Reservoir Level Controller Circuit
Accessed 1253 times.How to cite this article: VERTULO, Rodrigo Cesar. Reservoir Level Controller Circuit. Available at: . Accessed on: 12/02/2026.
SPANISH VERSION: https://labdeeletronica.com.br/en/eletronicaanalogica/circuito-controlador-de-nivel-de-reservatorio/
A water pump control circuit is very useful in situations where it is necessary to ensure that a reservoir (water tank, tank, etc.) always has a minimum amount of liquid and never exceeds a certain limit to avoid overflows. A solution like this can be implemented with simple components like the one shown in this article.
Consider the configuration below of the studied system.
In this system, when the liquid level drops below sensor 1 (s1), the pump is activated. At this point, the reservoir level begins to rise with the pump remaining activated until the liquid reaches sensor 2 (s2). When it reaches s2, the pump is switched off and remains so until the level drops below s1 again with the consumption of liquid from the reservoir.
An electronic circuit to meet these requirements requires the implementation of hysteresis. This is necessary so that the pump does not keep turning on and off around sensor 2. Note that without hysteresis, when the liquid reaches s2 the pump is turned off; however, as the level drops and s2 is deactivated, the pump is turned on again until the liquid reaches s2 again. This cycle would remain like this indefinitely if a solution with hysteresis were not implemented. With hysteresis, as soon as s2 is reached the pump is turned off and remains off as long as s2 and s1 are deactivated. In this scenario, with s1 and s2 deactivated, the pump turns on again.
The circuit shown below uses a few logic gates and a D-type Flip Flop. The Flip Flop clock can be implemented with a 555 IC in astable mode with a low frequency, around a few Hertz. In the circuit shown, the clock is represented by a square wave generator. The Flip Flop output is connected to a LED representing the pump. In a real situation, this LED should be replaced by a power stage. The logic gates can be ICs with TTL logic. The upper switch represents sensor s1 and the lower one represents sensor s2.
I hope you enjoyed the article and if you have any questions, leave your question.
Prof. Rodrigo Vertulo holds a Bachelor's degree in Computer Science and Electronic Engineering, is a specialist in Software Engineering and has been an Electronics Technician for almost 30 years. He worked for more than 10 years as a Software Engineer at IBM Brazil, and was also a researcher at the Federal University of São Paulo and a University Professor at Fatec de São Caetano do Sul in the Paula Souza Center. He has almost three decades of professional experience in the area of Computer Science and extensive experience in Electronic Engineering projects.
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