On Thursday, October 5, 2023 at 5:20:53 PM UTC+11, Klaus Vestergaard Kragelund wrote:> On 03-10-2023 16:59, Anthony William Sloman wrote: > > On Wednesday, October 4, 2023 at 1:41:37 AM UTC+11, Klaus Vestergaard Kragelund wrote: > >> On 03-10-2023 14:37, John Larkin wrote: > >>> On Tue, 3 Oct 2023 09:46:44 +0200, Klaus Vestergaard Kragelund <klau...@hotmail.com> wrote: > >>>> On 29-09-2023 04:09, John Larkin wrote: > >>>>> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund <klaus.k...@gmail.com> wrote: > >>>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: > >>>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> wrote: > >>>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus > >>>>>>>> Kragelund <klaus.k...@gmail.com> wrote in <903144ac-6642-4a3f...@googlegroups.com>: > >>>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: > >>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin > >>>>>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: > >>>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> wrote: > >>>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: > >>>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> wrote: > >>>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin > >>>>>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: > >>>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> wrote: > > > > <snip> > > > >>> One can stuff a bunch of current into an inductor and then dump it into a mostly-capacitive load. That can make a high-voltage half-sine. > > > > A transformer would work better - perhaps several of them in series. > > > > Dump a bunch of current into the primaries in parallel - perhaps time shifted to allow the high voltage pulse to propagate through the series connected secondaries - and rely on the parallel capacitances of the secondaries to shape the pulse into a half-sine. > > > That's what I was considering doing, but still the individual > transformer needs to be able to handle the 4.5kV isolation from winding > to winding.Multisection formers make that easy enough. A single layer of 25 micron kapton tape is good for 4kV, and several layers for rather more, so you can do it on a single section former. -- Bill Sloman, Sydney
500 volt power supply
Started by ●September 24, 2023
Reply by ●October 5, 20232023-10-05
Reply by ●October 5, 20232023-10-05
On Thu, 5 Oct 2023 08:25:19 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:>On 29-09-2023 18:16, Lasse Langwadt Christensen wrote: >> fredag den 29. september 2023 kl. 15.41.10 UTC+2 skrev Klaus Kragelund: >>> On Thursday, 28 September 2023 at 23:09:44 UTC+2, Lasse Langwadt Christensen wrote: >>>> torsdag den 28. september 2023 kl. 22.58.46 UTC+2 skrev Klaus Kragelund: >>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> >>>>>> wrote: >>>>>> >>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>>>>> Kragelund <klaus.k...@gmail.com> wrote in >>>>>>> <903144ac-6642-4a3f...@googlegroups.com>: >>>>>>> >>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin >>>>>>>>>>> <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>>>>> >>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>>>> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>>>>> >>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> This is pleasingly weird. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>>>>>>>>>>>>>> flyback. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> What's strange is that adding the two snubbers increases the LT spice >>>>>>>>>>>>>>> sim speed radically, about 10:1. >>>>>>>>>>>>>> >>>>>>>>>>>>>> Since I couldn't find a suitable flyback transformer, and I only need >>>>>>>>>>>>>> 500 volts at 10 mA, a flyback/C-W multiplier makes sense. >>>>>>>>>>>>>> >>>>>>>>>>>>>> https://www.dropbox.com/scl/fi/aquzpawfn8mfmfsnx70ra/T875_HV_6.jpg?rlkey=vfs9pexa0rgyxpo7pg1grqlb7&dl=0 >>>>>>>>>>>>> >>>>>>>>>>>>> Do you still need C11 R8 in that circuit? >>>>>>>>>>>> >>>>>>>>>>>> It doesn't need them to work, but there is a big high-Q ring when the >>>>>>>>>>>> fet turns off, and the RC damps it. It would reduce radiated EMI. And >>>>>>>>>>>> it speeds up the simulation some. >>>>>>>>>>> >>>>>>>>>>> Did you scope that? >>>>>>>>>> >>>>>>>>>> All Spice now. I'll build it when the customer gets serious. >>>>>>>>>> >>>>>>>>>>> There is a load of capacitance hanging from the MOSFET drain in that flyback multiplier ciruit >>>>>>>>>>> I would expect it to damp RF oscillations but could be wrong... >>>>>>>>>>> HV diodes have capacitance too.. >>>>>>>>>> >>>>>>>>>> The real circuit will have a lot of inductances too, what with those >>>>>>>>>> long strings of parts. It needs to be built and tested. Dremeled, to >>>>>>>>>> start. >>>>>>>>>> >>>>>>>>>> Here's an old auto-flyback C-W miltiplier prototype. I think that was >>>>>>>>>> 1400 volts. Worked fine. >>>>>>>>>> >>>>>>>>>> https://www.dropbox.com/s/yd19osiwz1z74s4/HV_Proto_2.JPG?rsw=1 >>>>>>>>> Yea, >>>>>>>>> I did a PMT supply this way: >>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_with_regulator_img_3175.jpg >>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_componet_side_img_3180.jpg >>>>>>>>> http://panteltje.nl/pub/PMT_regulated_power_supply_diagram_img_3182.jpg >>>>>>>>> >>>>>>>>> It has been in use now for many years, sits with PMT in the cardboard tube on the right, runs on batteries: >>>>>>>>> http://panteltje.nl/pub/gamma_soectrometer_IMG_4505.JPG >>>>>>>>> >>>>>>>>> Of course that is very low power, but for a bit more power, and using a real TV muliplier: >>>>>>>>> https://panteltje.nl/panteltje/pic/sc_pic/ >>>>>>>>> >>>>>>>>> No dremeling, boards are OK when they work.. >>>>>>>>> >>>>>>>>> And old TV circuits.. if you want a few kV there was / is? plenty stuff to be found on ebay. >>>>>>>> For my case, I am working on a 5W 24V to 4.5kV converter. Right now looking to use a flyback topology, with possibly usage of >>>>>>>> CCFL transformer bobbins. >>>>>>>> >>>>>>>> I am thinking about staggering the windings on 2 transformers, so the voltage across the windings will be lower, but still the >>>>>>>> individual transformer needs to handle 4.5kV insulation (functional, not safety) >>>>>>>> >>>>>>>> Due to the limiting power, it could also be tempting to use the capacitive doublers as listed elsewhere in the thread >>>>>>>> >>>>>>>> My worry goes beyond the design, also about corona effects, which comes into play at +kV voltages. Potting is surely needed. >>>>>>> >>>>>>> For a HV transformer, old TV transformers (from the CRT times) may perhaps be an option: >>>>>>> https://www.google.com/search?client=firefox-b-e&q=ebay+horizonatl+TV+output+transformer >>>>>>> 4.5 kV diodes were used for focus in color TV sets... >>>>>>> >>>>>>> >>>>>>> For a flyback, my rule of thumb (I do not use El Tea Spice), is 1 V per turn for DC input. >>>>>>> So 24 turns primary for 24 V DC supply. >>>>>>> The flyback voltage is (70/12) * 24 = 140V positive pulse if positive DC supply. >>>>>>> To get a 4.5 kV pulse you would then wind 4500 / 140 is about 32, multiplied by 24 makes 768 turns. >>>>>>> This for an EI core running at about 15 kHz (math comes from building TV output stages). >>>>>>> 768 turns is not a big deal.. >>>>>>> Spreading the turns over a segmented coil former is a good idea. >>>>>>> If you want to use a voltage multiplier then less turns are needed, use a TV multiplier, those are 'potted' >>>>>>> The 70/12 factor depends on the PWM on/off ratio of the drive you feed into the switch transistor. >>>>>>> I use Microchip PICs for that, it has a PWM unit., hardware comparators that can directly stop the PWM drive >>>>>>> for cycle by cycle current limiting, and ADCs to measure voltage and currents. >>>>>>> Maybe an old TV horizontal output transformer with build in rectifier / multiplier would do. >>>>>>> https://www.ebay.com/b/flyback-transformer/bn_7024744628 >>>>>>> to adapt use 15 kHz and add 24 turns to the core primary? >>>>>>> ... >>>>>>> :-) >>>>>>> >>>>>>> Maybe like this? >>>>>>> https://www.ebay.com/p/1692562663?iid=374326473542 >>>>>>> plenty space for 24 turns thick wire, its a 30 kV DC out, so use less PWM ... or more primary turns >>>>>>> or whatever you can find... on ebay. >>>>>>> >>>>>> High turns ratios can have two problems: voltage breakdown in the >>>>>> insulation, and winding capacitance limiting the flyback ratio. That's >>>>>> where a C-W diode multiplier helps. >>>>> I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier >>>>>> >>>>>> Old TV flybacks were pie wound to help with both problems. That makes >>>>>> a hand-wound transformer yet nastier; Sloman would love to (have >>>>>> someone else) wind that. >>>>> Pie wound, so that's adding on layers instead of across the bobbin? >>>>>> >>>>>> There are some cool old parts from CRT TVs but we wouldn't use Ebay >>>>>> parts for production. Even ISDN transformers are hard to get these >>>>>> days. And most of our boards have a component height limit below about >>>>>> 1". >>>>> I agree, Ebay does not work for production items :-) >>>>>> >>>>>> I've gravitated to the classic C-W layout with all series strings of >>>>>> caps. That's driven by the poorly-or-never defined C/V behavior of >>>>>> available ceramic caps, which encourages their use at a small fraction >>>>>> of rated voltage. >>>>> In any case for the C-W multiplier to work properly, the charging of the caps needs to be kept low. >>>>>> >>>>>> There are lots of cute flyback controller chips that do peak current >>>>>> limiting control. >>>>>> >>>>> I am using a microcontroller. Microcontroller and kV design does not sound good, right? >>>>>> I don't know how much voltage we dare generate on a regular PCB >>>>>> without coating or potting. I'm guessing that 1KV is safe and I know >>>>>> that 7KV isn't. >>>>> Potting or conformal coating is probably needed to avoid carbonization of PCB surface. >>>> how about something crazy, a car ignition coil? ratio about 1:100, isolation good for +20kV >>>> coil-on-plug can be pretty small, if you need access to both ends of the secondary a dual output coil for wasted spark has that >>> These are used for old style flash: >>> >>> https://www.aliexpress.us/item/32521417603.html?gatewayAdapt=4itemAdapt >> >> coilcraft have some ccfl transformers, but the isolation rating is quite a bit lower than your 4.5kV >> >> https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/ > >Maybe the isolation can be achieved by potting. That's a reasonable >cheap way to boost the isolation voltage.Potting is an expensive mess. A C-W multiplier can be spread out to maintain surface creepage limits. As an extreme defense against dust, it can have a cover or be conformally coated. My current plans are to have a single-inductor flyback and a C-W multiplier. That will use all multi-sourced parts (except for the control chip) and be all pick-and-place assembled, cheap parts off reels. Designing for production is different from personal projects.
Reply by ●October 5, 20232023-10-05
On Wed, 4 Oct 2023 08:24:08 -0700 (PDT), John Smiht <utube.jocjo@xoxy.net> wrote:>On Tuesday, October 3, 2023 at 10:30:48?PM UTC-5, Anthony William Sloman wrote: >> On Wednesday, October 4, 2023 at 3:00:46?AM UTC+11, John Larkin wrote: >> > On Tue, 3 Oct 2023 16:41:27 +0200, Klaus Vestergaard Kragelund<klau...@hotmail.com> wrote: >> > >On 03-10-2023 14:37, John Larkin wrote: >> > >> On Tue, 3 Oct 2023 09:46:44 +0200, Klaus Vestergaard Kragelund <klau...@hotmail.com> wrote: >> > >>> On 29-09-2023 04:09, John Larkin wrote: >> > >>>> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund <klaus.k...@gmail.com> wrote: >> > >>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >> > >>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> wrote: >> > >>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus Kragelund <klaus.k...@gmail.com> wrote in <903144ac-6642-4a3f...@googlegroups.com>: >> > >>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >> > >>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >> > >>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> wrote: >> > >>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >> > >>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> wrote: >> > >>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >> > >>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> wrote: >> <snip> >> > >>> I will generate a single pulse, about 5us long, shaped like a half wave sinusoid, at 100kHz repetition frequency. That's why I was looking at flyback, since I can control the voltage delivered simply by adjusting the primary peak current. Power seems to be less than 5W, at 4.5kV peak, duty of let's say 25%. probably below 10mA >> > >> >> > >> One can stuff a bunch of current into an inductor and then dump it into a mostly-capacitive load. That can make a high-voltage half-sine. >> > >> >> > >> This boosts 48 volts to 1400v at MHz pulse rates. >> > >> >> > >> http://www.highlandtechnology.com/DSS/T850DS.shtml >> > >> >> > >> by switching an inductor around. The energy is recovered and returned to the 48v supply after each pulse, which keeps the power dissipation under control. >> > >> >> > >> https://www.dropbox.com/scl/fi/lkjg19hvcus9xz8aeecxy/T850_Rev_C.JPG?rlkey=0pitv0zdmb0x1tz0fkw0gj3ob&raw=1 >> > >> >> > >> The really tricky stuff is on the bottom of the board, dumping heat into the water-cooled baseplate. >> > >> >> > >> At 5 us, you could make a 4KV DC supply and switch that into your load with a high-voltage mosfet. Brute force. >> > >> >> > >Yes, that could also be an idea. Will have some losses though, since it's switching into a capacitive load. >> > >> > Switching a DC supply into a capacitive load is inherently lossy, and people usually discharge the cap and waste that energy, too. >> It isn't, if the load hasn't got any resistance. Discharging the capacitor into a separate supply isn't clever. >> > So power dissipation is C*F*V^2. The inductor trick has, ideally, zero power dissipation... it just sloshes energy around. That's how I got 4 MHz out of a tiny Pockels Cell driver. >> What on earth is "F"? > >To an engineer it means, in this context, frequency. So to you it might mean something else in your fancy vocabulary. >Sloman isn't an engineer, he's a failed chemist. I don't know what symbol failed chemists use for frequency.
Reply by ●October 5, 20232023-10-05
On Thursday, October 5, 2023 at 9:22:50 AM UTC-5, John Larkin wrote:> On Wed, 4 Oct 2023 08:24:08 -0700 (PDT), John Smiht > <utube...@xoxy.net> wrote: > >> > Switching a DC supply into a capacitive load is inherently lossy, and people usually discharge the cap and waste that energy, too. > >> It isn't, if the load hasn't got any resistance. Discharging the capacitor into a separate supply isn't clever. > >> > So power dissipation is C*F*V^2. The inductor trick has, ideally, zero power dissipation... it just sloshes energy around. That's how I got 4 MHz out of a tiny Pockels Cell driver. > >> What on earth is "F"? > > > >To an engineer it means, in this context, frequency. So to you it might mean something else in your fancy vocabulary. > > > Sloman isn't an engineer, he's a failed chemist. I don't know what > symbol failed chemists use for frequency.+1
Reply by ●October 5, 20232023-10-05
On Thu, 5 Oct 2023 08:15:00 -0700 (PDT), John Smiht <utube.jocjo@xoxy.net> wrote:>On Thursday, October 5, 2023 at 9:22:50?AM UTC-5, John Larkin wrote: >> On Wed, 4 Oct 2023 08:24:08 -0700 (PDT), John Smiht >> <utube...@xoxy.net> wrote: >> >> > Switching a DC supply into a capacitive load is inherently lossy, and people usually discharge the cap and waste that energy, too. >> >> It isn't, if the load hasn't got any resistance. Discharging the capacitor into a separate supply isn't clever. >> >> > So power dissipation is C*F*V^2. The inductor trick has, ideally, zero power dissipation... it just sloshes energy around. That's how I got 4 MHz out of a tiny Pockels Cell driver. >> >> What on earth is "F"? >> > >> >To an engineer it means, in this context, frequency. So to you it might mean something else in your fancy vocabulary. >> > >> Sloman isn't an engineer, he's a failed chemist. I don't know what >> symbol failed chemists use for frequency. > >+1I'd respect his language skills more if he can ever learn the difference between its and it's.
Reply by ●October 5, 20232023-10-05
On Thu, 5 Oct 2023 08:25:19 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:>On 29-09-2023 18:16, Lasse Langwadt Christensen wrote: >> fredag den 29. september 2023 kl. 15.41.10 UTC+2 skrev Klaus Kragelund: >>> On Thursday, 28 September 2023 at 23:09:44 UTC+2, Lasse Langwadt Christensen wrote: >>>> torsdag den 28. september 2023 kl. 22.58.46 UTC+2 skrev Klaus Kragelund: >>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> >>>>>> wrote: >>>>>> >>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>>>>> Kragelund <klaus.k...@gmail.com> wrote in >>>>>>> <903144ac-6642-4a3f...@googlegroups.com>: >>>>>>> >>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin >>>>>>>>>>> <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>>>>> >>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>>>> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>>>>> >>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> This is pleasingly weird. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>>>>>>>>>>>>>> flyback. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> What's strange is that adding the two snubbers increases the LT spice >>>>>>>>>>>>>>> sim speed radically, about 10:1. >>>>>>>>>>>>>> >>>>>>>>>>>>>> Since I couldn't find a suitable flyback transformer, and I only need >>>>>>>>>>>>>> 500 volts at 10 mA, a flyback/C-W multiplier makes sense. >>>>>>>>>>>>>> >>>>>>>>>>>>>> https://www.dropbox.com/scl/fi/aquzpawfn8mfmfsnx70ra/T875_HV_6.jpg?rlkey=vfs9pexa0rgyxpo7pg1grqlb7&dl=0 >>>>>>>>>>>>> >>>>>>>>>>>>> Do you still need C11 R8 in that circuit? >>>>>>>>>>>> >>>>>>>>>>>> It doesn't need them to work, but there is a big high-Q ring when the >>>>>>>>>>>> fet turns off, and the RC damps it. It would reduce radiated EMI. And >>>>>>>>>>>> it speeds up the simulation some. >>>>>>>>>>> >>>>>>>>>>> Did you scope that? >>>>>>>>>> >>>>>>>>>> All Spice now. I'll build it when the customer gets serious. >>>>>>>>>> >>>>>>>>>>> There is a load of capacitance hanging from the MOSFET drain in that flyback multiplier ciruit >>>>>>>>>>> I would expect it to damp RF oscillations but could be wrong... >>>>>>>>>>> HV diodes have capacitance too.. >>>>>>>>>> >>>>>>>>>> The real circuit will have a lot of inductances too, what with those >>>>>>>>>> long strings of parts. It needs to be built and tested. Dremeled, to >>>>>>>>>> start. >>>>>>>>>> >>>>>>>>>> Here's an old auto-flyback C-W miltiplier prototype. I think that was >>>>>>>>>> 1400 volts. Worked fine. >>>>>>>>>> >>>>>>>>>> https://www.dropbox.com/s/yd19osiwz1z74s4/HV_Proto_2.JPG?rsw=1 >>>>>>>>> Yea, >>>>>>>>> I did a PMT supply this way: >>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_with_regulator_img_3175.jpg >>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_componet_side_img_3180.jpg >>>>>>>>> http://panteltje.nl/pub/PMT_regulated_power_supply_diagram_img_3182.jpg >>>>>>>>> >>>>>>>>> It has been in use now for many years, sits with PMT in the cardboard tube on the right, runs on batteries: >>>>>>>>> http://panteltje.nl/pub/gamma_soectrometer_IMG_4505.JPG >>>>>>>>> >>>>>>>>> Of course that is very low power, but for a bit more power, and using a real TV muliplier: >>>>>>>>> https://panteltje.nl/panteltje/pic/sc_pic/ >>>>>>>>> >>>>>>>>> No dremeling, boards are OK when they work.. >>>>>>>>> >>>>>>>>> And old TV circuits.. if you want a few kV there was / is? plenty stuff to be found on ebay. >>>>>>>> For my case, I am working on a 5W 24V to 4.5kV converter. Right now looking to use a flyback topology, with possibly usage of >>>>>>>> CCFL transformer bobbins. >>>>>>>> >>>>>>>> I am thinking about staggering the windings on 2 transformers, so the voltage across the windings will be lower, but still the >>>>>>>> individual transformer needs to handle 4.5kV insulation (functional, not safety) >>>>>>>> >>>>>>>> Due to the limiting power, it could also be tempting to use the capacitive doublers as listed elsewhere in the thread >>>>>>>> >>>>>>>> My worry goes beyond the design, also about corona effects, which comes into play at +kV voltages. Potting is surely needed. >>>>>>> >>>>>>> For a HV transformer, old TV transformers (from the CRT times) may perhaps be an option: >>>>>>> https://www.google.com/search?client=firefox-b-e&q=ebay+horizonatl+TV+output+transformer >>>>>>> 4.5 kV diodes were used for focus in color TV sets... >>>>>>> >>>>>>> >>>>>>> For a flyback, my rule of thumb (I do not use El Tea Spice), is 1 V per turn for DC input. >>>>>>> So 24 turns primary for 24 V DC supply. >>>>>>> The flyback voltage is (70/12) * 24 = 140V positive pulse if positive DC supply. >>>>>>> To get a 4.5 kV pulse you would then wind 4500 / 140 is about 32, multiplied by 24 makes 768 turns. >>>>>>> This for an EI core running at about 15 kHz (math comes from building TV output stages). >>>>>>> 768 turns is not a big deal.. >>>>>>> Spreading the turns over a segmented coil former is a good idea. >>>>>>> If you want to use a voltage multiplier then less turns are needed, use a TV multiplier, those are 'potted' >>>>>>> The 70/12 factor depends on the PWM on/off ratio of the drive you feed into the switch transistor. >>>>>>> I use Microchip PICs for that, it has a PWM unit., hardware comparators that can directly stop the PWM drive >>>>>>> for cycle by cycle current limiting, and ADCs to measure voltage and currents. >>>>>>> Maybe an old TV horizontal output transformer with build in rectifier / multiplier would do. >>>>>>> https://www.ebay.com/b/flyback-transformer/bn_7024744628 >>>>>>> to adapt use 15 kHz and add 24 turns to the core primary? >>>>>>> ... >>>>>>> :-) >>>>>>> >>>>>>> Maybe like this? >>>>>>> https://www.ebay.com/p/1692562663?iid=374326473542 >>>>>>> plenty space for 24 turns thick wire, its a 30 kV DC out, so use less PWM ... or more primary turns >>>>>>> or whatever you can find... on ebay. >>>>>>> >>>>>> High turns ratios can have two problems: voltage breakdown in the >>>>>> insulation, and winding capacitance limiting the flyback ratio. That's >>>>>> where a C-W diode multiplier helps. >>>>> I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier >>>>>> >>>>>> Old TV flybacks were pie wound to help with both problems. That makes >>>>>> a hand-wound transformer yet nastier; Sloman would love to (have >>>>>> someone else) wind that. >>>>> Pie wound, so that's adding on layers instead of across the bobbin? >>>>>> >>>>>> There are some cool old parts from CRT TVs but we wouldn't use Ebay >>>>>> parts for production. Even ISDN transformers are hard to get these >>>>>> days. And most of our boards have a component height limit below about >>>>>> 1". >>>>> I agree, Ebay does not work for production items :-) >>>>>> >>>>>> I've gravitated to the classic C-W layout with all series strings of >>>>>> caps. That's driven by the poorly-or-never defined C/V behavior of >>>>>> available ceramic caps, which encourages their use at a small fraction >>>>>> of rated voltage. >>>>> In any case for the C-W multiplier to work properly, the charging of the caps needs to be kept low. >>>>>> >>>>>> There are lots of cute flyback controller chips that do peak current >>>>>> limiting control. >>>>>> >>>>> I am using a microcontroller. Microcontroller and kV design does not sound good, right? >>>>>> I don't know how much voltage we dare generate on a regular PCB >>>>>> without coating or potting. I'm guessing that 1KV is safe and I know >>>>>> that 7KV isn't. >>>>> Potting or conformal coating is probably needed to avoid carbonization of PCB surface. >>>> how about something crazy, a car ignition coil? ratio about 1:100, isolation good for +20kV >>>> coil-on-plug can be pretty small, if you need access to both ends of the secondary a dual output coil for wasted spark has that >>> These are used for old style flash: >>> >>> https://www.aliexpress.us/item/32521417603.html?gatewayAdapt=4itemAdapt >> >> coilcraft have some ccfl transformers, but the isolation rating is quite a bit lower than your 4.5kV >> >> https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/ > >Maybe the isolation can be achieved by potting. That's a reasonable >cheap way to boost the isolation voltage.Seems that VMI used to have more multipliers. https://www.voltagemultipliers.com/products/multipliers/pvm-multipliers/ Those are pretty dinky.
Reply by ●October 5, 20232023-10-05
On 05-10-2023 19:29, John Larkin wrote:> On Thu, 5 Oct 2023 08:25:19 +0200, Klaus Vestergaard Kragelund > <klauskvik@hotmail.com> wrote: > >> On 29-09-2023 18:16, Lasse Langwadt Christensen wrote: >>> fredag den 29. september 2023 kl. 15.41.10 UTC+2 skrev Klaus Kragelund: >>>> On Thursday, 28 September 2023 at 23:09:44 UTC+2, Lasse Langwadt Christensen wrote: >>>>> torsdag den 28. september 2023 kl. 22.58.46 UTC+2 skrev Klaus Kragelund: >>>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>> wrote: >>>>>>> >>>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>>>>>> Kragelund <klaus.k...@gmail.com> wrote in >>>>>>>> <903144ac-6642-4a3f...@googlegroups.com>: >>>>>>>> >>>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>>> wrote: >>>>>>>>>>> >>>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin >>>>>>>>>>>> <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>>>>>> >>>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>>>>> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >>>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> This is pleasingly weird. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>>>>>>>>>>>>>>> flyback. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> What's strange is that adding the two snubbers increases the LT spice >>>>>>>>>>>>>>>> sim speed radically, about 10:1. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Since I couldn't find a suitable flyback transformer, and I only need >>>>>>>>>>>>>>> 500 volts at 10 mA, a flyback/C-W multiplier makes sense. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> https://www.dropbox.com/scl/fi/aquzpawfn8mfmfsnx70ra/T875_HV_6.jpg?rlkey=vfs9pexa0rgyxpo7pg1grqlb7&dl=0 >>>>>>>>>>>>>> >>>>>>>>>>>>>> Do you still need C11 R8 in that circuit? >>>>>>>>>>>>> >>>>>>>>>>>>> It doesn't need them to work, but there is a big high-Q ring when the >>>>>>>>>>>>> fet turns off, and the RC damps it. It would reduce radiated EMI. And >>>>>>>>>>>>> it speeds up the simulation some. >>>>>>>>>>>> >>>>>>>>>>>> Did you scope that? >>>>>>>>>>> >>>>>>>>>>> All Spice now. I'll build it when the customer gets serious. >>>>>>>>>>> >>>>>>>>>>>> There is a load of capacitance hanging from the MOSFET drain in that flyback multiplier ciruit >>>>>>>>>>>> I would expect it to damp RF oscillations but could be wrong... >>>>>>>>>>>> HV diodes have capacitance too.. >>>>>>>>>>> >>>>>>>>>>> The real circuit will have a lot of inductances too, what with those >>>>>>>>>>> long strings of parts. It needs to be built and tested. Dremeled, to >>>>>>>>>>> start. >>>>>>>>>>> >>>>>>>>>>> Here's an old auto-flyback C-W miltiplier prototype. I think that was >>>>>>>>>>> 1400 volts. Worked fine. >>>>>>>>>>> >>>>>>>>>>> https://www.dropbox.com/s/yd19osiwz1z74s4/HV_Proto_2.JPG?rsw=1 >>>>>>>>>> Yea, >>>>>>>>>> I did a PMT supply this way: >>>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_with_regulator_img_3175.jpg >>>>>>>>>> http://panteltje.nl/pub/PMT_HV_supply_componet_side_img_3180.jpg >>>>>>>>>> http://panteltje.nl/pub/PMT_regulated_power_supply_diagram_img_3182.jpg >>>>>>>>>> >>>>>>>>>> It has been in use now for many years, sits with PMT in the cardboard tube on the right, runs on batteries: >>>>>>>>>> http://panteltje.nl/pub/gamma_soectrometer_IMG_4505.JPG >>>>>>>>>> >>>>>>>>>> Of course that is very low power, but for a bit more power, and using a real TV muliplier: >>>>>>>>>> https://panteltje.nl/panteltje/pic/sc_pic/ >>>>>>>>>> >>>>>>>>>> No dremeling, boards are OK when they work.. >>>>>>>>>> >>>>>>>>>> And old TV circuits.. if you want a few kV there was / is? plenty stuff to be found on ebay. >>>>>>>>> For my case, I am working on a 5W 24V to 4.5kV converter. Right now looking to use a flyback topology, with possibly usage of >>>>>>>>> CCFL transformer bobbins. >>>>>>>>> >>>>>>>>> I am thinking about staggering the windings on 2 transformers, so the voltage across the windings will be lower, but still the >>>>>>>>> individual transformer needs to handle 4.5kV insulation (functional, not safety) >>>>>>>>> >>>>>>>>> Due to the limiting power, it could also be tempting to use the capacitive doublers as listed elsewhere in the thread >>>>>>>>> >>>>>>>>> My worry goes beyond the design, also about corona effects, which comes into play at +kV voltages. Potting is surely needed. >>>>>>>> >>>>>>>> For a HV transformer, old TV transformers (from the CRT times) may perhaps be an option: >>>>>>>> https://www.google.com/search?client=firefox-b-e&q=ebay+horizonatl+TV+output+transformer >>>>>>>> 4.5 kV diodes were used for focus in color TV sets... >>>>>>>> >>>>>>>> >>>>>>>> For a flyback, my rule of thumb (I do not use El Tea Spice), is 1 V per turn for DC input. >>>>>>>> So 24 turns primary for 24 V DC supply. >>>>>>>> The flyback voltage is (70/12) * 24 = 140V positive pulse if positive DC supply. >>>>>>>> To get a 4.5 kV pulse you would then wind 4500 / 140 is about 32, multiplied by 24 makes 768 turns. >>>>>>>> This for an EI core running at about 15 kHz (math comes from building TV output stages). >>>>>>>> 768 turns is not a big deal.. >>>>>>>> Spreading the turns over a segmented coil former is a good idea. >>>>>>>> If you want to use a voltage multiplier then less turns are needed, use a TV multiplier, those are 'potted' >>>>>>>> The 70/12 factor depends on the PWM on/off ratio of the drive you feed into the switch transistor. >>>>>>>> I use Microchip PICs for that, it has a PWM unit., hardware comparators that can directly stop the PWM drive >>>>>>>> for cycle by cycle current limiting, and ADCs to measure voltage and currents. >>>>>>>> Maybe an old TV horizontal output transformer with build in rectifier / multiplier would do. >>>>>>>> https://www.ebay.com/b/flyback-transformer/bn_7024744628 >>>>>>>> to adapt use 15 kHz and add 24 turns to the core primary? >>>>>>>> ... >>>>>>>> :-) >>>>>>>> >>>>>>>> Maybe like this? >>>>>>>> https://www.ebay.com/p/1692562663?iid=374326473542 >>>>>>>> plenty space for 24 turns thick wire, its a 30 kV DC out, so use less PWM ... or more primary turns >>>>>>>> or whatever you can find... on ebay. >>>>>>>> >>>>>>> High turns ratios can have two problems: voltage breakdown in the >>>>>>> insulation, and winding capacitance limiting the flyback ratio. That's >>>>>>> where a C-W diode multiplier helps. >>>>>> I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier >>>>>>> >>>>>>> Old TV flybacks were pie wound to help with both problems. That makes >>>>>>> a hand-wound transformer yet nastier; Sloman would love to (have >>>>>>> someone else) wind that. >>>>>> Pie wound, so that's adding on layers instead of across the bobbin? >>>>>>> >>>>>>> There are some cool old parts from CRT TVs but we wouldn't use Ebay >>>>>>> parts for production. Even ISDN transformers are hard to get these >>>>>>> days. And most of our boards have a component height limit below about >>>>>>> 1". >>>>>> I agree, Ebay does not work for production items :-) >>>>>>> >>>>>>> I've gravitated to the classic C-W layout with all series strings of >>>>>>> caps. That's driven by the poorly-or-never defined C/V behavior of >>>>>>> available ceramic caps, which encourages their use at a small fraction >>>>>>> of rated voltage. >>>>>> In any case for the C-W multiplier to work properly, the charging of the caps needs to be kept low. >>>>>>> >>>>>>> There are lots of cute flyback controller chips that do peak current >>>>>>> limiting control. >>>>>>> >>>>>> I am using a microcontroller. Microcontroller and kV design does not sound good, right? >>>>>>> I don't know how much voltage we dare generate on a regular PCB >>>>>>> without coating or potting. I'm guessing that 1KV is safe and I know >>>>>>> that 7KV isn't. >>>>>> Potting or conformal coating is probably needed to avoid carbonization of PCB surface. >>>>> how about something crazy, a car ignition coil? ratio about 1:100, isolation good for +20kV >>>>> coil-on-plug can be pretty small, if you need access to both ends of the secondary a dual output coil for wasted spark has that >>>> These are used for old style flash: >>>> >>>> https://www.aliexpress.us/item/32521417603.html?gatewayAdapt=4itemAdapt >>> >>> coilcraft have some ccfl transformers, but the isolation rating is quite a bit lower than your 4.5kV >>> >>> https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/ >> >> Maybe the isolation can be achieved by potting. That's a reasonable >> cheap way to boost the isolation voltage. > > Seems that VMI used to have more multipliers. > > https://www.voltagemultipliers.com/products/multipliers/pvm-multipliers/ > > Those are pretty dinky. >Haven't seen them before. Sadly, Unobtanioum
Reply by ●October 5, 20232023-10-05
On 05-10-2023 08:56, Anthony William Sloman wrote:> On Thursday, October 5, 2023 at 5:20:53 PM UTC+11, Klaus Vestergaard Kragelund wrote: >> On 03-10-2023 16:59, Anthony William Sloman wrote: >>> On Wednesday, October 4, 2023 at 1:41:37 AM UTC+11, Klaus Vestergaard Kragelund wrote: >>>> On 03-10-2023 14:37, John Larkin wrote: >>>>> On Tue, 3 Oct 2023 09:46:44 +0200, Klaus Vestergaard Kragelund <klau...@hotmail.com> wrote: >>>>>> On 29-09-2023 04:09, John Larkin wrote: >>>>>>> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund <klaus.k...@gmail.com> wrote: >>>>>>>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>>>>>>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> wrote: >>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>>>>>>>> Kragelund <klaus.k...@gmail.com> wrote in <903144ac-6642-4a3f...@googlegroups.com>: >>>>>>>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>>>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> wrote: >>>>>>>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> wrote: >>>>>>>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> wrote: >>> >>> <snip> >>> >>>>> One can stuff a bunch of current into an inductor and then dump it into a mostly-capacitive load. That can make a high-voltage half-sine. >>> >>> A transformer would work better - perhaps several of them in series. >>> >>> Dump a bunch of current into the primaries in parallel - perhaps time shifted to allow the high voltage pulse to propagate through the series connected secondaries - and rely on the parallel capacitances of the secondaries to shape the pulse into a half-sine. >>> >> That's what I was considering doing, but still the individual >> transformer needs to be able to handle the 4.5kV isolation from winding >> to winding. > > Multisection formers make that easy enough. A single layer of 25 micron kapton tape is good for 4kV, and several layers for rather more, so you can do it on a single section former. >Yes, possible. Then a little dirt creeps in, poluted path, ionization, and sparks. Joerg would write "tssss, kaboom" etc ;-)
Reply by ●October 5, 20232023-10-05
On Thursday, October 5, 2023 at 11:25:28 AM UTC-5, John Larkin wrote:> On Thu, 5 Oct 2023 08:15:00 -0700 (PDT), John Smiht > <utube...@xoxy.net> wrote: > >On Thursday, October 5, 2023 at 9:22:50?AM UTC-5, John Larkin wrote: > >> On Wed, 4 Oct 2023 08:24:08 -0700 (PDT), John Smiht > >> <utube...@xoxy.net> wrote: > >> >> > Switching a DC supply into a capacitive load is inherently lossy, and people usually discharge the cap and waste that energy, too. > >> >> It isn't, if the load hasn't got any resistance. Discharging the capacitor into a separate supply isn't clever. > >> >> > So power dissipation is C*F*V^2. The inductor trick has, ideally, zero power dissipation... it just sloshes energy around. That's how I got 4 MHz out of a tiny Pockels Cell driver. > >> >> What on earth is "F"? > >> > > >> >To an engineer it means, in this context, frequency. So to you it might mean something else in your fancy vocabulary. > >> > > >> Sloman isn't an engineer, he's a failed chemist. I don't know what > >> symbol failed chemists use for frequency. > > > >+1 > I'd respect his language skills more if he can ever learn the > difference between > > its > > and > > it's.Another +1
Reply by ●October 5, 20232023-10-05
On Thursday, October 5, 2023 at 12:56:58 PM UTC-5, Klaus Vestergaard Kragelund wrote:> On 05-10-2023 08:56, Anthony William Sloman wrote:> Multisection formers make that easy enough. A single layer of 25 micron kapton tape is good for 4kV, and several layers for rather more, so you can do it on a single section former.> > > Yes, possible. Then a little dirt creeps in, poluted path, ionization, > and sparks. Joerg would write "tssss, kaboom" etc ;-)Where is Joerg? I miss him.
