This water level detector circuit diagram is a circuit that will produce an alaram when the water level reaches a present level. This circuit based on multivibrator wired around 555 IC timer. When there is no water up to probe A and probe B, it will be open circuit so the multivibrator will not produce oscillation and the alarm will not sounding. When there is water on the probes, the current will pass through the water, the circuit will be closed to some extend and the IC will start producing oscillation in frequency. The operating frequency of astable multivibrator are depends on to the value of R1, R2, C1 and the resistance between the probes. The alarm will active to indicate the presence of water up to the level of the sensing probes. This circuit can be powered with 3V battery, its preferred to make the probes from two insulated copper aluminum wires.
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