Elenco Projects 1-101 - Manual (Page 45)

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OBJECTIVE: To sound an alarm when water is detected.
Build the circuit shown but initially leave the jumper wires outside the
cup. Turn on the slide switch (S1); nothing happens. Place the
jumper wires into a cup of water and an alarm sounds!
You could use longer wires and lay them on your basement floor, if
your basement floods during a storm, then this circuit will sound an
alarm.
Project #99
Simple Salt
Water Alarm
OBJECTIVE: To detect salt water.
Add salt to the water and the tone of the
alarm is louder and faster, telling you that salt
is in the water you detected. Also, try holding
the jumper wires with your fingers to see if
your body can set off the alarm.
Project #100
Ambulance
Water Alarm
OBJECTIVE: To show a variation of the
circuit in Project #98.
Modify the circuit in Project 98 by making a
connection between A & B. The water alarm
works the same way but now it sounds like an
ambulance.
Project #101
Ambulance
Contact Alarm
OBJECTIVE: To show a variation of the
circuit in Project #98.
The same circuit also detects if the jumper
wires get touched together, so connect them
to each other. The tone of the sound is now
much different. Therefore, this circuit will tell
you if there is water between the jumper wires
or if the wires are touching each other.
Project #98 Simple Water Alarm