Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!tikal!sigma!bill
From: bill@sigma.UUCP (William Swan)
Newsgroups: sci.electronics
Subject: the drip
Message-ID: <1626@sigma.UUCP>
Date: 12 Apr 88 21:42:59 GMT
References: <8287@oberon.USC.EDU> <2763@saturn.ucsc.edu>
Reply-To: bill@sigma.UUCP (William Swan)
Organization: Summation Inc, Kirkland WA
Lines: 43

In article <2763@saturn.ucsc.edu> spcecdt@ucscb.UCSC.EDU (Space Cadet) writes:
>     As for other "joke" circuits... my favorite is still "the drip".  I saw
>the idea in a ca. 1970 electronics magazine and implemented a modern version.
>It is a small (hidable) device that emits a periodic chirp.  It can drive you
>up the wall just as effectively as a dripping water faucet.  
>     The last one I built used a PUJT timer set to produce a pulse every five
>minutes. [...description deleted...]
>In fact the average current was about 2.7 uA, so it would last at
>least half a year on a 9v battery...


The original "drip" from, I think, the Feb '67 Popular Electronics, used 
a germanium transistor that would periodically emit short bursts of AF. A
very clever circuit, powered by a 1.5V cell. I built several of these 
around 1970, and thought I'd lost them all until late one especially quiet 
night in '74 when I heard that old familiar crying-kitten squeal.

[I had modified the component values somewhat to use available parts, 
which resulted in longer intervals between chirps, the chirps were
lower in frequency, and lasted longer.]

It was about two days before I finally found it; it turned out to be
one of the first I'd built, soldered to a Radio Shack "C" cell, using
a super-cheap speaker, and still functioning four years later.

It emitted, as I recall, a 5 second squeal every two minutes, with the 
periods increasing as the battery discharged.

A frat which had a preponderance of EE types built several of these
when they lost their building to a rival frat, around '77. They were
left behind in various places in the building (ducts, etc.). I visited 
the new frat shortly after they moved in - seems they weren't sleeping
all that well! :-)


I just went to look for the circuit, but I seem to have thrown it out
recently in a cleaning fit. If somebody still has the schematic (I 
remember it was a modified Colpitts oscillator), I would enjoy seeing
it posted. (I can only remember an approximation of it...)


-- 
William Swan  {ihnp4,decvax,allegra,...}!uw-beaver!tikal!sigma!bill