Perpetual Projects - Part 3
Approx construction cost US$6.50 (Loop Burglar Alarm), $11.50 (Touch-Sensitive Door-Light), $8.00 (Solar-Powered Rain Alarm)
This month, in the penultimate of our four-part series of “perpetual’’ projects, we give details of a further three circuits that will find many possible uses in and around the home.
Loop Burglar Alarm: This circuit works on the principle that when a continuous electrical loop is broken, an alarm is triggered. The loop may include a thin wire snare, which would be snapped by an intruder or by the removal of an object through which the loop-wire is threaded. The “loop’’ could also include contacts which would be broken by, for example, a gate or a window opening.
Touch-Switch Door-Light: This circuit has several possible applications – among them being to light an entrance upon entering, to illuminate a switchboard during a power failure, or to help you find a keyhole on approaching a door at night.
Once the door-light is triggered, by a touch switch, it shines for roughly half a minute at a time. It could be used more than 10 times in the darkness before the regulator’s capacitor C1 is exhausted.
Solar-Powered Rain Alarm: This circuit is triggered by falling rain. When the alarm sounds, a touch of the finger puts it to sleep again for an hour or so.
More details on this construction project can be found in the September 2001 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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