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RE: [VanDeGraaffGenerator] resistors value

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  • DOUG
    Thanks again Bert. Doug ... From: VanDeGraaffGenerator@yahoogroups.com [mailto:VanDeGraaffGenerator@yahoogroups.com] On Behalf Of Bert Hickman Sent: Tuesday,
    Message 1 of 15 , May 7, 2013
    • 0 Attachment
      Thanks again Bert.
      Doug

      -----Original Message-----
      From: VanDeGraaffGenerator@yahoogroups.com
      [mailto:VanDeGraaffGenerator@yahoogroups.com] On Behalf Of Bert Hickman
      Sent: Tuesday, May 07, 2013 12:03 PM
      To: VanDeGraaffGenerator@yahoogroups.com
      Subject: Re: [VanDeGraaffGenerator] resistors value

      Hi Doug,

      No problem - here's a PDF of the low pass filter circuit:
      http://www.capturedlightning.com/PDF/HV_Low_Pass_Filter.pdf

      Bert

      DOUG wrote:
      >
      >
      > Hi Bert; Sorry for my ignorance, but I don't know how to do the
      > (fixed font) thing.
      >
      > Doug
      >
      > ------------------------------------------------------------------------
      >
      > *From:*VanDeGraaffGenerator@yahoogroups.com
      > [mailto:VanDeGraaffGenerator@yahoogroups.com] *On Behalf Of *Bert
      > Hickman *Sent:* Monday, May 06, 2013 12:42 PM *T**o:*
      > VanDeGraaffGenerator@yahoogroups.com *Subject:* Re:
      > [VanDeGraaffGenerator] resistors value
      >
      > Hi Doug,
      >
      > Sounds great! Marx generators are notorious for blowing up charging
      > supplies via back-fed transients through the HV lines and via ground
      > bounce :^)
      >
      > You can mitigate these problems by connecting a HV low-pass filter
      > between your HV source and the input of the Marx generator. I'd
      > recommend using the following RC circuit which will prevent both
      > types of transients from nuking your HV supply. Use a fixed font
      > (Courier) to display properly.
      >
      > R1 R1 <----/\/\/\/\----o-----/\/\/\/\------> | o--/\/\/\/\-- To | R2
      > | To HV ----- | Marx Supply ----- | input | | o------------ |
      > <----/\/\/\/\----o-----/\/\/\/\------> R1 R1
      >
      > The R1 resistor values are not critical, but they should all be
      > identical - anything above 100k will work. R2 is a bleeder, so it
      > should be in the 500 - 1000 Meg range to limit power dissipation.
      > Each resistor must be capable of handling transients at least as high
      > as your maximum supply voltage (25 kV in your case). The capacitor
      > can be a simple 30 - 40 kV ceramic doorknob cap in the 500 - 2000 pF
      > range.
      >
      > Be careful not to operate your Marx generator near any solid state
      > equipment, network wiring, computers, scopes, etc., since the EMP
      > can easily trash these devices.
      >
      > Good luck and play safely!
      >
      > Bert -- Bert Hickman Stoneridge Engineering
      > http://www.capturedlightning.com
      > ***********************************************************************
      >
      >
      World's source for "Captured Lightning" Lichtenberg Figure sculptures,
      > magnetically "shrunken" coins, and scarce/out of print technical
      > books
      > ***********************************************************************
      >
      > DOUG wrote:
      >>
      >>
      >> Thanks Bert; I do have a source for the VR68 1 watt 200K ohm
      >> resistors @.25 cents each so that sounds really good to me.
      >>
      >> Do you think I will need anything between my power supply and the
      >> first stage of the Marx?
      >>
      >> Doug
      >>
      >> ----------------------------------------------------------
      >>
      >> *From:*VanDeGraaffGenerator@yahoogroups.com
      > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
      >> [mailto:VanDeGraaffGenerator@yahoogroups.com
      > <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of *Bert
      >> Hickman *Sent:* Monday, May 06, 2013 1:21 AM *T**o:*
      >> VanDeGraaffGenerator@yahoogroups.com
      > <mailto:VanDeGraaffGenerator%40yahoogroups.com> *Subject:* Re:
      >> [VanDeGraaffGenerator] resistors value
      >>
      >> Hi Doug,
      >>
      >> A couple of alternatives would be VR68 or HVR68 1 watt HV metal
      >> film or ceramic resistors.These can handle 10 kV pulses, so you'll
      >> need to use at least two, and preferably three, resistors in series
      >> per stage. In your Marx application, the resistance value is not
      >> very critical since your stage capacitance is relatively small.To
      >> limit peak power stresses, use 100k - 200kohm resistors. You may
      >> also find something similar at a better price via eBay or through
      >> other electronic surplus vendors.
      >>
      >> Bert
      >>
      >> DOUG wrote:
      >>>
      >>>
      >>> Hi Bert;Thank you for your reply. I will be charging with a 25KV
      >>> power supply. Can you suggest something other than the 1 or 2
      >>> watt resisters?
      >>>
      >>> Douglas Johnson
      >>>
      >>> ----------------------------------------------------------
      >>>
      >>> *From:*VanDeGraaffGenerator@yahoogroups.com
      > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
      >> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
      >>> [mailto:VanDeGraaffGenerator@yahoogroups.com
      > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
      >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of
      >> *Bert Hickman
      >>> *Sent:* Sunday, May 05, 2013 12:10 AM *T**o:*
      >>> VanDeGraaffGenerator@yahoogroups.com
      > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
      >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
      >>> *Subject:* Re: [VanDeGraaffGenerator] resistors value
      >>>
      >>> HiDouglas,
      >>>
      >>> There is little difference in the voltage breakdown rating for
      >>> 1W and 2W carbon composite resistors. Your resistors must be able
      >>> to withstand the transient discharge voltage (i.e., the DC
      >>> charging voltage per resistor) when the Marx fires. If they flash
      >>> over, you'll dramatically decrease the output of your Marx
      >>> generator and any internal flashovers may cause the affected
      >>> resistor to explode or permanently change resistance value.
      >>>
      >>> For short (<10 uSec) pulse duty such as your Marx generator, a 1
      >>> or 2 watt carbon composition resistor can repetitively handle a
      >>> maximum of ~5-6 kV between terminals. So, if you plan to charge
      >>> your capacitors to 30 kV per stage, you'll need to use five-six
      >>> identical resistors in series (for each stage) to share the
      >>> voltage stress.
      >>>
      >>> Bert -- Bert Hickman Stoneridge Engineering
      >>> http://www.capturedlightning.com
      >>> ***********************************************************************
      >>>
      >>>
      >
      >>>
      World's source for "Captured Lightning" Lichtenberg Figure sculptures,
      >>> magnetically "shrunken" coins, and scarce/out of print
      >>> technical books
      >>> ***********************************************************************
      >>>
      >>>
      >>>
      >
      >>>
      drj11642 wrote:
      >>>> Here is my dilemma today, I need a bunch of 2 watt solid
      >>>> carbon resistors which are almost impossible to find, and when
      >>>> they can be found they are very expensive. On the other hand I
      >>>> have lots of 240ohms 1 watt solid carbon resistors. What would
      >>>> the resulting value be with 2 of these 1 watt resistors in
      >>>> series?
      >>>>
      >>>> My project that I need these for is a Marx generator using
      >>>> 30kv-1000pf ceramic disc caps.
      >>>>
      >>>> Thanks in advance to any response to my queries.
      >>>>
      >>>> Douglas Johnson
      >>>>
      >>>>
      >>>>
      >>>>
      >>>> ------------------------------------
      >>>>
      >>>> Yahoo! Groups Links
      >>>>
      >>>>
      >>>>
      >>>>
      >>>>
      >>>
      >>>
      >>>
      >>>
      >>
      >> -- Bert Hickman Stoneridge Engineering
      >> http://www.capturedlightning.com
      >> ***********************************************************************
      >>
      >>
      >
      >>
      World's source for "Captured Lightning" Lichtenberg Figure sculptures,
      >> magnetically "shrunken" coins, and scarce/out of print technical
      >> books
      >> ***********************************************************************
      >>
      >>
      >>
      >>
      >>
      >
      >>
      >
      >
      >



      ------------------------------------

      Yahoo! Groups Links
    • DOUG
      Hi Again Bert; will 3 of the 1 watt 200 ohm VR68 s work for R2? ... From: VanDeGraaffGenerator@yahoogroups.com [mailto:VanDeGraaffGenerator@yahoogroups.com] On
      Message 2 of 15 , May 7, 2013
      • 0 Attachment
        Hi Again Bert; will 3 of the 1 watt 200 ohm VR68's work for R2?

        -----Original Message-----
        From: VanDeGraaffGenerator@yahoogroups.com
        [mailto:VanDeGraaffGenerator@yahoogroups.com] On Behalf Of Bert Hickman
        Sent: Tuesday, May 07, 2013 12:03 PM
        To: VanDeGraaffGenerator@yahoogroups.com
        Subject: Re: [VanDeGraaffGenerator] resistors value

        Hi Doug,

        No problem - here's a PDF of the low pass filter circuit:
        http://www.capturedlightning.com/PDF/HV_Low_Pass_Filter.pdf

        Bert

        DOUG wrote:
        >
        >
        > Hi Bert; Sorry for my ignorance, but I don't know how to do the
        > (fixed font) thing.
        >
        > Doug
        >
        > ------------------------------------------------------------------------
        >
        > *From:*VanDeGraaffGenerator@yahoogroups.com
        > [mailto:VanDeGraaffGenerator@yahoogroups.com] *On Behalf Of *Bert
        > Hickman *Sent:* Monday, May 06, 2013 12:42 PM *T**o:*
        > VanDeGraaffGenerator@yahoogroups.com *Subject:* Re:
        > [VanDeGraaffGenerator] resistors value
        >
        > Hi Doug,
        >
        > Sounds great! Marx generators are notorious for blowing up charging
        > supplies via back-fed transients through the HV lines and via ground
        > bounce :^)
        >
        > You can mitigate these problems by connecting a HV low-pass filter
        > between your HV source and the input of the Marx generator. I'd
        > recommend using the following RC circuit which will prevent both
        > types of transients from nuking your HV supply. Use a fixed font
        > (Courier) to display properly.
        >
        > R1 R1 <----/\/\/\/\----o-----/\/\/\/\------> | o--/\/\/\/\-- To | R2
        > | To HV ----- | Marx Supply ----- | input | | o------------ |
        > <----/\/\/\/\----o-----/\/\/\/\------> R1 R1
        >
        > The R1 resistor values are not critical, but they should all be
        > identical - anything above 100k will work. R2 is a bleeder, so it
        > should be in the 500 - 1000 Meg range to limit power dissipation.
        > Each resistor must be capable of handling transients at least as high
        > as your maximum supply voltage (25 kV in your case). The capacitor
        > can be a simple 30 - 40 kV ceramic doorknob cap in the 500 - 2000 pF
        > range.
        >
        > Be careful not to operate your Marx generator near any solid state
        > equipment, network wiring, computers, scopes, etc., since the EMP
        > can easily trash these devices.
        >
        > Good luck and play safely!
        >
        > Bert -- Bert Hickman Stoneridge Engineering
        > http://www.capturedlightning.com
        > ***********************************************************************
        >
        >
        World's source for "Captured Lightning" Lichtenberg Figure sculptures,
        > magnetically "shrunken" coins, and scarce/out of print technical
        > books
        > ***********************************************************************
        >
        > DOUG wrote:
        >>
        >>
        >> Thanks Bert; I do have a source for the VR68 1 watt 200K ohm
        >> resistors @.25 cents each so that sounds really good to me.
        >>
        >> Do you think I will need anything between my power supply and the
        >> first stage of the Marx?
        >>
        >> Doug
        >>
        >> ----------------------------------------------------------
        >>
        >> *From:*VanDeGraaffGenerator@yahoogroups.com
        > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
        >> [mailto:VanDeGraaffGenerator@yahoogroups.com
        > <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of *Bert
        >> Hickman *Sent:* Monday, May 06, 2013 1:21 AM *T**o:*
        >> VanDeGraaffGenerator@yahoogroups.com
        > <mailto:VanDeGraaffGenerator%40yahoogroups.com> *Subject:* Re:
        >> [VanDeGraaffGenerator] resistors value
        >>
        >> Hi Doug,
        >>
        >> A couple of alternatives would be VR68 or HVR68 1 watt HV metal
        >> film or ceramic resistors.These can handle 10 kV pulses, so you'll
        >> need to use at least two, and preferably three, resistors in series
        >> per stage. In your Marx application, the resistance value is not
        >> very critical since your stage capacitance is relatively small.To
        >> limit peak power stresses, use 100k - 200kohm resistors. You may
        >> also find something similar at a better price via eBay or through
        >> other electronic surplus vendors.
        >>
        >> Bert
        >>
        >> DOUG wrote:
        >>>
        >>>
        >>> Hi Bert;Thank you for your reply. I will be charging with a 25KV
        >>> power supply. Can you suggest something other than the 1 or 2
        >>> watt resisters?
        >>>
        >>> Douglas Johnson
        >>>
        >>> ----------------------------------------------------------
        >>>
        >>> *From:*VanDeGraaffGenerator@yahoogroups.com
        > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
        >> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
        >>> [mailto:VanDeGraaffGenerator@yahoogroups.com
        > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
        >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of
        >> *Bert Hickman
        >>> *Sent:* Sunday, May 05, 2013 12:10 AM *T**o:*
        >>> VanDeGraaffGenerator@yahoogroups.com
        > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
        >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
        >>> *Subject:* Re: [VanDeGraaffGenerator] resistors value
        >>>
        >>> HiDouglas,
        >>>
        >>> There is little difference in the voltage breakdown rating for
        >>> 1W and 2W carbon composite resistors. Your resistors must be able
        >>> to withstand the transient discharge voltage (i.e., the DC
        >>> charging voltage per resistor) when the Marx fires. If they flash
        >>> over, you'll dramatically decrease the output of your Marx
        >>> generator and any internal flashovers may cause the affected
        >>> resistor to explode or permanently change resistance value.
        >>>
        >>> For short (<10 uSec) pulse duty such as your Marx generator, a 1
        >>> or 2 watt carbon composition resistor can repetitively handle a
        >>> maximum of ~5-6 kV between terminals. So, if you plan to charge
        >>> your capacitors to 30 kV per stage, you'll need to use five-six
        >>> identical resistors in series (for each stage) to share the
        >>> voltage stress.
        >>>
        >>> Bert -- Bert Hickman Stoneridge Engineering
        >>> http://www.capturedlightning.com
        >>> ***********************************************************************
        >>>
        >>>
        >
        >>>
        World's source for "Captured Lightning" Lichtenberg Figure sculptures,
        >>> magnetically "shrunken" coins, and scarce/out of print
        >>> technical books
        >>> ***********************************************************************
        >>>
        >>>
        >>>
        >
        >>>
        drj11642 wrote:
        >>>> Here is my dilemma today, I need a bunch of 2 watt solid
        >>>> carbon resistors which are almost impossible to find, and when
        >>>> they can be found they are very expensive. On the other hand I
        >>>> have lots of 240ohms 1 watt solid carbon resistors. What would
        >>>> the resulting value be with 2 of these 1 watt resistors in
        >>>> series?
        >>>>
        >>>> My project that I need these for is a Marx generator using
        >>>> 30kv-1000pf ceramic disc caps.
        >>>>
        >>>> Thanks in advance to any response to my queries.
        >>>>
        >>>> Douglas Johnson
        >>>>
        >>>>
        >>>>
        >>>>
        >>>> ------------------------------------
        >>>>
        >>>> Yahoo! Groups Links
        >>>>
        >>>>
        >>>>
        >>>>
        >>>>
        >>>
        >>>
        >>>
        >>>
        >>
        >> -- Bert Hickman Stoneridge Engineering
        >> http://www.capturedlightning.com
        >> ***********************************************************************
        >>
        >>
        >
        >>
        World's source for "Captured Lightning" Lichtenberg Figure sculptures,
        >> magnetically "shrunken" coins, and scarce/out of print technical
        >> books
        >> ***********************************************************************
        >>
        >>
        >>
        >>
        >>
        >
        >>
        >
        >
        >



        ------------------------------------

        Yahoo! Groups Links
      • Bert Hickman
        Hi Doug, Yes. Bert ... *From:*VanDeGraaffGenerator@yahoogroups.com ... World s source for Captured Lightning Lichtenberg Figure sculptures, ... World s
        Message 3 of 15 , May 7, 2013
        • 0 Attachment
          Hi Doug,

          Yes.

          Bert

          DOUG wrote:
          > Hi Again Bert; will 3 of the 1 watt 200 ohm VR68's work for R2?
          >
          > -----Original Message----- From:
          > VanDeGraaffGenerator@yahoogroups.com
          > [mailto:VanDeGraaffGenerator@yahoogroups.com] On Behalf Of Bert
          > Hickman Sent: Tuesday, May 07, 2013 12:03 PM To:
          > VanDeGraaffGenerator@yahoogroups.com Subject: Re:
          > [VanDeGraaffGenerator] resistors value
          >
          > Hi Doug,
          >
          > No problem - here's a PDF of the low pass filter circuit:
          > http://www.capturedlightning.com/PDF/HV_Low_Pass_Filter.pdf
          >
          > Bert
          >
          > DOUG wrote:
          >>
          >>
          >> Hi Bert; Sorry for my ignorance, but I don't know how to do the
          >> (fixed font) thing.
          >>
          >> Doug
          >>
          >> ------------------------------------------------------------------------
          >>
          >>
          >>
          *From:*VanDeGraaffGenerator@yahoogroups.com
          >> [mailto:VanDeGraaffGenerator@yahoogroups.com] *On Behalf Of *Bert
          >> Hickman *Sent:* Monday, May 06, 2013 12:42 PM *T**o:*
          >> VanDeGraaffGenerator@yahoogroups.com *Subject:* Re:
          >> [VanDeGraaffGenerator] resistors value
          >>
          >> Hi Doug,
          >>
          >> Sounds great! Marx generators are notorious for blowing up
          >> charging supplies via back-fed transients through the HV lines and
          >> via ground bounce :^)
          >>
          >> You can mitigate these problems by connecting a HV low-pass filter
          >> between your HV source and the input of the Marx generator. I'd
          >> recommend using the following RC circuit which will prevent both
          >> types of transients from nuking your HV supply. Use a fixed font
          >> (Courier) to display properly.
          >>
          >> R1 R1 <----/\/\/\/\----o-----/\/\/\/\------> | o--/\/\/\/\-- To |
          >> R2 | To HV ----- | Marx Supply ----- | input | | o------------ |
          >> <----/\/\/\/\----o-----/\/\/\/\------> R1 R1
          >>
          >> The R1 resistor values are not critical, but they should all be
          >> identical - anything above 100k will work. R2 is a bleeder, so it
          >> should be in the 500 - 1000 Meg range to limit power dissipation.
          >> Each resistor must be capable of handling transients at least as
          >> high as your maximum supply voltage (25 kV in your case). The
          >> capacitor can be a simple 30 - 40 kV ceramic doorknob cap in the
          >> 500 - 2000 pF range.
          >>
          >> Be careful not to operate your Marx generator near any solid state
          >> equipment, network wiring, computers, scopes, etc., since the EMP
          >> can easily trash these devices.
          >>
          >> Good luck and play safely!
          >>
          >> Bert -- Bert Hickman Stoneridge Engineering
          >> http://www.capturedlightning.com
          >> ***********************************************************************
          >>
          >>
          >
          >>
          World's source for "Captured Lightning" Lichtenberg Figure sculptures,
          >> magnetically "shrunken" coins, and scarce/out of print technical
          >> books
          >> ***********************************************************************
          >>
          >>
          >>
          DOUG wrote:
          >>>
          >>>
          >>> Thanks Bert; I do have a source for the VR68 1 watt 200K ohm
          >>> resistors @.25 cents each so that sounds really good to me.
          >>>
          >>> Do you think I will need anything between my power supply and
          >>> the first stage of the Marx?
          >>>
          >>> Doug
          >>>
          >>> ----------------------------------------------------------
          >>>
          >>> *From:*VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
          >>> [mailto:VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of
          >> *Bert
          >>> Hickman *Sent:* Monday, May 06, 2013 1:21 AM *T**o:*
          >>> VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:VanDeGraaffGenerator%40yahoogroups.com> *Subject:* Re:
          >>> [VanDeGraaffGenerator] resistors value
          >>>
          >>> Hi Doug,
          >>>
          >>> A couple of alternatives would be VR68 or HVR68 1 watt HV metal
          >>> film or ceramic resistors.These can handle 10 kV pulses, so
          >>> you'll need to use at least two, and preferably three, resistors
          >>> in series per stage. In your Marx application, the resistance
          >>> value is not very critical since your stage capacitance is
          >>> relatively small.To limit peak power stresses, use 100k - 200kohm
          >>> resistors. You may also find something similar at a better price
          >>> via eBay or through other electronic surplus vendors.
          >>>
          >>> Bert
          >>>
          >>> DOUG wrote:
          >>>>
          >>>>
          >>>> Hi Bert;Thank you for your reply. I will be charging with a
          >>>> 25KV power supply. Can you suggest something other than the 1
          >>>> or 2 watt resisters?
          >>>>
          >>>> Douglas Johnson
          >>>>
          >>>> ----------------------------------------------------------
          >>>>
          >>>> *From:*VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
          >>> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
          >>>> [mailto:VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
          >>> <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of
          >>> *Bert Hickman
          >>>> *Sent:* Sunday, May 05, 2013 12:10 AM *T**o:*
          >>>> VanDeGraaffGenerator@yahoogroups.com
          >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
          >>> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
          >>>> *Subject:* Re: [VanDeGraaffGenerator] resistors value
          >>>>
          >>>> HiDouglas,
          >>>>
          >>>> There is little difference in the voltage breakdown rating for
          >>>> 1W and 2W carbon composite resistors. Your resistors must be
          >>>> able to withstand the transient discharge voltage (i.e., the
          >>>> DC charging voltage per resistor) when the Marx fires. If they
          >>>> flash over, you'll dramatically decrease the output of your
          >>>> Marx generator and any internal flashovers may cause the
          >>>> affected resistor to explode or permanently change resistance
          >>>> value.
          >>>>
          >>>> For short (<10 uSec) pulse duty such as your Marx generator, a
          >>>> 1 or 2 watt carbon composition resistor can repetitively handle
          >>>> a maximum of ~5-6 kV between terminals. So, if you plan to
          >>>> charge your capacitors to 30 kV per stage, you'll need to use
          >>>> five-six identical resistors in series (for each stage) to
          >>>> share the voltage stress.
          >>>>
          >>>> Bert -- Bert Hickman Stoneridge Engineering
          >>>> http://www.capturedlightning.com
          >>>> ***********************************************************************
          >>>>
          >>>>
          >>
          >>>>
          >
          >>>>
          World's source for "Captured Lightning" Lichtenberg Figure sculptures,
          >>>> magnetically "shrunken" coins, and scarce/out of print
          >>>> technical books
          >>>> ***********************************************************************
          >>>>
          >>>>
          >>>>
          >>
          >>>>
          >
          >>>>
          drj11642 wrote:
          >>>>> Here is my dilemma today, I need a bunch of 2 watt solid
          >>>>> carbon resistors which are almost impossible to find, and
          >>>>> when they can be found they are very expensive. On the other
          >>>>> hand I have lots of 240ohms 1 watt solid carbon resistors.
          >>>>> What would the resulting value be with 2 of these 1 watt
          >>>>> resistors in series?
          >>>>>
          >>>>> My project that I need these for is a Marx generator using
          >>>>> 30kv-1000pf ceramic disc caps.
          >>>>>
          >>>>> Thanks in advance to any response to my queries.
          >>>>>
          >>>>> Douglas Johnson
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>>> ------------------------------------
          >>>>>
          >>>>> Yahoo! Groups Links
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>>
          >>>>
          >>>>
          >>>>
          >>>
          >>> -- Bert Hickman Stoneridge Engineering
          >>> http://www.capturedlightning.com
          >>> ***********************************************************************
          >>>
          >>>
          >>
          >>>
          >
          >>>
          World's source for "Captured Lightning" Lichtenberg Figure sculptures,
          >>> magnetically "shrunken" coins, and scarce/out of print technical
          >>> books
          >>> ***********************************************************************
          >>>
          >>>
          >>>
          >>>
          >>>
          >>
          >>>
          >>
          >>
          >>
          >
          >>>
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
        • DOUG
          Hi Bert; Thank you again and thanks also to all the other members who responded to my questions regarding the build of a Marx Generator. All components are
          Message 4 of 15 , May 9, 2013
          • 0 Attachment
            Hi Bert; Thank you again and thanks also to all the other members who
            responded to my questions regarding the build of a Marx Generator.
            All components are ordered and on their way, so I will soon be soldering
            away!
            It is great to find people such as yourselves that can find time to respond
            to a, non-technical, person with a hobby quite over his head. LOL
            Thanks again to all;
            Douglas Johnson

            -----Original Message-----
            From: VanDeGraaffGenerator@yahoogroups.com
            [mailto:VanDeGraaffGenerator@yahoogroups.com] On Behalf Of Bert Hickman
            Sent: Tuesday, May 07, 2013 12:03 PM
            To: VanDeGraaffGenerator@yahoogroups.com
            Subject: Re: [VanDeGraaffGenerator] resistors value

            Hi Doug,

            No problem - here's a PDF of the low pass filter circuit:
            http://www.capturedlightning.com/PDF/HV_Low_Pass_Filter.pdf

            Bert

            DOUG wrote:
            >
            >
            > Hi Bert; Sorry for my ignorance, but I don't know how to do the
            > (fixed font) thing.
            >
            > Doug
            >
            > ------------------------------------------------------------------------
            >
            > *From:*VanDeGraaffGenerator@yahoogroups.com
            > [mailto:VanDeGraaffGenerator@yahoogroups.com] *On Behalf Of *Bert
            > Hickman *Sent:* Monday, May 06, 2013 12:42 PM *T**o:*
            > VanDeGraaffGenerator@yahoogroups.com *Subject:* Re:
            > [VanDeGraaffGenerator] resistors value
            >
            > Hi Doug,
            >
            > Sounds great! Marx generators are notorious for blowing up charging
            > supplies via back-fed transients through the HV lines and via ground
            > bounce :^)
            >
            > You can mitigate these problems by connecting a HV low-pass filter
            > between your HV source and the input of the Marx generator. I'd
            > recommend using the following RC circuit which will prevent both
            > types of transients from nuking your HV supply. Use a fixed font
            > (Courier) to display properly.
            >
            > R1 R1 <----/\/\/\/\----o-----/\/\/\/\------> | o--/\/\/\/\-- To | R2
            > | To HV ----- | Marx Supply ----- | input | | o------------ |
            > <----/\/\/\/\----o-----/\/\/\/\------> R1 R1
            >
            > The R1 resistor values are not critical, but they should all be
            > identical - anything above 100k will work. R2 is a bleeder, so it
            > should be in the 500 - 1000 Meg range to limit power dissipation.
            > Each resistor must be capable of handling transients at least as high
            > as your maximum supply voltage (25 kV in your case). The capacitor
            > can be a simple 30 - 40 kV ceramic doorknob cap in the 500 - 2000 pF
            > range.
            >
            > Be careful not to operate your Marx generator near any solid state
            > equipment, network wiring, computers, scopes, etc., since the EMP
            > can easily trash these devices.
            >
            > Good luck and play safely!
            >
            > Bert -- Bert Hickman Stoneridge Engineering
            > http://www.capturedlightning.com
            > ***********************************************************************
            >
            >
            World's source for "Captured Lightning" Lichtenberg Figure sculptures,
            > magnetically "shrunken" coins, and scarce/out of print technical
            > books
            > ***********************************************************************
            >
            > DOUG wrote:
            >>
            >>
            >> Thanks Bert; I do have a source for the VR68 1 watt 200K ohm
            >> resistors @.25 cents each so that sounds really good to me.
            >>
            >> Do you think I will need anything between my power supply and the
            >> first stage of the Marx?
            >>
            >> Doug
            >>
            >> ----------------------------------------------------------
            >>
            >> *From:*VanDeGraaffGenerator@yahoogroups.com
            > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
            >> [mailto:VanDeGraaffGenerator@yahoogroups.com
            > <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of *Bert
            >> Hickman *Sent:* Monday, May 06, 2013 1:21 AM *T**o:*
            >> VanDeGraaffGenerator@yahoogroups.com
            > <mailto:VanDeGraaffGenerator%40yahoogroups.com> *Subject:* Re:
            >> [VanDeGraaffGenerator] resistors value
            >>
            >> Hi Doug,
            >>
            >> A couple of alternatives would be VR68 or HVR68 1 watt HV metal
            >> film or ceramic resistors.These can handle 10 kV pulses, so you'll
            >> need to use at least two, and preferably three, resistors in series
            >> per stage. In your Marx application, the resistance value is not
            >> very critical since your stage capacitance is relatively small.To
            >> limit peak power stresses, use 100k - 200kohm resistors. You may
            >> also find something similar at a better price via eBay or through
            >> other electronic surplus vendors.
            >>
            >> Bert
            >>
            >> DOUG wrote:
            >>>
            >>>
            >>> Hi Bert;Thank you for your reply. I will be charging with a 25KV
            >>> power supply. Can you suggest something other than the 1 or 2
            >>> watt resisters?
            >>>
            >>> Douglas Johnson
            >>>
            >>> ----------------------------------------------------------
            >>>
            >>> *From:*VanDeGraaffGenerator@yahoogroups.com
            > <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
            >> <mailto:%2AVanDeGraaffGenerator%40yahoogroups.com>
            >>> [mailto:VanDeGraaffGenerator@yahoogroups.com
            > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
            >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>] *On Behalf Of
            >> *Bert Hickman
            >>> *Sent:* Sunday, May 05, 2013 12:10 AM *T**o:*
            >>> VanDeGraaffGenerator@yahoogroups.com
            > <mailto:VanDeGraaffGenerator%40yahoogroups.com>
            >> <mailto:VanDeGraaffGenerator%40yahoogroups.com>
            >>> *Subject:* Re: [VanDeGraaffGenerator] resistors value
            >>>
            >>> HiDouglas,
            >>>
            >>> There is little difference in the voltage breakdown rating for
            >>> 1W and 2W carbon composite resistors. Your resistors must be able
            >>> to withstand the transient discharge voltage (i.e., the DC
            >>> charging voltage per resistor) when the Marx fires. If they flash
            >>> over, you'll dramatically decrease the output of your Marx
            >>> generator and any internal flashovers may cause the affected
            >>> resistor to explode or permanently change resistance value.
            >>>
            >>> For short (<10 uSec) pulse duty such as your Marx generator, a 1
            >>> or 2 watt carbon composition resistor can repetitively handle a
            >>> maximum of ~5-6 kV between terminals. So, if you plan to charge
            >>> your capacitors to 30 kV per stage, you'll need to use five-six
            >>> identical resistors in series (for each stage) to share the
            >>> voltage stress.
            >>>
            >>> Bert -- Bert Hickman Stoneridge Engineering
            >>> http://www.capturedlightning.com
            >>> ***********************************************************************
            >>>
            >>>
            >
            >>>
            World's source for "Captured Lightning" Lichtenberg Figure sculptures,
            >>> magnetically "shrunken" coins, and scarce/out of print
            >>> technical books
            >>> ***********************************************************************
            >>>
            >>>
            >>>
            >
            >>>
            drj11642 wrote:
            >>>> Here is my dilemma today, I need a bunch of 2 watt solid
            >>>> carbon resistors which are almost impossible to find, and when
            >>>> they can be found they are very expensive. On the other hand I
            >>>> have lots of 240ohms 1 watt solid carbon resistors. What would
            >>>> the resulting value be with 2 of these 1 watt resistors in
            >>>> series?
            >>>>
            >>>> My project that I need these for is a Marx generator using
            >>>> 30kv-1000pf ceramic disc caps.
            >>>>
            >>>> Thanks in advance to any response to my queries.
            >>>>
            >>>> Douglas Johnson
            >>>>
            >>>>
            >>>>
            >>>>
            >>>> ------------------------------------
            >>>>
            >>>> Yahoo! Groups Links
            >>>>
            >>>>
            >>>>
            >>>>
            >>>>
            >>>
            >>>
            >>>
            >>>
            >>
            >> -- Bert Hickman Stoneridge Engineering
            >> http://www.capturedlightning.com
            >> ***********************************************************************
            >>
            >>
            >
            >>
            World's source for "Captured Lightning" Lichtenberg Figure sculptures,
            >> magnetically "shrunken" coins, and scarce/out of print technical
            >> books
            >> ***********************************************************************
            >>
            >>
            >>
            >>
            >>
            >
            >>
            >
            >
            >



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