Next message: Kevin Redden: "T&T: Lake Champlain (was: Re: No discharge silliness)"
In a message dated 11/10/04 12:01:37 AM,
writes:
<< The easest alarms are very simple and will run on 12 volts. I have made a
number using a piece of plastic fairing compound spreader. Cut the 4"
spreader into four 1" pieces. Put a hole in the thicker edge. Put the thin
edge under a normally closed micro switch (Radio shack)--this makes the
circuit normally open. Attatch 30# monofiliment (fishing line) to the hole in
the spreader piece. Attatche the other end of the monofiliment to the cover,
to a gate, cross it over the deck etc. If anyone pulls the monofiliment, it
pulls the wedge out of the microswitch. The micro switch is connected to a
relay--when the switch closes, it trips the relay, which then sounds a horn,
siren, strobe light etc--all Radio Shack. For $30 to $50 you can have a very
good alarm--for another $30 you get a solar charger. The alarm uses no
current, unless the monofiliment is pulled.
There are any number of other varients.
>>
My father had a similar alarm system he used in a warehouse in the '30s. It
was almost identical to the system Bob describes except that it substituted
spring operated clothes pins for the microswitch and relay. When the line pulled
the insulating chip out of the clothes pin, the jaws clamped shut, pressing
the alarm wires together. No microswitches or relays necessary. The circuit was
wired to a large alarm bell outside of the building. I recall that it was
powered by a bank of four drycells. The alarm pull lines were at about knee
height. When my brother and I were kids, we used to see if we could limbo under the
wires without setting off the alarm.
Larry Z
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