-63-
Let’s demonstrate a use for the timer circuit you just built
by combining it with Experiment 28, the Alarm. Connect
the wires according to the Wiring Checklist (noting that
the transistor bases and transformer springs 23 and 24
are not connected although their wires cross in the
schematic). Connect the alarm trip wire and then
connect the battery wire to turn the circuit on. Press the
switch once. Now disconnect the trip wire to activate the
alarm. The alarm stays on for a few seconds and then
goes off. Reconnect the trip wire and press the switch to
reset the alarm and timer. If you only re-connect the trip
wire without resetting the timer then the alarm won’t work
the next time. You could use a circuit like this where you
get lots of false alarms and you want to shut off the alarm
before the battery gets weak. Automobile alarms, for
example, get lots of false alarms.
EXPERIMENT #44: Alarm with Shut-off Timer
Wiring Checklist:
o 11-to-16-to-36-to-56
o 10-to-14
o 17-to-20-to-26-to-55
o 37-to-51-to-18
o 44-to-42-to-19
o 15-to-45
o 5-to-21
o 6-to-22
o 23-to-33-to-47
o 12-to-32-to-46
o 13-to-38
o 39-to-25
o 12-to-14 (use a long wire,
this will be referred to as
the “trip” wire)
o 43-to-52-to-27-to-24
Schematic
Long “Trip”Wire
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