RE: The PING Test

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

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Antonio -

It may be possible to make a Ping oscillator using a 555 but I have not
tried this circuit. It may be necessary to add an operational amplifier to
provide a low impedance source.

In Terman's Radio Engineer's Handbook he points out that the secondary
voltage in the coupled circuit (Tesla coil) and the effective Q would be
slightly lower than the actual voltage and Q of the secondary coil alone. I
take this to mean that losses determine the amount of secondary voltage in
the TC system. Part of these losses are in the secondary circuit and are
determined by the Q factor of the secondary coil as in the equation
    R = 6.283 FL/Q
where R represents the losses. A smaller R would mean a larger Q and a
higher secondary voltage.

Do you have any comments on my question in the original post? Should the
turns be increased or decreased to increase the secondary voltage and spark
length with the same H/D coilform?

John Couture

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, September 24, 2002 6:53 PM
To: tesla-at-pupman-dot-com
Subject: Re: The PING Test


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: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
> The Ping Test is the most fundamental of all Tesla coil tests. The TC
> operates using a dampened wave and the Ping test also uses a dampened wave
> unlike other tests. A robust pulse generator is needed for good results. I
> used a HP 214A which can produce  pulses of 100 volts into a 50 ohm load.
> These pulse generators are still available on the surplus market at
> resonable prices.

A simple oscillator made with a 555 timer, directly connected to the
coil, produces the same effect. Smaller of course, but the ringing
can easily be observed with an oscilloscope and an antenna.

> A crucial and difficult to determine TC parameter of the secondary coil is
> the Q factor of the coil. The Q factor can be used to estimate the
secondary
> voltage of the TC. The equation is
>       Vs = Q x Vp   where Vs = secondary voltage
>       Vp = primary voltage

This is not correct. The maximum output voltage is given, in a
capacitive
discharge coil, by Vp*sqrt(C2/C1), where C2 is the combination of the
secondary coil self-capacitance and the capacitance of the terminal, and
C1 is the primary capacitor. A good fraction of this absolute maximum
can be easily reached with any decent Q, and infinite Q will not cause
the limit to be exceeded.

Antonio Carlos M. de Queiroz