself, no power supplies, no nothing.

/>
The port and connector layout from the manual shows that the HP T-620 models needs a 19VDC power supply. A little searching showed that it was not as simple as just supplying it with 19VDC. HP has put in a few tricks to make a "smart laptop charger" so that you can only use their chargers.



The "smart laptop charger" restriction can be bypassed with a simple current limiting hack as per this little schematics.



All credits for this hack goes to:  http://nerdipedia.com/wiki/tiki-index.php?page=Smart+laptop+charger

The machine itself is powerful enough to put a little work into modding it into a PC, running Linux or Windows off a USB disk or for some models, you can even find a spare SSD slot on the motherboard, unlucky for me, this model does not have that option.


Pages: [1] 2 3 ... 57

* Recent Topics and Posts

post Re: CW multiplier resistor string suggestions
[Voltage Multipliers]
MRMILSTAR
Today at 05:28:09 PM
post Aethra CCD Webcam Teardown - From Back When Streaming Was Expensive!
[Electronic circuits]
Mads Barnkob
Today at 01:33:30 PM
post Platter resistance & inductance
[Induction launchers, coil guns and rails guns]
klugesmith
Today at 11:41:00 AM
post Re: CW multiplier resistor string suggestions
[Voltage Multipliers]
davekni
Today at 06:50:11 AM
post Re: CW multiplier resistor string suggestions
[Voltage Multipliers]
plasma
Today at 12:00:00 AM
post CW multiplier resistor string suggestions
[Voltage Multipliers]
MRMILSTAR
December 07, 2019, 11:32:49 PM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
klugesmith
December 07, 2019, 09:54:31 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 07, 2019, 09:48:21 PM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
klugesmith
December 07, 2019, 08:59:57 PM
post Re: Cost reduction in consumer electrics
[Electronic circuits]
MRMILSTAR
December 06, 2019, 08:35:29 PM
post Re: Full bridge showing half the voltage
[Beginners]
plasma
December 06, 2019, 05:19:26 AM
post Re: Cost reduction in consumer electrics
[Electronic circuits]
davekni
December 06, 2019, 03:48:34 AM
post Re: Cost reduction in consumer electrics
[Electronic circuits]
the_anomaly
December 06, 2019, 03:35:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General chatting]
AstRii
December 06, 2019, 01:27:03 AM
post Re: Full bridge showing half the voltage
[Beginners]
plasma
December 05, 2019, 11:38:59 PM
post Re: Cost reduction in consumer electrics
[Electronic circuits]
Mads Barnkob
December 05, 2019, 07:33:01 PM
post Re: Cost reduction in consumer electrics
[Electronic circuits]
sjsimmo
December 05, 2019, 11:09:20 AM
post Cost reduction in consumer electrics
[Electronic circuits]
klugesmith
December 05, 2019, 07:25:20 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 05, 2019, 05:52:11 AM
post Re: HV resistor in oil
[Voltage Multipliers]
davekni
December 05, 2019, 05:21:07 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 04, 2019, 06:05:11 PM
post Re: Full bridge showing half the voltage
[Beginners]
shrad
December 04, 2019, 02:57:02 PM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
Uspring
December 04, 2019, 12:40:51 PM
post Re: Full bridge showing half the voltage
[Beginners]
plasma
December 04, 2019, 11:20:25 AM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
klugesmith
December 04, 2019, 08:28:15 AM
post Re: Full bridge showing half the voltage
[Beginners]
klugesmith
December 04, 2019, 07:41:21 AM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
MRMILSTAR
December 04, 2019, 05:15:49 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 04, 2019, 05:06:39 AM
post Re: HV resistor in oil
[Voltage Multipliers]
davekni
December 04, 2019, 04:31:16 AM
post Re: Full bridge showing half the voltage
[Beginners]
davekni
December 04, 2019, 04:26:38 AM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
klugesmith
December 04, 2019, 04:10:16 AM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
klugesmith
December 04, 2019, 12:28:15 AM
post Re: Full bridge showing half the voltage
[Beginners]
plasma
December 04, 2019, 12:11:32 AM
post Re: HV resistor in oil
[Voltage Multipliers]
johnf
December 03, 2019, 07:58:41 PM
post Re: Driving Nixie-tubes with arduino
[Electronic circuits]
johnf
December 03, 2019, 07:54:08 PM
post Re: Full bridge showing half the voltage
[Beginners]
klugesmith
December 03, 2019, 07:41:00 PM
post Re: Driving Nixie-tubes with arduino
[Electronic circuits]
kamelryttarn
December 03, 2019, 02:14:00 PM
post Re: Driving Nixie-tubes with arduino
[Electronic circuits]
Mads Barnkob
December 03, 2019, 01:24:00 PM
post Re: Driving Nixie-tubes with arduino
[Electronic circuits]
klugesmith
December 03, 2019, 10:45:58 AM
post Driving Nixie-tubes with arduino
[Electronic circuits]
kamelryttarn
December 03, 2019, 09:04:42 AM
post Re: Full bridge showing half the voltage
[Beginners]
plasma
December 03, 2019, 07:29:48 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 03, 2019, 05:07:28 AM
post Re: HV resistor in oil
[Voltage Multipliers]
davekni
December 03, 2019, 04:34:46 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 02, 2019, 09:06:07 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
T3sl4co1l
December 02, 2019, 10:51:33 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 02, 2019, 05:49:05 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
December 02, 2019, 04:10:14 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
December 02, 2019, 04:09:37 AM
post Re: HV resistor in oil
[Voltage Multipliers]
davekni
December 02, 2019, 03:42:16 AM
post Re: HV resistor in oil
[Voltage Multipliers]
MRMILSTAR
December 01, 2019, 10:47:18 PM