Saturday, April 13, 2013

Simple Gate Alarm

A cheap and easy gate alarm comprised of a single CMOS Integrated Circuit.

Figure 1 characterizes a low cost and simple Gate Alarm, that is supposed to run off a small universal AC-DC energy supply.

IC1a is a fast oscillator, and IC1b a gradual oscillator, which can be blended through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, and so on.) is opened. The circuit is meant no longer so much to sound like a siren or warning tool, but quite to present the impression: \"You were now noticed.\" R1 and D1 may be ignored, and the value of R2 perhaps decreased, to make the Gate Alarm sound more like a warning software. VR1 adjusts the frequency of the sound emitted.

IC1d is a timer which lead tos the Gate Alarm to emit some 20 to 30 further pips after the gate has been closed again, sooner than it falls silent, as if to say: \"Im more clever than a easy on-off tool.\" Piezo disk S1 may be changed with a LED if preferred, the LED being wired in collection with a 1K resistor.

Figure 2 shows how an bizarre reed swap may be transformed to close (a \"normally closed\" swap) when the gate is opened. A continuity tester makes the work straightforward. Note that many reed changees are refined, and subsequently wires that are soldered to the reed change should not be flexed at all near the swap. Other forms of swapes, one of theses microswitches, can be used.