Elenco Electronics EP-130 - Pulse Alarm

-
84
-
Now you will let one oscillator control another t
o
create an alarm. Here we have a multivibrator-typ
e
osc
ill
ator contro
lli
ng a pu
l
se osc
ill
ator.
Th
e pu
l
s
e
oscillator produces frequency in the audible rang
e
(the ran
g
e that our ears can hear, about 20 to 20k
Hertz
)
. The multivibrator circuit on the left side of th
e
schematic should look familiar. The multivibrato
r
comman
d
s t
h
e pu
l
se osc
ill
ator
b
y a
ll
ow
i
ng current t
o
f
low to the transistor base.
Build the experiment and press the key to hear th
e
alarm sound comin
g
f
rom the speaker. You hear th
e
alarm resonate turning on and o
ff
as the puls
e
oscillator turns on and o
ff.
This intermittent sounding alarm is more bene
f
icia
l
than a continuous tone, because it is more
noticeable. You can experiment with this experimen
t
by varying the values of the 22k
Ω
k
k
, 47k
Ω
k
k
, and 100k
Ω
k
k
resistors, and the 0.0
2
μ
F
capacitor.
N
o
t
es
:
EXPERIMENT #
66
: P
U
L
S
E ALARM
Wiring
S
equence:

1-29

2-
30

3
-1
03
-1
09

4
-
42
-
4
5-
138

5
-47-110

4
0
-11
3
-
8
7

41-112-7
5

43
-
111
-
8
5

44-114-7
3
-
89

4
6
-1
0
4-
90

7
6
-
86
-
88
-7
4
-
48
-
124

119-137

121-122
Schemati
c