LM1830 flow switch circuit

An very simple flow switch circuit can be designed using the LM1830 fluid level detector device that sense the presence or absence of aqueous solutions.
Using this flow switch circuit you can implement HIGH and LOW limit control controlling the operation of pumps or solenoid actuated valves .
The LM1830 is a monolithic bipolar integrated circuit designed to detect the presence or absence of aqueous fluids.
An AC signal generated on-chip is passed through two probes within the fluid. A detector determines the presence of the fluid by using the probes in a voltage divider circuit and measuring the signal level across the probes. An AC signal is used to prevent plating or dissolving of the probes as occurs when a DC signal is used. A pin is available for
connecting an external resistance in cases where the fluid impedance is not compatible with the internal 13 k divider resistance.

CD4016 quad CMOS analog switch allows the LM1830 to be used for HIGH and LOW limit
control applications. The switch sections are opened and closed by a control signal, where a HIGH level turns the switch ON and a LOW level turns the switch OFF.
The last switch section controls the base of a transistor which in turn drives a relay or solenoid actuated valve.

The start and stop probes are set at their appropriate levels in the fluid container, and the ground return is connected to a third probe located at a depth greater than the start and
stop probes. If the container is conductive, it may be used as the ground return.
By reversing the labeling on the probes, as well as reversing the polarity of the relay drive, a container "fill" control is implemented such as would be used in a water tower (necessary circuit changes are shown in Figure 2).
This fluid level detector circuit require a 6 volts dc power supply or it can be connected to the 220 or 110 volts outlets using a transformer .