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Re: Another capacitive transformer TC
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
-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.
Would TIP 31 npn and TIP32 pnp power transistors be suitable for the emitter
---- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Wednesday, October 09, 2002 2:24 AM
Subject: Re: Another capacitive transformer TC
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
> Tesla list wrote:
> > Original poster: "Jolyon Vater Cox by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
> > For the Ping circuit a 555 astable will be used
> > driven from 9 volt battery.
> > R1 will mainly control frequency and R2 will mainly control the "ping"
> > length.
> > I anticipate R1=100k
> > R2=1K
> > C1=10nF
> > that should give
> > Time high =0.7*(1e5+(2*1e3))*1e-8 = 707 uS
> > Time low = 0.7*1e3*1e-8 = 7 uS
> > Frequency 1400.560224 Hz.
> > Is this OK? I understand the "ping" is produced during the "low" period.
> > this due better current sinking than sourcing capability with a 555 or
> > faster switching time on the "low" than the "high" period?
> I prefer to use a small R1 and a large R2, to have an almost square
> wave output. This leaves enough time for the dissipation of the
> transient caused by the low-high transition.
> > Would variable frequency/ "ping" length be desirable?
> It's interesting to see the effects. For example, if you adjust the
> system to produce a low pulse that lasts for twice the duration of
> the energy transfer, the pulse with start a transient, and will
> stop it when the energy returns after the first notch, removing all
> the energy from the system (except for what is lost). Curious to
> > Can Pin 3 be used for the direct excitation of circuits -without any
> > amplification or short-circuit protection for the IC or will this have
> > provided- any suggestions?Also, will a ground clip be necessary to act
> > return path for the signal?
> It's possible to use pin 3 directly. A somewhat better result is
> obtained with a transistor emitter follower driven by the 555, with
> a small (100 Ohms) emitter resistor.
> The ground connection of the system must be the same ground of the
> > I have a Telequipment D67 oscilloscope
> > (25 MHz dual-trace , analog not digital, with no storage capability)
> > this suffice for observing the results of the ping test?
> > how are the test leads connected between the ping tester, the circuit to
> > tested, and the oscilloscope?
> Ground connection to ground of system and 555. Atennuator probe
> connected to the top of L1-C1. A regular probe is ok too.
> You can use the other probe connected to the 555 output for trigger,
> or use it as an antenna to see the output voltage. Connect it to a
> piece of wire suspended close to the terminal to be observed. Look
> at the primary voltage at the same time, and put the antenna just
> close enough to be able to see the output waveform without disturbing
> the primary waveform.
> > Finally, could the "ping" tester also double as a lamp tester (with
> > antiparallel LEDs in Pin 3 output) to determine the resonant frequency
> > through the brightness of the LEDs?
> Yes, but it's easier to use the oscilloscope. You will see the resonance
> frequency directly in the ping test. The oscillator would have to run
> at the resonance frequency (or frequencies) for use with the LEDs.