Tube Challenge!! - neon

media at media at
Sun Nov 21 17:04:19 CET 1999

100V ----/\/\/----+----@@@@@@-----------+
         510K     |    L 100H           |
         R1       |                     |
                  +--( neon )--+---| |--+--/\/\/---| |---> ~100Hz
                               |  .005      5.1M   .05
                               |    C1

>A neon lamp in a tank circuit? Cool.
>I'm a little lost (normal condition for me) how it works though.
>Where is the power return?
>This is interesting stuff. More please.

This is based on a circuit patented in 1936 by Dr. Winston E. Kock of Bell
Laboratories (2,046,463).

The ground is connected between the neon lamp and C1.  The 5.1M resistor
limits the current of the output, isolating the oscillator circuit.

In a "regular" neon oscillator the timing capacitor is put across the neon
tube.  The capacitor charges until the voltage accross the cap exceeds the
breakdown point of the lamp, the neon ionizes and the resistance of the
lamp drops, discharging the cap, the voltage across the lamp and capacitor
drops, and the capacitor starts to charge again.  Taking the voltage off
the capacitor gives a saw wave, and taking the voltage off of the ground
side of the lamp generates a pulse.

When an inductor is added, it slows the discharge of C1 -- making the saw
waveform approximate a sine wave.  It's far from a perfect sine.  The wave
is more like a like a rounded triangle.  So it would have some harmonics
and a strong fundamental.  Perhaps it would be good for bass :)

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