The liquid detector is a detector with liquid alternating voltage and can be built using some common electronic components. Voltage alternative for this circuit is made using a gate with Schmit trigger function, which works as an alternative power oscillator.
A touch switch sensor electronic project can be designed using this simple electronic diagram below. This touch switch sensor use one sense switch that allows shareholders "on / off". The capacitor C1 stores the switching state at the time. Depending on the signal output of gate N1, capacitor C1 is loaded or unloaded. On reaching the sensor, the signal is returned to the entrance of N1, so that switching state change occurs .
This fluid level sensor circuit is based on a simple common 741 op amp IC used as an comparator . When that two fluid level sensor are not placed in liquid the output voltage from the 741 op amp is negative and the T1 is blocked resulting a 0 volts voltage on the R5 resistor .