Well before annoying smoke-detector chirping, there was a mischievous 'cricket' for Mrs. Librarian
Who needed to be in college to have that kind of pranking fun?
Sophomore year in high school (circa 1977) my buddies and I were having
all kinds of fun with a book we'd stumbled into in the reference section of the
school library - it had been published in the 40s, and had all kinds
things that teenage boys would love in it. Explosive mixtures, self igniting paper airplanes, NI(3), you name it.
But the librarian gave us grief over the excited talking we'd do in the
reference section when we found the next fun thing to try...
It was annoying.
She annoyed us, so we decided to annoy her.
Between the three of us, we knew just enough about electronics to hack
together a simple little circuit. ( We may have had help from a article
in Popular Electronics, but I'm not sure on that one, it was a long time ago!)
Nothing more than an oscillator, a simple amplifier, a speaker, and a 9V battery.
The catch was the battery didn't directly power the rest of the circuit. Instead we used the
leakage current from a transistor to charge a capacitor. When that
cap charged to the right voltage, which took a few minutes, depending
on the temperature of the room, it would turn on another transistor that
allowed power into the oscillator/amp, and discharge the cap.
What's that noise?
End result was
a roughly 1/2 second "chirp" every couple of minutes. Note that this predates
smoke detectors, but it was like a detector with a low battery. And just as
hard to find, and just as annoying.
Especially since we hid it in her desk, behind the drawers.
And left it there for a month.
They called in exterminators to get rid
of the "cricket" at least twice we know of. IIRC, we estimated that the circuit
could run for 6+ months before the battery was exhausted.
Of course, now ThinkGeek sells an "annoy-a-tron" that is similar in function
but can only run for 2 weeks on it's little lithium battery. I have a few of them.
I use them.
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