> It is probably possible to build a current limiter that
provides
> immediate visual feedback. I challenge you, or anyone
for that matter,
> to come up with such a design that is as cheap, easy,
simple, and
> foolproof as an incandescent bulb. (Well, not cheap
once the ban hits,
> which is the problem.)
Actually, this reminds me of another application... the
audio oscillator.
As is well-known, it's very difficult to make an adjustable
LC oscillator
at audio frequencies. An RC oscillaotr is possible, but
stabilising it
(so you get a reasonably non-distorted sine wave output) is
the problem.
Now many yeats ago, a guy working for Prof Terman (you do
know who I
mean, right...) solved this problem. He used a Wien bridge
circuit as the
'resonant element', in the feedback loop of a *3 amplifier.
The gain of
the latter was stabilised by a light bulb as a non-linera
resistor with
just about the right time constant.
Anyway, I read somewhere (possibly in one of Bob Pease's
columns) that
somebody had tried to improve upon this circuit using a more
modern
approach, an FET to cotnrol the gain, a carefully-designed
control loop,
etc. The result was a an oscillator with a more distorted
output than the
simple light-ulb-stailised one...
-tony
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