: I remember seeing a VERY simple circuit in something like Radio
: Electronics way back in the early 1970's. Once or twice I went
: back and searched to try to find that again, without success. It
: seems like it was only a few components but would latch to record
: spikes or power failures. I can't remember which, too many years,
: too many dead brain cells.
In the same boat here with memory, so take this with a grain of salt...
I think the project was in Popular Electronics, being Elementary Electronics
was more "kids" and Radio Electronics was more "adult".
From what I remember, I'm pretty sure I built one, but it wasn't very good.
It was a simple over or under voltage monitor (one led for each and a reset
button).
I think it used a "surplus junk transformer" out of your junk drawer that
had either a 6.3v or 12.6v secondary. Whatever chip it used (could of been
like a LM317) had a simple circuit around it to monitor the secondary
voltage of the transformer (probably after passing through a 1N4004, no
filters). I think the point of the article was if you used a 12.6v
transformer, you were dealing with 10:1 ratios or something.
Anyway, whatever adjustment was inside set the high or over voltage led to
come on and stay on. Think that was set to (in theory) to 130v.
It didn't really detect low voltage if I remember correctly, was it did was
if voltage was lost completely, when restored the other led would light.
Same bit when you first plugged it in, the low led automatically lit, you
pressed reset to clear.
So I guess if you came home and the low led was on, you knew you lost power.
I remember this thing because it was around the same time Radio Shack
started selling that chip, which for the life of me I can't remember now, it
was like designed for building an audio sound VU meter. There was a follow
up at some point on building "an improved version" of the monitoring gizmo
using it. So instead of a simple two led thing, you could read the voltage
directly using 10 or so led's.
Remember this was all prior to cheap LCD meters being around (probably pixie
tubes were the closest digital meters) so it was sort of neat having a
visual multi-led ac meter, even if it only worked from 108-130 or whatever
the range was.
Point is, even the fancy version didn't detect spikes.
Pretty sure Sam G. had articles in all those mags at that time, if there is
an index to be had, he should know.
-bruce
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