Elenco 130-in-1 Electronics Playground - Manual (Page 17)

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This circuit works as a rain detector. This circuit stays
off and draws no current if the resistance between the
long wires is more than about 250k
Ω, whether the
key is open or closed. The speaker produces a tone
when the key is closed and water (or anything else
that has a resistance of less than about 250k
Ω) is
connected to both of the test wires.
Connect the wires to other wires or metallic plates
laid out on an insulated surface. The alarm turns on
when water completes the circuit by spanning the two
wires or plates.
This oscillator is the basic pulse-type that we’ve used
several times in this experiment kit. The 22k
Ω resistor
protects the circuit against excess base current, in
case the wires are shorted together. The 100k
Ω
resistor keeps any transistor leakage current from
turning on the oscillator.
Notes:
EXPERIMENT #122: AUDIO RAIN DETECTOR
Schematic
Wiring Sequence:
o 1-29
o 2-30
o 3-104-110
o 124-4-WIRE
o 5-41-109
o 86-89-103-40
o 42-90-138
o 85-WIRE
o 119-137
o 121-122
In this experiment you are going to make a circuit
that that sounds like the mockingbird.
Follow the wiring sequence and observe the
drawings. Don’t forget to make all the proper
connections and have fun!
To finish the circuit below, slide the switch to the A
position to turn on the power. No sound will come
from the speakers yet. When you press the key you
will hear a sound quite like a bird chirping from the
speaker. When you release the key, you will still be
able to hear the chirping sound but eventually it will
slow down and stop. The first transistor “Q1” is
dropped off from the battery when the key is
released. Transistor “Q2” still produces the bird sound
until the controlling current from transistor “Q1” stops.
Try using a different value capacitor instead of the
10
μF and the 100μF capacitors. These capacitors
control the amount of electricity reaching the
transistors. Listen for the difference. Make sure to
start keeping notes on your experiments.
Notes:
EXPERIMENT #6: TWEETING BIRD
Wiring Sequence:
o 1-29
o 2-30
o 3-106-110
o 4-41-131-138
o 5-44-109
o 40-114-91-75
o 42-85
o 43-105-86-77
o 119-45-115-113-92
o 76-137
o 78-116
o 120-132
Schematic