>> I really don't get what the problem is.

> You have forgotten who is asking a favor of whom.

Not wanting to be rude, really, but he is asking questions of people
who are "happy enough" with his mode of presentation and is not asking
them of those who are not. Most people understand this implicitly.
Still not meaning to be rude - you he has not asked explicitly, but
you won't accept that. He doesn't want you to answer, he is asking you
not to answer, and he would consider his world a better place if you
didn't intrude, as requested. Now, it may well be that his world would
be better still if he could either just ignore your input completely,
or could lightly sift it for the larger gems and take any he finds and
let the rest go. But he says he is unable o ignore your input even
though he doesn't want it. So ... .

> The really amazing thing
> is that he spent more time whining about my response than to simply provi=
de
> the link that takes you straight to the real schematic.

Genuinely - one could equally argue that you spent more time asking
(and whining could arguably be used, but whatever ...) than just
clicking on the links he provided.

An issue is that, while there is often considerable or some merit in
your suggestions, your standards will always be uncertain of having
been attained, are liable to be set higher if they seem to have been
reached and do not always seem as reasonable to others as they do to
you. The top/bottom/middle posting argument is a parallel example.
While I agree with your comments in general about posting style, and
while I find blind thoughtless top posting and lack of trimming
annoying, there are occasions where it is OK enough that it doesn't
matter very much at all. To pedantically hew to a rule set for the
sake of doing so doesn't help overall.

Here you say that he should provide a single link directly to a single
circuit. I agree that that would have been easier on people's minds
and time than to do what he did BUT the difference seems (to me and
probably to most others) so vanishingly small as to be utterly not
worth commenting on or complaining about. A worse feature of his
approach was the slight uncertainty introduced by showing  the circuit
in  two parts.Even if these had been on a single page and accessed
with a single click on a link, there would still be some slight
uncertainty.

>> Not the ultimate diagram, I'll be bound, but conveys his point well
>> enough , I think. (BIMBW).

> Why are you making diagrams for him?

I didn't make the diagram per se - I simply juxtaposed  the two
diagrams that he had provided on a single sheet and attached it to my
email. The diagrams proper are his.

> Not only does that waste your time
> although that's your business, but it lets him get away with being stubbo=
rn
> and refusing to provide a single clear link.

This is philosophy.
There is merit in what you say BUT it is not the only way to do
things. It may seem a better way to some or many, but he doesn't HAVE
to do things the very best way, as long as his way is acceptable to
most or (as is probably the case here) acceptable enough to the vast
majority.

>> A few more suitably located resistors may tame it.

> The circuit as drawn is a bad idea because of the zener leakage and the v=
ery
> unpredictable minimum fire current of the SCR. =A0Either put a pulldown o=
n the
> SCR gate, or lose the zener altogether and replace it with a voltage divi=
der
> if the fire voltage doesn't need to be all that accurately controller.

Yes.
That sounds remarkably like "a few more suitably located resistors :-).

One may also have to specifically play with the holding current of the
pseudo-SCR and this will probably be Beta dependant and so not easy or
reasonably possible to set accurately. Going to a formal Schmitt
trigger makes the on/off action voltage driven which is amenable to
design.

>> But, using one of the zillion flasher circuits on the page I
>> provided today, ...

> I think the problem with those is they won't be powered by the input sign=
al.

The input signal becomes the flasher power supply and this achieves his aim=
..

> I don't know why he wants that,

That's the subject of the thread - self-powered SCR logic probe.

> and it sounds like a bad idea, but that was
> the stated problem anyway.

Possibly not a good idea where all tested nodes are not low impedance,
fine enough in many cases. The flasher arrangement allows the 500 uA
of the input to pulse drive a LED at higher brightness intermittently.
As long as the 500 uA load does not affect the node voltage it is
potentially OK (pun almost not intended.)

> Why not switch to 100V logic and use a neon bulb ;-)

It's a 5V logic probe. TTL (or most CMOS) doesn't work for very long
at 100V, tends to get too hot, and the package markings get hard to
read - or the packages may be hard to find.



        Russell

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