EXPERIMENT 6
24
Clever alarm
system
YOU WILL NEED
+ your alarm system from
Experiment 5
HERE’S HOW
Insert the long wire into the alarm
circuit again. What do you notice?
What do you notice?
When you re-install the long wire, the
red LED won’t go out!
You can only cut off the alarm and get
the system ready again by pressing the
pushbutton. Can you figure out why you
might not want the LED to go out again,
even when you re-establish the original
connection?
The explanation is simple: If that weren
’t
the case, an intruder could simply turn
off the alarm himself!
So if, instead of the long wire, you use a
thin tripwire that an intruder breaks, it
won’t do him any good to mend the wire
again.
C
WHAT’S HAPPENING?
LED1
LED2
T1
Pb1
+
–
T2
A
A
C
C
R1
470 Ω
C1
10 µF
R5
3.3 kΩ
R6
220 kΩ
R3
100 kΩ
R2
470 Ω
R4
22 kΩ
A
B
+
Содержание Electronics
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