Re: Another capacitive transformer TC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

Antonio,

With regard to increasing the capacitance of the timing
capacitor C3 from 1.8nF is there any suggested
value/construction/tolerance?
maybe increase C3 by 10 to 18nF or (next best) 22nF?
Or would 10nF be acceptable?

How critical is capacitor construction/tolerance for the
timing cap?
I understand electrolytic not advisable for timing
plastic film is possibly OK and
polystyerene or silver mica is better.

My visualisation of the output circuit is this:-
 Vcc------+
          | c
          /   TR1
Pin 3-+--|    BC337
      |   \ e
      +---|------>   O/P Up to 1nF              |
          +------>   O/P Greater than1nF
          |
          100R
          |
          +------> low volt/ low Z
          |
          1R
          |
     0V --+------>GND

Am I correct?

Jolyon

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, October 11, 2002 2:31 AM
Subject: Re: Another capacitive transformer TC


> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
>
> Tesla list wrote:
> >
> > Original poster: "Jolyon Vater Cox by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
> >
> > Would Terry Fritz' Tesla Coil Tuner
> > http://hot-streamer-dot-com/TeslaCoils/Misc/TCT/TCT.htm
> > -possibly modified to include an emitter-follower output stage- be
> > sufficient to perform the ping test.
> >
> > This is an equal mark/space astable giving almost symmetrical square
wave.
>
> It would work, but with a larger timing capacitor, and with the
> output directly connected to the gap. I prefer the connection that
> uses two resistors and leaves pin 3 just for output.
>
> > Would TIP 31 npn and TIP32 pnp power transistors be suitable for the
emitter
> > follower?
>
> A complementary follower would not work correctly as a buffer with a
> direct connection to a 555 (the output would change +/- 1.2 V at each
> current reversal). What I am using is a simple emitter follower
> with a BC337 NPN transistor and a 100 Ohms resistor. The direct
> connection was enough when I was using a 1 nF primary capacitor. When
> I increased it to 5 nF I had to add the follower. I added a 1 Ohm
> resistor in series with the 100 Ohms for another output, at low voltage
> but very low impedance.
>
> Antonio Carlos M. de Queiroz
>
>
>
>
>