Owner manual
-
147
-
This experiment is a pulse-tone oscillator with a
n
a
djustable frequency that can obtain a wide ran
g
e of
notes.
Y
ou can p
l
ay tunes on
i
t t
h
at soun
d
lik
e an
electronic organ, but it takes some practice.
To pla
y
a tune, modif
y
the control to the proper not
e
a
nd press the key. Readjust the control for the nex
t
note an
d
press t
h
e
k
ey a
g
a
i
n.
When you close the key the
f
irst time, the base
current
f
lows around the loop
f
ormed by the battery
,
the 10
k
Ω
resistor, the 50
k
Ω
resistor, the transistor
base and emitter, and the key.
The base current causes the collector current to flow
around the loop
f
ormed by the 3V supply, the lowe
r
h
al
f
o
f
the trans
f
ormer windin
g
, the transistor
co
ll
ector an
d
em
i
tter, an
d
t
h
e
k
ey.
The current throu
g
h the trans
f
ormer causes a curren
t
to flow around the loop formed by the top transforme
r
w
i
n
di
ng, t
h
e 0.0
5
μ
F
capac
i
tor, t
h
e trans
i
stor
b
ase
an
d
em
i
tter, t
h
e
k
ey, t
h
e
b
attery an
d
b
ac
k
to t
he
transformer’s center terminal
(
terminal 4
)
. Thi
s
current quickly (in less than 0.0001 seconds)
c
h
arges t
h
e 0.0
5
μ
F
to a
b
out 4
V
or so w
i
t
h
a po
l
ar
i
t
y
n
egative on the trans
f
ormer side and positive on th
e
transistor base lead side. The speaker is onl
y
activated while the current
f
lows in the trans
f
ormer
.
When the induced volta
g
e
f
rom the top hal
f
o
f
the
transformer windin
g
stops, the char
g
in
g
of the
0
.
0
5
μ
F capacitor stops, then the capacitor begins to
c
h
arge aga
i
n.
A
s soon as t
h
e
di
sc
h
arge
b
eg
i
ns, t
he
capacitor volta
g
e becomes hi
g
her than the battery
vo
l
tage.
Th
e reverse po
l
ar
i
ty vo
l
tage
i
s app
li
e
d
to t
h
e
base and the transistor turns o
ff
. Now
,
all transistor
j
unctions act as open circuits. The capacitor
discharges around the loop
f
ormed by the top
transformer winding, the 10k
Ω
k
k
resistor, and the 50k
Ω
k
k
resistor. When you reduce the control setting, th
e
dischar
g
e is
f
aster, so the process is repeated at
a
f
aster rate causing a higher
f
requency. The cycle
repeats when the 0.05
μ
F capacitor discharges to
slightly below the 3V of the battery.
N
o
t
es:
EXPERIMENT #12
5
: P
U
L
S
E T
O
NE
G
ENERAT
OR
Schemati
c
Wiring Sequence:
1-29
2-30
3-108-110
4-82-120
27-40-107
28-81
5-41-109
42-137
119-138