Can air cored inductors be influenced by proximity to other conductive things such as heatsinks even if nothing actually enters the inside of the windings? I'm talking about simple ones such as this:

Hi, been away for while but back messing with electronics again 

Has anyone tried those bluetooth to aux adaptors to get an audio signal into their high voltage projects? These are the things I'm talking about.

I'm finding they have a lot of background hiss which makes the plasma speaker sound worse than it actually is (I've isolated it to the bluetooth adaptor).

Problem is these days phones all have touch screens which makes them behave weird when directly connected to such RF heavy high voltage projects so isolation is needed, old dumb phones with buttons behave when connected directly using an aux cable but then you can't use youtube videos for audio content on the fly with such old devices.

Only thing that helped was to heavily passive RC low pass the input at the plasma speakers aux jack (hiss from the bluetooth is still there but nowhere near as noticable in the arc), but the corner cutoff frequency is right down around 30khz so it cuts into the audio range too.

Is there some elaborate filter circuit I could use or maybe even some chokes to filter out this bluetooth induced hiss? Or maybe someone has found a bluetooth to aux adaptor which has clear hiss free audio.

Please share thoughts and ideas here.

Hello,

I've whipped up a plasma speaker using a flyback transformer and TL494 (sounds pretty good and loud for the lowish 30 watts power consumption), however when the high voltage is running the touchscreen on my phone goes bananas. The phone is connected to the circuit as an audio source using the 3.5mm audio jack.

What sort of filtering would I need to prevent the high voltage from interfering with the touchscreen? This is what I've currently got but it's not enough. The "clip on ferrite bead" is on the aux cable between the phone and circuit.


When I use a Bluetooth to aux adapter as a means of isolating the phone from the circuit the screen works fine. The high voltage is about 20kV open circuit and about 30 watts, switching frequency is 40khz. The circuit is 24v battery powered so all floating, the phone is also on its internal battery power.

Maybe an audio isolation transformer and more aggressive common mode/differential(?) choke? I recall this happening years ago too with an older circuit design except it was a laptop and its touchpad going haywire, back in those days phones didn't have touch screens however so it was never a problem using phones as an audio source.
 
I'm guessing the capacitive touch screen is being charged up by the high frequency high voltage with one end of the loop being completed using the audio cable.

Any advice would be appreciated!

Sorry if this is a basic question but I'm a bit rusty after almost a year since messing with this stuff.

You know those ZVS drivers and induction heater kits you get on ebay, does anyone know what types of resonant capacitors they use on them? I know they're rated for high frequency and high RMS currents, but have forgotten the what they're called such as polypropylene and MKP etc. Having to trawl through datasheets and find out if pulse and resonant duty is mentioned is very slow.

The red resin dipped job I'm currently using is getting pretty warm even in a 30w switcher!

Not my websites but some sites I've come across full of resources for HV nuts. Is it ok to still post?

http://flyback.org.ru/index.php
Its Russian but google translate is good enough for me, it's like a parallel 4hv except all the archives and posts + images from the last two decades are still up (sometimes you have to right click and open images in new tab to see them). Some interesting schematics hiding around there including designs which think outside the box.

http://danyk.cz/index_en.html
DiodeGoneWild from youtube, I swear this guy is a genius.

https://4hv.org/e107_plugins/forum/forum.php
Need I say more? Unfortunately the images don't work anymore and the archives are no longer accessible, but there's still a wealth of information in the remaining posts. The forum doesn't seem that active anymore sadly (I think that's why this place was created).

http://kaizerpowerelectronics.dk/
Ran by our lord and master Mads Barnkob, lots of good circuits and theory on there.

Any tips and tricks you guys could recommend? I've got an Nikon D3100 DSLR, but I'm having trouble getting a good shot of high voltage arcs like some of the photos I've seen around here.

I can't really explain it, but the shots and videos come out looking underwhelming. I'm thinking its the transparent nature of these arcs which are low current purple-blue color. I'm actually trying video too but the camera wants to set up for the rest of the room rather than the arc. I've tried closing the blinds slightly to darken the room during day time, but the camera adjustments are all geared toward low light in that situation.

The arcs stretch to 2 inches and when the electrodes are closer together they're at that state where the arc is pink and just starting to look like a flame. When stretched out to the max it turns that pale blue color and the arc starts to break up.

Mads I've seen on your website lots of good arc pictures and videos, any DSLR pointers?

Hello again, I'm in lockdown and have gone flyback mad!

What TVS reverse stand off and breakdown voltage would you guys select for a 400v transistor?

I've gotten myself confused when it comes to TVS datasheets. I'm running a TV flyback transformer like in the pic at 12v, it's actually quite efficient with nothing getting that warm drawing about 2 amps from the 12v supply and a 2 inch arc (still working on 24v mode). Frequency is about 15khz.

The TVS will not conduct under normal operation as the capacitor is selected to limit the peak voltage to something sensible (about 170v peak right now when the output is unloaded), the TVS is just added protection for unloaded flyback output and capacitor charging situations.


However by reducing the capacitor value and allowing the primary voltage to peak higher I can get more hv on the output without needing to increase the supply voltage, so I want to select a TVS which protects the transistor but doesn't conduct under normal operation.

But here's where I'm stuck, I've currently got a 200v TVS in there and when I retuned the capacitor to allow for more peak primary voltage the TVS clamps much harder than I expected. I'm looking at the datasheet for the P6KE200 and was expecting maximum peaks of 274v, but reality it clamps pretty close to the 200v breakdown rating rather than shooting up that large exponential curve.


I'm guessing the energy in the circuit isn't enough to push the TVS to such a high clamping level? And if that's the case what TVS voltage can I safely go up to for protecting my 400v NPN transistor (MJE13007)? Maybe the 300-350v standoff versions would be best suited, they're pretty expensive so I wanted check before ordering something which might not be a good choice, then there's the whole transistor safe operating area to further complicate things.

tl;dr which TVS diode breakdown would be a good choice for protecting a 400v transistor switching 15khz tv flyback at 2 amps average primary current?

Thanks.

In a crt tv/monitor hv flyback transformer what is the effect of making the gap in the core bigger or smaller? Let's assume the drive topology is flyback, would making the gap bigger between the two core halves allow for more output voltage/power if everything else like primary voltage, number of turns, drive frequency and duty cycle stayed the same?

Would what this guy is doing be classed as a flawed method of testing power MOSFETs? https://www.youtube.com/watch?v=YWXgMJz9IBU

To summarize, he's connected a HV ferrite cored transformer to some kind of single ended oscillator driver (not sure but could be a 555 timer) and is swapping MOSFET's on the fly to determine their worthiness based on how big of an arc he can make when used to drive the primary coil, but in a few tests he had to retune the circuit to get any kind of spark.

Is this just a case of parasitic capacitance being changed with every different fet thus the harmonic sweet spot for best arc size is being shifted around? He deems any fet which doesn't work as "not fast switching". Obviously on resistance and the breakdown/avalanche rating of the fet probably has something to do with the final output voltage (it's being run with no snubbing at 15v so avalanche ratings are probably going to clamp and limit some of them).

I'm not trying to be mean to the guy as I like his channel, but to me it doesn't seem like an accurate test.

You know those film capacitors people put in series with the tesla coils and gate drive transformer primary, how do they decide the value? Is it just a case of capacitive reactance or is there something else going on?

I've seen some people use 100nF all the way up to 10uF for tesla coils, how do they choose? I've got a little half-bridge running a CRT flyback transformer at 40khz and at first I used 1uF, but saw some improvement to the gate drive waveforms when I added an extra 1uF in parallel.