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RE: [TCML] RF Ground and Brass
Hi Bart,
I'm curious how you came to noting several Amps of secondary base current. On what size/power coil? Are you talking about peak or RMS Amps? On my 15/60-powered coil, I once placed a small flashlight bulb in line with the secondary base, and I think it only registered a modest glow (though my recollection is also dim). I recall that Terry Fritz (in a post dated 7-21-2000) had measured his base current, also with a 15/60 NST, as 350mA RMS.
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Tuesday, March 04, 2008 10:03 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] RF Ground and Brass
>
> Hi Gary,
>
> There can be several amps on the secondary base current to ground (much
> higher than the currents in the secondary which diminish over length)
> and in some coils too high for 18 awg if it was a continuous current.
> However, this current is time dependent, so I agree that smaller wire
> size can be used.
>
> I run 18 awg hv wire from the base to a terminal point (about 12"
> length). From the terminal point to RF ground I use 6 awg high strand,
> about 1 meter length. I haven't noticed the 18 awg getting warm, so I'm
> sure the small length from base to terminal is fine. Like everything
> else, if after running, a coiler finds the base current wire warm, then
> it's time to go bigger (thermal losses are never good). But if it's at
> ambient temp then "all is good".
>
> BTW Gary, I received my fiber optic cable and voltage converters today.
> So hopefully I can get this bps measurement going soon. Just need to
> proto up a simple circuit and I should be off and running (hoping for
> this weekend).
>
> Take care,
> Bart
>
> Lau, Gary wrote:
> > Hi Scott,
> >
> > I think folks often go overboard with unnecessarily large RF ground cables and
> connections. It's important to remember that the actual RMS current in these
> conductors is very small. It may be useful to use a fat conductor for portions that
> are very long, as a means of minimizing conductor inductance, but I'm not even
> sure that this is critically important. Minimizing the total conductor length to the
> ground rod(s) is probably the most useful point. But for a couple feet or less from
> the secondary base to a central tie-point, it's pointless to use anything heavier than
> simple stranded #14 or #18AWG - it only needs to be heavy enough to not be
> fragile. Same with the connection to the NST, Terry filter, and strike rail. I don't
> think copper vs. brass makes any difference for the ground connection, but since
> wire is typically copper, I would use that.
> >
> > The secondary base connection method advocated in the COILBUILD documents
> is silly. These are very old documents and in need of revision. Trying to secure a
> copper strap ground conductor to a copper plate, both subject to surface oxidation,
> with a rubber band, sounds like a very poor and unreliable connection. I use a 1/4-
> 20 screw connection to each end of the secondary, as both a mechanical and
> electrical connection. See http://www.laushaus.com/tesla/secondary.htm If you
> don't have access to press-fit threaded inserts, there are other ways using common
> hardware.
> >
> > Your EMI filter hookup sounds correct. My thoughts on the topic are at
> http://www.laushaus.com/tesla/emifilter.htm.
> >
> > As for surge protectors in a power strip, I've always wondered whether they are
> attempting to protect against differential (hot to neutral) spikes, or common mode
> (ground to hot & neutral) spikes. IMO, common-mode spikes are more likely, so
> I've added a couple of MOV's inside of my Variac case from hot & neutral to
> ground.
> >
> > Regards, Gary Lau
> > MA, USA
> >
> >
> >> -----Original Message-----
> >> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> >> Behalf Of Scott
> >> Sent: Sunday, March 02, 2008 7:49 PM
> >> To: tesla@xxxxxxxxxx
> >> Subject: [TCML] RF Ground and Brass
> >>
> >> Hi all,
> >>
> >> I hate to touch on two topics that are so widely discussed here, but I have
> >> a question that kind of falls into a gray area.
> >>
> >> First off, I'm on the last stage of my coils construction, the
> >> grounding. This topic has been fought over many times on the list (I just
> >> spent 2.5 hours reading over all the entries about RF ground) and have
> >> decided on the following scheme:
> >>
> >> Connections to RF ground:
> >> --Secondary Coil, follwing these insuctions :
> >> http://www.pupman.com/howto/COILBLD3.GIF
> >> --NST case
> >> --Strike Rail
> >> --"RF Power Ground" line coming out of Terry Filter. (The "NST Ground" line
> >> coming out of the Terry Filter will go into the NST case I guess...refer to
> >> the Terry Filter diagram to see the lines I'm refering too ;) )
> >>
> >> Now the Mains supply will go like this:
> >> 1.) A power strip with a surge protector will plug into a wall outlet
> >> 2.) From the surge protector, a cable will go into a EMI Filter, from Tesla
> >> Stuff:
> >> http://cgi.ebay.com/RFI-EMI-Tesla-Filter-2-x-20-Amps-115-
> >>
> 250vac_W0QQitemZ140211303737QQihZ004QQcategoryZ7288QQssPageName
> >> ZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting
> >> The side with the 3 terminals will be hooked up to the output from the surge
> >> protector, with the center terminal being the ground.
> >> 3.) The side of the EMI filter with 2 terminals will run into the NST's hot
> >> and neutral inputs.
> >>
> >> Simple Enough right?
> >>
> >> Now the RF ground itself will be right next to the coil: outside, 4 steel
> >> spikes hammered 3 feet into the Earth.
> >>
> >> Now here's my question:
> >> I have this ribbon coming off the secondary coil and 10 AWG wire coming from
> >> the NST case and strike rail, how do I actually connect them all together to
> >> the physical RF spikes? I was just gonna solder the ribbon to the spikes,
> >> and then thread the other wires through a hole in them.
> >>
> >> And a second question:
> >> For the metal grounding ribbon coming off the secondary, does it need to
> >> copper for sure? I wanted to use brass instead. At my hardware store,
> >> brass is 1/4 the cost of copper and available in more thickness's. And does
> >> the ribbon need to go all the way from the secondary base to ground
> >> spike? It would be 3 feet of ribbon that way even is the coil is right next
> >> to the RF ground!
> >>
> >> Also, the grounding on the Terry Filter seemed a little weird too, maybe
> >> someone could confirm could I'm doing it right as described.
> >>
> >> Sorry for the massive post again, but I have been piecing together this
> >> problem for the better part of the day, and would like some loose ends tided
> >> up.
> >>
> >> Thanks for all responses!
> >>
> >
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> >
> >
> >
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