RE: Multi-layered Sec + bat (fwd)

To: tesla-at-pupman-dot-com
Subject: RE: Multi-layered Sec + bat (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Tue, 31 Mar 1998 22:51:41 -0700 (MST)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: 31 Mar 1998 13:57:16 -0800
From: Dale Hall <Dale.Hall-at-trw-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Cc: Alex Erpel <aerpel-at-pil-dot-net>
Subject: RE: Multi-layered Sec + bat

RE: Multi-layered Sec + batt

snips....
From:  Alfred C. Erpel (Home) [SMTP:aerpel-at-pil-dot-net]
Sent:  Tuesday, March 24, 1998 6:14 PM
To:  Tesla List
Subject:  RE: Multi-layered Sec + batt

> From:  Dale Hall [SMTP:Dale.Hall-at-trw-dot-com]
> Sent:  Monday, March 23, 1998 5:11 PM

> Hi  Alfred,
> I have been using battery power TC's regularily. I use conventional.....

>Please explain the details of your vacuum switch
>(manufacturer, size, part number, etc.) I was thinking of using a small
>vacuum tube as a spark gap for this type of low power application.....

I picked up the "T" shaped vacuum switch at the TRW electronics swapmeet. 
It has no markings. A soleniod coil is attached for switching which I do not use.
The movable electrode of the SPDT is attached by a metal diaphram bonded to
 the glass.  Right now I have it over top and out of the way, forming a spark gap
 between the two remaining electrodes. They appear to be 1/8" tungsten.

>From my Ipri scope photos using .1uF -at-5kVDC the current was ~600A p-pk so 
somewhat beefy electrodes are necessary - and ones that will not create (W) ion 
clouds that will spoil an otherwise nice quench (opening of the switch).

You are unlikely to find tubes with beefy enough elements close enough
 together but what else are tubes good for ? You may have to set up a trigger
mechanism which may get vaporized upon first use.

I have alot of SPST vacuum switches from Jennings that work nicely and are 
just a little larger than the "T" with electrode diameters from 1/8" up to 1"  (glass
encl = 3"x6" rated 50kV,  Irms=400A  ~$80 -at- swapmeet) I purchased Jennings
25-50kV Vac Sw's from Bill Wysock for ~$20 at the swapmeet. I looked at the
Jennings site - not much help, but they have mf'd a great variety of vacuum 
switches (interrupters).  The cupped electrode variety may take more repititions
as the tungsten gets deposited in the metal cup rather than the glass, though I 
have some glass ones that are almost opague that still work OK.

>.......I just acquired but
>have not yet learned how to use a very nice dual channel Hewlett-Packard
>analog scope, I also have a function generator and counter.  I  would love
>to pay someone to tutor me to kick start me in their use. I live 30 miles
>north of Philadelphia....

I am originally from Pittsburgh -- K3MNN. (previous girlF lives in Reading)
What is your age and background ?  What model is the hp scope ?
It is likely you will learn the scope very quickly. Send Email with questions.
Use your pulse generator to switch a FET or bipolar transistor connected to
an inductor and observe the ringdown at LOW voltage - a bonus would be to be
variable rise/fall times (quench) and observe affect on ring.. now you know
what to expect from your Tesla Coil ! (spark gap is messier than controlled sw.
Controlled (DC) tesla excitation is easier to scope. But you will need a camera
or computer interface to capture the waveforms to review, or use a fast enough 
repetition rate for presistent viewing (an advantage of newer DSO's=print/display)
Do you have 10x or 100x or current probe(s) ?
For my tests I used an active current probe on the low side of the Pri and 
sync on it (the gap firing starts the sweep). Ch 2:  a 10x probe with 1" wire
antenna probe situated about 4' from the base of the coil (adj as necessary).
I've read some coilers just use a piece of coax but that provides no isolation
to the sensitive scope electronics (read -- ZAP).  (BTW I saw a Tek storage 
scope at last Sat's Swapmeet for $80 and thought of you).

Dale