The circuit uses a 555 timer in astable mode with R1=220 ohms, R2= 150 ohms and C1=1 uF. The frequency of the given astable circuit is around 1.18 KHz.
The two probes which are shown in the circuit should be kept at the high level for the water. The distance between the probes should be less than a few centimetres to ensure that the conduction between the probes will take place when water is touched to these probes.
When the water level rises to the height of the probes, then the 555 circuit will get enabled and the output of the 555 timer produces a square wave output with a frequency of about 1.18Khz. This output is given to the mini loudspeaker which then beeps at an audio frequency of 1.18KHz.
The logic Implemented in this circuit is, 555 timer is enabled when its reset pin is connected to logic high. But initially it is connected to ground. When the water level is maximum this pin is enabled and this drives the 555 timer into astable mode. Learn more about 555 timer.
Required Components
- IC 555 timer.
- Loud Speaker.
- Capacitors.
- Resistors.
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