[GreenKeys] Eico EC 700 - Re: Loop supply, or are we still beating out wifes and kicking the dog

[drlegendre .]

Fair enough, sounds as reasonable as anything said so far. So let's see if
we can tip that balance as bit.. to my disfavor. ;-)

Simply put, I don't see why this circuit should work. If you notice, both
leads of +all+ caps are connected to what should be the same voltage
potential. Both leads connect to B- with a 3M3 resistor in series with each
lead. No functional level of current should flow into any capacitor, at any
point. It seems that the operation of the circuit is predicated on the
initial discharge of at least one NE-2E lamp.

But with 3M3 series resistors, the current could never rise high enough to
break-over the lamp, could it? Datasheet calls for a 100K resistor for
100-125V operation. 3M3 is, well, 33X that figure.

Quiescent neon lamps are generally considered to be open-circuit. Of
course, there must be +some+ leakage.. but in the nano-amps? Is that
leakage the factor that actually allows this circuit to function?

(Normally, RC / neon oscs. consist of a C across the neon, and a series R
in one leg to limit the charging rate of the C. When the C rises to
breakdown voltage, the lamp discharges and the cycle repeats. Output
voltage is a sawtooth / ramp wave.)

On Tue, May 31, 2016 at 10:01 AM, Jones, Douglas W <
douglas-w-jones at uiowa.edu> wrote:

> On May 29, 2016, at 7:23 PM, drlegendre . wrote:
>
> >
> http://www.spoilsportmotors.com/Eico%20Electronic%20Mystifier%20kit%20from%206th%20grade.pdf
>
> > Rather than just six identical neon / RC relaxation oscs. (6 pcs. each
> of R, C and NE-2) it has 3 additional caps. It looks like the caps are
> wired such that the discharge of one circuit prompts the discharge a second
> connected circuit, and so on down the line..?
>
> No, the wiring is such that the discharge of any lamp will turn off 2 or 3
> of the others (or if they are off, do nothing to them).  For example, when
> NE-3 turns on, it turns off NE-1, NE-5 and NE-6.  When NE-1 turns on, it
> turns off NE-4 and NE-5.  When NE-5 turn on, it turns off NE-1 and NE-2.
>
> I'm not convinced that it's fully deterministic, since the turn-on times
> of NE bulbs in relaxation oscillators are influenced by things like cosmic
> rays, and there are races in this circuit where multiple bulbs may come on
> at the same time.  The winning bulb in such a race may suppress the turn-on
> of the other.
>
> However, not all sequences are possible, so I'd suggest that this is at
> most a semi-deterministic circuit.  Cute.
>
>                 Doug Jones
>                 jones at cs.uiowa.edu
>
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