Elenco Electronics EP-130 - Sawtooth Oscillator

-
142
-
When you connect the si
g
nal from this oscillator t
o
an oscillosco
p
e, it creates a
p
attern that looks like
the teeth of a saw (as shown below)
.
The shape o
f
this wave results
f
rom the slo
w
c
harging o
f
the 0.
1
μ
F capacitor through the contro
l
and the 100
k
Ω
resistor, and the capacitor’
s
di
sc
h
arge t
h
roug
h
t
h
e
PNP
an
d
NPN
trans
i
stors
.
Th
e vo
l
tage
di
v
id
er - t
h
e 470Ω
a
n
d
10
0
Ω
res
i
stors
-
provides about 1.6 volts to the transistors. Current
f
lowin
g
f
rom the 9V supply into the 0.
1
μ
F capacito
r
(through the control and the 100k
Ω
k
resistor
)
slowl
y
c
h
arges up t
h
e capac
i
tor.
Wh
en t
h
e capac
i
tor
’s
char
g
e exceeds the volta
g
e of the volta
g
e divider
(
1.6V
)
, the transistors turn on and provide a path for
the 0.1
μ
F capacitor to dischar
g
e quickly. Now, th
e
transistors turn o
ff
a
g
ain, and the capacitor be
g
in
s
to slowly char
g
e to repeat the cycle
.
You can modi
f
y the oscillator
f
requency by changing
the values of the com
p
onents in the timer circuit - th
e
control, the 100k
Ω
k
k
res
i
stor an
d
t
h
e 0.
1
μ
F
capac
i
tor
.
T
ry a 47
k
Ω
r
es
i
stor or a 220
k
Ω
resistor in place o
f
t
h
e 100
k
Ω
resistor, and try several di
ff
eren
t
capacitors. If
y
ou connect one of the electrol
y
ti
c
capacitors, be sure that you use the proper polarit
y
(
+ and –
).
No
t
es
:
EXPERIMENT #12
0
:
S
AWT
OO
TH
OSC
ILLAT
OR
Schematic
Wiring Sequence:

73-81-27-119

28-89

71-74-47-40

41-46

42-43-90-109

124-44-48-110-72-EARPHONE

45-82-EARPHONE

121-122