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Re: Small tesla coil (1sq ft) findings (fwd)



---------- Forwarded message ----------
Date: Thu, 25 Jun 1998 13:20:17 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Small tesla coil (1sq ft) findings

I might be able to help:

> From:  Jeff Corr [SMTP:corr-at-enid-dot-com]
> Sent:  Wednesday, June 24, 1998 1:42 AM
> To:  Tesla List
> Subject:  Re: Small tesla coil (1sq ft) findings
> 
> As am I, but that did not cover the question.
> One or two single 9 volt batteries.  Assuming each one
> can put out around one amp of current at any given time
> for short periods of time, then that only gives you 9 watts.
> Although as demonstrated with any basic photoflash circuit,
> the instantaneous discharge of one of these is higher than 300
> watts for the two circuits I have.  (350 volts at .98 amp peak
> around 343 watts) This from a battery (1.5v AA) only capable of
> supplying around 1.5 watts.
> 
> This of course would only generate one spark.  Could one, I wonder,
> perfect a circuit, taking into account of one 9 volt alk. cell, to
> supply a specific rate of discharge.  For ex, a POT allowing the user
> to adjust the discharge rate from 2 discharges a second up to 20 or
> so, but of course, the higher the rate, the smaller the wattage would
> be.  I would be interested in bread-boarding a circuit if anyone wants
> to design one...

I did design a 30W+ true flyback switcher (custom designed 
transformer and all) which I published on the HVLIST for those 
interested. With a much improved output smoothing cap, it generates 
nearly 20kVDC. It is one of my key pieces of test gear for 
investigating TC operation. I do run very small coils from it 
repetitively for a laff but it is really used for serious single shot 
testing on much larger coils.

     I currently have a new design on the drawing board for direct 
offline charging. Output capacity is 700W+. The transformer is built
and waiting for me to get around to doing some more construction of 
the electronics when time permits.

     My love affair with constant power switchers has to do with 
knowing accurately the primary power the coils are running from
so making meaningful comparisons possible. Quenching is a breeze and 
I have a scheme on the drawing board involving optical feedback from 
the gap to assist with quenching at higher power levels by shutting 
the circuit down. Close the gap up and watch BPS rise in proportion. 

Malcolm
<snip>