LM1830 Fluid/Liquid/Water Level Control

This is Fluid/Liquid/Water Level Control circuit using LM830. The LM830 can be used to detect absence and presence of aqueous fluids. This application uses two probes and a voltage divider circuit to detect the presence of the fluid. Sometimes, there is a dissolving or plating of the probe is occurred when A DC signal is used. To prevent that problem, this application uses AC signal. When the fluid impedance is not compatible with the internal 13 kX divider resistance, an external resistance can be added to this application. Here is the schematic diagram of the  circuit :

This circuit uses a signal control, to control the switch. When the signal is LOW, the switch is off and when the signal is HIGH, the switch is ON. To allow the LM1830 to be used for HIGH/LOW limit control applications, this circuit added with a CD4016 quad CMOS analog switch. This circuit also equipped with inverter that is created by pulling the output of a CD4016 quad CMOS analog switch up with a resistor and grounding the input of one switch section. the detector input is the outputs of CD4016 quad CMOS analog switch that connected to pin 10 of the LM1830. Beside that, the CD4016 also used to buffer the open collector output of the LM1830. The transistor’s base is controlled by the last section of the switch that turn drives a solenoid actuated valve or relay. [Circuit’s schematic diagram source: National Semiconductor Application Note]