Elenco Electronics EP-130 - EXPERIMENT #115: WATER LEVEL WARNING

-
13
7-
This experiment uses the LED and an audio oscillato
r
a
larm to indicate three different levels of water in a
c
ont
a
in
e
r. Th
e
w
a
t
e
r i
s
used
as
a
c
on
duc
tor t
o
complete the circuits and show the water level
.
When the water is below all three of the wir
e
connections, only the bottom se
g
ment (D) of the LED
is on
(
indicatin
g
a low water level
).
When the water is at a level that touches the two lon
g
wires connected to terminals 77 and 124
(
but is below
the shorter wire), the base current turns on transisto
r
Q2 and the middle segment of the LED (G) turns o
n
(
indicatin
g
a moderate water level
).
I
f
the water rises to a level hi
g
h enou
g
h to touch al
l
three wires, the base current is supplied to transisto
r
Q1, and the top segment of the LED (A) lights. The
a
udio oscillator is also activated as a warning o
f
a
high water level
.
Of course, you can alter this wiring to make the LED
display show other letters o
f
symbols to indicate th
e
different water levels. Can
y
ou think of an
y
othe
r
symbols? (How about L = low,
C
= center, and H
=
hi
g
h?
)
N
o
t
es:
EXPERIMENT #11
5
: WATER LEVEL WARNIN
G
Wirin
g
S
equence
:

1
-29

2
-
30

3
-1
03
-1
09

4
-
1
7-
41
-
8
7

5
-47-110

20
-42-4
5
-11
9

2
2-44

2
5-48-124-
WIRE

40
-7
6

43
-7
8

46
-
104
-
88

7
5-
WIRE

7
7-WIRE

1
21-122
Schemati
c