Here is the greatest little trouble
shooting tool since sliced bread! It's not that hard to
build. And it can save you hours of searching hopelessly
for the cause of the problem: The TROUBLE FINDER.
The Intermatic SP440B is a magnetically actuated security alarm... very loud.
The response time of the combined circuit is fast... with no noticeable delay.
One note on adapting the SP440B to this application: The SP440B alarm sounds
when the alarm's magnetically actuated switch opens, not when it closes as
one might expect. Unsolder and remove the magnetic switch and connect
2 wires in its place. Bring these to the relay and switch as drawn
but notice that since the alarm only sounds when these 2 wires are not connected,
the 2 labels on the switch will be wrong and must be reversed.
The switch
used in the unit pictured below does not have a center (off) position.
It is not needed. The SP440B has its own off/on switch.
This is
all there is to it, inside and out. This is the Trouble Finder unit I have used
for years.
(The small white Box glued to the top of the bigger gray box
is the SP440B.)
Though I have designed
electronic versions with various added "Bells and Whistles"
that do offer advantages, the original version as detailed above has
time after
time proven itself to be more than useful and adequate for the task.
