Electrochemistry: Liquid Power Resistor for 2000VAC
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From: Jon Slaughter on 12 Mar 2010 19:04 D from BC wrote: > In article <hne3hb$taj$1(a)news.eternal-september.org>, > Jon_Slaughter(a)Hotmail.com says... >> >> D from BC wrote: >>> In article <hndvkc$ejp$1(a)news.eternal-september.org>, >>> Jon_Slaughter(a)Hotmail.com says... >>>> >>>> D from BC wrote: >>>>> I'm setting up a test circuit and I need a 100k resistor that can >>>>> handle 2000VAC for a few seconds. >>>>> >>>>> I was going to run off to the local surplus shop but got the idea >>>>> of making a liquid resistor. Saves a trip. >>>>> >>>>> I added some salt to water and got 100kohm. Copper electrodes >>>>> (all I got at the moment). >>>>> >>>>> Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? >>>>> My circuit only needs to run for 5 seconds. >>>>> >>>>> iows...Does salty water resistance vary with voltage? >>>> >>>> Why not experiment with it since you already have the setup? Try >>>> putting a 100k res in series and measure the voltage. Sweep up to >>>> 200VAC and see if the volage devates from 100VAC at the divider. >>>> >>>> I imagine if the liquid gets hot the resistance will change so you >>>> might try an ice bath. You could then try with and without the ice >>>> bath and find the deviation to get some temperature dependence >>>> relation. >>> >>> I might. I do have a isolated variable transformer and a single 2W >>> 100k resistor. >>> And I could try graphite electrodes. I found a pencil. >>> >>> I'm just wobbling between curiosity /laziness vs practicality. >>> To set up an experiment or... forget about that and run off to the >>> surplus store and get some real resistors. mmm >> >> >> If it's just for an experiment then why not put the resistor in an >> ice bath? I'm not sure how well this will help out but it should >> easily allow a 1/4W resistor to last 5 seconds? I imagine the >> resistor may last 5 seconds without the bath. The main issue is, of >> course, that the resistance may change drastically but you could try >> it and see. >> >> Use the 2W 100k resistor in an ice bath and you should be fine. You >> could put 200 liquid containers in series or parallel if you really >> wanted to have fun ;) > > I'll do that. Will report later if the 2W 100K with 2000VAC across it > failed in cold bath. You might want to insulate the wiring too, just to be on the safe side.
From: Vladimir Vassilevsky on 12 Mar 2010 19:19 John Larkin wrote: > On Fri, 12 Mar 2010 17:42:28 -0600, Vladimir Vassilevsky > <nospam(a)nowhere.com> wrote: >>John Larkin wrote: >> >> >> >>>I've seen big (as in 50' high, 12 megavolt) Marx generators that used >>>water-filled clear plastic pipes, about like a garden hose, as the >>>capacitor charging resistors. They were blue inside, copper sulphate >>>solution I think. >> >>That must be Lenin generator. >> > > I came up with a neat isolated DC-DC converter circuit. I showed it to > Phil Hobbs and he called it the Groucho Marx Generator. Yes. Everything associated with Marx is infallible by definition. However, if you mentioned Marx, you absolutely must mention Lenin unless you are speaking in pure historical context :-) VLV
From: D from BC on 12 Mar 2010 19:31 In article <gbjlp5d03n35gdoar4csrl58njp0c4q5cc(a)4ax.com>, jjlarkin(a)highNOTlandTHIStechnologyPART.com says... > > On Fri, 12 Mar 2010 10:53:36 -0800, D from BC > <myrealaddress(a)comic.com> wrote: > > >In article <hndvkc$ejp$1(a)news.eternal-september.org>, > >Jon_Slaughter(a)Hotmail.com says... > >> > >> D from BC wrote: > >> > I'm setting up a test circuit and I need a 100k resistor that can > >> > handle 2000VAC for a few seconds. > >> > > >> > I was going to run off to the local surplus shop but got the idea of > >> > making a liquid resistor. Saves a trip. > >> > > >> > I added some salt to water and got 100kohm. Copper electrodes (all I > >> > got at the moment). > >> > > >> > Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? > >> > My circuit only needs to run for 5 seconds. > >> > > >> > iows...Does salty water resistance vary with voltage? > >> > >> Why not experiment with it since you already have the setup? Try putting a > >> 100k res in series and measure the voltage. Sweep up to 200VAC and see if > >> the volage devates from 100VAC at the divider. > >> > >> I imagine if the liquid gets hot the resistance will change so you might try > >> an ice bath. You could then try with and without the ice bath and find the > >> deviation to get some temperature dependence relation. > > > >I might. I do have a isolated variable transformer and a single 2W 100k > >resistor. > >And I could try graphite electrodes. I found a pencil. > > > >I'm just wobbling between curiosity /laziness vs practicality. > >To set up an experiment or... forget about that and run off to the > >surplus store and get some real resistors. mmm > > > > I've seen big (as in 50' high, 12 megavolt) Marx generators that used > water-filled clear plastic pipes, about like a garden hose, as the > capacitor charging resistors. They were blue inside, copper sulphate > solution I think. > > John I do have CuSO4. http://en.wikipedia.org/wiki/Electrolysis_of_water 'The following cations have lower electrode potential than H+ and are therefore suitable for use as electrolyte cations: Li+, Rb+, K+, Cs+, Ba2+, Sr2+, Ca2+, Na+, and Mg2+. Sodium and lithium are frequently used, as they form inexpensive, soluble salts.' Those are all group 1 and 2 elements.. So I suppose I should use CuSO4 to prevent H2 and O2 bubbles creating resistance error on the electrodes. btw.. I barely know electrochemistry.
From: markp on 12 Mar 2010 19:36 "D from BC" <myrealaddress(a)comic.com> wrote in message news:MPG.26041fc5df0edf429896f1(a)209.197.12.12... > I'm setting up a test circuit and I need a 100k resistor that can handle > 2000VAC for a few seconds. > > I was going to run off to the local surplus shop but got the idea of > making a liquid resistor. Saves a trip. > > I added some salt to water and got 100kohm. Copper electrodes (all I got > at the moment). > > Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? > My circuit only needs to run for 5 seconds. > > iows...Does salty water resistance vary with voltage? > EBG do a nice range. You could for example put 5 560k SSP52 in parallel: http://www.ppmpower.co.uk/downloads/products/PPM295.pdf Mark.
From: D from BC on 12 Mar 2010 19:40
In article <8004pkFd3U1(a)mid.individual.net>, map.nospam(a)f2s.com says... > > "D from BC" <myrealaddress(a)comic.com> wrote in message > news:MPG.26041fc5df0edf429896f1(a)209.197.12.12... > > I'm setting up a test circuit and I need a 100k resistor that can handle > > 2000VAC for a few seconds. > > > > I was going to run off to the local surplus shop but got the idea of > > making a liquid resistor. Saves a trip. > > > > I added some salt to water and got 100kohm. Copper electrodes (all I got > > at the moment). > > > > Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? > > My circuit only needs to run for 5 seconds. > > > > iows...Does salty water resistance vary with voltage? > > > > EBG do a nice range. You could for example put 5 560k SSP52 in parallel: > http://www.ppmpower.co.uk/downloads/products/PPM295.pdf > > Mark. I might track down where I can get one. |