User Manual

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Required parts: 9V battery, 10K resistor (brown black orange gold), 470K resistor (yellow
purple yellow gold), buzzer, 2x BC547 transistor, 2 wires
How it works: The 2 sensor wires
must be placed in a tank at a certain
distance (e.g. use a drinking cup). Fill
up the tank with a conducting liquid
(e.g. water) until the level reaches both
sensor wires. A small current will ow
via R2 towards the base of T2. The
base is protected against interference
with a resistor R1.
T1 & T2 are congured as a Darlington switch hence only a very small current is needed to
make T1 conduct and activate the alarm sound.