bill@sigma.UUCP (William Swan) (04/13/88)
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
bill@sigma.UUCP (William Swan) (04/14/88)
In article <1625@sigma.UUCP> I wrote: >> As for other "joke" circuits... my favorite is still "the drip". > >The original "drip" from, I think, the Feb '67 Popular Electronics, used >a germanium transistor that would periodically emit short bursts of AF... For those who are interested, here is a pseudo-SPICE listing for the device as built from available components 19 years ago: VCC 1 0 1.55V (old Radio Shack "Steel Clad" 15c C cell :-) R1 1 2 3.3M R2 2 3 1k C1 3 0 5uf L1 1 4 ?speaker (~50-100 ohm? el cheapo) L2 4 5 448mH Q1 5 2 6 NPN (germanium?, type unknown) C2 5 6 .1u C3 6 0 .22u D1 6 0 DIODE (1N448 germanium) With some manipulation of values (esp. reducing C1 and making L2 "real" by adding series resistance - not shown here) and introduction of a small "noise" source I've been able to induce SPICE to simulate the circuit (with silicon devices and a higher supply voltage, as far as I've tested). -- William Swan {ihnp4,decvax,allegra,...}!uw-beaver!tikal!sigma!bill