midnight raid detector

12-12 — elektor december 1980 midnight raid detecto D. Butler This canned alarm is intended to repel inmates who insist on delving into the fridge late at night in order to quench their thirst or make off with a tasty snack. It can also be used as a deterrant for "extra-curricular" snacks by persons on a diet. Although the age of Viking invasions has long since passed, a certain amount of small scale plundering still goes on. In particular, the nocturnal wanderings of certain members of the family on their way to raid the fridge, comes to mind. Upon investigation the following morning a few crumbs scattered on the plate is all that remains of the large chunk of cheese you were saving, the last drop of your favourite beer has mysteriously evaporated and there is no sign of the culprit. One deterrant would be to lock the fridge, another to elec- and capacitor C3, form a squarewavE oscillator with a frequency of around 1 kHz. This oscillator is turned on anc off by a second compris...